AN ECOLOGICAL SURVEY OF THE RIPARIAN ZONE
OF THE COLORADO RIVER
BETWEEN LEES FERRY AND GRAND WASH CLIFFS
Steven W. Carothers and Others
Technical Report No. 10

Colorado River
Research Program
REPORT SERIES
GRAND CANYON NATIONAL PARK

United States
Department of the Interior
National Park Service

COLORADO RIVER RESEARCH PROGRAM
Grand Canyon National Park
Grand Canyon, Arizona 86023

The Colorado River Research Program was initiated by the National Park
Service in 1974 to secure scientific data to provide a factual basis for the
development and the implementation of a plan for appropriate visitor-use
of the Colorado River from Lee's Ferry to Grand Wash Cliffs and for the
effective management of the natural and cultural resources within the
Inner Canyons. The intensified research program consists of a series of
interdisciplinary investigations that deal with the resources of the riparian
and the aquatic zones and with the visitor-uses including river-running,
camping, hiking, and sight-seeing of these resources, as well as the impact
of use and upstream development upon canyon resources and visitor
enjoyment.
Final reports that result from these studies will be reproduced in a series
of Program Bulletins that will be supplemented by technical articles published as Program Contributions in scientific journals.
Merle E. Stitt, Superintendent
R. Roy Johnson, Program Director

Cover Drawing by J.G. Carswell, University of Virginia

AN ECOLOGICAL SURVEY OF THE RIPARIAN ZONE
OF THE COLORADO RIVER
BETWEEN LEES FERRY AND GRAND WASH CLIFFS
Steven W. Carothers and Others
Technical Report No. 10

Grand Canyon National Park
Colorado River Research Series
Contribution No. 38

AN ECOLOGICAL SURVEY OF THE RIPARIAN ZONE
OF THE COLORADO RIVER BETWEEN LEES FERRY AND
THE GRAND WASH CLIFFS, ARIZONA

FINAL RESEARCH REPORT
June 1976

Prepared for and Sponsored by
U. S. Department of Interior, National Park Service
Grand Canyon National Park, Arizona 86023
Contract No. CX821500007

Submitted by
Steven W. Carothers
Head of Biology Department
Harold S. Colton Research Center
Museum of Northern Arizona
Flagstaff, Arizona 86001
Compiled by the Biology Staff
Harold S. Colton Research Center
Steven W. Carothers
Stewart W. Aitchison
Martin M. Karpiscak
George A. Ruffner
N. Joseph Sharber
Philip L. Shoemaker
Lawrence E. Stevens
Michael E. Theroux
Dennis S. Tomko
Edited by
Steven W. Carothers
Stewart W. Aitchison

30 June 1976

DEDICATION
To future generations in the hope that "running the Grand"
will be as exciting, fulfilling, wonderful, and mysterious
for them as it has been for us.

ii

ABSTRACT
An ecological survey of the riparian zone of the Colorado
River from Lees Ferry to the Grand Wash Cliffs, Arizona, was
initiated between 1 June 1974 and 30 June 1976. The purposes
of this study were:
First, to describe vegetational changes as a result of
the controlled water release from Glen Canyon Dam, second,
preparation of a vegetation map from river level up to
the 500 foot contour level, third, to describe population
densities, home ranges, and demography of important
vertebrates, fourth, to inventory insects of the riparian zone,
fifth, to describe the distribution and impact caused by
feral burros, and sixth, to describe the interrelationships
of humans with the biota.
The major findings include the following: (1) The
construction of Glen Canyon Dam has permitted the development
of a new riparian community. This community is characterized
by salt cedar, arrowweed, coyote willow, desert broom, and
seep willow. (2) Botanical investigations in the riparian
and adjacent habitats discerned the presence of 807 species of
vascular plants representing 92 families. Also, two species,
previously undescribed, Flaveria mcdougallii and Euphorbia
rossii, are presented. (3) An accessment of important vertebrates and insects revealed: a) rodent communities on beaches
tend to be less productive and less stable than those rodent
communities of the terrace areas, b) Peromyscus eremicus
appears to be the most successful small mammal in the riparian
zone, c) rodent survivorship is very low and suggests a nearly
annual population turnover, d) 178 species of birds utilize
the riparian zone, of these 41 breed there, e) the most common
bird species is the Lucy's Warbler, f) over 12,000 insect specimens in 20 orders and 247 families were collected and prepared,
g) insect production on the exotic salt cedar fluctuate
dramatically in comparison to insect production on dominant
native plants. (4) Feral ass distribution was found to be
greater than previously believed. It has been determined that
the expanding feral ass populations are systematically destroying
riparian and desert habitats within the study area and their
immediate removal is suggested. (5) Human impact seems to be
a function of visitor activities and the specific biotic sensitivity of the use area rather than a function of the total number
of users. (6) In 1974, 395 different campsites were reported
between Lees Ferry and Pierce's Ferry. In 1975, 350 different
campsites were used. (7) Establishment and maintenance of an
inner canyon trail system, the removal of all future human
fecal waste material and education of river users may be the
means to minimize habitat destruction rather than just setting
a user-day limit.

iii

TABLE OF CONTENTS
Abstract

iii

Table of Contents

v

Acknowledgements

ix

Preface

xi

CHAPTER I
Vegetational Changes Along the Colorado River
by Martin M. Karpiscak

1

CHAPTER II
Vascular Flora of the Grand Canyon
by Michael E. Theroux

ill

CHAPTER III
D i e t a r y C h a r a c t e r i s t i c s o f Some Grand C a n y o n
Amphibians and Reptiles
b y D e n n i s S. T o m k o

1+5

CHAPTER IV
Demography of Three Species of Grand Canyon
Lizards
by Dennis S. Tomko

55

CHAPTER V
Mammals of the Colorado River
by George A. Ruffner and Dennis S. Tomko

6l

CHAPTER VI
Birds of the Colorado River
by Steven W. Carothers and N. Joseph Sharber

109

CHAPTER VIi
An Insect Inventory of Grand Canyon
by Lawrence E. Stevens

123

CHAPTER VIII
Insect Production of Native and Introduced Dominant
Plant Species
by Lawrence E. Stevens

129

CHAPTER IX
Distribution of Feral Asses
by Philip L. Shoemaker

137

v

CHAPTER X
Feral Asses on Public Lands: An Analysis
of Biotic Impact
by Steven W. Carothers

lUl

CHAPTER XI
Campsite Usage and Impact
by Stewart W. Aitchison

155

CHAPTER XII
Interrelations of Man and the Biota
by Steven W. Carothers, Stewart W. Aitchison
and Dennis S. Tomko

173

CHAPTER XIII
Summary

179

APPENDIX 1
Publications and related manuscripts resulting
from this study.

I89

APPENDIX 2
Professional papers presented and/or abstracted.

191

APPENDIX II-l
Vascular flora inventory*
APPENDIX II-2
Ten-mile sort of plant species locations*
APPENDIX VI-1
A checklist of birds occurring along the Colorado
River from Lees Ferry (mile 0.0) to the Grand
Wash Cliffs of Lake Mead (mile 279.0).

193

APPENDIX VI-2
Annotated list of breeding species found along
the Colorado River from Lees Ferry (mile 0.0)
to Diamond Creek (mile 225.0).

202

APPENDIX VII-1
Families of insects collected in Grand Canyon
National Park

218

*These are computer print-outs and are under separate
cover.
VI

APPENDIX VII-2
Some Arachnida of the Colorado River riparian
zone in Grand Canyon National Park

2h3

APPENDIX VII-3
Tests used in identification of insects

2l+7

APPENDIX XI-1
Directions for campsite evaluations sheet-2

2l+9

Vll

ACKNOWLEDGEMENTS
This project could never have been accoumplished without
the assistance of a myriad of scientists, technicians, boatmen,
cooks, universities, and research centers.
First and foremost, our thanks go to the National Park
Service for the conception and financial and logistical support
of this project; in particular, M. E. Stitt, R. R. Johnson,
D. Ochsner, P. Bennett, and S. Stockton. Dr. R. R. Johnson,
Director of the NPS River Research Project, was a constant source
of aid and his interaction has greatly expedited this project.
In many cases help came from individuals from outside
institutions; namely, Dr. H. S. Gentry, and J. H. Lehr,
Desert Botanical Gardens; Dr. C. Mason and his staff, University
of Arizona; Dr. G. Ownbey, University of Minnesota, Dr. D. J.
Pinkava, E. Lehto, T. Keil and T. Reeves, Arizona State
University; Dr. J. Rominger, Northern Arizona University;
and Dr. M. willson and R. Von Neuman, University of Illinois.
The acquirement of the rafts and all the accessories and
training of scientists to become boatmen was a project of
its own. We wish to thank the American River Touring Association
and especially Lou and Bob Elliot for generously donating the
frames and oars for the two snout-rig crafts. The expertise
and incredible patience of boatmen Peter Winn and Scott Imsland
made the dream of negotiating the rapids, whirlpools, and other
hazards of the Colorado River a reality. Without them and
many other boatmen this project could have never been done.
The people on our biology staff contributed much time and
effort above and beyond the "call of duty." Thanks goes out
to George Bain, James Bain, Debra Crisp, Jill Downs, Steve
Kreigh, Dr. W. B. McDougall, Don Morehouse, Dr. 0. J. Reichman,
Kathy Shoemaker, Don Wertheimer, and Bill Williams. Special
thanks to Pam Lunge, Museum of Northern Arizona Artist, for
doing all the illustrations for this report. Photography
was graciously done by John and Helen Running and Carroll
Bennett. Ralph Heinz undertook the arduous task of locating
and photographing the matching pictures found in Chapter I.
We are particularly grateful to the commercial and
private river running outfitters that abided with our wishes and
turned in their visitor usage forms.
The typing, proofing, and photocopying of this report was
a colossal task. To this end we wish to thank Nancy Morgan and

IX

Nancy Goldberg. Others who graciously helped include, Bonnie Haldeman,
Melanie Neuman, and Sandy Martin.
Steven W. Carothers
Stewart W. Aitchison
Martin M. Karpiscak
George A. Ruffner
N. Joseph Sharber
Philip L. Shoemaker
Lawrence E. Stevens
Michael E. Theroux
Dennis S. Tomko

June 1976

Figure 1.--Between 1967 and 1972, the total number of
river runners increased 682 percent.

x

PREFACE
The Setting and The Problem
Until the early 1960's human usage of the Colorado
River and its attendant riparian vegetation was so
minimal that impact upon the biota was no doubt
negligible. However, beginning in 1963, the gates
of Glen Canyon Dam were closed and the riverine ecosystem
was altered by the hand of man as never before. Instead
of a river of mud and silt, "too thick to drink and too
thin to plow," a clear, cold green flow was released
from the dam. No longer would the annual spring
run-off scour the canyon and deposit new beach sands
and replenish driftwood.
For Colorado River rafters, the dam presents
mixed blessings. On the one hand, daily river level
fluctuations now occur in response to power demands
in distant cities. Sometimes these fluctuations
make certain rapids impossible to navigate. Commonly
a boat moored at high water is left high and dry
by next morning's low water. On the other hand,
controlled release of water makes fall and winter
trips possible during dry years when natural run-off
would have been insufficient to float a boat.
However, today river running itself is one of
the major problems confronting managers of our wilderness
rivers. Between 1967 and 1972, river running in the
Grand Canyon grew from 2099 users to 16,432, an increase
of 682 percent (Figure 1 ) . This alarming user-growth
rate forced the National Park Service to initiate a
ceiling on the number of boaters. The commercial
allotment for 1972 was set at 105,000 passengerdays (pds). Of these only 88,135 pds were used, so
for 1973 the allotment was adjusted downward to
89,000 pds. In 1973, 86,264 pds were used therefore
the 89,000 figure was maintained to date. The public
has been advised no final decision will be made until
a carrying capacity figure is derived from the multidisciplinary research underway at Grand Canyon.
The Harold S. Colton Research Center, Biology
Department, was charged by the National Park Service with
the investigation of the biotic resources of the
riparian zone of the Colorado River.

XI

The objectives were:_
1.
To describe successional changes in vegetational
patterns as a result of the controlled water release
from Glen Canyon Dam. This was to be accomplished
primarily through comparison of present day with pre-dam
photographs.
2.
Preparation of a vegetation map from river
level up to the 500 foot contour level along the Colorado
River from Lees Ferry to the Grand Wash Cliffs.
3.
To describe population densities, home ranges,
and demography of important vertebrates.
4.
zone.

To inventory insect species of the riparian

5.
To describe impact of feral burros in the
riparian zone.
6.
To describe the interrelationships of visitors
with the biota.
These objectives were pursued from 1 June 1974
through 30 June 1976. A total of 17 river trips and
numerous backpacking trips representing a grand total
of 2484 person-field days were expended.
Although work was done along the entire 300 river
miles from Lees Ferry to the Grand Wash Cliffs, several
study areas were set up for intensive investigation.
These were:
1.
Nankoweap Control, river mile 52.5Rrarea receives little human usage.

This

2.
Nankoweap Impact, river mile 53.OR. This is a
favorite camping and attraction area due to a large
beach and a picturesque ancient Indian granary perched
in a nearby cliff.

1/ These objectives do not appear in this combination
in the contract but rather have been reorganized into a
more logicical sequence. The intended purposes of
research have remained the same.
2/
All locations are given as river mile from Lees
Ferry. The letters R and L are used to designate right
or left side of river while looking downstream.

xii

3.
Cardenas Beach, river mile 71. OL. This area
a heavily camped at site and was largely chosen because
of relatively easy access (via Tanner Trail) and wide
diversity of habitats.
4.
Granite Park, river mile 208.6 L. A heavily used
area by river runners but without feral asses.
5.
209 Mile Canyon, river mile 208.6 R. Little
used by campers but devastated by burros.
The results of our research efforts are presented
in a scientific symposium format. The overall conclusions
are summarized in Chapter XIII.
As an introduction to previous biological investigations
within the Grand Canyon the reader is referred to the following
literature.
Aitchison, S. W., S. W. Carothers, M. M. Karpiscak,
M. E. Theroux, and D. S. Tomko. 1974. An
ecological survey of the Colorado River and its
tributaries between Lees Ferry and the Grand
Wash Cliffs. Phase I. Unpublished National
Park Service Report.
Carothers, S. W., J. H. Overturf, D. S. Tomko,
D. B. Wertheimer, W. W. Wilson, and R. R.
Johnson. 1974. History and bibliography
of biological research in the Grand Canyon
region with emphasis on the riparian zone.
Unpublished National Park Service Report.
Wertheimer, D. B. and J. H. Overturf. 1975.
A history of biological research in the Grand
Canyon region. Plateau 47 (4):123-139.
(Contribution No. 10 in Grand Canyon National
Park Colorado River Research Series.

xiii

CHAPTER I
VEGETATIONAL CHANGES ALONG THE COLORADO RIVER
Martin M. Karpiscak
INTRODUCTION
Substantial photographic data have been collected
on the riparian zone of the Colorado River between Lees
Ferry and the Grand Wash Cliffs. Comprehensive analysis
and evaluation of this information indicate that man's
activities on the river have considerably affected
the vegetation of the area.
Prior to the construction of Hoover and Glen
Canyon Dams there existed three distinctive vegetation
belts which paralleled the river from Lees Ferry to the
Grand Wash Cliffs. These collinear vegetational zones
varied in composition; however, the species which
existed within each of these belts were generally
ecological equivalents. The zone closest to the river
and thus subjected to flooding was composed of numerous
short-lived species able to adapt to periodic disturbance.
Above this ephemeral zone was a belt of vegetatation whose lower
boundaries were delineated by the high water line of
major floods which periodically sweep away the vegetation
below this zone. This belt was typified by three
species, mesquite (Prosopis juliflora), catclaw acacia
(Acacia greggii), and Apache plume (Fallugia paradoxa)
which is most common in the upper portion of the
Canyon. On the talus above this zone were to be found
species typical of the desert such as creosote bush
(Larrea divaricata), ocotillo (Fouguieria splendens),
beavertail cactus (Opuntia basilaris) and brittlebush
(Encelia farinosa).
The construction of Hoover Dam flooded out the
existing vegetational belts and established two distinctive
zones below mile 240.0. The lower one is characterized
by almost impenetrable thickets of salt cedar (Tamarix
chinensis) and the upper one is composed of the typcial
desert flora which existed there before Lake Mead.
The construction of Glen Canyon Dam in 1963 and
thus the partial elimination of flooding from Lees Ferry
downstream to mile 240.0 has permitted the development

1

of a new riparian community. This vegetational community
characterized by salt cedar, arrowweed (Pluchea sericea),
coyote willow (Salix exigua), desert broom (Baccharis
sarothroides) and seep willow (Baccharis glutinosa has
become more firmly established in the zone once
subjected to periodic flooding. Variations in
water released from the power plant at Glen Canyon
Dam determine the lower boundary of this new community.
These variations in flooding of the area below this
zone have prohibited the establishment of any extensive
communities; however, cattail (Typha latifolia) and horsetails (Equisetum spp.) have become established in some
locations below the new salt cedar belt.
In many areas this new community occupies all the
former ephemeral zone, while in other locations little
or no discernable change has occurred in the vegetation.
Between this vegetation belt and the pre-dam high water
mark from Lees Ferry to approximately mile 240.0, we
find another vegetational zone composed of numerous
ephemeral species capable of completing their life
cycle before the influx of river boat parties, such as
red brome (Bromus rubens), tansy mustard (Descurainia
pinnata), sixweek's fescue (Festuca octoflora) and
Chaenactis fremontii. Many of these same species are
also found on the numerous trails in and around camping
areas and points of interest in the early spring and
disappear with the coming of summer. Other speices,
such as Russian thistle (Salsola kali) and bermuda
grass (Cynodon dactylon) have also become well established
in areas subjected to intensive use by man.
Today, therefore, we find four visually distinct
vegetation belts from Lees Ferry to mile 240.0. The
lowest is characterized by a salt cedar/seep willow/
willow zone; above this is the zone of ephemeral plants
which is heavily utilized by man. We then find a
mesquite/acacia/Apache plume belt and beyond this we
have the communities of typical desert species on the
talus slopes.
In order to fully comprehend the impact of man
upon the vegetation of the Colorado River within the
Grand Canyon, we must understand the tremendous influence
of the construction of Glen Canyon and Hoover Dams, in
addition, we have to acknowledge the invasion of
numerous exotic species, such as salt cedar, camelthorn
(Alhegi camelorum), red brome, bermuda grass and

2

smotherweed (Bassia hyssopifolia) especially into areas
disturbed by man's actual presence.
As noted above, man's activities are concentrated
in the present dam-dependent communities below the
mesquite/acacia zone. Photographic evidence appears
to suggest that without the continued presence of
man the entire area below the mesquite/acacia belt
would be exposed to possible accelerated invasion by
the species of the new post-dam dependent community,
especially salt cedar. This would likely produce a
situation very similar to what presently exists around
Lake Mead where salt cedar thickets have become all
but impenetrable. Therefore, the disturbance caused
by man may have partially substituted for the
disturbance formally produced by periodic flooding and
may be a factor in helping to maintain areas such as
Red Wall Cavern and Granite Park. This is not in any
way to suggest that man's presence in the Canyon does not
have associated sociological, biological or geological
problems, such as waste accumulation, deterioration
of camping areas or erosion.
This apparent effect of man's presence on the
river only applies to the areas below the mesquite/
acacia belt because the desert community above is
very sensitive to disurbance by man. The surrounding
territory of camping areas and points of interest such
as the ruins at Nankoweap are subjected to heavy
disturbance as numerous unnecessary trails are cut
and recut. These trails in turn prevent the
establishment of the typical vegetation of the area
and instead are similar in species composition to
the lower ephemeral zone. In addition, they are
subjected to substantial erosion.
Man is not the only organism which has had
great impact on the vegetaion. Burros have also
influenced the vegetation of the mesquite/acacia
belt and the desert community both by trail cutting
and over browsing.
METHODS
Photographs of pre-dam beach conditions were
obtained from the U. S. Geologic Survey and National
Archives and were duplicated during 1974.

3

SUMMARY
The rematching of photos taken before the construction
of Hoover and Glen Canyon Dams indicates that obvious
vegetational changes have taken place in many areas of the
Canyon while other areas appear to have changed very
little. Exotics, such as salt cedar, camelthorn, red
brome, Russian thistle and native species, such as
coyote willow, desert broom, seep willow, cattails and
arrowweed have flourished since the construction of the
dams.
Vigorous new riparian communities have become
established along the banks of the river from Lees
Ferry to Lake Mead. The old high water vegetation belt
of mesquite/acacia/Apache plume continues to endure and
shows little observable change and may be moving down
slope in some areas. However, only by continued monitoring
of the changes that are occurring as a new equilibrium
is slowly established will we know if it can survive
in competition with salt cedar.
In conclusion, we can say that man has had tremendous
impact on the flora and the riparian zone of the Colorado
River region and continues to do so today. The exact
nature of man's impact on the present flora will depend
on the interactions of the plant species involved and the
regulation of their exposure to man.

RESULTS AND DISCUSSION
The following comparisons will serve as examples
of areas that have been photographically rematched and
evaluated in regard to changes that have occurred in
the vegetation. In all cases, there are paired photos—
an old, pre-dam (a) and contemporary Museum of Northern
Arizona (b) photo.

5

CA

Figure I-la.--Soap Creek Rapids, Mile 11.5, August 2, 1023.
Upstream view of Marble Canyon taken from the right side of the Colorado River (elevation 3100
feet) by E. C. LaRue. The location of the photo station is just below the mouth of Soap Creek
Rapids, which can be seen right-center in the old photograph, 10.6 miles below the Paria River at
mile 11.5. In the original photograph note the absence of any densely vegetated areas on either
side of the river. Four-wing salt bush (Atriplex canescens) can be seen on the sand dune on the
left.

-J

Figure I-lb.--Soap Creek Rapids, July 23, 1974
This matched photograph shows salt cedar along both sides of the river. A dense
stand can be seen growing on the north bank (on the right side of the photograph)
below the rock slide which is on the opposite side of the river. Arrowweed and willow
are found in the sandy areas of the beach near the river while four-wing salt bush,
pepper grass (Lepidium spp.), Mormon tea (Ephedra spp.) and a Brickellia sp. are found
in the foreground near the photo station. A large pile of driftwood can be seen which
is not visible in the original photograph.

00

Figure I-2a.--Whale Head Rock, Mile 24.5, 1923.
E. C. LaRue photographed this view of mile 24.5 rapids from the left side of the river looking
upstream, elevation 3000 feet. Note a complete absence of any visible vegetation on either side of
the river. The most outstanding physical features to be seen are the large accumulation of driftwood in the small cove and the very distinctive boulders. The first of these boulders rests at the
upper edge of the cover just behind and to the left of the men and boats. The other boulder,
resembling an inverted whale head, is on the right.

vO

Figure I-2b.--Whale Head Rock. July 2k, 1977. This photograph was taken slightly downstream from the
original photo station. Nevertheless, as shown in the 1977 photograph the large boulders (Jonah and
the Whale) are still there as is the large flat rock (center-left) on the opposite shore. The water
level appears to be approximately the same in both photos; however, the river is substantially more
muddy in the old photo. Portions of the large accumulation of driftwood observed in the old photo are
still to be seen and many of the large boulders seen in the old photo can still be found in the same
relative positions. Vegetation which was obviously absent in LaRue's photo is quite abundant today.
Russian thistle, Opuntia spp. and dropseed are present on the right. Young salt cedar seedlings are
developing along the edge of the river as well as in the foreground. Brickellia longifolia can be seen
both in the foreground and extensively inland from the dense salt cedar stand in the center

Figure I-3&.—E. C. LaRue at Vasey's Paradise, Mile 31-9, ca, 192-3.
Vasey's Paradise taken by L. R, Freeman from a sand bar in the center of
the river, elevation 300.0 .feet...-. Lush, vegetation covers the base of the
falls with redbud (Cercis. o.ccident.alis) covering the upper portion of
the slope. Poison ivy (Rhus radicans) can be seen on the left below
the small falls, just behind LaRue.

10

Figure I-3b.--Vasey's Paradise, March 17, 197k-.
Dead branches of many of the redbud trees can be seen in this matching
photo. The herbaceous layer directly beneath the redbuds is covered by
shoulder high poison ivy which extends over to the left. Horsetails,
watercress (Rorripa nasturtium-aquaticum) and monkey flower (Mimulus
cardinalis)both red and yellow flowered cover the area below the poison
ivy. These species are probably the same ones that were shown in the
original photo; however, because of flood control by Glen Canyon Dam
they have been able to extend their distribution down slope so that
today they can be easily seen below the large projecting rock in the
center of the photograph. Meanwhile, salt cedar as seen in the foreground has been able to establish a foothold on the sand bar from
which the photo was taken.

11

H
ro

Figure I-k&.--Red Wall Cavern, Mile 33-0, ca, 1923.
The next area downstream is Red Wall Cavern on the left side of the river, elevation 2879 feet.
In 1923, L. R. Freeman photographed this downstream view from inside the upstream end of the Cavern.
Note that in this older photo there is a large amount of erosion visible along the river bank. The
beach itself is almost completely void of vegetation except for the dogbane (Apocynum sibericum var.
salignum) which is to be seen in the foreground.

H
U)

Figure I-4b.— Red Wall Cavern, March 1'J, 1974.
Today, we still find the same large boulder on which one of the men was standing in the 1923 photo.
The dogbane is gone and the only vegetation to be seen is salt cedar. Two individuals of salt cedar
can be seen on the sand dune while more can be found just behind the large boulder where the rafts are
moored. The sharp edge of erosion is no longer visible; and the topography of the beach itself has
changed very little in the fifty-one years since the original photo was taken.

H

Figure I-5a.--View from Indian Ruins at Nankoweap, Mile 52.1, ca. 1923.
The United States Geological Survey took this picture of the Indian ruins at Nankoweap
looking downstream from just above the ruins at an elevation of 3500 feet. Note the very
distinct mesquite/acacia/Apache plume belt on both sides of the river downstream from the
ruins. The vegetational belt on the south side of the river is dominated by Apache plume
while on the right side of the river the dominant forms are mesquite and acacia, thus
accounting for the apparent difference in the width of the zone.

H

Figure I-5b.~-N&nkoweap Ruins, March 19, 197^.
In this recent photograph we can still see the old mesquite/acacia/Apache plume vegetation belts but
we can also observe the development of the new salt cedar/willow/seep willow belt. The apparent decrease
in the density of the old belt is probably due to the fact that at the time when the recent photograph
was taken the mesquite and acacia had not fully leafed out. Moreover, the mesguite and acacia stand just
above the boat and thus the camping area was damaged approximately seven years before by a man-caused
fire. Many of the burnt trees are coming back from their roots; however, most of these plants have not
fully recovered. Moreover, salt cedar has invaded some of the area once occupied by mesquite. Observe
that the once barren beaches are dissected by the newly developed salt cedar vegetation belt on both sides
of the river. Numerous trails on the slopes leading up to the ruins have been established since the
original photo was taken. Above the new mesquite belt and below the burnt mesquite/acacia belt other
species which may be found are Russian thistle, prince's plume (Stanleya pinnata), Baccharis emoryi, red
brome, and pepper grass. Numerous ephemeral species covered the trail as well as the beach in March but
were gone by April. The upstream edge of the small cove where the boats are moored is dominated by
coyote willow (Salix exigua) with arrowweed having extensive stands on the sand dunes above the willow.

H
ON

Figure I-6a.— Bright Angel Creek, Mile 87.3, August 26, 1923.
Bright Angel Creek (mile 87.3)» elevation 2425 feet, is shown in this 1923 photograph taken
by E. C. LaRue from the south end of the Kaibab Suspension Bridge looking downstream. In the
center of the photo the Park Service buildings are clearly visible because the cottonwood trees
(Populus fremontii) have not yet hidden them. The beaches on both sides are devoid of extensive
vegetational development while the remains of the mesguite/acacia belt which has been dissected
by the Kaibab trail are visible.

H

Figure I-6b.— Bridges at Bright Angel Creek, March 21, 197'+.
The matching photo shows the development, just below the northern end of the Kaibab Bridge, of salt cedar,
while arrowweed is to be seen behind the large sandy beach downstream from the bridge. The large plant above
the downstream end of the sandy beach is a mesquite with numerous acacias found downstream from it, near the
trail. Large amounts of arrowweed are growing below the mesquite/acacia belt. Numerous Mormon tea are found
near the trail and several well developed individuals of brittle bush (Encelia farinosa) are also found here.
On the left side of the photo proceeding toward the river from the large cottonwoods at the downstream
end of the delta, we have mesquite, salt cedar and Baccharis spp. as well as other species typical of the
post-darn high water vegetation belt. Some of the other species from behind the salt cedar belt in the creek
bed include desert trumpet (Eriogonum inf'latum), Mormon tea and sacred datura (Datura meteloides). At the
upstream edge of the creek bed where it meets the river we find horsetails. The rocky beach behind the Museum
of Northern Arizona boats is covered with Brickellia spp., Dyssodia spp., arrowweed, red brome and numerous
other species. A large expanse of salt cedar and arrowweed is to be found on the once barren beach of the
left side. Note that although the water level in the original photo was higher than in the matched photograph
there appears to be very little change in the shoreline. However, one very obvious physical change has occurred
since the original photo was taken and that is the construction of the downstream suspension bridge.

Figure I-7a.~Deer Creek Falls, Mile 136.2, ca. 1923.
L. R. Freeman took this photo of Deer Creek Falls at an elevation
of 2000 feet from the south hank of the river. Note the complete absence
of any visible vegetation in the photo.

18

Figure I~7b.-~Deer Creek, August 1, 197M-.
This recent photo, .shows a .conipl,e.t.ely. different story. Monkey flower
and maidenhair fern (Adiantum capillus-veneris) are found growing up the
sides of the falls. On the upstream side of the falls we find Opuntia sp..
Mormon tea and sacred datura, to mention just a few. The dense area of
vegetation below the falls is dominated by seep willow and evening primrose
(Oenothera hookeri) while some scattered salt cedar individuals are to be
found near the river. Most of the plants at the foot of the falls were
covered with red mud. and were beaten down to the ground because of a recent
flash flood.
19

Figure I-8a.—Kanab Creek, Mile 11-3 • 5^ ca. I872.
W. Bell of the Wheeler Expedition of 1872 took this photograph of
the mouth of Kanab Creek, at an elevation of 19OO feet from the upstream
side of the canyon looking downstream.

20

Figure I-8b,--Kanab Creek, March 25, 1974.
Mo visible vegetation is to be seen on the beach in Bell's picture;
however, in the photo Figure I-8b, we find arrowweed in the foreground,
as well as extensive development of salt cedar on the left towards the
river. The plants just behind the large rock in the center of the photo
are acacia, part of the mesquite/acacia belt also visible in the original
Bell photo. Some reduction in the amount of sand around the large
boulder in the center is also evident.
21

Figure I-9a.—Mile 170.6, ca. 1923.
L. R, Freeman took this downstream photo at mile 178.6, elevation 1700
feet, approximately one mile above Lava Falls Rapids from the south side.
The mesquite/acacia belt is well developed; however, no vegetation is
visible below this zone.

22

Figure I-9b.~Mile 178.6, March 25, 197U.
The matching photograph shows that the mesquite/acacia community is
still present, although at the time of the photograph they had not fully
leafed out. Salt cedar in the interim has established itself as indicated
by the seedlings in the foreground. On the opposite shore a well developed
salt cedar, seep willow, desert broom, arrowweed and willow belt is present.
Behind this zone, Russian thistle, red brome and creosote bush are to be
found. Above the old mesquite/acacia belt, creosote and barrel cactus
(Ferrocactus sp.) are abundant. Several small mesquite were found to be
mixed in with the salt cedar. Cattail is found below the willow.
Note the large boulders on the upper part of the talus slopes which
are present in both photos. The large boulder on the beach in Freeman's
photo is still in place although hidden within the new dam-dependent
community.
23

ro
•p-

Figure I-10a.--Downstream View of Spring Canyon, Mile 20a.U, Elevation 1000 Feet, September 27, 1923.
The typical mesquite/acacia belt is to be seen on the left side of the river in which acacia
predominates. The hillside in the foreground is covered with brittle bush, ocotillo, barrel cactus
and creosote. (Photo taken by E. C. LaRue.)

Figure I-10b.--Spring Canyon, August 3? 197*+.
The matching photo shows the same small island just below the right bank as well as the same
vegetation as the old photograph taken by LaRue. On the left side of the river we can see the now
typical double belted system. The upper belt in this instance is mostly acacia and the lower one
is mostly desert broom. The beach on the right side downstream from the small island which was
barren in the original photo today is covered with salt cedar, seep willow, and arrowweed, and the
higher area with mesquite and acacia.

0>

Figure I-lla.--Granite Park Overview, Mile 209.0, September 28, 1923.
E. C. LaRue took this upstream photo of Granite Park from a point on the left wall
at an elevation of 2800 feet. On the right side of the photo we have Granite Park just
upstream from the island and on the left side of the photograph we have 209 Mile Canyon.
The mesquite/acacia zone is well developed on both sides of the river. On the beach at
Granite Park at the water's edge we can see the willows pictured in the following set
of matched photos.

ro
-3

Figure I-llb.--Granite Park, March 27, 197k.
In this 197k" photograph there appears to be a decrease in the mesquite/acacia belt on
both sides of the river but this is largely the result of the phenological status of the
plants. However, 209 Mile Canyon on the river's right side has been subjected to heavy
impact by burros. Also note that the once almost vacant beaches at Granite Park on the
left side of the river now are covered with salt cedar, willow, camelthorn and arrowweed.
The sand dune area above the beach is covered by evening primrose, sand verbena (Abronia
elliptica), dropseed and red brome. Creosote comes in on the bajada and as the slope
increases we find white bursage (Franseria dumosa), ocotillo, range ratany (Krameria
parvifolia), pepper grass, Opuntia spp., barrel cactus, brittle bush and desert trumpet.

IV)
CO

Figure I-12a.--Granite Park, Mile 209.0, ca. 1923.
E. G. LaRue photographed this site at an elevation of 1500 feet, across from
209 Mile Canyon. The mesquite/acacia belt is well developed below the lava
palisades and extends across the mouth of the canyon.

ro
vo

F i g u r e I - 1 2 b . - - G r a n i t e P a r k B e a c h , M a r c h 3 0 , 197'+.
The large b o u l d e r w i t h d e s e r t b r o o m g r o w i n g o n its left s i d e , found o n the. r i g h t side o f the old

photo, can still be seen in this recent photograph. The large red willow (Salix laevigata) shown in the
original picture is also present; however, all the small willows on the right side of the small cove in
LaRue's photo appear to be gone. Nevertheless, young Goodding willow (Salix gooddingiii) can be seen
today behind the old willow area. .Just to the right of where the willows once were is an area of arrowweed and this stand continues to endure in the present photograph. The hillside on the right side is
part of the mesquite/acacia belt. In the center of the present photo we find salt cedar and arrowweed.
Evening primrose, sand verbena and dropseed dominate the upland sandy dune on the right. A well developed
stand of camelthorn is to be found to the left of the present photo while under the large willow is an
area of bermuda grass. In the spring, red brome covers the sandy beach. Looking across to 209 Mile
Canyon some other species present are desert willow (Chilopsls linearis), datura, and pigmy cedar
(Porophyllum gracile).

LA)

o

Figure I-13a.--A downstream view at Mile 225.2, above Diamond Creek, Elevation
IH-00 Feet, October 2, 1923.
Wo vegetation appears to be present in this old photo by E. C. LaRue except
for the few trees on the north shore which are probably mesquite.

H

Figure I-13b.--Downstream view at Mile 225.2, August k, 197,+ The matching photo shows that some seep willow, but predominately salt cedar with cattails
at the river's edge make up the vegetation which covers the north beach. On the south side of
the river we have many young salt cedar seedlings as well as a lev/ Baccharis spp. individuals.
A mesquite seedling can also be seen on the extreme right of the photo while bermuda grass is
to be found at the river's edge around the base of the large clump of salt cedar on the right.
Note the rocks on the left side of the photo which indicate that the new photo site v/as
slightly below and to the left of the original photo station. Moreover, the beach from which
the photo was taken appears to have increased in size since the original photo and there has
been a corresponding decrease in the amount of visible sand piled against the large boulders
in the foreground.

CO

ro

F i g u r e I-lt-a.--Diamond C r e e k , Mile 2 2 1 . 7 , E l e v a t i o n 1 3 5 0 f e e t , .Tune 2 0 , 1 9 U 9 .
N o t e the a r r o w w e e d n e a r t h e r i v e r ' s edge and salt c e d a r in t h e b a c k g r o u n d w i t h
a B a c c h a r i s sp. n e a r the w a t e r ' s e d g e .

Figure I-lk-b.—Diamond Creek, August h, 197^In the matched photo taken from the sand bar we can still see some Baccharis sp. at a new
downstream location. The dominant species along the river is now mostly salt cedar with an
occasional seep willow with a small area of arrowweed on the left side. The sand area visible
downstream on the left side is the area presently used as a landing site for some boat parties
leaving the river and going up to Peach Springs. Also note that the talus slope on the left is
the location of the photo station for the following photo of the overview of Diamond Creek.

CO

Figure I-lSa.--Overview of Diamond Creek, by E. C. LaRue, September 22, 1922.
Diamond Creek looking upstream from the talus slope shown in preceding photo. Note the absence
of any visible vegetation in the creek bed itself as well as on the beach. The dense area of vegetation on the lower right is predominately mesquite while creosote can be seen on the upper parts of
the sand dune toward the upstream edge of the Canyon wall. The hillside from which the photo was
taken was covered with white bursage, Mormon tea, ocotillo and some creosote.

Co
en

Figure I-15b.—Diamond Creek Overview, August h, 197^ <
In the recent matched photo we can find a ramada which has been built by the Ilaulapai Indians for
campers. The dense area of mesquite seen in the old photo still remains. It is now the location of the
rest facilities and a small willow can be found in with the mesquite. Just below and towards the river
from the mesquite is a dense stand of arrowweed which extends back upstream towards the ramada. The
dense vegetation behind the ramada consists of salt cedar, seep willow and arrowweed. Diamond Creek
itself is densely covered with salt cedar seedlings (just out of view). Acacia is also to be found
with mesouite in the vegetated area above the ramada. Also to be found on the dune are sand verbena,
evening primrose, datura, brittle bush, salt bush and Brickellia spp. The upstream canyon wall is
dominated by brittle bush.

CO

Figure I-l6a.--Downstream view of Mile 2^3.0, Elevation 1250 feet, October 10, 1Q23.
Note the absence of vegetation on either shore.

(Photo by E. C. LaRue.)

Figure I-l6b.--Mile 21-3,0, August 5, 197^This matching photo shows a dense stand of salt cedar on the opposite (left) side of the river.
Arrowweed is found in the foreground with salt cedar on the rocks downstream from the photo station.
Also observe the rising water level of Lake Mead as seen from the comparison of photos.

CD
CD

Figure I-17a.--E. C. LaRue' s downstream photo of Mile 262.U, elevation 1000 feet,
October 15, 1923Note the large sandy beach in the foreground and the mesquite/acacia belt on
the left side of the river. Observe the lava palisades on the left and the steep
canyon walls on the right. This site is now under water.

CO

vo

Figure I-17b.—Mile 262.4, August 5, 1974.
In this matching photo, note that the only obvious vegetation is salt cedar on the
left, with numerous seedlings at the vmter's edge. The small rock palisades which were
seen at the center of the old photograph are presently just above the water line.

CHAPTER II
VASCULAR FLORA OF THE GRAND CANYON
Michael E. Theroux
INTRODUCTION
The purpose of this study was to inventory and describe
the vegetation of the vascular flora occurring along the
Colorado River from Lees Ferry to the Grand Wash Cliffs.
In an earlier report (see Aitchison et al., 1974)i we
described the vascular flora of the canyon's riparian
zone based on our first years work. This report is a
continuation and update of that plant inventory,
summarizing our findings during the entire project.
METHODS
Botanical research of the vascular plant species
composition in the study area for the current contract
has involved 17 field excursions by Museum of Northern
Arizona staff and associates during all seasons totalling
approximately 200 man-days. During this field time,
approximately 1500 specimens have been taken within
Grand Canyon National Park, with an additional 242 from the
Supai Indian Reservation within Haulapai and Havasu Canyons.
The staff has utilized river craft, aerial transport
and backcountry hiking to faciliatate the work.
General collecting has been accomplished using a
vasculum and standard plant press. Field data for each
specimen included, (1) date, (2) river mile (measured
from Lees Ferry) and side (designated "left" or "right"
looking downstream), (3) collector's number and name,
(4) field identification, if possible, (5) general habitat
description, as "river-edge" or "upper talus," (6) soil
texture/type, as "fine sand" or "granite rock face,"
(7) surrounding dominant vegetation, (8) slope exposure
in cardinal direction and relative degree, and (9)
any unusual site or plant characteristics, as "recent
burn" or "heavily infested with mistletoe." Further data
was then computer coordinated to include for each collection
site, elevation and further site names, and for each species
the taxonomic nomenclature and synonomy, structure (growthform) etc.
1/ Aitchison,
Theroux, D. S.
Colorado River
the Grand Wash

S. W., S. W. Carothers, M. M. Karpiscak, M. E.
Tomko. 1974. An ecological survey of the
and its tributaries between Lees Ferry and
Cliffs. Unpubl. ms.
41

The bulk of taxonomic identification was performed
at the Museum of Northern Arizona. Many problem situations
arose for the various families; in such cases specialists
were contacted where possible.
A few noted exceptions, the systematic taxonomy follows
the most recently recognized authorities. Synonomy is
presented in the more confusing cases, especially where
previously recognized species have been "lumped" into one
species (example: Yucca whipplei Torr., LILIACEAE includes
Y. newberryi McKelvey and Y. navajoa J. M. Webber), and
where past collections were listed under now archaic
nomenclature. Sub-specific information has been combined,
and entered only at the species level, as conflicting
data must be further studied before varietal and sub-species
habitat differentiation may be depicted.
Each plant species entry in the computerized inventory
is accompanied by extensive data. An exemplary entry is
presented and described per data item in Appendix II-l.
Three local herbaria were searched in entirety for
holdings from the study area. These were the Museum of
Northern Arizona Herbarium (MNA), the Deaver Herbarium
at Northern Arizona University and the Grand Canyon National
Park Herbarium, located at the South Rim research facility.
Additional extensive spot-checking for specific holdings
have involved the herbaria of the Arizona State University,
the University of Arizona at Tucson and the Desert
Botanical Gardens at Papago Park, Tempe.
RESULTS AND DISCUSSION
The vascular flora inventory (Appendix II-l) represents
all collection records known by the author to occur along
the 280 miles of the Colorado River within the Grand Canyon.
A total of 807 species representing 92 families is presented.
The inventory includes two species that may be considered
new to science. These are Flaveria mcdougalli (Theroux et al.,
in press) and Euphorbia rossii (species nova proposed by Dr.
A. Holmgren). Flaveria mcdougalli is a large shrubby member
of the Compositae and has thus far been collected in two
localities within the study area, Cove Canyon (mile 174.2R)
and Matkatamiba Canyon (mile 148.8L). Euphorbia rossii
is a low-growing member of the Euphorbiaceae and has thus
far been collected from one area within the upper reaches of
Marble Canyon (mile 19.0L).

1+2

The vascular plant inventory is presented in Appendices
II-l and II-2. Both of these appendices are computer
print-outs, Appendix II-l, presenting the 807 species in
phylogenetic order (after Kearney and Peebles, 1951),
and Appendix II-2 presents the 807 species in a 10 mile
sort, based on the distribution of the flora within the
canyon (i.e., for a given 10 mile section of the canyon,
all plants knwon to occur in that area are presented).
The inventory presents a total of 210 species that may
be considered new to the flora of the localized flora of the
riparian zone of the Grand Canyon. Many of these "new"
additions to the flora were discovered during the extensive
herbaria search, however, 74 new plants were collected during
this project. The plant inventory of the riparian zone
of the Colorado River is by no means complete nor will it
ever be. Plant communities are dynamic, ever changing
entities of the natural world, and there will always be
new species or new records appearing. We are, however,
much closer to being able to describe the vascular plant
resources of this area than we were before this project
began.
SUMMARY
1.

Botanical investigations within the riparian and
adjacent habitats of the Colorado River study
area have discerned the presence of 807 species
of vascular plants representing 92 families.

2.

Two species, previously undescribed, Flaveria
mcdougallii and Euphorbia rossii, are presented.

3.

A total of 210 species are new to the local flora,
74 of which resulted from collections during this
project. The remainder are from refined herbaria
and literature searches that took place during the
contract period.

REFERENCES CITED
Kearney, T. H. and R. H. Peebles. 1951.
Univ. of Calif. Press, Berkeley.

R-3

Arizona flora.

Table III-l.—A Collection Gazetteer of Specimens. Entries
Read as : River Mile (Sample Size) Month.
Uta stansburiana
35(5)VII, 52(10)VI, 52(1)VII, 66(4)VII, 69(10)VIII,
70(10)VIII, 71(8)IV, 71(8)IV, 71(35)V, 71(20)VI, 71(10)VII,
71(10)VIII, 87(2)VII, 93(2)VII, 95(12)X, 109(5)VII,
117(1)VII, 125(11)VII, 134(6)VII.
Urosaurus ornatus
18(5)VII, 33(4)VII, 35(1)VII, 117(1)VII, 134(3)VII.
Sceloporus magister
0(1)VII, 32(L)VI, 32(1)VII, 39(1)VIII, 41(1)VIII,
52(1)VI, 52(1)VII, 66(6)VII, 71(1)VII, 71(1)VIII, 94(3)VII,
109(2)VII, 117(1)VII, 125(1)VII, 131(1)VII, 131(1)VIII,
157(1)IV, 166(1)V, 180(1)VII.
Crotaphytus insularis
125(1)VII, 131(1)VIII, L36(3)VII, 208(1)VIII.
Cnemidophorus tigris
52(10)VI, 66(3)VII, 71(1)V, 71(4)VI, 71(4)VII, 94(1)VII.
Bufo woodhousei
64(1)IX, 71(15)VII
Bufo punctatus
35(1)VII, 125(1)VII, 270(1)VII.
Hyla arenicolor
35(2)VIII, 41(2)VIII.

kk

CHAPTER III
DIETARY CHARACTERISTICS OF SOME GRAND CANYON
AMPHIBIANS AND REPTILES
Dennis S. Tomko
INTRODUCTION
The present study is a survey of the dietary characteristics
and interrelationships of eight herptile; i.e., reptile and
amphibian, species commonly found along the shores of the Colorado
River from Lees Ferry to the Grand Wash Cliffs.
Some effort has been put forth to extend this study beyond
a simple list of diet items. The common side-blotched lizard,
Uta stansburiana, is used to demonstrate many of the principles
which apply to all the Grand Canyon's diurnal lizards. Interspecific diet differences are discussed in terms of general
ecological differences existing between species.
METHODS
The Study Area
Collection locations, months, and sample size data are
presented in Table III-l. Most specimens were collected in
the Tamarix/Salix/forb habitat existing between the Colorado
River and the old, pre-dam high water line. The substrate here
is essentially sandy with gravels and/or boulders scattered
over it.
Field and Laboratory Methods
Specimens were collected either by noosing or shooting
with a "BB" gun. Knowlton (1936) has shown that insects in
the stomachs of Uta stansburiana loose their taxonomic
integrity several hours after ingestion so the lizards and
amphibians used in this study were all sacrificed within two
hours after collection. It was also found that if the
animals were not taken until 1 to 2 hours after the start
of their daily activity period, the stomachs contained a
large amount of prey matter.
Each stomach was excised and place in a vial of 70 percent
isopropyl alcohol. The eviserated body was preserved
in 57 percent formalin and stored for later autopsy.
In some cases, specimens already in the herpetology collection

^5

of the Museum of Northern Arizona were used to supplement the
field data.
Insect material was identified to order using the
keys in Borror and DeLong (1970) and Borror and White (1970) .
Absolute density and relative volume estimates of prey in each
stomach were made visually. Bolus volume was measured by
displacement to the nearest 0.1 ml. Prey categories may be found
in Table III-2.
Analysis
Stomach content lists were used to formulate quantified
composite diets for each species and to provide a basis of
inter- and intraspecific comparisons. Various aspects of
diets were calculated. Relative density of prey items reflects
the impact of predators upon the prey resources. Relative
volume reflects the potential value of items to the caloric
needs of a predator. A composite of these two parameters is
the importance value, a modified form of the statistic used
by botanists in plant ecology (Curtis and Mcintosh, 1951).
An importance value is calculated for each prey category as
follows:
I.V. = _1_ (% density + % volume)
200
Thus, the sum of importance values for any species must equal
1.00.
Certain comparative ecological statements were made
based upon diet information in the form of I.V. lists. These
included comments on interspecific relationships (paired species
comparisons), location characteristics (one species at different
locations during the same month), and temporal changes in forage
behavior (one species at the same location during many months).
These comparisons were all based upon the statistic, percent
similarity (Bray and Curtis, 1957) which totals the amount
of shared importance value (w.^) within each prey category, i, in
two species' diet lists:
PS = 2 w i
(a + b)
where a + b is the sum of each species importance value total
and must, by definition, be equal to 2.00. Thus, PS may be
described as diet similarity, food niche overlap, or (in the case
of two species) a measure of potential competition. PS
values range from 0, complete separation, to 1, complete identity.
The Species
The following brief species accounts represent information

1+6

gathered during field work in the Grand Canyon and from Stebbins
(1966).
Uta stansburiana.—By far the most common lizard in the
Grand Canyon, this small species (Snout-vent length = 46mm)
reaches its highest density in the riparian zone along the
Colorado River. Its wide geographical distribution and
range of habitats identify it as the most generalized of the Canyon's
riparian lizards. The high densities Uta attains are the
reason it is chosen as the indicator species for this study.
Primarily saxicolous and highly territorial, Uta employs
a "sit and wait" type of foraging strategy. In the Canyon it
can be seen foraging on any day of the year, weather permitting.
Urosaurus ornatus.—Because of its small size (SVL = 52mm)
and similar foraging behavior, this species is a potential
competitor with Uta. However, Urosaurus, though locally common,
is most often found within 1 or 2 meters of a permanent
water source where large rocks and an appreciable amount of
overhead cover are available. Uta is usually not found within
Urosaurus territories in the Grand Canyon so that these
two similar species can coexist due to microhabitat separation.
Sceloporus magister.—This is a large species (SVL = 90mm)
which reaches its highest densities in the riparian zone where the
availability of Prosopis, Acacia, Tamarix and Salix trees
provide a high quality habitat for this semi-arboreal lizard.
Although it makes ample use of rocks occurring within its
territories as basking sites, Sceloporus probably carries out
most of its foraging activity on or around the bases of trees.
Apparently, this species also employs a "sit and wait" type
of foraging strategy.
Cnemidophorus tigris.--This medium sized (SVL = 73mm)
lizard is second only to Uta in relative density of riparian
lizard species. It is the most exclusively terrestrial of all
the lizards included in this study as evidenced by the
observation that it is never seen in trees and only very
rarely on rocks. Unlike the previously described species,
Cnemidophorus is a very active forager and is constantly
in motion searching out prey items, most often within 50cm
of the base of trees and shrubs. This seems to be the only
common terrestrial lizard species whose foraging activity
is evenly distributed from the lower edge of the desertscrub
to the wet, sandy shores of the Colorado River.
Crotaphytus insularis.—A large (SVL = 89mm) uncommon
species, this saxicolous lizard is actually characteristic

^7

of boulder-strewn desert scrub habitats but can be found
on rocky, open beaches. It also employs a "sit and wait"
foraging strategy.
Bufo punctatus, Bufo woodhousei.—These are the only
two toads commonly found in the riparian zone. They are
nocturnal and, judging from the tracks found in the sand,
they spend their days under large rocks or among the roots
of shrubs away from the river bank, emerging at night
to forage along the shore.
Hyla arenicolor.—This tree frog may actually be the
nocturnal counterpart of Urosaurus ornatus with respect
to its microhabitat requirements.
RESULTS AND DISCUSSION
Diet Descriptions
The diet information for eight species of reptiles and
amphibians is summarized in Table III-2. Although 18 taxonomic
categories of animal prey are listed, three orders, Diptera,
Hymenoptera, and Coleoptera account for 70 percent of the
mean importance value totals for these 8 predatory species.
In some instances orders were broken down into smaller
units. Within Hymenoptera the ratio of ants to bees and
wasps was 1.6 to 1.0 in Uta, 7.6 to 1.0 in Sceloporus, and
0.3 to 1.0 in Cnemidophorus. Within Diptera the ratio of
flies to other Dipterans was 0.1 to 1.0 in Uta and 0.1 to 1.0
in Cnemidophorus. The apparent similarity of the last pair of
numbers is modified somewhat by the fact that flies are only
about 1/3 as important to Uta as they are to Cnemidophorus.
Although all the predators are primarily insectivorous,
several minor exceptions are found. Aquatic crustaceans, ie.,
amphipods, were consumed by Urosaurus and Cnemidophorus
(which also ingested snails). These two species frequently
forage close to the water's edge and it is quite likely
that the aquatics were taken from very shallow (< 5mm) pools
created by the daily ebb of the Colorado River. In this sense,
Glen Canyon Dam has had a direct, though minor, effect upon lizard
diets since these water conditions did not exist prior to
1963.
Vertebrates appear in the diets of Sceloporus and
Crotaphytus. These are Uta and are not taken by Sceloporus
in large quantities although they are fairly important to
Crotaphytus.

U8

Table III-2.—Reptile and amphibian diets along the Colorado River, Grand Canyon, Arizona.
Uta
stansburiana
%den- %vol - I.V.
INSECTA
Thysanura
Collembola
Orthoptera
Isoptera
Thysaroptera
Hemiptera
Homoptera
Coleoptera
Neuroptera
Tricoptera
Lepidoptera
Diptera
Hymenoptera
Misc. Larvae
ARACHNIDA
CRUSTACEA
MOLLUSCA
REPTILIA
VEGETATION
SAMPLE SIZE

00.02
01.36
00.08
02.85
00.01
01.81
02.77
03.23
00.28

00.01
00.02
01.52
04.25
00.01
03.19
00.99
11.28
01.36

.001
.005
.008
.036
.001
.025
.018
.073
.008

00.22
55.66
24.93
02.93

02.12
25.64
34.35
05.15

.012
.407
.296
.040

Urosaurus
ornatus
%den - %vol - I.V.

02.78 00.75 .018
00.73 07.81 .043

Sceloporus
magister
%den - %vol - I.V.

Crotaphytus
insularis
%den - %vol - I.V.

00.72 14.33 .075
20.31 04.28 .123

19.00 51.18 .351
06.00 00.39 .032

00.31
00172
06.08
00.10

00.13
08.11
18.79
00.44

.002
.044
.124
.003

00.22 03.72 .020

03.85 10.17 .070

94.88 70.39 .826
00.95 04.69 .028
00.07 02.98 .015

.4.54 07.84 .112
55.58 31.98 .438
00.82 01.49 .012

00.29 02.98 .016
00.07 06.69 .034

00.72 00.90 .008

00.10 04.05 .021
07.66 .038
162

14

29

13.00 08.07 .105
50.00 01.38 .258

13.00 32.48 .227
06.50 .027
6

Table II1-2.— continued.

o

INSECTA
Thysanura
Collembola
Orthoptera
Isoptera
Thysaroptera
Hemiptera
Homoptera
Coleoptera
Neuroptera
Tricoptera
Lepidoptera
Diptera
Hymenoptera
Misc. Larvae
ARACHNIDA
CRUSTACEA
MOLLUSCA
REPTILIA
VEGETATION

SAMPLE SIZE

Cnemidophorus
tigris
%den - %vol - I.V.

Bufo
woodhousei
%den - %vol -I.V.

00.03 0 0 . 0 1 .001
00.06 01.60 .008

19.83 22.38

Bufo
punctatus
%den - %vol - I.V.

.211
12.59 04.67

00.10
01.13
03.60
00.52

00.22
02.86
21.15
06.05

.002
.020
.124
.033

00.45
91.05
00.81
00.71

18.02
26.60
04.34
05.78

.092
.588
.026
.032

00.88 06.47 .037
00.49 05.57 .030
00.16 0 1 . 3 3 .007

23

Hyla
arenicolor
%den - %vol - I.V.

05.56 25.67

.161

50.00 54.67

.523

05.56 01.33

.034

33.33 07.15
05.56 08.00

.202
.068

.086

01.40 03.33 .024
05.59 26.67
01.40 06.67

.161
.040

05.17 03.60 .044
01.72
.001 .009
13.79 01.38 .076

00.70 00.33
76.92 56.67

.005
.668

05.17 00.41 .025

01.40 00.03 .007

5 4 . 3 1 5 6 . 5 1 .554

15.72 .079

01.67 .008

16

3

4

Vegetation is occasionally encountered in stomachs.
The importance value of plant matter is quite small and the
ingestion of vegetation is probably accidental. When the
data are examined closely it becomes apparent that the
large-mouthed predators have the greatest amount of vegetation.
Presumably, a large-mouthed predator is more likely to
ingest the leaf an insect is resting on than a smallmouthed species.
Table III-3 reveals a great deal of variability in the
dietary relationships between lizard species. PS values
less than .500 can be interpreted as "more dissimilar than
similar." Uta is a generalized lizard in the sense that it
is commonly found in the habitats of the other 3 species;
Cnemidophorus ranks second in this respect. Therefore,
it is not surprising to find the highest and second highest
mean PS values for these two species which indicate a relatively
high amount of diet sharing between each of them and the other
species. The least amount of overlap is found in Sceloporus,
a large semi-arboreal lizard, and Urosaurus, a small terrestrial
rocky shoreline forager. The greatest overlap is found between
Urosaurus and Cnemidophorus, both of which are terrestrial
shoreline foragers.
The precision of the PS values in Table III-3 is somewhat
modified by the fact that they are based upon composite diet
lists from many locations along the Colorado River during
several months. The effect of different locations upon
diet lists can be seen in the Uta data in Table III-4. When
5 different locations are compared a mean PS value of .458
results. Therefore, even when data are collected during
the same month, a great deal of interlocational variability
is introduced into the resulting composite diet list. This
also points out the fallacy of basing a diet estimate for
a Grand Canyon species based upon collections made at one
or two sites.
Table III-5 presents data which emphasize the effect of
seasonal change upon diet. When 5 months of data from the same
location are compared a mean value of .539 results. Thus,
a great deal of temporal variability as well as locational
variability exists in lizard diets in the Grand Canyon. The
locational and monthly comparisons suggest that variability
through space may be slightly greater than through time.
An estimate of food niche overlap between Uta and
Cnemidophorus which are sympatric in space and time is given
in Table III-6. The estimated overlap value is fairly high

51

Table III-3.—PS values of diets of common diurnal lizards
using June and July importance values.
SPECIES
NAME

Uta
stansburiana

.448

Uta stansburiana
Urosaurus ornatus

Urosaurus Sceloporus Cnemidophorus
ornatus
tigris
magister

.448

.663

.527

.221

.736

Sceloporus magister .663

.221

Cnemidophorus
tigris

.527

.736

.315

mean (PS)

.546

.468

.399

.315

.526

Table III-4.—Importance value PS comparisons of Uta stansburiana
diets of various locations in mid-summer^ Mean
value (PS) = .458.
Mi. 52
Mi- 52
Mi- 71

Mi. 71

Mi. 109

Mi. 125

Mi. 134

.652

.287

.312

.476

.265

.576

.724

.237

.341

Mi. 109
Mi. 125

#714

Mi. 134

52

Table III-5.—Monthly importance value PS comparisons of
Uta stansburiana diets at Cardenas (mi. 71).
Mean value (PS) = .539.
April
April

May

June

July

August

.723

.524

.715

.388

.580

.581

.480

.676

.378

May
June
July

.351

August

Table III-6.—PS values of Uta stansburiana and Cnemidophorus
tigris (sympatric in space and time) and PS
contribution of Diptera in percent of total PS
value.
Nankoweap
June

Cardenas
June

Cardenas
July

PS Overlap

00.728

00.511

00.607

Diptera Percent

57.000

48.700

58.000

53

and indicates more similarities than dissimilarities.
When the PS values are analyzed in detail it is apparent that
a great deal of the estimated overlap is accounted for by
shared predation of Diptera. The two sites which were
examined are heavily used by Canyon visitors and it is likely
that the densities of Diptera at these sites have responded
positively to this usage. Therefore, it is not unreasonable
to postulate human interference into one competitive
mechanism which regulates species diversity. This assumes,
of course, that insect prey is a limiting factor in
population dynamics.
REFERENCES CITED
Borror, D. J. and DeLong, D. M. 1970. An introduction
to the study of insects. Holt, Rinehart and Winston, Inc.,
N.Y.
Borror, D. J. and R. E. White. 1970. A field guide to insects.
Houghton Mifflin Co., Boston.
Bray, J. R. and J. T. Curtis. 1957. An ordination of upland
forest communities of southern Wisconsin.
Ecol. Mono.
27:325-349.
Curtis, J. T. and R. P. Mcintosh. 1951. The upland forest
continuum in the prairie-forest border region of
Wisconsin. Eco. 32:476-496.
Knowlton, G. F.

1936.

Lizard digestion studies. Herp. 1:9-10.

Stebbins, R. C. 1966. A field guide to western reptiles
and amphibians. Houghton Mifflin Co., Boston.

5k

CHAPTER IV
DEMOGRAPHY OF THREE SPECIES OF GRAND CANYON LIZARDS
Dennis S. Tomko
INTRODUCTION
The study of reptile and amphibian demographic
characteristics in the Grand Canyon was undertaken to
help establish the position of these species in the ecology
of the Canyon's fauna. It was decided to limit this work to a
consideration of the lizards Uta stansburiana, Sceloporus
magister, and Cnemidophorus tigris since these are
common species. In this way a significant amount
of information was obtained for a single faunal group
rather than fragmentary data for a diverse herptile
assemblage.
This study is largely descriptive in nature and it
is hoped that future studies of a more theoretical nature
will be undertaken. Certainly, the Canyon provides a
compressed geographical area for testing concepts
such as the recently postulated relationships of reproductive
effect in lizards to latitudinal gradients (Tinkle and
Hadley, 1975) and life history evaluations (Tinkle, 1969).
MATERIALS AND METHODS
Lizards were collected within the riparian zone of the
Grand Canyon during 7 months of the year. In all instances
lizards were field-fixed in 7 percent formalin and later
changed to 50 percent isopropyl alcohol.
Male reproductive stages were characterized by the
length of right testes to the nearest 0.1m. In so doing
the reproductive cycles could be compared with similar
data from other areas. Female reproductive stages were
assessed by the presence of ovaductal eggs. This provided an
approximation to the timing of egg deposition.
The intensity of predation upon lizards was estimated
using tail-break frequencies. Since tail autonomy is a
primary predator escape mechanism in lizards, the
frequency of broken tails can be used as a relative
indicator of encounters with predators (Pianka, 1967).
A tail was considered broken regardless of the amount
of regeneration which had taken place.

55

RESULTS AND DISCUSSION
The male reproductive data are shown in Figure IV-1.
All three species undergo testicular regression during
the summer. The morphological patterns shown in Figure
IV-1 indicate a histological pattern of winter and spring
spermatogenesis followed by a cessation of interstitial
cell activity in late summer (Fox, 1958). The timing of
events in the Grand Canyon is very similar to that found
in other southwestern desert lizard studies (Parker and
Pianka, 1975; Vitt and Ohmart, 1974; Parker, 1972).
Female Uta stansburiana reproductive cycle data is
shown in Figure IV-2. Late spring to early summer is the
period of greatest activity for these lizards. The
occurrence of multiple clutches in Uta is well documented
(Tinkle, 1961; Parker and Pianka, 1975). Tinkle (1961)
has estimated 38 days as the time required to produce
a clutch. Dividing 38 days into the reproductive season
in Figure IV-2 an estimate of 4 clutches per adult female
is reasonable. Females yielded a modal clutch size of
3 eggs. Therefore it is likely that a female Uta reproduces
approximately 12 young per year.
Reproductive data from other studies have been
gathered to supplement the information gained during the
present work (Table IV-1). A survey of the literature
for any single species reveals a great deal of variability
in time and space. For example, the annual clutch frequency
for Uta has been recorded from 1 (Parker and Pianka, 1945)
to 12 (Medica, pers. comm.). Annual precipitation and
the timing of the frost-free period probably account for
the greatest amount of variability in the Table IV-1 data.
Tail break data is summarized in Table IV-2. If the
lower Canyon data for Sceloporus and Cnemidophorus are
dropped due to small sample size, the significant
intraspecific differences in tail break frequencies
(p less than .05) occur in comparisons of upper and
middle Cnemidophorus and of middle and lower Uta. If
all data is pooled, weighed mean lizard tail break
frequencies are: upper, .48; middle, .60; lower, .26.
A standard "Z test" reveals a significantly lower level
of predator pressure in the lower canyon than in the
upper and middle portions which are not significantly
different from each other. Thus, it seems likely that predator
pressure on lizards below Havasu is less than it is
above mile 155.0.

56

Figure IV-1.—Testicular cycles of Grand Canyon lizards.
O = Uta stansburiana (n = 82),+ = Cnemidophorus
tigris (n = 3 1 ) , • = Sceloporus magister (n = 17).

Figure IV-2.—Frequency of oviductal female Uta stansburiana.
Numbers at column tops indicate sample size.
Total n = 135.

57

Table IV-1.—Demographic parameters for the four common riparian
lizard species. Sources: 1-Tinkle, 1969; 2-Parker
and Pianka, 1975; 3-Parker, 1973; 5-Vitt and Ohmart,
1974; 6-Parker, 1972.
TIME TO
MATURITY
Uta
—~—
stansburiana
Urosaurus
ornatus

1

SVL (mm)
MATURE

NO. CLUTCHES
PER YEAR

7

MEAN CLUTCH
SIZE

7

4 mo.

45

multiple

7
3-4

6 mo.

45 3

multiple3

4-63

Sceloporus
magister

2-3 yr. 4

814

multiple 5

3-124

Cnemidophorus
tigris '

1 yr. 6

63 6

multiple 6

1-66

Table IV-2.—Tail break data for Grand Canyon riparian lizards.
Mi. 0-75
n
freq

Mi. 76-155
n
freq

Mi. 156-280
n
freq

127

.53

40

.60

21

.33

Sceloporus
magister

18

.55

9

.55

4

.00

Cn em i dopho r u s
tigris

29

.24

16

.62

2

.00

Uta
stansburiana

Table IV-3.—Male, female tailbreak data. (*) indicates
departure from 1.00 significant at p = .05.
n

freq

n

*

freq

freq/ freq

?

*/ ?

Uta
stansburiana

99

.56

78

.45

1.24

Sceloporus
magister

15

.33

16

.63

0.53

Cnemidophorus
tigris

30

.47

17

.18

2.61*

58

Table IV-3 summarizes tail break data in terms of sexual
categories. The only evidence of uneven sexual pressure
is found in Cnemidophorus where males are attacked more
frequently than females. This is puzzling since this
species is the least territorial and dimorphic of the
three and it is therefore impossible to see why males
should be differentially exposed to predators.
A third aspect of demography, that of lizard
population density, was scheduled for investigation
according to standard mark/recapture methodology
(Medica et al., 1971). A total of five attempts to
do this were carried out at the Nankoweap and Granite Park
mammal grid sites (see work plan for National Park Service
contract No. CX821500007). None of these efforts yielded
data in sufficient quantity to provide density estimates.
The problems inherent in any grid site density investigation of
Grand Canyon lizards are of such a magnitude as to make
a density study a major project in itself. A team of
4 to 6 workers would be required to noose lizards because
of the very dense riparian understory which provides
excessive escape cover. Such a team would, ideally,
need 5 to 10 consecutive days of undisturbed work in
the spring or summer. This time requirement is complicated
by the very few sites with sufficient area (at least 1 ha.)
and the frequency of boat party landings. A major problem
at Nankoweap was the appearance of visitors which cancelled
several mornings work. If the above conditions could be
met, then realistic density figures could be estimated
for Uta stansburiana, Cnemidophorus tigris and Sceloporus
magister.
Some general density trends can be described. Spring
is the period of greatest overt (i.e., behavioral)
reproductive activity since courtship and territorial
defense take place during this time. By late summer
the apparent density of lizards seems to have dropped
but this is most likely an artifact of decreased
activity making them less obvious visually. This type
of early courtship and later reproduction is possible
since female lizards can store viable sperm for at least
80 days after copulation (Cuellar, 1966).

59

REFERENCES CITED
Cuellar, O. 1966. Delayed fertilization in the lizard,
Uta stansburiana. Copeia 1966:549-552.
Fox, W. 1958. Sexual cycle of the male lizard, Anolis
carolinensis. Copeia 1958:22-29.
Medica, P. A., G. A. Hoddenbach, and J. R. Lannon. 1971.
Lizard sampling techiques. Rock Valley Misc. Publ.
No. 1.
Parker, W. S. 1972. Ecological study of the western
whiptail lizard, Cnemidophus tigris gracilis, in
Arizona. Herpetologica 28:360-369.
. 1973. Natural history notes on the iguanid
lizard, Urosaurus ornatus. J. Herp. 7:21-26.
Parker, W. S. and E. R. Pianka. 1973. Notes on the ecology
of the iguanid lizard, Sceloporus magister. Herpetologica
29:143-152.
. 1975. Comparative ecology of populations of the
lizard, Uta stansburiana. Copeia 1975:615-633.
Pianka, E. R. 1967. On lizard species diversity: North
American flatland deserts. Ecology 48:333-351.
Tinkle, D. W. 1961. Population structure and reproduction
in the lizard Uta stansburiana stejnegeri. Am. Midi.
Nat. 66:206-234.
~~
"
1967. The life and demography of the sideblotched lizard, Uta stansburiana. Misc. Publ. Mus.
Zool. Univ. Mich. No. 132.
. 1969. The concept of reproductive effort
and its relation to the evolution of life histories
of lizards. Am. Nat. 103:501-516.
Tinkle, D. W. and N. F. Hadley. 1975. Lizard reproductive
effort: caloric estimates and comments on its
evolution. Ecology 56:427-434.
Vitt, L. J. and Ohmart, R. D. 1974. Reproduction and ecology
of a Colorado River population of Sceloporus magister
(Sauria:Iguanidae). Herpetologica 30:410-417.

6o

CHAPTER V
MAMMALS OF THE COLORADO RIVER
George A. Ruffner
Dennis S. Tomko
INTRODUCTION
Rodents are an amazingly successful group. They are
the largest order of mammals, ubiquitously distributed and are
an important part of all terrestrial mammalofauna (Golley
et al., 1975). Ecological interactions of rodents in many
areas have been studied, although voids do exist. One
such void is the Grand Canyon.
Several important contributions resulting from the
study of rodent distribution and taxonomy in and around
the canyon are available (c.f., Goldman, 1937; Hoffmeister,
1972). However, investigations on rodent demography and
feeding habits within the Canyon are sorely lacking.
We have initiated studies of rodent populations, diets,
reproduction and habitat distribution in the riparian zone
of the canyon. We hope that the data herein will stimulate
further, more intensive studies of rodent communities
in the riparian zone of the Grand Canyon.
We chose to study small rodents because of several
reasons. There are at least thirteen species of rodents,
representing seven genera, that we know to occur in the
riparian zone. This great diversity provides the
ideal conditions for studying interactions of co-existing
species. However, we found that it was impractical to study
all thirteen species of rodents occurring in the riparian
zone and therefore limited ourselves to nine species
of nocturnal rodents of the genera Perognathus,
Reithrodontomys, Peromyscus and Neotoma. Rodents are
relatively simple to study and are very common in the
riparian zone. Literally volumes of literature dealing
with the ecology of rodents are available and these
data provide a valuable basis for the analysis and
interpretation of the information we have gathered.
Several investigators have reported the results of longterm studies of rodent populations. Chew and Chew (1970)
investigated energy relationships among Sonoran Desert
rodents. MacMillen (1964) studied demographic characteristics

61

Table V - l . — G e n e r a l i z e d descriptions of the grid sites and their habitat units.
Site

Nankoweap
DR

River Mile

53.5

General Topography

Characteristic Veget.
in Order of Importance

Low, rolling dunes
grading to packed
sand flats
Flat, packed sand
grading to lower
talus
low, rolling dunes
gravel edge near
river
Rock strewn and cut
deeply where it
contacts terrace

Tamarix, Salix, Pluchea,
Festuca, Plantago

Beach

Low dunes to rock
strewn sand

Tamarix, Salix, Pluchea
Alhagi

Terrace

Generally flat
with some wash
dissection

Acacia, Prosopis,
Ehphedra, Larrea

Beach

Rock strewn low
sand dunes

Tamarix, Pluchea,
Baccharis, Encelia

Terrace

Irregularly flat
Prosopis, Acacia,
and dissected
Creosote
deeply by washes,
packed sand to rock
strewn

Side Elevation Habitat
Ft. (m)
Unit

R

2800'

Beach

Terrace

Nankoweap
UR

52.5

R

2800'

Beach

Wash

Granite
Park

208.6

L

1480'

Prosopis, Lepidium,
Festuca, Plantago, Acacia
Equisetum, Tamarix,
Echinochloa,
Juncus, Salix
Gutierrezia,
Stephanomeria, Mentzelia, Eriogonum

ON

ro

209 Mile
Canyon

208.6

R

1480'

of a southern California rodent fauna. M'Closkey (1972)
discussed temporal changes of populations and species
diversity in coastal sage scrub habitats of California.
More recently Whitford (1976) reported the results of a
four year study of Chihuahuan Desert rodent density
and diversity. In general there are data available
for rodents in most major habitats of North America.
However, Carothers et al. (1974) and Hubbard (1971) noted
the paucity of information available on vertebrates in
southwestern riparian habitats. Those authors presented
data on avian inhabitants of riparian habitats.
We are not aware of any studies dealing with small mammals
of southwestern riparian habitats.
Description of the Study Sites
The major objectives in this study have been to
monitor demographic characteristics and diets of small
mammals in the riparian zone. To facilitate these
studies we have established four major study sites in
the canyon. At each study site habitats are usually
defined by one of three topographic characteristics (beach,
terrace or wash) and plant species typically associated
with each (Table V-l). The riparian zone in the canyon is
arranged in belts of vegetation with mesically adapted species
on the beaches and xerically adapted species in the
washes and on the terraces. In a few instances some
mesically adapted species are present on the terraces,
a relict of pre-Glen Canyon Dam high water lines
Most of the present beach vegetation has been established
since the gates of Glen Canyon Dam were closed in 1963.
Mile 52.5R, Nankoweap UR.—Low rolling sand dunes
and sandy flats are prevalent along the beach. A wash,
strewn with boulders, traverses the area and the
adjoining terrace is cut along the wash/terrace
interface. The terrace is characterized by large sand
dunes with sandy flats interspersed throughout. The
beach vegetation is characterized by dense stands of
Tamarix and Salix with an understory of Equisetum,
Echinocholoa and Juncus. The wash habitat is sparsely
vegetated with Gutierrezia, Stephanomeria,
Mentzelia and Eriogonum. Because of periodic flash
flooding much of the vegetation in the wash habitat is
temporary at best. The terrace is covered with dense
clumps of Acacia and Opuntia. The understory is
typified by Festuca, Lepidium and PIantago.

63

Mile 53.5R, Nankoweap DR.—The beach at this study
site is typified by low rolling sand dunes interspersed
with sandy flats. Terrace habitats represent the pre-dam
high water line and are comprised of level packed sand and
grading into the lower edges of an adjoining talus slope.
Vegetation on the beach is characteristically dense
with clumps of Tamarix, Salix and Pluchea
Ground
cover is typically Festuca and Plantago. Terraces
have an overstory of Prosopis, some of which was burned
in the summer of 1968. Lepidium, Festuca and
Plantago are common members of the understory.
Mile 208.6L, Granite Park.—A sandy beach with low
dunes and a terrace provide the principal topographic
relief at this study site. Thickets of Tamarix, Salix
and Pluchea are common. Dense clumps of Alhagi are
also encountered. Understory vegetation includes
Oenothera, Bromus and Sporobolus. Terrace vegetation
is characterized by scattered Larrea or Acacia and dense
clumps of Prosopis with an understory of Encelia,
Bromus and Ephedra.
Mile 208.6R, 209 Mile Canyon.—Two habitats are
apparent at this study sie, the beach and the terrace.
Low rocky sand dunes characterize the beach while the
terrace is irregularly flat and dissected by several
small washes. Soil is sandy and became rocky
near adjacent talus slopes. Tamarix, Pluchea Baccharis
and Encelia are associated with the beach at this study
site. On the terraces Prosopis, Acacia and Larrea are dominant.
This site is inhabited by a small burro herd and consequently
vegetation was drastically altered when compared with the
mile 209.6L site.
Animals snap-trapped for analysis of diets were
taken at mile 52.5R and mile 208.6L in areas with habitats
similar to those found on the live-trapping grids.

METHODS AND MATERIALS
The overall objective of this study entailed a survey
of the demographic characteristics of small mammal species and
involved measurements distributed over space and time. To
accomplish this four live-trap grids were established and operated
at irregular intervals from November 1973 through June 1975.

6k

The location of each grid, the size and distribution of
major habitat units within it, and its orientation is shown in
Figure V-l. Some of the information contained in
this section is supplemented by non-grid snap-trapping
carried out from March 1974 through August 1975.
Each grid was sampled with 120 Sherman live-traps placed
at 15m intervals and distributed in a 10 x 12 array. An
exception to this array was made at Nankoweap because
of the narrowness of the riparian habitat there, requiring
an 8 x 15 array. The 10 x 12 grids each covered 2.23 ha. (5.58
acres); the 8 x 15 grid covered 2.21 ha. (5.53 acres). These
grids were run for four consecutive nights per trapping
period and resulted in a total effort of 14,400 trap nights.
Traps were opened and baited with oats and scratch grain
each day at 1700 hours and were checked and closed the
following morning at 0700 hours. New animals were marked
by toe clipping. Each animal's number, species, sex, reproductive condition, weight, and trap location was recorded
prior to its release at the point of capture.
All density data are drawn from the grid work and are based
upon the number of individuals trapped per hectare of each
habitat during each 4 night period. The area of each
habitat was determined from grid maps using a polar
planimeter.
An individual was assigned to a
particular habitat according to the location of his recapture
center (Hayne, 1949) during a given trapping period. In
actuality the parameter, density of species i in habitat z
is the number of centers of species i per hectare
of habitat z(Npfz). This is a simplistic approach to density
similar to the parameter, no./lOO trap nights, and probably
lends itself to slight underestimations. However, the use
of trappable population estimators such as the Lincoln
Index (Bailey, 1952) necessitates a grid size correction
factor and this would be extremely imprecise considering
the irregularly shaped habitats within each grid. It was felt,
then, that within the context of the present locally comparative
study, the more conservative method was most informative.
Finally, the initial practice of estimating the total numbers
of mammals per whole grid area (which did satisfy the Lincoln
Index/grid correction requirements) was abandoned because the
rodent species responded so differently in each habitat
(as will be shown) that it was often uninformative to
speak of a grid site as a homogeneous unit.
Relative density is an expression of a species importance
in its particular habitat and is calculated as:
r

i,z

= Ni,2 /Nt,z

65

where N^ „ is the density of species i in habitat z and
1 , z.

Nt

is
S%
through
This is
z

the total rodent density in that habitat.
is used here as an expression of density stability
time and, as such, is a weighted variance function.
calculated as:
S% = S

N t ,z ^ ' Z

where SJJ.
is the standard deviation of the mean density, N t
for an area. S%, then, is an inverse measure of stability or
predictability.

z

Habitat Distributions
The distribution of each species over z major habitats
of each grid is expressed as:
_
9 _
D
i,z = Ni,z / K N i , z )
z=l
where N^ z is the mean density (no./ha.) of species i in
habitat z. The value D- „ does not consider the relative
size of each habitat, z, and is, therefore, a measure of
frequency of occurrence.
Annual Survival
Annual survival is a probability function, modeled after
Kreb's (1966) design and is applied to species i with
respect to the entire grid which, for this purpose was
considered as a single riparian unit. The capture records for
species i were arrayed with respect to time in order to
record the proportion of animals alive at time x and surviving
to time x + 1. An individual was included among the
survivors even if he was not caught at time x + 1 but
was trapped at some future date. Since the intervals between
trapping periods were irregular, this surviving proportion, p,
was used to estimate a mean biweekly survival probability,
p as:
1
P = (P) b
where b is number of two-week time units between trapping
periods. Each grid yielded a number of p's equal to
one less than the number of trapping periods. The estimated
annual survival probability S was calculated from the mean
(p) as:

s- (PV 6
66

Nankoweap OR

Ncmkoweap UR

209 Mile Canyon

Granite Park

Figure V-l.—Habitat maps of the four grid sites.
T = Terrace, B = Beach, W = Wash. Numbers
indicate area of each in hectares. The bottom
of each map is coincidental with the river's edge.

67

Of the nine species involved in this study, only five were
used in survival calculations. It was felt that Neotoma spp.
were often non-grid residents and that an estiamte of their
grid survival was unrealistic. The other species yielded
too small a sample to allow for practical use of their data.
Species Diversity
Species diversity, a community parameter, is a description of the complexity of the rodent community in habitat
z at each grid site. This measure utilizes mean relative
densities (r^ „) and treats each set of data as a sample of
the rodent community found in habitat z. In the case of
sampling, the use of H' (Shannon and Weaver, 1963) is
appropriate (Pielou, 1975) as the basic unit of species
diversity:
n _
—
H'z = Z r i f Z lnr i / Z
i=l
for n species, H1 itself is difficult to use as a comparative
between habitat parameter because of different values of n and
thus it needs to be adjusted by n (Pielou, 1975).
A better value is J1, which measures the evenness of
community structure as:
J' = H'/H max,where H max = Inn
Home Range
Home range, as used here, is an expression of minimal
movement of species and is used as a population, rather
than an individual, descriptive parameter. The values which this
analysis yielded are somewhat relative since they are
based on four-night periods and cannot possibly include
all the trap locations which an animal might visit over
an extended period of time.
The home range model used treats the animals'
movements as an elliptical bivariate function based on an
x,y grid coordinate system (Koeppl et al., 1975).
Mathematically, it considers an individual's coordinate distances
from its recapture center (Hayne, 1949) on a variance/
covariance matrix. It is this x and y distance characteristic which facilitated the pooling of data from many
individuals into a single matrix which represented data from
a hypothetical composite rodent; thus, the sample size could be

68

greatly increased beyond the four night limit. To be considered
as a contributor to the matrix, an individual had to have been
captured 3 or 4 times and recorded at 2 or more different
locations. These restrictions eliminated all but P. eremicus
and P. maniculatus from home range consideration.
The home range analysis yielded the following kinds of
information: (a) size of range (herein referred to as
capture range) in hectares, (b) slope of the major axis
of the capture range ellipse; this considers the grid as an
x,y system with the side paralleling the river's shore as the
x-axis, (c) shape of the range; designated x/ y, this is
a ratio of major axis to minor axis and increases as the
shape becomes more non-circular.
Cluster Analysis
The relationship or affinity of one rodent species
for another based on mean density in each of nine subsites;
i.e., N^ z was analyzed using a nine species by nine subsite
matrix. The indices of similarity was that of Euclidian
Distance (ED) and the cluster method was the weighted pair-group
method (WPGM) as described by Sokal and Sneath (1963).
ED is a negative measure of ecological similarity and
WPGM groups pairs of species by ascending ED. In this
manner groups, i.e., clusters, of rodent species with similar
habitat distributions, were identified.
Reproduction
During 14,400 live-trap nights on the grids used
to study rodent populations each captured animal was
assigned to one of seven reproductive categories (nonreproductive male, non-reproductive female, scrotal
male, vagina perforate and not lactating female,
vagina perforate and lactating female, estrous female
and pregnant female). The data were summarized for the
females of each species so that pregnant females,
estrous females, lactating females and females with
perforate vaginas were treated as reproductively active.
Information on mean litter size was gathered from
specimen catalog cards of 695 specimens collected during
the last four years throughout the riparian zone of the canyon.
Diet Studies
Small rodents were snap-trapped at mile 52.OR and
mile 209.0L using museum special traps baited with oatmeal.

69

Seventy individuals (5 species) were taken during three
trap periods of one night in duration in April, June and
July of 1974 at mile 52.0. Twenty-five individuals (2
species) were taken during a three trap period of one
night in duration in May 1974. Trap-lines were selected
at the discretion of the biologist, however, traps
were placed in all accessible habitats from the water's
edge to the talus slopes.
Mammals were picked up in the morning, identified
weighed and assessed for age and reproductive characteristics.
Each individual was injected with an stored in 10 percent
formalin during the remainder of the stay in the field.
Upon return to the laboratory specimens were rinsed in
cold tap water and placed in 70 percent 2-propanol.
Stomachs were removed from each specimen, dried
at 60°C for 24 hours, and weighed before and after the
contents were removed. Microscope slides were prepared
as described by Reichman (1975).
Four major food classes were established to classify
stomach contents (i.e., green vegetation, seed, arthropod
and miscellaneous). The miscellaneous category included
hair, pollen or unidentified material. Percent
volume of each food class was estimated to the nearest
5 percent in 20 random fields examined at 100 X magnification
on each slide. From these data relative volume (relative
volume = volume of a food class in all stomachs/total
volume of all food classes in all stomachs (x 100) and
frequency of occurrence (number of fields in which a
food class occurred/total number of field examined x 100)
were calculated.
The data reflect dietary composition during the spring
and early summer of one year. Several authors (Franz
et al., 1973; Vaughan, 1974; Reichman, 1975) have shown the
degree of seasonal and annual variation in rodent diets.
Due to insufficient sample sizes it was not possible to
document diets of all the species found on the study areas.
We chose to document the diets of sympatric species
of cricetid rodents at mile 52.5R and 2 sympatric species
at mile 208.6L.
RESULTS AND DISCUSSION
Density
Density and relative density data are summarized in

70

Tables V-2 through V-9. The volume of data contained on
these tables is considerable and this information has
been summarized in Figures V-2 and V-3 which trace total rodent
density changes through time on the terraces and beaches.
The communities at both Nankoweap sites show a sharp
decline in density going into the winter of 1974-1975
but both terrace communities appear to recover faster
than those of the beach. The most consistent and precipitous population crashs occurred at Granite Park and
209 Mile Canyon, particularly on the terraces where
the total rodent density decreased by factors of 10 and
13 respectively (beach densities dropped by factors
of 9 and 11 at these locations). Thus, although
the Nankoweap communities may be characterized as being
in a state of dynamic equilibrium, the same cannot be
said at Granite Park and 209 Mile Canyon which were
apparently in a stage of population decline.
The data on Figures V-2 and V-3 demonstrate the difficulty
of assigning density values for any single area or
habitat. This low predictability is probably a
function of high temporal variability which has been
expressed in terms of S% (Table V-10). Using variance as a
relative rather than absolute value, the two upper canyon
(Nankoweap) areas appear more stable than those in the
lower canyon. However, this statement must be qualified
by the evidence of population crashes at Granite Park
and 209 Mile Canyon. It should also be noted that,
at a given location, the beach communities are less
stable, i.e., show a higher S%, than the terrace communties.
Paired linear correlation analysis was run with the
species densities from Nankoweap DR and Granite Park to
test for the presence of synchronous relationships
between species (Table V-ll). Only major species, those
with f"^ z more than 2, were considered since the others
were often absent from the data. Twenty percent of the
pairs at Nankoweap DR and 67 percent at Granite Park showed
significant correlations through time. All these relationships were positive so that instances of interspecies
inhibition could be identified. M'cioskey (1972), in a
16 month study of sagebrush mammal densities, found that
only 6 of 15 possible species pairs showed evidence of
significant correlations. Of these, 4 were positive.
Thus, it appears that when conditions are favorable (at
least at Nankoweap) no species benefits to the measurable
detriment of another.

71

Table V-2.—Density of small mammals at Nankoweap DR as no./ha.
T = Terrace (1.54 ha.) B= Beach (0.67 ha.)
Species

Apr 74

June 74

July 74

Oct 74

T 51.95
B 8.96

46.75
20.90

33.77
29.85

24.03
13.43

49.35
52.24

11.04
4.48

4.55
0.00

14.29
23.88

29.46
19.34

T 5.19
B 8.96
P. crinitus T 0.00
B 0.00
P. boylii
T 0.00
B 0.00
N. lepida
T 0.00
B 0.00
R. megalotis T 0.00
B 0.00
P. formosus T 0.00
B 0.00
TOTAL
T 57.14
B 17.92

0.00
16.42
1.95
5.97
0.00
1.50
1.30
0.00
0.00
1.50
11.69
0.00
61.69
46.29

0.00
14.93
1.30
0.00
0.00
1.50
2.60
2.99
0.70
0.00
12.99
10.45
51.36
59.72

0.00
17.91
7.14
8.96
0.00
0.00
5.19
4.48
0.00
0.00
14.94
8.96
51.30
53.74

0.00
14.93
7.14
19.40
0.00
0.00
2.60
0.00
0.70
0.00
5.84
5.97
65.63
92.54

1.30
4.48
2.60
0.00
0.00
0.00
1.30
0.00
0.00
0.00
0.65
0.00
16.89
8.96

0.00
2.99
3.90
0.00
0.00
0.00
1.30
1.49
0.00
0.00
14.29
4.48
24.04
8.96

0.00
19.40
5.84
4.48
0.00
3.00
8.44
7.46
0.00
0.00
19.48
10.45
48.05
68.67

0.81
12.50
3.73
4.85
0.00
0.75
2.84
2.05
0.18
0.19
9.99
5.04
47.01
44.72

P. eremicus
P.
maniculatus

(V)

Dec 73

Jan 75

Mar 75

June 75

Mean

Table V-3.—Relative density of small mammals at Nankoweap DR
( (density sp4 divided by total density) x 100).

LO

Species

Dec 73

Apr 74

June 74

July 74

Oct 74

Jan 75

Mar 75

June 75

Mean

P. eremicus T
B
P.
maniculatus T
B
P. crinitus T
B
P. boylii
T
B
N. lepida
T
B
R.
megalotis
T
B
P formosus T
B

90.90
50.00

75.80
45.20

65.80
50.00

46.80
25.00

75.20
56.50

65.40
50.00

18.90
00.00

29.70
34.80

58.60
38.90

9.10
50.00
00.00
00.00
00.00
00.00
00.00
00.00

00.00
35.50
3.20
12.90
00.00
3.20
2.10
00.00

00.00
25.00
2.50
00.00
00.00
2.50
5.10
5.00

00.00
33.30
14.90
16.70
00.00
00.00
10.10
8.30

00.00
16.10
10.90
21.00
00.00
00.00
4.00
00.00

00.00
50.00
15.40
00.00
00.00
00.00
7.70
00.00

00.00
33.40
16.20
00.00
00.00
00.00
5.40
16.60

00.00
28.30
12.20
6.50
00.00
4.40
17.60
10.90

2.10
34.00
9.30
7.10
00.00
1.30
6.50
5.10

00.00
00.00
00.00
00.00

00.00
3.20
18.90
00.00

1.40
00.00
25.30
17.50

00.00
00.00
29.10
16.70

1.10
00.00
8.90
6.50

00.00
00.00
3.80
00.00

00.00
00.00
59.40
50.00

00.00
00.00
40.50
15.20

0.30
0.40
23.20
13.20

Table V-4.—Density of small mammals at Nankoweap UR as no./ha.
T = Terrace (0.85 ha.); W = Wash (0.85 ha.); B = Beach (0.53 h a . ) .
Species
P. eremicus

P.
maniculatus

-p-

Nov 73
T 29.41
W 36.47
B 20.75

T
W
B
P. crinitus T
W
B
P. boylii
T
W
B
N. lepida
T
W
B
R. megalotis T
W
B
P. formosus T
W
B
TOTAL
T
W
B

00.00
2.35
7.55
2.35
3.53
00.00
00.00
1.18
1.89
00.00
2.35
00.00
00.00
00.00
00.00
00.00
1.18
1.89
31.76
47.06
32.08

Apr 74

June 74

July 74

Oct 74

Jan 75

Mar 75

June 75

Mean

15.29
22.35
16.98

10.59
17.65
11.32

11.76
15.29
18.87

18.82
29.41
26.42

9.41
11.76
5.66

8.24
7.06
5.66

4.71
8.34
11.32

13.53
18.53
14.62

00.00
4.71
5.66
5.88
2.35
5.66
00.00
2.35
3.77
4.71
00.00
5.66
00.00
00.00
5.66
7.06
3.53
3.77
32.94
35.29
47.16

00.00
5.88
5.66
1.18
4.71
00.00
1.18
1.18
00.00
10.59
3.53
3.77
00.00
00.00
00.00
12.94
8.24
7.55
36.48
41.19
28.30

00.00
1.18
7.55
00.00
3.53
00.00
1.18
1.18
3.77
15.29
3.53
1.89
00.00
00.00
1.89
7.06
3.53
3.77
35.29
28.24
37.74

2.35
10.59
9.43
1.18
10.59
00.00
1.18
00.00
00.00
12.94
3.53
00.00
00.00
00.00
00.00
8.24
4.71
1.89
44.71
58.83
37.74

1.10
5.88
3.77
00.00
00.00
00.00
00.00
00.00
00.00
1.18
1.18
00.00
00.00
00.00
00.00
00.00
00.00
00.00
11.77
18.82
9.43

00.00
3.53
3.77
1.18
9.41
00.00
00.00
00.00
00.00
7.06
1.18
00.00
00.00
00.00
00.00
12.94
2.35
00.00
29.42
23.53
9.43

00.00
00.00
3.77
1.18
5.88
1.89
00.00
00.00
00.00
18.82
15.29
11.32
00.00
00.00
00.00
11.76
7.06
5.66
36.47
36.47
33.96

0.44
4.26
5.90
1.62
5.00
0.94
0.44
0.74
1.18
8.82
3.82
2.83
00.00
00.00
0.94
7.50
3.82
3.07
32.36
36.18
29.48

Table V-5.—Relative density of small mammals at Nankoweap UR
( (density species ^divided by total density) x 100).
Species

Nov 73

Apr 74

June 74

July 74

P. eremicus

T 92.60
W 77.50
B 64.70

46.40
63.30
36.00

29.00
42.90
40.00

33.30
54.10
50.00

T 00.00
W 5.00
B 23.50
P. crinitus T 7.40
W 7.50
B 00.00
£-• b°ylii
T 00.00
W 2„50
B 5.90
N. l e p i d a
T 00.00
W 5.00
B 00.00
R. megalotis T 00.00
W 00.00
B 00.00
P. formosus T 00.00
W 2.50
B 5.90

00.00
13.30
12.00
17.90
6.70
12.00
00.00
6.70
8.00
14.30
00.00
12.00
00.00
00.00
12.00
21.40
10.00
8.00

00.00
14.30
20.00
3.20
11.40
00.00
3.20
2.90
00.00
29.00
8.60
13.30
00.00
00.00
00.00
35.50
20.00
26.70

00.00
4.20
20.00
00.00
12.50
00.00
3.30
4.20
10.00
43.30
12.50
5.00
00.00
00.00
5.00
20.00
12.50
10.00

P.
maniculatus

-J
V71

oct 74
42.10
50.00
70.00
5.30
18.00
25.00
2.60
18.00
00.00
2.60
00.00
00.00
28.90
6.00
00.00
00.00
00.00
00.00
18.40
8.00
5.00

Jan 75

Mar 75

June 75 Mean

79.90
62.50
60.00

28.00
30.00
60.00

12.90
22.60
33.30

45.50
50.40
51.80

10.00
31.20
40.00
00.00
00.00
00.00
00.00
00.00
00.00
10.00
6.30
00.00
00.00
00.00
00.00
00.00
00.00
00.00

00.00
15.00
00.00
4.00
40.00
00.00
00.00
00.00
00.00
24.00
5.00
00.00
00.00
00.00
00.00
44.00
10.00
00.00

00.00
00.00
11.10
3.20
16.10
5.60
00.00
00.00
00.00
51.60
41.90
33.30
00.00
00.00
00.00
32.20
19.40
16.70

12.60
12.60
24.00
4.80
14.00
2.20
1.10
2.00
3.00
25.10
10.70
8.00
00.00
00.00
2.10
21.40
10.30
9.00

Table V-6.—Density of small mammals at Granite Park as no./ha.
T = Terrace (1.27 ha.); B = Beach (0.96) ha.).

Species
P. eremicus
P. boylii
N. albigula
P.
intermedins
TOTAL

cA

Mar 74

May 74

June 74

T 66.14
B 60.42
T 00.00
B 1.04
T 1.54
B 2.08

55.91
25.00
00.00
00.00
1.57
00.00

41.73
29.17
00.00
00.00
2.36
00.00

T 37.80
B 19.79
T 105.51
B 83.33

21.26
13.54
78.74
38.54

21.26
13.54
65.35
42.71

Nov 74

Jan 75

Apr 75

42.52
18.75
1.57
00.00
3.15
3.13

21.26
13.54
00.00
00.00
0.79
00.00

13.39
3.13
00.00
00.00
00.00
1.04

6.30
8.33
00.00
00.00
00.00
00.00

35.32
22.62
0.22
0.15
1.35
0.89

22.83
16.67
70.07
38.55

13.39
7.29
35.44
20.83

8.66
1.04
22.05
5.21

3.94
1.04
10.24
9.37

18.45
10.42
55.34
34.08

Aug 74

Mean

Table V-7.—Relative density of small mammals at Granite Park.
( (density species J divided by total density) x 100)
Species
P. eremicus
P. boylii
N. albigula
P.
intermedins

Mar 74

May 74

June 74

T 62.71
B 72.50
T 00.00
B 1.20
T 1.50
B 2.50

71.00
64.90
00.00
00.00
2.00
00.00

63.90
68.30
00.00
00.00
3.60
00.00

T 35.80
B 23.70

27.00
35.10

32.50
31.70

Nov 74

Jan 75

60.70
48.60
2.20
00.00
4.50
8.10

60.00
65.00
00.00
00.00
2.20
00.00

60.70
60.10
00.00
00.00
00.00
20.00

61.50
88.90
00.00
00.00
00.00
00.00

62.90
66.90
0.30
0.20
2.00
4.40

32.60
43.20

37.80
35.00

39.30
19.90

38.50
11.90

34.80
28.60

Aug 74

Apr 75

Mean

->3

Table V-8.—Density of small mammals at 209 Mile Canyon as no./ha.
T = Terrace (1.76 ha.); B = Beach (0.47 ha.).
Species
P. eremicus
P. crinitus
P. boylii
N. lepida
P. formosus
TOTAL

Mar 74
T
B
T
B
T
B
T
B
T
B
T
B

27.27
44.68
00.00
00.00
00.00
2.13
0.57
00.00
0.57
00.00
28.41
46.81

May 74

June 74

9.66
14.89
0.57
2.13
00.00
00.00
00.00
00.00
1.14
00.00
11.37
17.02

5.68
19.15
1.14
12.77
00.00
00.00
00.00
00.00
0.57
00.00
7.39
31.91

Aug 74
13.64
10.64
3.98
6.38
00.00
00.00
00.00
00.00
0.57
00.00
18.18
17.02

Nov 74

Jan 74

7.95
10.64
1.14
4.26
00.00
00.00
00.00
00.00
00.00
00.00
9.09
14.89

3.98
2.13
1.70
2.13
00.00
00.00
00.00
00.00
00.00
00.00
5.68
4.26

Apr 74
1.14
2.13
1.14
2.13
00.00
00.00
00.00
00.00
00.00
00.00
2.27
4.26

Mean
9.90
14.89
1.38
4.26
00.00
0.30
0.08
00.00
0.41
00.00
11.77
19.75

Table V-9.—Relative density of small mammals at 209 Mile Canyon
( (density species . divided by total density) x 100).
Species
P. eremicus
P. crinitus
P. boylii
N. lepida
P. formosus

-g

T
B
T
B
T
B
T
B
T
B

Mar 74

May 74

June 74

96.00
95.40
00.00
00.00
00.00
4.60
2.00
00.00
2.00
00.00

85.00
87.50
5.00
12.50
00.00
00.00
00.00
00.00
10.00
00.00

76.90
60.00
15.40
40.00
00.00
00.00
00.00
00.00
7.70
00.00

Aug 74
75.00
62.50
21.90
37.50
00.00
00.00
00.00
00.00
3.10
00.00

Nov 74

Jan 74

87.50
71.50
12.50
28.60
00.00
00.00
00.00
00.00
00.00
00.00

70.10
50.00
29.90
50.00
00.00
00.00
00.00
00.00
00.00
00.00

Apr 74
50.00
50.00
50.00
5.00
00.00
00.00
00.00
00.00
00.00
00.00

Mean
77.20
68.10
19.20
31.20
00.00
0.70
0.30
00.00
3.30
00.00

—1

Figure V-2.—Density fluctuations on the beaches.
— — = Nankoweap DR, — — = Nankoweap UR,
— — = Granite Park,---- = 209 Mile Canyon.

CO

o

Figure V-3.—Density fluctuations on the terraces.
= Nankoweap DR,
= Nankoweap UR,
Granite Park,
= 209 Mile Canyon.

Table V-10.—Rodent community demographic parameters.

Beach
Wash
Terrace

co
H

Nankoweap DR
S%Nt
N

J"

00.68

44.72

00.73

00.37

47.01

00.59

Nankoweap UR
S%Nt
Nt

J'

00.46
00.36
00.29

00.70
00.74
00.67

29.48
36.18
32.36

Granite_Park
S%Nt
Nfc

J'

209_ Mile_ Canyon
S%Nfc
Nfc
J'

00.77

34.08

00.56

00.78

19.45

00.41

00.61

55.34

00.54

00.75

11.77

00.40

Table V-ll.—Density through time correlation tests for major species. Terrace is
above each major matrix axis; beach data is below. (*) indicates significance
at p = 0.05.
Nankoweap DR
P_. eremicus
P_.
P.
P.
N.
P.

eremicus
maniculatus
crinitus
lepida
formosus

P_. maniculatus

P_. crinitus

0.39
0.62
0.78*
0.57
0.40

N. lepida

-0.26
-0.60

0.51
0.57
0.58

-0.05
0.21

Granite Park
P_. eremicus
P. eremicus
N. albigula
P_. intermedius

N. albigula
0.68*

0.16
0.83

0.52

P. intermedius
0.95*
0.65*

-0.36
-0.48
0.66*
0.82*

P_. formosus
-0.40
-0.71
0.20
0.66*

The relative density data indicate that P.
eremicus is numerically dominant throughout the riparian
zone, showing mean r^ z values of 61.1 and 56.4 on the terraces
and beaches respectively.
This role is maintained rather
consistently through time and space. With the exception of
the 209 Mile Canyon communities, Perognathus spp. assumes a
generally secondary importance role.
The hierarchial stability of a species was estimated by
i z • M e a n values for all species on all beaches and
terraces were 1.23 + .85 and 1.12 + .77 respectively and
demonstrated no significant difference with respect to
this, a community stability parameter. Thus, the average
magnitude of positional shifts by species in beach and
terrace communities is nearly the same.
s% r

Rank correlation values were computed to test the
relationship between a species' mean rank {r±rZ)
and the
amount of temporal shifting of its rank within its
community (S% rj_ z ) . The linear coefficients were:
Nankoweap DR, -.73; Nankoweap UR, -.86; Granite Park, -.80;
209 Mile Canyon, -.83. All these values are significant
at p<.05. Thus, it appears that, as relative density
increases, the stability of a species' hierarchial
position also increases.
Two population stability statistics, S% r^ z and
S%N^ z show a powerful relationship of r = .93 which is
significant at p less than .01. A species which is best
able to maintain a steady equilibrium population level
is also best able to maintain its position within the
importance sequence of its community. Conversely, those
species which occur at the bottom of a community's
(numerical) importance list are those species which are
least able to maintain a constant population size. This
last statement arises from the relationship between
mean relative density (rj./Z) and density instability
(S%N- ) where r = .63 and is significant at p less than
.01. Thus, a small mammal species occuring at high
density at a riparian location in the Grand Canyon has
the additional advantages of stability with respect to
population density and community hierarchial position.
Species Diversity
The comparative diversity parameter, J' is contained in
Table V-10. Beach rodent communities tend to be slightly more

82

Figure V-4.—The relationship of total rodent density stability
to community complexity. The linear correlation
value is significant at the .05 level.

83

complex than those on the terrace. Also, a given community
in the upper canyon may be expected to be more diversified
than its counterpart in the lower canyon. No correlation
between mean density (Nt 2 ) and J' was established (r = .43).
However, an inverse relationship between density instability
(s%Nt,z) anQl J' does exist at the p .05 level (Figure V-4) .
Therefore, a highly complex community can be expected to be a fairly
stable community. It should be noted that this is a case of
complexity within a single trophic level whereas most of the
arguments concerning complexity and stability deal with several
trophic levels (see MacArthur, 1955; Pimentel, 1961; May, 1973).
However, if the formulations of May (1973) are accepted and
applied here, a stable rodent community tends to predict a
stable total food web. Now, since rodent community complexity,
i.e., J' predicts rodent community instability, i.e., S%N.u z ,
the rodent J' value (which can be estimated at a single point
in time) may be developed as an indirect measure of total food
web stability for a given riparian site. At the present
stage, J' seems to have value as a qualitative predictor.
Habitat Distribution
Habitat distributions, in terms of percent of density, are
presented in Table V-12. A pronounced avoidance of the terrace
is obvious with P_. maniculatus; snap-trap data support these
figures. The species of Neotoma and Perognathus tend to
concentrate their distributions on the terraces. The only
species with a heavy emphasis on wash distribution is P. crinitus.
It is difficult to recognize a clear pattern for the numerically
dominant P. eremicus.
J1 values for density distributions of each species on all nine
habitats were calculated with the assumption that all species
had an equal opportunity to disperse to each of these sites (Table V13). This assumption was known to be invalid in the case of the
two Perognathus which are restricted by the side of the River
so both species were lumped into a single taxonomic generic unit.
P_. eremicus displays a very evenly distributed diversity which
qualitatively correlates well with snap-trap data for the rest
of the Canyon. Perognathus, Peromyscus crinitus, P_. boylii
and N. lepida comprise a moderately diversified group. An
unevenly distributed group includes P_. maniculatus, N. albigula,
and R. megalotis.
A positive relationship, significant at p<. 05 exists
between a species distribution J1 (Table V-13) and its unweighed
mean relative density (r^) giving a rank correlation
value of r = .66. A high habitat J1 value is equivalent to a
broad habitat niche. That is, a species with a high J1 (P.

84

Table V-12.—Habitat distribution of noctural small mammals. Species' distributions are
expressed for each grid as density in habitat divided by density in all habitats.
Nankoweap DR
Beach Terrace
P.
P.
P.
P.
N.
N.
R.
P.
P.

eremicus
maniculatus
crinitus
boylii ~
lepida
albigula
megalotis
formosus
intermedius

Nankoweap UR
Beach Terrace Wash

Granite Park
Beach Terrace

209 Mile Canyon
Beach Terrace

0.39

0.61

0.60

0.40

0.41

0.59

0.76
1.00
0.00

0.24
0.00
1.00

0.40

0.60
0.00

1.00

0.36

0.62

0.40
0.94
0.54
1.00
0.42

0.60
0.06
0.43
0.00
0.58

0.31
0.56
0.12
0.50
0.18

0.29
0.04
0.21
0.19
0.57

0.40
0.40
0.66
0.31
0.25

0.51
0.34

0.49
0.66

1.00
0.27

0.00
0.52

0.00
0.21

co

Table V-13.—Habitat distribution diversity as J' assuming equal
opportunity to disperse to all nine habitats.
P_. eremicus
P_. maniculatus
P_. crinitus
P. boylii
N. lepida
N. albigula
P. megalotis
Perognatus spp.

.97
. 54
.82
.79
.67
.31
.36
.82

eremicus) may be considered very successful in colonizing
the variety of habitats with which it is presented. Such a
species is an ecological generalist with respect to habitat
selection within the spatial_limitations of the Grand Canyon's
riparian system. The J1 to r^ relationship predicts that
the most common species within a given rodent community may be
also the most generalized. This applies not only to habitat
distributions but to a species' adaptability to environmental
change as demonstrated in the previous r^ to S%Nj_ relationship. Thus, wide habitat niche breadth, stable hierarchial
positions, stable density, and high hierarchial positions
are all positively interrelated..
Home Range
The movement data for 2 species at Nankoweap DR and one
at Granite Park are summarized in Table V-14. Although a
considerable amount of temporal variation exists, all three
mean values are quite similar. The range size variation
for P. eremicus and P_. maniculatus can be partially explained
at Nankoweap DR by variation in minimum nightly temperature.
A significant negative correlation exists between nightly
temperature and range size at p<.05 (Figure V-5). The data
from December, 1973, were deleted from this calculation
since P_. eremicus and P_. maniculatus were the only species
apparently active at that period, a condition never
recorded since. It was felt that, due to possible lack of
movement interference by other species, the December, 1973,
figures could not be used validly in a temperature-torange relationship. It is interesting to note that the slopes
of the regression lines in Figure V-5 are identical (-.02).
At Granite Park no such temperature-to-range relationship
was established though this may be an artifact of a small
sample of only 5 points.
At Nankoweap DR P_. eremicus and P_. maniculatus are
species which are evenly distributed between the two
habitats and very unevenly distributed respectively
(Table V-12). The slope data in Table V-14 indicate no strong
River orientation in the movements of the evenly distributed
P_. eremicus. However, during 7 of the 8 periods, the
beach restricted P_. maniculatus demonstrated movement
vectors that were nearly parallel to the River; the map in
Figure V-l illustrates this. P_. eremicus at Granite Park
also lacked a river-to-range orientation as was the case
at Nankoweap DR.
The shapes of home ranges for the three sets of data
summarized in Table V-14 are very strongly linear. Although

86

Table V-14.—Home range approximations. Size of range given in ha. Slope refers to
alignment of major axis with the River (a value less than 1 indicates
nearly parallel association) . 7\x/}\y is a coefficent of shape (as values
approach 1 the range approaches a circular shape).
Nankoweap DR

ha.
slope

P. eremicus

/W/\y
P.
maniculatus

ha.
slope
^x/ny

Dec 73 Apr 74 June 74 July 74 Oct 74 Jan 75 Mar 75 June 75 Mean
.14
.24 + .13
.09
.25
.44
.40
0.17
.29
.12
-3.33
13.36
.20
-1.25 -.67
0.07
-.59
100.00 -.77
9.30
5.10
1.50
3.60 8.00
11.00
1.60
3.60 2.10
0.06
-.05
2.60

.23
0.37
5.90

.06
-.07
3.20

.07
0.11
4.80

.05
2.50
1.60

.46
-.71
1.40

.09
-.43
7.50

.16
.07
25.10

.15 + .14
.54
6.50

Granite Park
co
-o
P. eremicus

ha.
slope
>\x//\y

Mar 74 May 74 June 74 Aug 74 Nov 74 Mean
0.07
0.13
0.29 0.07
0.23
0.16 + .10
0.04 -0.52
-11.11 -2.00
-0.92
2.92
36.30
3.00
2.60 4.30
2.80
9.80

Table V-15.—Annual survival probabilities of major grid-resident rodent species.

P. eremicus
P_. maniculatus
P. crinitus
P_. formosus

Nankoweap DR

Nankoweap UR

Granite Park

.029
.007
.014
.058

.076
.001
.296
.062

.009

209 Mile Canyon
.001

circular distribution is a popular assumption in many studies,
it cannot be used here.
Survivorship
Non-age specific survival data are summarized in Table
V-15. Only those species which were encountered in fairly
high densities were used due to sample size considerations.
The survival probabilities at the two lower canyon sites
are lower than those from the upper canyon sites. In
general, a nearly annual population turnover can be
predicted from these data.
A relationship exists at the upper canyon sites between the
relative amount of productivity a species invests in the
new (beach) habitat and the old (terrace and wash) habitat
versus that species' survival probability. This relationship
is shown in Figure V-6 where the new habitat investment is
used in its inverse form and called <=C . Thus, an investment
in the new habitat seems to be made at the cost of decreased
survivorship. This explains the extremely high survivorship
of P_. crinitus at Nankoweap UR (0.296) where 87 percent of
the density occurs in old habitats which make up 76 percent
of the grid area.
A partial explanation of the negative effect of
beach colonization upon riparian species survivorship
deals with the effect of temperature upon density.
The beach habitats are, by virtue of their proximity to
the Colorado River and their low elevation, colder than
the adjacent terraces (V. Shaeffer, pers. coram.). Thus,
it is reasonable to expect the total rodent densities on
the beaches to respond more sharply to temperature
change than densities on the terraces. The data from
Nankoweap DR support this hypothesis. Both beach and
terrace densities are correlated with minimum nightly
temperature (r = .78 and .67 respectively, significant
at p<.05) but the slopes of the regression equations
are 3.18 and 1.03 respectively. Thus, the response of
the beach community is approximately 3 times greater than that
of the terrace (Figure V - 7 ) .
Although the beach habitat has become a relatively
stable surface since 1963, species have still not fully
adapted to it as well as they have the terrace habitats
as is demonstrated by the survival data (Table V-15), the
density stability data (Table V-10) and the species
diversity data (Table V-10). The temperature-to-density data

88

MINIMUM NIGHTLY TEMPERATURE (°C)

Figure V-5.—The regression of movement on temperature.
(*) indicates the December 1973 data which
were not used in the regression analysis.

Figure V-6.—Annual survival probability as influenced by
a species' investment in colonizing the new
(beach) habitat. o C = old habitat density -t Beach Density
Each point represents data for a single
species at either Nankoweap DR or Nankoweap
UR.

89

Figure V-7.—The influence of temperature on beach and terrace
densities at Nankoweap DR.

90

H

Figure V-8.—Cluster analysis (WPGM) of rodent species
according to their densities on each of nine
sub-sites shown in Figure V-l. Merge levels
are in Euclidean Distance Units.

from Nankoweap DR suggest that newness alone may not be
solely (if at all) responsible for this; the beach presents
a thermally harsh environment and this may be endured only
at the expense of increased mortality.
Cluster Analysis
The cluster dendrogram (Figure V-8) emphasizes the
ubiquitous distribution of P. eremicus. It can be argued
that there are two major "groups": a habitat generalist
"group" comprised of P. eremicus, and a group of mammals
showing degrees of habitat preference comprised of the
rest of the riparian system's small mammals. If the
analysis is to have any value at all, this second group
must be examined by subgroups.
Two species are eliminated at relatively high levels
within the non-generalist group. P_. maniculatus is quite
restricted to beach habitats and Perognathus intermedius
is limited in its distribution to the south side of the
river. This last species has been eliminated from the
non-generalist cluster at a misleading level since only
2 of the 9 habitat subunits are on the south side of
the River.
Two groups of non-generalists remain, these are:
a 4 species group (I) of P_. crinitus, P_. boylii, R.
megalotis, and N. albigula; and a 2 species group (II)
of N. lepida and Perognathus formosus. Habitat distribution
alone does not explain the integrity of group I but
group II is obviously a non-beach assemblege as
indicated by averaging the beach distribution values
in Table V-12 where D = .20.
Food Habits
The diets of five sympatric species of cricetid
rodents at mile 52.5R are summarized in Figure V-9 and Table
V-16. Two species were preferentially herbivores and
a third exploited insects. The final two species were
generalists, one relied heavily on greenery while the
other favored insects. No species displayed a heavy
reliance upon seeds.
It is most fruitful to consider the dietary preferences
in relation to the habitat preferences of the species
examined at mile 52.5R. We have summarized these data
in Figure V-8 and Table V-12.

92

Table V-16.—Diets of five sympatric species of small mammals at mile 52.5R during the
spring and early summer of 1974. Numbers of parentheses represent the
number of stomachs sampled.

R.
P.
P.
P.
P.

Relative Volume (%)
Green
Seed
Arthropods
megalotis (5)
54
13
32
crinitus (8)
41
13
45
eremicus (33)
54
12
34
maniculatus (13) 42
7
50
boylii (6)
67
4
28

Misc.
1
1
1
1
1

% Frequency of Occurrence
Green
Seed
Arthropods
92
84
31
66
32
84
89
86
34
92
68
20
97
10
88

Misc.
8
6
5
5
5

LO

Table V-17.—Diets of two sympatric species of small mammals at mile 208.6 during the
spring and early summer of 1974.
Relative Volume
Green
Seed
P. crinitus (3)
60
7
P. eremicus (22)
66
1

(%)
Arthropods
37
31

Misc.
1
2

% Frequency of Occurrence
Green
Seed
Arthropods
Misc.
93
5
97
8
88
4
75
12

VD

Figure V-9.—Relative volume of four major food categories
in the diets of five sympatric cricetid rodents
at mile 52.5R.

R. megalotis populations at mile 52.5R were most commonly
associated with beach habitats. Relative volume and
frequency of occurrence are shown in Figure V-9 and Table
V-16. Greenery was the most important food source in the
diet of this species, both in terms of relative volume
and frequency of occurrence. Although insects were often
encountered, they represented only 32 percent of the
relative volume in the diet.
P. boylii populations at mile 52.5R also favored the
beach habitat. This species preferred greenery to other
food categories. Relative volume and frequency of
occurrence of greenery was greater in brush mice than
in any other species studied. Insects were less important
in the diet of P_. boylii than they were in R. megalotis
diets, although they were encountered more frequently
in P_. boylii stomachs.
These two species showed closer similarities with respect
to their habitat prefereneces than did any other pair of
rodent species present on the study area (Figure V-8). Likewise,
a similarity is evident in dietary preferences of the two
species. Although it is possible that these species exploit
different plants or plant parts (i.e., stems versus foliage)
within the beach habitat, it is remarkable that, overall, diets
are so similar. Reithrodontomys exploits seeds
in a greater volume and they are more commonly encountered
in Re ithrodontomys stomachs than they are in P. boylii.
P. maniculatus were confined to the beach
habitat for the most part. We have shown that
deer mice are not closely related to any other species in
terms of habitat preferences. Insects were the major item
in the diet of this species, both in terms of relative
volume and percent frequency.
Stevens (see Chapters VII and VIII) found that insect
density and diversity were greatest in the beach habitat of
the riparian zone within the canyon. The importance of insects
in the diets of P_. maniculatus may, in part, be due to the
abundance of this prey within their habitat.
The habitat preferences of P_. crinitus were typified
by washes, cliff faces and talus slopes. Habitat
preferences of this species elsewhere were
previously discussed by Egoscue (1964). Diets of canyon mice
at mile 52.5R were extremely diverse. No single food
category comprised more than 45 percent of the relative
volume. Insects were the most prevalent item both in terms

95

of relative volume and percent frequency. Greenery was of
secondary importance while seeds were only used occasionally.
P. eremicus was the most commonly encountered
species during the study and occurred in all major habitats
in the riparian zone (Table V-12). At mile 52.5R greenery
was the most important item in the diet of this
species. Insects and seeds were of lesser significance
but the former was more important than the latter.
Two species were sampled in sufficient numbers to
analyze diets at mile 208.6L. The data for P_. crinitus and
P. eremicus are summarized in Figure V-10 and Table V-17.
R. megalotis and P_. maniculatus were not taken
at this study site.
P. boylii was uncommonly encountered
and a sufficient number of stomachs were not available to
analyze the diet of this species at mile 208.6L.
Greenery was far more important in the diet of P_. crinitus
at mile 208.0L than at the mile 52.5R site. Utilization
of arthropods and seeds was reduced in P_. crinitus diets
at mile 208.6L although arthropods were more frequently
encountered. This species was not present on the live
trapping grid at this site (Table V-12).
P. eremicus at mile 208.6L was found in both the
beach and terrace habitat but favored the latter (Table V-12).
Greenery was the major item in the diet of this species.
Insects were frequently encountered but made up less than
one-third of the relative volume. Seeds were almost absent
from P. eremicus stomachs at this site.
Comparisons of P_. crinitus and P. eremicus diets from
mile 52.5R and mile 208.6L are striking. Greenery was much
more important in the diets of both species at mile 208.6L,
being encountered at higher relative volumes and more frequently.
Insects and seeds were generally taken less commonly by the
two species at mile 208.6L than at mile 52.5R.
Seeds were the least important item in R. megalotis and
Peromyscus spp. diets at both study sites. Flake (1973) and
Vaughan (1974) found seeds to be the most important item in
P_. maniculatus diets from two different habitats in Colorado.
Seed production is probably highest on the terrace habitats
of the riparian zone (M. Theroux, pers. comm.). This is the
preferred habitat of both heteromyid rodents in the riparian
zone. As a group, heteromyids are better suited to exploit
seeds than are cricetids.
This may account for the paucity
of seeds in cricetid rodent diets in the riparian zone.

96

-1

Figure V-10.—Relative volume of four major food categories in
the diets of two sympatric cricetid rodents at
mile 208.6L.

Insects provide a fairly stable and important food source
for R. megalotis and Peromyscus spp. in the riparian zone.
They are preyed upon to different degrees by the cricetids
examined in this study. This may account, in part, for the
diversity of several closely related species. We are currently
investigating rodent diets at a number of localities in the
canyon to more precisely define the mechanism(s) which permit
co-existence of a number of closely related species.
REPRODUCTION
Perognathus formosus had a mean litter size of 6.25
(n = 4) as determined from embryo counts. Corpora lutea counts
revealed a mean litter size of 4.43 (n = 7). Mean number of
embryos reported here is greater than reported by French et al.
(1974), while placental scar counts were less than reported
by those authors. During live trapping, carried out in
all seasons of the year during 18 months, reproductively
active females were observed in April (58 percent, N = 12;
33 percent, N = 3), June (10.5 percent, N = 19; 70 percent,
N = 23; 8 percent, N = 12) and July (14 percent, N = 7).
We have no data to suggest reproductive activity in
this species outside of the spring and early summer months.
These data are supported by the findings of Chew and Turner
(1974), who found that in Nevada reproductive activity
was limited to the period between March and August.
Perognathus intermedius had a mean litter size
of 5.00 (n = 4). No data on mean numbers of corpora lutea
were available for this species. During a 4 month study in
southern Arizona, Franz et al. (1973) found mean litter sizes
at 3.3 and 3.4 as indicated by embryo and corpora lutea
counts respectively. Larger sample sizes may bring our
estimates of litter size closer to those of previous studies.
Live-trapping data gather during all seasons over a period of
14 months at mile 208.6L revealed reproductively active
females in March (12 percent, N = 24), April (20 percent,
N = 5), May (15 percent, N = 20), and June (15 percent,
N = 13). Reichman and Van De Graaff (1973) found that
reproductive activity in P. intermedius was characteristically
limited to the spring months. Elsewhere, these authors (Reichman
and Van De Graaff, 1975) suggest that the ingestion of green
vegetation and heteromyid reproduction are related. If such
a relation does exist it is not surprising that reproductive
activity is characteristic of the spring and early summer
months when ample resources are available for female parents,
and later, the offspring.

98

We have no data on litter sizes of Reithrodontomys
megalotis in the canyon. Indeed, there is a paucity of data
available in the literature dealing with reproduction of this
species. Limited information on reproductive cycles
is available for this species in the canyon. Individuals
were observed in reproductive conditon in April, May and
June; however, small sample sizes prohibit conclusions.
This species is relatively rare and has been taken
from only a few localities in the canyon. Further
work on all aspects of the ecology of this species is
needed in the riparian zone.
Embryo counts of Peromyscus crinitus revealed a
mean litter size of 4.75 (n = 4) while corpora lutea counts
showed a litter size of 2.50 (n = 2 ) . Other authors have
reported mean litter (n = 2 ) . Other sizes of 4.10
in Nevada (Moor and Bradley, 1974) and 3.00 in Utah
(Egoscue, 1964) as revealed by embryo counts. However,
Egoscue's study was on a laboratory population. Reproductive
activity was observed in May (100 percent, n = 5; 50 percent,
n = 4) and June (50 percent, n = 4; 88 percent, n = 8) on
the study sites at miles 52.5R and 53.OR. At mile 208.6R
reproductive activity was limited to June (75 percent, n = 4 ) .
Moor and Bradley (1974) recorded bimodal reproductive activity
(May-August and November-February) for this species in
southern Nevada. Young were produced in every month of
the year in Egoscue's (1964) study in the laboratory,
however, the majority (109 to 135 litters) were born
between January and August. We found no evidence
of reproduction outside of the spring and early summer
months in this species.
Mean litter size of the Peromyscus eremicus was 3.25
(n = 8 ) , as determined by embryo counts.
Franz et al. (1973)
recorded a mean litter size of 2.60 for this species in southern
Arizona using embryo counts and corpora lutea counts.
MacMillen (1964), using embryo counts, found that cactus
mouse populations in southern California had a mean litter
size of 2.90. Cactus mouse reproductive cycles
during the study are summarized in Table V-18. Reproductive
activity is most intense in the spring and early summer
months. Late fall reproduction did not occur during
our study.
Franz et al. (1973) and MacMillen (1964)
have discussed year around reproductive activity in females
of this species. Our live-trapped animals showed no evidence
of reproduction during trap periods in October, November
or December; however, reproductive activity was noted
on one study site (mile 53.OR) in January, 1975.

99

Table V-18.—Percent of reproductive females P. eremicus captured on the
four live trapping grids during the study. Numbers in parentheses
are sample sizes.
Miles 52.5R

H
O
O

November, 1973
December, 1973
March, 1974
April, 1974
May, 1974
June, 1974
July, 1974
August, 1974
October, 1974
November, 1974
January, 1975
March, 1975
April, 1975
June, 1975

0(31)
—
—
48(25)
—
62(16)
70(17)
—
0(36)
—
0(15)
100(8)
—
67(9)

Mile 53.OR
—
0(39)
—
74(49)
—
46(33)
0(22)
—
0(51)
—
46(11)
75(4)
—
42(26)

Mile 208.6L
—
—
19(83)
—
30(47)
30(37)
—
26(35)
—
0(20)
0(8)
—
100(10)
—

Mile 208.6R
—
—
0(28)
—
9(11)
75(4)
—
0(12)
—
0(10)
0(7)
—
0(0)
—

Mean litter size of Peromyscus maniculatus as determined
by embryo counts, for this was 4.67 (n = 3). Flake (1974) found
mean litter size of this species to be 4.70, as indicated by
embryo counts. MacMillen (1964) found that southern
California populations of deer mice had a mean litter size
of 4.30. Unfortunately, the small sample sizes prohibit
us from reaching any conclusions concerning litter sizes
of this species in the canyon. We found that female
reproductive activity was limited to the months of March
(100 percent, n= 5), April (75 percent, n = 4; 25 percent,
n = 5) and June (60 percent, n = 5; 40 percent, n = 5;
62 percent, n = 8). MacMillen (1964) captured pregnant
females every month from December to May in southern
California.
From embryo counts we established a mean litter size
for Peromyscus boylii of 3.17 (n = 6). This compares
favorably with the data of Jameson (1953). During our
live-trapping studies we did not find any reproductively
active female P. boylii. Jameson's (1953) data indicate
two breeding periods per year in the Sierra Nevada, one
during May and a second in September. Reproductive
biology of this species deserves further study in the
canyon.
Reproductive biology of Neotoma albigula
is poorly known in the canyon. We have no data on litter
sizes or reproductive cycles of this species in the canyon.
Finley's (1958) data from embryo counts show a mean litter
size of 2.19 for N. albigula in Colorado and that reproduction
was usually limited to Aprl, May and June.
Mean litter size, of Neotoma lepida was 2.67 (n = 3)
as determined by embryro counts. Burt (1934) reported that
N. lepida bore 4.00 young per litter while MacMillen's
(1964) study indicated a mean litter size of 2.7, as
determined by embryo counts. On the live trap grids at
mile 52.5R reproductively active females were captured
in March (89 percent, n = 9), April (60 percent, n = 5)
and June (44 percent, n = 9; 44 percent, n = 18). At
mile 53.0 reproductively active females were captured
only in June (33 percent, n = 9). In Colorado young
N. lepida are born in early spring and early summer
(Finley 1958). While in southern California MacMillen
(1964) found pregnant and lactating females between November
and May.
Although our sample sizes for most species are small,
101

two general trends are reflected by the data. First, mean
litter sizes reported herein are generally larger than
those reported elsewhere. Secondly, reproduction is
generally confined to the spring and summer months. Our
data for R. megalotis, P_. boylii and N. albigula are
inconclusive. However, five other species or rodents
(Perognathus intermedius, P_. f ormosus, P. crinitus,
P_. maniculatus and N. lepida) limited reproductive
efforts to the spring and early summer months. The
P_. eremicus showed evidence, at one study site, of
reproductive activity in January, otherwise reprodution
was limited to the spring and early summer months.
The available information suggests that a reproductive
period confined to one season of the year. This is
contrary to the findings of MacMillen (1964) for P.
eremicus and Moor and Bradley's (1974) data for
P_. crinitus. It is plausible perhaps that by increasing
litter sizes, the riparian zone rodents are able to
concentrate reproductive activity into the most favorable
time of the year (i.e.; spring) when sufficient resources
for parents and young are available.
SUMMARY
The demographic data yield several generalizations
regarding the small mammals of the riparian zone.
1. The beach and terrace rodent communities
should be considered as separate entities in spite
of the opportunities for exchange of individuals across
ecological borders. Beach communities tend to be less
stable, less productive, and very slightly more complex
with respect to species diversity.
2. Intracommunity structural analysis indicates
a positive series of relationships between single
species' population stability, mean rank (i.e.,
importance), rank positional stability, and ecological
distributional evenness. If all these are interpreted
as indicators of ecological success, then P_. eremicus
is the most successful small mammal in the riparian
zone of the Grand Canyon.
3. Home range data indicate an inhibitory effect
of high temperature upon movement in at least two
species. Home ranges are apparently linear in
horizontal distribution and, in the special case of
a beach restricted species, they tend to be oriented

102

parallel to the Colorado River.
4. Survivorship is very low and suggests a nearly
annual population turnover rate. Low survival in the
riparian system tends to be associated with a heavy
investment in the colonization of the new (12 year-old)
beach habitat.
5. Diets of sympatric cricetids were studied at mile
52.5R and 208.6L during the spring and early summer
of 1974. Five species of cricetids were studied at
mile 52.5R. Two beach dwelling species JR.. megalotis
and P_. boylii) were most dependent upon greenery.
The precise mechanism that permits the coexistance
of the two species is currently unknown. We are now
examining diets and habitat characteristics with more
precise methodology in hopes of determining how resources
in the beach habitat are allocated.
6. P. maniculatus also preferred the beach habitat
of the riparian zone at mile 52.5R. Those mice
utilized insects to a greater degree than did
any other species. Insects were more abundant
on beach habitats than on terrace habitats in the
canyon. Insects were also the most important
item of P_. crinitus, a species that typically
is found in association with washes, cli.ff faces and
talus slopes.
7. P. eremicus were most reliant upon green vegetation.
Insects and seeds were of less importance. P. crinitus
were ubiquitous in all habitats within the riparian
zone.
The diets of two species of cricetids were
analyzed at mile 208.6. In contrast to mile 52.5R,
P_. crinitus at mile 208.6 were more dependent upon
green vegetation. However, these mice were not
captured in habitat similar to that found on the live
trapping grid. P_. eremicus were captured in all
habitats at mile 208.6L. Green vegetation was the
most important food category in the diet of this
species.
8. The low representation of seeds in cricetids diets
in the riparian zone of the Canyon is puzzling. Seed
production is probably greatest on the terraces yet
the only cricetid studied that regularly occurs on

103

the terrace, P. eremicus, does not rely heavily upon seeds.
Terrace dwelling Perognathus spp. might be better suited
to exploit this resource. Insects were an important
resource in the diets of all the cricetids we examined during
the study, although different degrees of exploitation were
apparent.
9. Analysis of reproduction in nine species of rodents
found in the riparian zone of the canyon revealed two
interesting trends. Mean litter sizes reported herein
are generally larger than those reported elsewhere.
In addition, reproduction is generally confined to
the spring and summer months. Our data for two species
(P. crinitus and 1?. eremicus) are contrary to the findings
of other authors who have studied reproduction of these
species. Productivity within the riparian zone might
be such that all reproductive activity is concentrated
into the more favorable spring and early summer months.
Our future efforts will be directed toward examining
seasonal productivity and its role in reproduction of
riparian zone rodents.

lOU

REFERENCES CITED
Bailey, N. T. J. 1952. Improvements in the interpretation
of recapture data. J. Anim. Ecol. 21:120-127.
Burt, W. H. 1934. The mammals of southern Nevada.
San Diego Soc. Nat. His. 7:375-427.

Trans.

Carothers, S. W., R. R. Johnson and S. W. Aitchison. 1974.
Population structure and social organization of
southwestern riparian birds. Amer. Zool. 14:97-108.
Chew, R. M. and A. E. Chew. 1970. Energy relationships of
the mammals of a desert shrub (Larrea tridentata
community. Ecol. Monogr. 35:355-375.
Chew, R. M. and F. B. Turner. 1974. Effect of density
on the population dynamics of Perognathus formosus
and its relationships within a desert ecosystem.
U. S./IBP Desert Biome Res. Memo 74-20. 9 pp.
Egoscue, H. J. 1964. Ecological notes and laboratory
life history of the canyon mouse. J. Mamm.
45:387-396.
Finley, R. B., Jr. 1958. The woodrats of Colorado: distribution and ecology. Univ. Kansas Publ., Mus. Nat.
His. 10:213-552.
Flake, L. D. 1973. Food habits of four species of rodents
on a short-grass prairie in Colorado. J. Mamm.
54:636-647.
. 1974. Reproduction of four rodent species in a
short grass prairie of Colorado . J. Mamm. 55:213-216.
Franz, C. E., 0. J. Reichman and K. M. Van De Graaff. 1973.
Diets, food preferences and reproductive cycles of
some desert rodents. Prog_ Rept. Desert Biome, IBP,
RM 73-24:1-128.
French, N. R., B. G. Maza, H. 0. Hill, A. P. Aschwanden
and H. W. Kaaz. 1974. A population study of irradiated
desert rodents. Ecology Mono. 44:45-72.
Goldman, E. A. 1937. The Colorado River as a barrier in
mammalian distribution. J. Mamm. 18:427-435.

105

Golley, F. B., K. Petrusewicz and L. Ryszkowski, eds. 1975.
Small mammals: their productivity and population dynamics,
IBP 5. Cambridge Univ. Press, Cambridge. 451 pp.
Hayne, D. W. 1949. Calculation of size of home range.
Mamm. 30:1-18.

J.

Hoffmeister, D. F. 1971. Mammals of Grand Canyon. Univ.
of Illinois Press, Urbana and Chicago. 183 pp.
Hubbard, J. P. 1971. The summer birds of the Gila Valley,
New Mexico. Nemouria, 1-35, Occ. Pap., Deleware Mus.
Nat. His., May 13, #2.
Jameson, E. W., Jr. 1953. Reproduction of deer mice
(Peromyscus maniculatus and P_. boylii) in the Sierra
Nevada, California. J. Mamm. 34:44-58.
Koeppl, J. W., N. A. Slade and R. S. Hoffman. 1975. A
bivariate home range model with possible application
to ethological data analysis. J. Mamm. 56:81-90.
Krebs, C. J. 1966. Demographic changes in fluctuating
populations of Microtus californicus. Ecol. Monogr.
36:230-273.
MacArthur, R. H. 1955. Fluctuations of animal populations,
and a measure of community stability. Ecology
36:533-536.
M'Closkey, R. T. 1972. Temporal changes in populations
and species diversity in a California rodent community.
J. Mamm. 53:657-676.
MacMillen, R. E. 1964. Population ecology, water relations
and social behavior of a southern California semidesert
rodent fauna. Univ. Calif. Publ. in_ Zoology 7:1-59.
May, R. M. 1973. Stability and complexity in model ecosystems.
Princeton Univ. Press, Princeton, N. J.
Moor, K. S. and G. Bradley. 1974. Ecological distribution
and reproduction of the canyon mouse in southern Nevada.
Abstracts, Eighteenth Annual Meeting, Ariz. Acad. Sci.
9:9.
Pielou, E. C. 1975. Ecological diveristy.
Sons, New York, N. Y.

106

John Wiley and

Pimentel, D. 1961. Species diversity and insect population
outbreaks. Ann. Entomol. Soc. Am. 54:76-86.
Reichman, 0. J. 1975. Relation of desert rodent diets
to available resources. J. Mamm. 56:731-751.
Reichman, 0. J. and K. M. Van De Graaff. 1973. Seasonal
activity and reproductive patterns of five species of
Sonoran Desert rodents. Amer. Midi. Nat. 90:118-126.
. 1975. Association between green vegetation
and desert rodent reproduction. J. Mamm. 56:503-506.
Shannon, C. E. and W. Weaver.
theory of communication.
111.

1963. The mathematical
Univ. of 111. Press, Urbana,

Sokal, R. R. and P. H. S. Sneath. 1963. Principals of
numerical taxonomy. W. H. Freeman and Co., San Francisco.
Vaughan, T.A. 1974. Resource allocation in some sympatric,
subalpine rodents. J. Mamm. 55:764-795.
Whitford, W. G. 1976. Temporal fluctuations in density and
diversity of desert rodent populations. J. Mamm.
57:351-369.

107

CHAPTER VI
BIRDS OF THE COLORADO RIVER
Steven W. Carothers
N. Joseph Sharber
INTRODUCTION
Studies on the avifauna of the Grand Canyon region,
particularly within the inner gorge of the Canyon or along
the Colorado River have not been extensive. Ornithological
investigations began in the late 1920's and early 1930's with
the earliest publication treating the birds of Havasu
Canyon (McKee, 1927), soon followed by a second paper (Jenks,
1931) also on the birds of the Havasu Canyon area. The first
checklist of the birds of the Grand Canyon area was
published by Grater (1937) and Bailey (1939) followed
with an anecdotal account of all that was known
about the birds in the Grand Canyon up to that time.
From 1939 to
were periodically
naturalists, most
Park Service (see
and McKee, 1939).

the late 1950's, the bird checklists
revised and updated by various
of whom were employees of the National
Bryant, 1945a, 1945b, 1952; Huey, 1939

The Park wildlife observation files are replete with
bird observations for the intervening years, but little
recent information has been published with the exception
of the annual Christmas bird counts (see Hill, 1969, 1970,
1971; Leishman, 1973 and Ochsner, 1972) and more recently,
our investigations have resulted in two publications
(Carothers and Johnson, 1975a and Johnson et al., 1976)
dealing with the distribution and status of the birds of
the Grand Canyon area, with particular emphasis on the
Colorado River.
Unfortunately, the majority of the published works
on the avifanua within the Grand Canyon area are not
quantitative. This is especially distressing since many
habitat changes have taken place, particularly along
the Colorado River. Without any substantial information
on the birds of the Colorado River through the Grand
Canyon prior to the construction of Glen Canyon Dam,
we have no positive way of knowing how the avifauna
found in this area now compare with the pre-dam days
when the Colorado River was wild. As a direct influence
of the dam, the riparian (streamside) habitat of the

109

Colorado River is still changing. Gone forever are
the vegetation scouring floods of pre-dam days and each
year we witness an increased growth and proliferation
of this "new" riparian habitat. (See Chapters I and II
of this report for full description of these changes.)
This report deals with the birds that are found
throughout the year along the Colorado River from Lees
Ferry to the Grand Wash Cliffs. Breeding bird density
information is presented for only the area from Lees
Ferry to Diamond Creek, a distance of 225 miles.
As there is no previous account of the birds along
the river, this information must serve as our
"baseline" level, a yardstick or indicator of future
changes in the distribution and abundance of birds
within the inner gorge of the Grand Canyon.
METHODS
Although the time span of this project covers the
period 1 June 1974 to 30 June 1976, the field work on the
birds of the Colorado River and the inner gorge of the
Grand Canyon has been underway since 1968. For the most
part, the field work has consisted of recording breeding
and migrating birds as they were encountered during our
forays into the little known areas of the Grand Canyon
region. In an attempt to quantify the relative
densities of the breeding birds along the 225 mile river
corridor from Lees Ferry to Diamond Creek, we
recorded the number of individuals of each species
per mile of river that were encountered as we floated
the river in oar-powered boats. During the breeding
season (April-August) the activities of the birds were
also recorded (e.g., singing, nest construction, feeding
young etc.) and most of the relative density and
absolute density data have been based on singing males
encountered along the river. The absolute density
data cannot be considered in a literal sense as the
absolute numbers of birds within the study area, but
only as the absolute numbers we encountered. The
censusing method employed, and the speed with which
our craft were moving, have undoubtedly resulted in many
individuals being overlooked. The censusing usually
began early in the morning, as soon as the boats departed
from the previous night's camp. Normally, we moved at
a relatively constant speed (2-5 mph), and censusing
was discontinued if we stopped during the day, or if
the weather was such that the bird activities would
be obviously affected (e.g., wind or rain). Migrating

110

birds were censused in the same manner throughout the
year. An attempt to duplicate this data gathering
process on a motor-powered craft was undertaken with
poor results. The noise of the motor and the faster
rate of speed resulted in a substantial number of birds
being overlooked, that would otherwise have been
recorded on an oar-powered craft.
Over 20 separate river expeditions, covering every
month of the year with the exceptions of February and
December, are represented by the data presented herein.
In addition, at least 25 separate backpacking or land based
(helicopter support) forays into the tributaries of the
Colorado River and/or high interest areas along the
river (e.g., Nankoweap mile 52.0; Cardenas Creek, mile 71.0;
Granite Park, mile 209.0) were also a source of data on the
status and distribution of birds within the study area.
Bird species diversity was determined by using the
diversity index, H 1 , as developed for biological parameters
by MacArthur and MacArthur (1961). The formula used to
compute this value is H' = -<Pilog e pi, where pi equals
the relative density of each species. The evenness of
distribution of the species, J', is determined by
dividing B" by the maximum possible R" (log e N).
RESULTS AND DICUSSION
Birds Recorded in the Study Area
(Lees Ferry, mile 0.0 to the Grand Wash Cliffs, mile 279.0)
Approximately 240 species of birds have been recorded in
the Grand Canyon region (see Johnson, et al. 1976), an area
encompassing not only the Colorado River and its riparian
habitat, but also the wide variety of habitat types found
throughout the Grand Canyon area. These additional
habitats include the spruce-fir-aspen, ponderosa
pine, pinyon-juniper, oak woodland, chaparral, and desert
scrub associations. Each of these vegetative associations
contains an assemblage of breeding birds typical to that
particular habitat, assemblages which are generally distinct
between habitat types. The riparian habitat of the inner gorge
also contains its distinct assemblage of breeding birds,
yet during the non-breeding season, or migratory season,
the riparian areas are frequented by birds that breed in
all Grand Canyon habitats and some that breed elsewhere
throughout the United States and Canada. The riparian habitat
of the inner gorge provides a natural corridor for migratory

111

movements of birds on their way to or from breeding grounds.
Whether or not a species is on its way to the spruce-firaspen forests of the north rim (e.g., Ruby-crowned Kinglet)
or the pinyon-juniper forest of the south rim (e.g.,
Common Bushtit) or the wetlands of the far north (e.g., Canada
Goose) it will use portions of the Grand Canyon riparian
corridor as it makes its way to the breeding grounds.
The reasons for this are as varied as they are simple.
The very depth and size of the entire Grand Canyon
system provide for striking climatic differences between
canyon bottom and canyon rim. Generally, the spring
and fall weather along the Colorado River is much more
hospitable than that of either rim. The deciduous
riparian vegetation enjoys a longer growing season
within the Canyon, providing insects with a longer
period of food, which in turn provides a predictable
food source for some migrating birds. The water of
the Colorado River is an important resource for
migrating birds that should not be overlooked,
particularly in the arid Southwest where the presence or
absence of running water in some cases is the single
most important factor in determining the wildlife
resources of an area (see Carothers and Johnson, 1975b).
Although we know that only 41 species (high compared
to non-riparian areas in Arizona; e.g., transition zone
or spruce-fir) of birds utilize the Grand Canyon riparian
habitat for breeding (Table VI-1), we have recorded
178 species (see Appendix VI-1) representing 15
orders and 42 families, within the area. Thus, almost 80
percent of the bird species that are found along the Colorado
River are or. their way to breeding grounds elsewhere.
In addition to recently published revisions of bird
checklists and new distributional information concerning
Grand Canyon birds (see Carothers and Johnson, 1975a and
Johnson et al. 1976), we include here, eight additonal species
that have not been previously recorded in the Grand Canyon
region. They are as follows: White Pelican, Common
Goldeneye, Bonapart's Gull, Herring Gull, Forster's Tern, Lesser
Nighthawk, Wied'scrested Flycatcher, and Blackburnian Warbler
(hypothetical).
Seasonal Distribution of Birds in Study Area
Figure VI-1 illustrates the monthly distribution of the
numbers of species that may be found within the study area
throughout the year, and Figure VI-2 illustrates the relative
differences in actual densities that occur throughout

112

Table VI-1.—The breeding birds of the Colorado River from
Lees Ferry (mile 0) to Diamond Creek (mile 225).

Species

Preferred
Relative
Habitati/ Statusl/ Density

Turkey Vulture
Cooper's Hawk
Red-tailed Hawk
Golden Eagle
Prairie Falcon
Peregrine Falcon
Sparrow Hawk
Spotted Sandpipe r
Mourning Dove
Roadrunner
Great-horned Owl
Black-chinned
Hummingbird
Ladder-backed
Woodpecker
Ash-throated
Flycatcher
Black Phoebe
Say's Phoebe
Willow Flycatche r
Raven
Dipper

Average Absolute
Density Pairs/225 mi.—/

B
A
B
B
B
B
A
A
A
B
B

SR
SR
PR
PR
PR
PR
PR
SR
SR
PR
PR

0.76
0.11
0.50
0.25
0.15
0.15
0.84
6.44
9.92
0.11
0.11

6.8
1.0
4.5
2.3
1.4
1.4
7.5
57.0
87.8
1.0
1.0

A

SR

1.32

11.7

A

SR

0.11

1.0

A
A
A
A
B
A

SR
SR
SR
SR
PR
PR

Canyon Wren
Rock Wren
Blue-gray
Gnatcatcher
Phainopepla
Starling

B
B

PR
PR

A
A
A

SR
SR
SR

Lucy's Warbler
Yellow Warbler
Yellowthroat

A
A
A

SR
SR
SR

1.09
9.7
0.92
8.2
2.71
24.0
0.11
1.0
3.31
29.3
(not on river, in
flowing tributaries)
11.45
101.3
8.98
79.5
1.27
11.3
0.22
2.0
(only in heavily
popula ted areas)
19.67
172.5
1.86
16.5
0.92
8.2
(cent, on next page)

1/

A = riparian vegetation
B = desert scrub, talus slopes and vertical cliffs

2/

SR = Summer resident; PR = Permanent resident

3/

Average Absolute Density determined from field data
gathered in April, May and June.

113

Table VT-1.—cont.
Yellow-breasted
Chat
House Sparrow
Northern Oriole
Brown-headed
Cowbird
Blue Grosbeak
Indigo Bunting

A
A
A

SR
PR
SR

A
A
A

SR
SR
SR

Lazuli Bunting

A

SR

House Finch
Lesser Goldfinch
Black-throated
Sparrow

A
A

SR
SR

B

PR

Total

2.03
0.11
0.22

18.0
1.0
2.0

1.01
9.0
2.88
25.5
(only in Tapeats, Deer
and Havasu Creeks)
(only in Tapeats, Deer
and Havasu Creeks)
15.25
135.0
0.41
3.7
0.11

1.0

100.00

884.7

114

Figure VI-1.—Monthly distribution of the number of bird
species to be found within the study area.

115

Figure VI-2.—The relative occurrence of resident vs.
migrant birds by month on the Colorado River
from Lees Ferry (mile 0) to Diamond Creek
(mile 225).

116

the year between resident and migratory species. The months
of April and May show the greatest diversity in numbers
of species occurring within the study area, with 77 and 70
respectively. These high numbers reflect an overlapping
of summer residents, some of which have already begun
breeding by early April, and migrants, still on their
way to northern breeding grounds. By June, most if not ail
of the migrants are gone, leaving only the breeding species
on the study area. Most breeding activity is over by late
June,- however, the fall migration does not begin until midAugust, when we observe the number of species increasing again,
building up through September and early October (pers.
observations, quantitative October data lacking). By
November, the migration is essentially over and the diversity
of birds remains relatively constant through November and
December (pers. observations, quantitative data lacking for
December). During both the years 1974-1975 there was
an influx of many species of migratory waterfowl during late
December and early January, causing the increase in numbers
of species observed in January. By mid to late March, most
of the waterfowl species, with the exception of the teal
species, had left.
Figure VI-2 dramatically illustrates the periods of migration
and breeding within the study area. During the months April
through August, at least 85 percent of the birds observed
were resident species. By September, however, this drops
to about. 40 percent resident species, 60 percent migratory.
Although good quantitative data are lacking for October,
November shows that 17 percent of the birds are resident species.
This low level of resident species is maintained through
January and presumably February (data lacking), and then
begins to increase in early March (56 percent resident).
Breeding Birds within the Study Area
A total of 41 species are known to breed within the
study area. Of these, 27 species utilize the riparian
vegetation as nesting habitat, while the remaining 14 nest
in association with the surrounding desert scrub, the
vertical cliffs or the loose talus slopes of the inner
canyon. Three of the species which prefer the vertical
cliff areas for nesting habitat, the White-throated Swift,
the Violet-green Swallow and the Cliff Swallow are not
considered in this section of the report, but are treated
separately below. Although these species form a part of
the breeding bird community of the inner canyon, they
are typically colonial or partially (locally) colonial and

117

as such, are impossible to report as number of birds per
mile. In addition, the three above mentioned species
belong to a feeding or foraging guild (aerial insect
feeding) that naturally separates them from the ground
and vegetation foraging birds that represented the
remaining 38 species of breeding birds of the inner
canyon. The flycatchers, Willow Flycatcher and Ash-throated
Flycatcher are included in the ground and vegetation
foraging category here, as the majority of the aerial
insects they capture, originate from the vegetation along
the banks of the river.
Table VI-1 presents the general habitat preference (riparian
vegetation or cliff, talus or scrub), status (permanent or
summer residents), relative density and average number of
breeding pairs encountered within the study area. The
average density of the breeding birds for the entire
225
mile study area was 884.7 pairs, or 3.93 pairs per
mile. The bird species diversity (BSD) was 2.69, with
an evenness of distribution (J') of 0.76. The 12 permanent
resident species made up 26 percent of the total population
density, while the 2 3 summer resident species accounted
for the remainder. It is interesting to note, that the
riparian vegetation, habitat type A (see Table VI-1)
was preferred by 74 percent of the total population
of breeding birds in the inner canyon. Of these
74 percent, only two species were permanent residents. Thus,
it may be generalized, that the summer resident species of the
inner gorge are almost exlusively restricted to the narrow belt
of riparian vegetation along the river, while the permanent
residents are restricted to, or prefer, the desert
scrub, talus or vertical steep cliffs adjacent to the
riparian habitat. Some of the species have a clear preference
for the band of green vegetation immediately adjacent
to the river and below the old high water line (see
Dolan et al., 1974). These species are clearly
increasing in density from year to year and probably
have been ever since the flood gates of Glen Canyon
Dam were closed in 1963. Since that time, the vegetaion
scouring floods that would periodically denude the beaches
below the high water line have been curtailed. The species
most dramatically affected by this new stabilized vegetative
community are as follows: Willow Flycatcher, Bell's Vireo,
Yellow Warbler, Yellowthroat, Yellow-breasted Chat,
Northern Oriole, Brown-headed Cowbird and Blue Grosbeak.
These species account for about 14 percent of the total
breeding bird population along the Colorado River.
These are the animals that will continue to increase
in density as long as the vegetation below the old high

118

water line continues to proliferate. Also these are
probably species that did not occur with significant
frequencies along the river during the pre-dam era. Other
species that are equally dependent upon this green
vegetation such as Lazuli and Indigo Buntings might
be expected to begin utilizing this vegetation along
the banks of the river as well as the heavily vegetated
tributaries they are now in. Although birds such as the
Lucy's Warbler and the House Finch primarily utilize
the high water line vegetation (Acacia, Prosopis, Celtis,
Fallugia, etc.) we feel that their densities are
also influenced by the proliferating green vegetation
along the river as they frequently utilize this zone
for foraging.
The most common breeding bird of the study area
was the Lucy's Warbler, accounting for almost 20 percent
of the total population of breeding birds. The House
Finch was the second most common species (15 percent)
followed by the Canyon Wren (11 percent).
Four species, the Starling, the Dipper, the Lazuli
Bunting and the Indigo Bunting did not breed along
the Colorado River, but were found commonly breeding up
side canyons. The two buntings were only found in the
Tapeats and Deer Creek drainages, but the Dipper was
found in every tributary that contained permanent running
water. The Starling and House Sparrow, exotic "weed" species,
prefer only areas that are heavily inhabitated by humans.
They were found as a common breeding species at Indian Gardens,
Phantom Ranch, and Havasu campground and village.
Each of the breeding species is discussed separately in
Appendix VI-2.
SUMMARY
During this investigation, we determined that 178 species
of birds utilize the Colorado River and its riparian habitat
in the 279 mile area from Lees Ferry to Lake Mead.
Of these, only 41 species remain to breed. The majority
(74 percent) of breeding species are primarily restricted
to or prefer the narrow band of vegetation existing from the
high water line to the banks of the river, while
the remainder are restricted to the desert scrub, the
talus slopes or the vertical cliffs of the canyon walls.
Approximately 14 percent of the total breeding bird
community i s restricted to the "green" vegetation of
the river bank, the vegetation that has proliferated

119

since the construction of Glen Canyon Dam.
The breeding season within the area is April through
August, with most activity occurring from April through
June.
The most common breeding birds of the area are
the Lucy's Warbler, accounting for almost 20 percent of
the total popualtion, followed by the House Finch (15
percent) and the Canyon Wren (11 percent).
The total population density of the 225 mile breeding
bird study area was determined to be 3.93 pairs/mile, bird
species diveristy (H') was 2.69 and the evenness of distribution of the species (J') was .76.
Exotic bird species, the House Sparrow and Starling
were only found in areas of heavy human concentration.
Discussion on eight species new to the list of
Grand Canyon birds are included in this paper.

120

REFERENCES CITED
Bailey, F. M. 1939.
Canyon country.

Among the birds in the Grand
Govt. Print. Off. Washington.

Bryant, H. C. 1945a. Back-yard observations at
Grand Canyon Arizona. Gull, Audubon Association of
the Pacific 27(5):16-17.
. 1945b. The status of game birds in Grand Canyon
National Park. Ariz. Wildl.-Sportsm. 6(9):10-11.
1952. Additions to the checklist of birds of
Grand Canyon National Park. Condor 54:320.
Carothers, S. W. and R. R. Johnson. 1975a. Recent
observations on the status and distribution of some
birds of the Grand Canyon region. Plateau, 47 (4) :140-160.
. 1975b. Water management practices and their effects
on nongame birds in range habitats. Proc. of the
Sym. on Manag. of For. and Range Hab. for Nongame Birds.
USDA For. Ser. Gen. Tech. Rept. WO-1.
Dolan, R., A. Howard and A. Gallenson. 1974. Man's impact
on the Colorado River in the Grand Canyon. Am. Sci.
62:392-401.
Grater, R. K. 1937. Checklist of birds in the Grand Canyon
National Park. Nat. Hist. Bull. No. 8, Grand Canyon
Nat. Hist. Assoc.
Hill, W. 1969. Sixty-ninth Christmas bird count, Grand Canyon.
Audubon Field Notes 23:390.
. 1970. Seventieth Christmas bird count. Grand Canyon.
Audubon Field Notes 24:417.
. 1971. Seventy-first Christmas bird count, Grand Canyon.
Audubon Field Notes, 25:464.
Huey, L. M. 1939.
56:320-325.

Birds of Mount Trumbull region.

Auk,

Jenks, R. 1931. Recent bird records from Havasu Canyon.
Canyon Nature Note 7(5):37-38.

Grand

Johnson, R. R., S. W. Carothers and N. J. Sharber. 1976.
Grand Canyon Birds, field checklist. Grand Canyon Natural
History Association, Grand Canyon, Arizona.

121

Leishman, W.
Canyon.

1973. Seventy—third Christmas bird count, Grand
Audubon Field Notes 27:480.

MacArthur, R. H. and J. H. MacArthur.
diversity. Ecology, 2:594-598.

1961. On bird species

McKee, E. D. 1927. Birds of the Havasupai Canyon.
Nature Notes 2(3):2.

Grand Canyon

1939. Four species new to Grand Canyon National Park.
Condor 41:156-157.
Ochsner, D. 1972. Seventy-second Christmas bird count,
Grand Canyon. Audubon Field Notes 26:480.
Phillips, A., J. Marshall and G. Monson. 1964. The birds
of Arizona. Univ. of Ariz. Press, Tucson.
U. S. Fish and Wildlife Service. 1973. Threatened Wildlife
of the United States. Res. Publ. 114, Wash. D. C.

122

CHAPTER VII
AN INSECT INVENTORY OF GRAND CANYON
Lawrence E. Stevens
INTRODUCTION
An inventory of riparian insect life in Grand Canyon
was made over the twenty-five month interval of the project.
Specimens were prepared and identified to the Family
level and catalogued in the Museum of Northern Arizona
insect museum. Small collections of Arachnida and
other Arthropoda were also made however, most of this
material is, as yet, unidentified.
This represents the first comprehensive general
collection of insects from Grand Canyon over an extended
period of time. Previous researchers, such as Garth (1950)
and Polhemus and Polhemus (in press) were concerned only
with individual taxa and not with Grand Canyon insect
fauna as a whole. The amount of collecting time spent
in the Canyon by these and other workers was usually of
limited duration as the difficulties of travel there
generally prohibited more than a single collecting
expedition. The larger, more attractive species have
been collected (e.g., Schellbach's collections in the
National Park Service museum at the South Rim) while
smaller, less distinctive groups have been largely
ignored. Also, specimens have been deposited in various
museums around the United States but nowhere has an
extensive collection of Grand Canyon insects been
brought together as a single body of material. This
collection, now organized to facilitate further taxonomic
determination, is an initial step in the ecological
investigation of riparian insect life in Grand Canyon.
METHODS AND MATERIALS
Approximately two hundred man-days were spent in
Grand Canyon sampling insects during the period of
study. Collection sites ranged from Lees Ferry to
Pierce Ferry along the Colorado River and collections
were made in all major tributaries, in many minor sidecanyons and in all major places of interest along the
river in Grand Canyon. Extensive collections were made
at the following sites: Lees Ferry (mile 0.0, R ) , the
19 mile area (L), Vasey's Paradise (mile 31.9, R ) ,

123

Nankowcap (mile 52.5-53.0, R) , Cardenas Creek (mile
71.0, L ) , Unkar (mile 72.5, R), 75 mile area (L),
Phantom Ranch (mile 87.7, R), Phantom Creek, Hermit
Creek (mile 94.9, L) , Elves Chasm (116.4, L) , Forster
Camp (122.9, L ) , Tapeats Creek (133.8, R), Thunder
River, Mohawk Canyon (171.4, L), 182 mile area (R),
Granite Park (mile 208.6, L ) , Diamond Creek (mile
225.8, L), Spencer Canyon (mile 246.0, L ) , and Emery
Falls area (mile 274.3, L). Insect life in Grand
Canyon was sampled during every month of the year
except December.
A variety of sampling methods were employed.
General collection of specimens was performed with
fine-mesh, canvas and dip nets, water-color paint
brushes, forceps, aspirators, beating sheets and eyedroppers, as well as by hand (Peterson 1959). A number
of attracting techniques were employed including the
use of 15 watt ultra-violet light, white light (approximately 50 hours of black and white light trapping was
performed), carrion traps and sweet-bait traps.
Parasites were removed from birds, bats, rodents,
and other mammals. Gall-forming and driftwood-inhabiting
species, and species attacking dead, standing trees
were collected, as were dung-inhabiting species. Both
lentic and lotic aquatic habitats were sampled. Stomach
contents from collected fish, amphibians, reptiles and
birds were also examined for insect specimens.
Because of the harshness and difficulty of travel
in Grand Canyon preparation of insect material at the
collection sites was impossible. Specimens were transported
in acetate envelopes or in vials of 80 percent isopropyl alcohol to the laboratory and prepared and
identified there using a variety of taxonomic keys
(Appendix VII-3) .
RESULTS AND DISCUSSION
More than twelve thousand insect specimens in 20
orders and 247 families have been prepared and identified
thus far. Appendix VII-1 lists the families of insects
collected in Grand Canyon. Locations between which
specimens have been collected, general distribution
along the Colorado River, relative abundance (estimated
from field observations as well as from collected
specimens), habitat preferences, vegetation associations

124

(if any were noted) and methods of collections are also
indicated.
Generalizations concerning insect life in Grand
Canyon are not easily made with the amount of data
available. As expected, species compostion gradually
changes as one moves from the Great Basin and Upper
Sonoran habitat zones to the Lower Sonoran and Mojave
Desert zones. While this alteration is most evident in
Diptera (probably the dominant order in the riparian
ecosystem) and in Coleoptera, more data are needed
before ecological boundaries along the Colorado River
can be clearly delineated.
Grand Canyon may act as a barrier to some (particularly
aquatic) species. The Belostomatids should be represented
in the Canyon as the ranges of several species overlap
the area. Abedus in this study was collected only in
Spencer Canyon (mile 246.0, L) at the end of Grand
Canyon. Great distances between suitable aquatic
habitas (warm, lentic situations in general) probably
prevent this group from moving into the Canyon.
A comparison of riparian insect diversity in Grand
Canyon with riparian habitats at similar elevations in
southern Arizona indicates that, at least in the case
of aquatic Heteroptera (Hemiptera), the Canyon is
relatively depauperate (Polhemus and Polhemus, in
press). This is a further indication of the "barrier
effect" the Canyon exerts on some populations.
It is likely that localized populations of insects
occur in many instances, relatively isolated from
external genetic influx. Notonecta lobata (Notonectidae),
common in Grand Canyon, is considered isolated from the
rest of its range v.'hich is centered in southern Arizona
(Polhemus and Polhemus, in press). So too, certain
sheltered habitats within the Canyon permit the survival
of some species which could not otherwise exist at
those low elevations. For example, Plecoptera and some
Trichoptera occur only in the coolest side-streams
(Royal Arch Creek, Thunder River and Tapeats Creek). In
these cases Grand Canyon serves to protect some nichespecific populations.
There are, therefore, at least three ways in which
Grand Canyon affects insect population movements. It
may act, in a broad sense, as a channel between two

125

major habitat zones (Great Basin and Mojave Desert).
It may prevent the immigration of some forms, thus
acting as a barrier to population movement. Lastly, it
may protect and preserve relatively isolated populations
by providing unique and specific habitats. A species'
mobility and niche requirements will largely determine
its population movements within Grand Canyon.
The only insect family recorded actually using the
Colorado River was Chironomidae. The several Hydrophilid
beetles taken from the River (apparently having entered
inadvertantly) were unable to cope with the cold, swift
water. No dredging was performed in the River during
this investigation and more groups may be recorded with
further study; however, as an aquatic habitat the
Colorado River is generally non-productive.
Presumably the great turbulence and sediment load,
dramatic water fluctuations and cold temperatures serve
to limit aquatic insect life in the Colorado River.
Before Glen Canyon Dam was constructed concentrations
of insects in the Colorado were probably higher due to
warmer water and more gradual fluctuations in water
level. Pre-dam terrestrial riparian insect densities
may have been somewhat lower because of the scouring
effect of floods and limited amount of beach vegetation.
Little data exist, however, to confirm these hypotheses.
SUMMARY
This inventory can only be seen as an initial,
basic effort in the tremendously large task of the
study of insect ecology in Grand Canyon. If the National
Park Service is sincere in its quest into the study of
entomological resources in Grand Canyon, a study period
of twenty to forty man/years should provide a solid
base of entomological data. In this amount of time
species determinations, further collecting and mapping
of species ranges and overall insect communities could
be accomplished.
Several specific problems with regard to man's
inadvertant affect on insect populations are arising
along the Colorado River. Harvester Ant (Pogonomyrex
californicus) usually occur in low densities along the
beach-terrace interface near the river in Grand Canyon.
On many heavily used beaches, however, Pogonomyrex
densities are enormous and are probably directly

126

related to human activity (camping and food disposal)
there. Because of their great numbers and painful
sting this species represents a minor health hazard and
a source of discomfort for the many River users affected.
With a modicum of research into control methods this
problem species could be significantly reduced in an
environmentally non-disruptive manner.
Flesh Fly (Sarcophagidae) and Blow Fly (Calliphoridae)
populations, common in Grand Canyon, are frequently
linked with sanitation problems. If a comprehensive
program of general sanitation in beach areas is effected,
particularly with regard to fecal and organic waste
disposal, fly densities will diminish. If no program
is initiated some fly-vectored health problems may
arise.
Appendix VII-2 lists some Arachnida found in Grand
Canyon. The only potentially dangerous groups of
arachnids found along the River were scorpions (at
least five species in two Families) and Black Widow
Spiders (Latrodectus spp., Family Theridiidae). The
most common scorpion in Grand Canyon along the upper
section of the Colorado River is the occasionally
deadly Centruroides s_. sculpturatus Ewing (Family
Buthidae). Though quite common, because of their
secretive habits neither scorpions nor Theridiids pose
significant threats to visitor use of the Colorado
River.
REFERENCES CITED
Garth, J. S. 1950. Butterflies of Grand Canyon National
Park. Grand Canyon Nat. Hist. Assoc., Bull. #11.
Peterson, A. 1S59. Entomological techniques: how to
work with insects. 9th ed. Edwards Brothers, Inc.
Ann Arbor, Mich.
Polhemus, J. T. and Polhemus, M. s. In press. Aquatic
and semi aquatic Heteroptera of the Grand Canyon
(Insecta: Hemiptera). Great Basin Naturalist.

127

CHAPTER VIII
INSECT PRODUCTION ON NATIVE AND INTRODUCED
DOMINANT PLANT SPECIES
Lawrence E. Stevens
INTRODUCTION
In addition to general collecting, determination
of insect production on the dominant riparian plant
species was attempted on a small scale. Introduced
plant species have invaded much of the riparian habitat
and in some cases exist in dominant and predominant
capacities. An effort was made to determine insect
population densities, diversities and biomass on several
introduced and native dominant plant species. These
data should indicate the degree to which invading plant
species have been incorporated into the riparian ecosystem.
METHODS AND MATERIALS
Determination of relative insect densities and
diversities among dominant plant species along the
Colorado River was attempted during the spring and
summer of 1975. The plant species sampled included
Salix gooddingii, Prosopis juliflora, Acacia greggii
and Tamarix chinensis as well as several others. Fifty
uniform sweeps with a canvas and mesh collecting net
were made in full sunlight in pure stands (25m
or more) of a dominant plant species. Insects were
killed with sodium cyanide gas and transported to the
laboratory for identification and counting. Using this
technique general shifts in insect populations throughout
the season were demonstrated for the various dominant
plant species.
Absolute densities, diversities and biomass of
insects on each dominant plant species were determined
at the Unkeir area (mile 72.5R) during a four-day period in May,
1975. This was accomplished by "bagging" entire branches
or plants of the dominant species in 3 mil plastic
garbage bags. Ethyl acetate was used to kill the
insects which were then removed from the plant and
transported to the laboratory. There the specimens
were dried, weighed, counted and identified to family
level. All green material was removed from the collected
branch or plant, dried and weighed. Collections were
made during mid-day in an attempt to standardize the

129

Figure VIII-1.—Average relative numbers of insects
and average relative numbers of families of insects on beach
and terrace blooming plant species. Beach plant species
are shown on the left and terrace plant species are shown
on the right. Note (1) the high relative insect production
on blooming non-native plant species, and (2) the higher
densities and diversities of insects on beach species in
general.

130

activity level. This technique provided a comparison
of absolute insect densities, diversities and biomass
per unit of plant material between the dominant plant
species at Unkar in early May, 1975. The labor involved
with this technique for a single worker proved prohibitive
for more than one collection site.
RESULTS AND DISCUSSION
Average relative insect densities and diversities
on some plant species along the Colorado River are
shown in Figure VTII-1. This figure indicates the
degree to which introduced species (Melilotus albus,
Tamarix chinensis and Alhagi camelorum) are utilized by
insects during the blooming phase. It is obvious from
these data that some non-native plant species are
highly successful in attracting insects. This figure
also indicates a marked drop in insect densities as one
moves away from the more richly vegetated riparian zone
and onto the terrace and talus slope areas.
Insect density and diversity during the blooming
phase were shown to contrast sharply with that of the
non-blooming phase on Tamarix chinensis. Tamarix
chinensis in Arizona blooms bi-seasonally, usually
with peak seed production in late June and late August
(Warren and Turner, 1975). Figures VIII-2 and VIII-3
illustrate fluctuations in insect densities and familial
diversities between the non-blooming and blooming
dominant species (Salix gooddingii, Prosopis juliflora
and Tamarix chinensis). In these figures the average
numbers of insects per fifty sweeps and average number
of families of insects per fifty sweeps (respectively)
are compared in non-blooming dominant plant species.
Insect densities (Figure VIII-2) nearly doubled on the
two native dominant species when blooming occurred; on
Tamarix a 655 percent average rise in density was
noted. Average insect familial diversities (Figure
VIII-3 rose by approximately 15 percent on the native
dominants and by nearly 60 percent on Tamarix. Insect
densities and familial diversities on non-blooming
Tamarix were generally lower than those recorded on
non-blooming native dominants.
Results of insect production analyses on dominant
plant species occuring at Unkar (mile 72.5R) in May,
1975, are shown in Table VIII-1 and VIII-4. Tamarix
chinensis in bloom at that time supported a lower

131

Figure VIII-2.—Average relative numbers of insects
on three non-blooming and blooming dominant plant species.
Note the extreme increase in insect density on Tamarix
chinensis in comparison with the lesser rise in insect
utilization on the two native dominant species.

Figure VIII-3.—Average relative numbers of families
of insects on three non-blooming and blooming dominant
plant species. Note, again, the sharp rise in insect
utilization of Tamarix chinensis in comparison with the
native dominant plant species' insect utilization patterns.

132

Table VIII-1. —Insect Production on Blooming Dominant Riparian
Plant Species at Unkar (Colorado River Mile
72.5R), May 8-11, 1975.

PLANT SPECIES

NUMBER OF INSECTS
g PLANT

Salix gooddingii
Prosopis juliflora
Tamarix chinensis
Tamarix chinensis (NB*)
Pluchea sericea

1.06
2.34
3.85
0.225
0.120

AVERAGE WT.
INSECTS (mg)
0.512
0.132
0.053
0.226
0.610

g OF INSECTS
kg PLANT
0.543
0.308
0.205
0.047
0.073

*NB-Non-blooming

Figure VIII-4.—An illustration from Table VIII-1 of
the biomass of insects supported on various blooming
dominant plant species at Unkar (mile 72.5R). These data
were gathered in early May, 1975. At that time in the season
blooming Tamarix chinensis supported less absolute biomass
of insects than did the native dominants. Non-blooming
Tamarix chinensis displayed only approximately 10 percent
the insect production capacity of the native dominant
species. Blooming Pluchea sericea, a sub-dominant, is
also shown to be unproductive in terms of the insect biomass
supported.

133

biomass of insect life (g insects, kg plant) than was
in evidence on either Salix gooddingii or Prosopis .juliflora
Furthermore, Tamarix chinensis supported a proportionally
larger number of smaller insects (primarily Thripidae) at that
time. Non-blooming Tamarix chinensis supported only ten percent
of the insect biomass supported on those two native dominants.
While relative insect density and diversity data (above)
indicate that utilization of blooming-phase Tamarix
chinensis by insects increases as the summer progresses,
this pattern of early bloom insect depauperacy may be
important in terms of the amount of available food for
nesting birds.
Other trends noted in insect utilization of Tamarix
chinensis were observed. Use of green Tamarix chinensis
vegetation as a food source was noted only in Acrididae
(Schistocera sp.), Cicadellidae and Buprestidae (Hippomelas
sp.). Before the main blooming phase (late April
through June) one species of Cicadellidae fed on Tamarix
chinensis, in turn attracting some predators (primarily
Salticidae). In early July Tamarix chinensis produced a
new growth of green vegetation which was apparently an
attractive food source to Schistocera, Hippomelas, and
perhaps other herbivorous insect species.
A stand of Tamarix chinensis and Prosopis juliflora
was accidentally burned in 1974 at mile 49.9R. In 1975
this site was visited and the standing dead wood was
examined. The Tamarix chinensis wood at that time was
completely free from wood-boring insect damage. In
contrast, the Prosopis juliflora wood was riddled with
holes and damage from wood-boring beetles (primarily
Buprestidae).
The data and observations above indicate that
Tamarix chinensis is not evenly incorporated into the
riparian ecosystem. Within its cycles Tamarix chinensis
insect production fluctuates dramatically in comparison
to the more harmonious shifts noted on native dominant
species. Tamarix chinensis attracts large numbers of
pollinators when blooming but supports only a very
limited insect comunity when not blooming.
This may also prove to be the case with some of
the other non-native species, though data are lacking.
Alhagi camelorum was found to be free from seed-boring
bean weevils (Bruchidae) (C. D. Johnson, pers. comm.),
yet it was heavily utilized by major orders (particularly
Coleoptera, Diptera and Hymenoptera; see Chapter VII and

13H

Appendix VTI-1) when blooming. Melilotus albus,
another non-native, was the most productive plant
species sampled when blooming (Figure VIII-1).
In terms of insect use Salsola kali and Elaeagnus
angustifolia remain, as yet, unstudied in Grand Canyon.
REFERENCES CITED
Warren, D. K. and Turner, R. M. 1975. Saltcedar
(Tamarix chinensis) seed production, seedling
establishment, and response to inudation. J.
Ariz. Acad. Sci. 10 (3):144-151.

135

Go

Figure IX-1.—Distribution of feral asses in Grand Canyon.

CHAPTER IX
DISTRIBUTION OF FERAL ASSES
Philip L. Shoemaker
INTRODUCTION
Because of the limited work done on populations and
distributions of feral asses in the Grand Canyon, the
effectiveness of past control measures are not known.
The objectives of this survey were to delineate areas
occupied by feral asses and to locate areas of highest
concentration.
STUDY AREA
Grand Canyon National Park encompasses approximately
1 million acres of Coconino and Mohave Counties in
northern Arizona. Elevation ranges from 9,125 feet on
the Kaibab Plateau, on the north side of the river to 960
feet at the head of Lake Mead.
Vegetation ranges from spruce, fir, and ponderosa pine
forests on the Kaibab Plateau to the desert scrub on the
floor of the canyon (Lowe and Brown, 1973).
Precipitation ranges from 25 inches on the Kaibab
Plateau to 10 inches in the bottom of the canyon (Green
and Sellers, 1964).
The Park has very few roads, all of which are on
the rims, and a trail system which encompasses less than
one-quarter of the park. The rest of the canyon is
accessible only by aircraft or by boat (along the river).
METHODS AND PROCEDURES
During the initial stages of the survey, Park Service
records, consisting of years of feral ass observation cards,
were sorted and the sightings plotted on maps. Since most of
the observations were made on inner canyon trails, the
survey was begun by hiking the trails. Clear Creek, Tanner,
Red Canyon, Grand View, Kaibab, Bright Angel, Hermit, Bass,
and Tonto trails were hiked. All accessible side canyons
along these trails were explored and feral ass sitings
plotted on maps.

137

Because of the size and inaccessibility of the rest of
the canyon, aircraft were the most feasible means of
surveying. The high cost of helicopters excluded them
from the project and fixed-wing aircraft were used
instead. Cessna 150 and 172 type aircraft were used
because of their low operating costs, slow airspeeds
and because their high wing design allowed excellent
air to ground visibility.
Nine flights were made from April through August
1975. All flights were made during the mornings because
of the extremely hazardous flying conditions prevailing
during the afternoons. Flight elevations varied from
200 feet to 800 feet above the river and 100 feet to
500 feet above the plateaus, depending upon terrain.
Side canyons were examined as far up as terrain permitted.
Two flights were made from Kingman, Arizona, and
included only the canyon from mile 190.0 to Lake Mead.
Four flights were made from Grand Canyon, Arizona,
and included only miles 70.0 through 209.0. Three
flights were taken from Lees Ferry to Lake Mead
encompassing the entire National Park.
RESULTS AND DISCUSSION
After the first flight, it became apparent that
the rugged terrain would preclude an accurate aerial
survey of feral ass numbers by fixed-wing aircraft. During
the first flight, covering a 90 mile area reported to be
heavily infested with feral asses, only 24 asses were
counted. However, even from the air, extensive trail
networks, dust baths, defecatoria and vegetation damage
were readily seen and indicated much higher populations of
asses.
In 209 Mile Canyon, an area of extensive feral ass
damage, no asses were seen. However, a boating party had
reported 15 asses there a few days before (MNA boat trip
1975).
In seven flights over a 12 mile section of the Tonto
trail, no asses were noted. However, a survey on foot
in the interim counted 34 feral asses inhabiting the same
area.
The aerial surveys did, however, accurately indicate
areas of feral ass habitation. In canyons with known

138

resident ass populations of only 2 or 3, trails and dust
baths were visible from the air. The areas where asses
were consistently seen were covered with networks of
trails and dust baths visible from over a thousand feet
in elevation. Defecatoria and extensive vegetation
damage were observed at lower flights over these same
areas.
The areas occupied by feral asses in the Grand
Canyon are from Tanner Canyon to Crystal Creek on the
south side of the river. From Crystal Creek to
Tapeats Creek, asses inhabit both sides of the river.
This area between Crystal Creek and Tapeats Creek
is the only area where feral asses appear above the
Redwall of the Canyon in any numbers. Havasupai
Point and Pasture Wash on the South Prim have resident
ass populations. On the north side of the river,
asses occasionally go above the Redwall on Point
Sublime and Swamp Point.
From Tapeats Creek to Havasupai Creek, asses inhabit
only the south side of the river. From Whitmore Canyon
to 220 Mile Canyon, asses occur on the north side of
the river. From 215.0 mile to Lake Mead, asses inhabit
the south side of the river.
Areas of highest feral ass densities appear to be
from Red Canyon to Hermit Canyon on the south side of
the river, The Shinumo Amphitheater, Parashant Canyon
to 220 Mile Canyon on the north side of the river,
and mile 215.0 to Bridge Canyon on the south side of
the river.
The area from mile 215.0 to Lake Mead is part of the
Hualapai Indian Reservation and is not included in Grand
Canyon National Park. However, this area appears to
contain extremely large populations of feral asses.
SUMMARY
Feral asses have existed in the Grand Canyon since
the early 1900's. Because of the immensity of the canyon
and the inaccessibility of the asses' habitat, their
distribution in the canyon has not been known.
By low level fixed wing aircraft flights and extensive
cross-country hiking in the canyon, the distribution of
feral asses has been surveyed and mapped (see Figure IX-1).

139

These data can be used to set up study areas and gather
quantitative data on feral ass populations, home range, and
if and what damage is being done to native vegetation and
to native populations of animals.
Studies of this type will give National Park Service
Resource Managers much needed data on which to base
management policies.
LITERATURE CITED
Green, C. R. and W. D. Sellers. 1964. Arizona climate.
Univ. of Ariz. Press, Tucson.
Lowe, C. H. and D. E. Brown. 1973. The natural vegetations
of Arizona. Ariz. Res. Info. Syst.

140

CHAPTER X
FERAL ASSES ON PUBLIC LANDS: AN ANALYSIS OF
BIOTIC IMPACT
Steven W. Carothers
INTRODUCTION
The feral ass, or "wild burro," (Bquus asinus), a
native of northeastern Africa, was introduced into
North America in the sixteenth century by Spanish
explorers. Their value as "beasts of burden" had been
recognized as early as 3400 B.C. in Egypt and Mesopotamia
(Peake, 1933 and Antonius, 1937; fide McKnight, 1958)
and they are still used as such in many portions of the
world. Although the feral ass has been in North America
since the sixteenth century, it has been reasoned
(McKnight, 1958) that the species did not become feral
in the southwestern United States until sometime during
the nineteenth century. Prior to this, the animal was
much too valuable to both Indians and Anglos as a work
animal, and possibly food, to be allowed to become
feral. It was only after the great impetus of mineral
exploration subsided and the settlement of the region
ensued that some animals were released, or escaped, and
feralization began. By the end of the nineteenth
century, the feral ass had become established in many
isolated areas of the Southwest. Since their feralization,
they have been credited with a considerable amount of
habitat destruction resulting in alledgedly depriving
native animals of essential food and water. In many
areas where the feral ass has become established, it
has done so at the expense of the native desert bighorn
sheep (Ovis canadensis), an animal whose nuiabers have
been severely reduced in the Southwest (Russo, 1956;
Dixon and Sumner, 1939; Ferry, 1955: Laycock, 1974).
Also, in a recent analysis of the problem in New
Mexico, Koehler (1974) has found evidence that the
feral ass directly competes with the native mule deer
on certain ranges.

1/ This paper was presented at the North American
Wildlife and Natural Resource Conference, Washington,
D. C. With Merle E. Stitt and R. Roy Johnson, both
of Grand Canyon National Park.

141

In a recently completed study on feral ass behavior
and ecology in Death Valley, California, an area well
known for very high population densities of feral
asses, Moehlman (1972) denies noticeable habitat damage
by the feral ass by stating... "Contrary to a widely
held belief, the burros I observed did not strip the
land, foul water holes or endanger other animals." She
adds..."Although heavy browsing occurred within a mile
of water, my first appraisal of vegetation data indicates
[sic] that plants on which burros feed do not suffer
severely." Our photographic evidence from Death Valley
and the data presented in this paper from our investigations
in other areas show that these conclusions are not
valid. Blong and Pollard (1968) found that ewes,
lambs, and yearling bighorn were concentrated within
.75 miles (.46 km) of water during the summer of 1965.
Denniston (1965) working in the River Mountains of
southern Nevada found that desert bighorn concentrated
within .5 miles (.30 km) of their only water source
during the hot, dry months of summer. In a brief
review of alleged vegetation destruction by the feral
ass, Laycock (1974) writes..."The destruction of
vegetation may cut sharply into rodent populations,
reducing food for birds of prey, while habitat for such
small birds as quail vanishes." Moehlman (1974) further
attempted to evaluate the impact of feral asses on
small rodents by counting the number of supposedly
active rodent burros along transects ranging from high
to low ass densities. By using this method, no difference
was found in the number of apparently active burrows
along these transects. Thus, Moehlman concluded on the
basis of this questionable sampling technique that the
asses were having little or no effect on the rodent
populations.
The objective of our study was to quantitatively
and qualitatively evaluate the influence of feral asses
on desert riparian habitats in the Grand Canyon,
Arizona. Absolute densities of small mammal populations
and vegetative composition and structure were investigated.
We selected two similar study plots, separated by the
Colorado River, with feral asses present on one plot,
but not on the other, thereby providing a "control
plot" and an "impact plot."
History of the Feral Ass in Grand Canyon
The history of the feral ass' success in the Grand

142

Canyon may be considered typical of the problem throughout
the Southwest. By the early 1920's, many rangers in
Grand Canyon National Park were reporting to the Superintendent
that for the sake of the native wildlife, drastic
control measures were needed to restrict the destructive
and rapidly expanding feral ass population. Burros
were credited with much of the overgrazed range condition
within the Inner Canyon. This is illustrated by the
following quote found in an unpublished report written
by Chief Ranger J. P. Brooks in 1932: "Overgrazed
conditions existed on all areas ranged over by burros.
In many places herbage growth was cropped to the roots
and some species of shrubbery were totally destroyed.
Soil erosion was greater in burro infested areas..."
From 1924 to 1931, a "burro hunt" was conducted in
Grand Canyon National Park. The animals were shot with
high powered rifles and left to decompose. During this
7 year period, 1,467 feral asses were killed. It was
believed that the burro population in Grand Canyon
National Park had been reduced to possibly 50 to 75
head, thus, Park Biologists were confident that no more
"burro hunts" would be necessary. Yet, between 1932 and
1956, an additional 370 animals were removed. Between
1956 and 1968, 771 more were destroyed with an additional
252 having been captured and taken out of the park.
This represents a total removal of 2,860 feral asses
from the park in the 45 year period from 1924 to 1969.
No control has been attempted since 1969. One of the
main reasons for the lack of control efforts has been
the negative public sentiment engendered by the "burro
hunts" of the mid and late 1969's. This public sentiment,
largely initiated by articles written by assinophiles
(burro lovers) was quite effective in pushing through
protective legislation for wild horses and burros. 7An
example of the severity of public hysteria with which
land managers must deal may be found in the text of an
article by Weight and Weight (1953): "From time beyond
memory, the humble, gentle burro has been man's uncomplaining
servant and the playmate of his children. There is a
legend that because he carried Mary to Bethlehem and
Jesus along the desert trails of Palestine, he was
given the mark of the Cross—which you can see upon
his back and shoulders." An accompanying photo of a
dead burro bears the caption, "Sportsmen, satisfied
with the thrill of shooting a friendly burro at pointblank range, often do not even carry out the pretense
of hunting for meat, but leave the body as it fell.

193

This burro was shot and left in Great Falls Canyon, not
far from where the little colts, above, were found."
In the past, little quantitative data has existed
to be used by those who suspected or knew of the environmental
havoc that would be wrought by these "starlings" of the
mammalian world. Logic and other examples of great
ecological damage caused by introduced species, such as
rabbits in Australia and red deer in New Zealand, fell
way to anthropomorphized sentiments for "man's faithful
friend." The result was Public Law 92-195 in 1972,
which made killing a feral ass on most lands a felony.
Killing bighorn illegally is merely a misdemeanor. We
wish here to present quantitative and qualitative data
on the environmental hazards wrought by wild burros and
other information which raises questions concerning the
wisdom of this law if not indeed its legality. It may
very likely be that Public Law 92-195 is in conflict
with the National Environmental Protection Act of 1959
(Public Law 91-190) and the Endangered Species Act of
1973 (Public Law 93-205).
METHODS
The duration of our field studies was from 1 March
1974 through 31 January 1975. Both study plots receives
identical quantitative and qualitative vegetational and
mammalian analyses. Vegetation was sampled by means of
the line-intercept transects and 50 point-quarters
stations were censused per study area. Percentage
infestation of mistletoe (Phoradendron californicus)
was measured by absolute counts of parasitized trees
and shrubs on each study area. The vegetation data
presented herein are a condensation of our field data
collected during May, June, and August 1974.
For mammal censusing, each plot was sampled with a
10 by 12, 5.3 acres (2.2 ha.) grid of Sherman live
traps placed at 50 feet (ca. 15 m) intervals. These
traps were baited with a rolled oat/scratch grain
mixture. Traps were set for four consecutive nights at
4:00 p.m. during March, May, June, November, 1974, and
January 1975. They were checked once each day at 7:00
a.m. The following data were recorded: species and
individual identification, trap number, sex, reproductive
condition, weight (0.1 gram), and age class. Females
were classed according to obvious signs of pregnancy,
lactation, or vulvar condition. Age classes were
determined on the basis of adult or immature pelage.
All animals were toe clipped for individual identification.
ikk

The density of each species was estimated separately
by a modification of the Lincoln Index (Bailey, 1952).
The mammal and plant species diversity of each study
area was determined by using the diversity index, H'
(MacArthur and MacArthur, 1961).
DESCRIPTION OF STUDY AREAS
The sites selected for this investigation are
located within the lower reaches of the Grand Canyon
in the Mohave desertscrub vegetative community
(Lowe and Brown, 1973). The impact plot, 209 Mile
Canyon, is on the west side (right) of the Colorado
River and is inhabited by a small herd (8 to 15 individuals) of feral asses. The control plot, Granite Park,
is directly opposite 209 Mile Canyon and shows no
evidence of occupation by feral asses. Both study
plots are 5.3 acres (2.2 ha.) in size and include both
desertscrub and riparian habitats on the alluvial fans
of the respective drainages.
The riparian zone of the Colorado River in this
section of the Grand Canyon is typified by co-linearly
arranged belts of mesic to xeric vegetation. In addition,
both study plots are fronted by sand and gravel beaches
of river deposit origin. Elevations range from approximately
1,503 feet (458 m) at the river's edge to 1,601 (488 m)
on the upper terraces above the historic high water
line (Dolan et al., 1974).
Both plots show more similariries in gross vegetational
composition and structure than differences. An eastwest orientation, equal proximity to water and the
relatively flat topography of the sites, tends to
equalize the abiotic factors of irradiation, moisture
gradients and protection from local weather for both
sites.
RESULTS AND DISCUSSION
Vegetation
An analysis of the vegetation on the control plot
and impact plor. is presented in Table X-l. The control
plot supported greater vegetative diversity including
an understory of sub-shrubs and a dense carpeting of
grasses and forbs (especially plantain). The ground
cover and sub-shrub component was virtually aibsent on
the impact area. The control plot contained vegetation

145

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Table X-1.—cont.
00.96
11.76

01.65
13.32

00.12
02.84

02.73
27.92

00.48
05.88

00.83
06.69

00.29
06.94

01.60
19.51

01.93
23.53

00.33
07.89

03.30
26.63

05.56
58.05

07.85 79.22
52.89 173.84

45.41
95.92

20.35
85.00

00.85
90.14

66.61
271.06

00.59
01.52

00.09
00.58

01.55
03.09

01.93
04.08

• .48
15.00

00.09
09.86

04.50
28.94

a. 20.56
b. 23.18

04.71
12.12

04.01
22.95

29.28
58.25

a. 24.50
b. 27.61

05.29
13.63

03.50
23.58

33.29
64.82

Ephedra
SPP-

a.
b.

Lepidium
montana

a. 00.44
b. 21.74

Opuntia
spp.

a.
b.

PorphylLum
gracile

a. 00.09
b. 04.35

00.59
06. 58

01.07
49.34

01.75
60.37

Sphaeraleea
fendleri

a. 00.09
b. 04.35

00. 59
06.68

00.01
00.66

00.69
11.69

Bromus
rubens

3 a. 43.13
b. 48.22

28.24
72.73

Festuca
spp.

a. 00.87
b. 00.99

Plantago
spp.
Sporobolus
contractus

02.35
26.65

~

~

00.4d
21.85

03.27
70.24

GRASSES

1

1

Data summary comparing density, frequency and dominance of all species
in cac-claw/m-squite area.

2

Data summary comparing density, frequency and dominance only between
species of similar strata, i.e., shrubs, sub-shrubs and graminoids.

3

Exotic weed species.

147

cover on approximately 80 percent of the total transect
area surveyed compared to 20 percent vegetation cover
on the impact plot. The number of species found on the
control area was 30 percent higher than that on the
impact area.
The mean area (m2) occupied by each individual
o
cat-claw or mesquite on the control plot was 27.9mr
per plant, while the same species on the opposite side
of the river at the impact plot was not as large,
occupying only 20.7m per plant. Also, there was a
higher infestation of mistletoe (Phoradendron californicus)
on the impact plot, with 16.5 percent of all cat-claw/mesquite
(Acacia gregii/Prosopis juliflora) being infested with
this parasite as compared to only 5.4 percent of the
same species parasitized on the control plot. Cat-claw
and mesquite shrubs on the impact study area had been
heavily browsed by asses. The mistletoe infestation
may be correlated with over-browsing, but a definite
conclusion cannot be drawn without further study.
There was no significant difference in total
species diversity from one plot to the next, however,
the control plot showed a richer subshurb and grass
component (H' = 1.60042 and .821670) than the impact
plot (H1 = 1.28478 and .422710).
Small Mammals
The results of the small mammal population censuses
are presented in Table X-2. The most striking difference
between the populations on the two study areas is
dramatically demonstrated by comparing the average
absolute mammal density of both plots for the entire
sampling period. The control plot has an average
density of 128 mammals/acre (51.8/ha.), whereas the
impact plot contains only 32.6 mammals/acre (13.2/ha.).
It is also important to note that the species composition
is different between the two study areas. The mammalian
species diversity indices (H1) on the control plot and
the impact plot are .73652 and .69022 respectively.
The greater species diversity on the control plot is
also complemented by a greater evenness of species
distribution (J1) (.56736) than that found on the
impact plot (.42886).
The total absolute densities of the small mammal
populations on both plots were higher at the onset of

11+8

Table x-2. Snail mammal population densities on the two study areas.
CONTROL
Seeenos

Absolute Density (per hectare)
Mar
May
Jun
Aug
Nov
Jan

Relative Density (percent)
Mar
May
Jun
Aug
Nov

Jan

x

Peromyscus eremicus
Peromyscus boy]ii
Perognathus intermedins
Neotoma albigula

53.5
00.3
34.3
00.8

35.3
00.0
18.7
00.5

43.2
00.3
23.5
00.8

27.7
00.3
31.3
02.5

11.4
00.0
08.6
00.3

11.4
00.0
06.0
00.2

60.0
00.3
39.0
00.7

65.0
00.0
34.0
01.0

59.2
00.1
39.2
01.5

TOTAL

88.9

54.5

67.8

61.8

20.3

17.6

65.0
00.0
34.0
01.0

64.0
00.3
35.0
00.7

45.0

56.0
00.0
42.0
02.0

51.0
04.0

100.0 100.0 100.0

100.0 100.0 100.0

Average total Absolute Density March 1974 to January 1975 = 51.8 mammals per hectare.
H

IMPACT
Species

Peromyscus eremicus
Peromyscus crinitus
Peromyscus boyleii
Perognathus formosus
Neotoma lepida

30.4
00.0
00.3
00.3
00.3

09.4
00.3
00.0
00.3
00.0

08.2
02.3
00.0
00.3
00.0

09.1
04.4
00.0
00.3
00.0

08.7
01.4
00.0
00.0
00.0

02.9
01.4
00.0
00.0
00.0

TOTAL

31.3

10.0

10.8

13.8

09.1

04.3

97.0
00.0
01.0
01.0
01.0

94.0
03.0
00.0
03.0
00.0

76.0
23.0
00.0
02.0
00.0

66.0
32.0
00.0
02.0
00.0

85.0
15.0
00.0
00.0
00.0

67.0
33.0
00.0
00.0
00.0

80.0
17.5
00.2
01.3
00.2

100.0 100.0 100.0 100.0 100.0 100.0 100.0

Average total Absoluate Density, March 1974 to January 1975 = 1 3 . 2 mammals per hectare.

this study (March 1974) than they were at its termination
(January 1975). The fluctuations found in these densities
(a decline of 77.3/acre (31.3/ha.) to 10.6/acre (4.3/ha.)
on the impact plot and 219.7/acre (98.9/ha.) to 43.5/acre
(17.6/ha.) on the control plot) are consistent for both
plots and may be reflecting "normal" population fluctuations.
Nevertheless, in all trapping periods, the density and
diversity of the small mammal populations on the control
plot were substantially higher than those across the
river at the impact plot.
In addition to the total population densities,
another striking difference in the rodent communities
of the two study areas is in the relative species
composition (Table X-2). On the impact area, the
density of the cactus mouse (Peromyscus eremicus)
accounted for an average of 80.8 percent of the entire
rodent community, whereas on the control plot, this
species accounted for an average of 59.2 percent of the
population. The only other species which contributed
significantly to the impact plot population was the
canyon mouse (Peromyscus crinitus), averaging 17.5
percent of the total population. The canyon mouse was
never encountered on the control plot. Reasons for this
are a direct reflection of the habitat requirements of
this species and the state of the habitat on each study
area. The canyon mouse prefers rocky, near barren
areas that are usually devoid of vegetation and may be
found commonly throughout the Grand Canyon on upper
talus slopes and rocky outcrops. Clearly, the alteration
of the impact by feral asses has permitted a population
of canyon mice to become established in an area not
normally inhabited by this species.
The distribution and abundance of heteromyid
rodents on the two study areas also further demonstrates
the detrimental effects of feral asses. On the impact
plot, only a few heteromyids, the long-tailed pocket
mouse (Perognathus formosus), were captured, while the
control contained a relatively large and stable population
of the rock pocket mouse (Perognathus intermedius)
(Table X-2). The rock pocket mouse made up an average
of 39.2 percent of the rodent community on the control
plot while the long-tailed pocket mouse constitued an
average of only 1.3 percent of the population density
on the impact plot. In the Grand Canyon, we have found
that the long-tailed pocket mouse is exclusively restricted
to the north and west banks of the Colorado River and
the rock pocket mouse is restricted to the south and

150

east banks. However, where suitable habitat exists,
there is no measurable difference in the population
densities of these two species. On the two study
areas, differences in the population densities of these
heteromyid rodents were directly related to their
dietary requirements and the availability of food. The
primary food of both species of Perognathus probably
consists of seeds, especially the seeds of forbs (Reichman,
1975). As mentioned above (see Table X-l) the forb
strata of the impacted area has been thoroughly decimated
through grazing and trampling by feral asses, thus
rendering the habitat of this study area inhospitable
to a population of Perognathus.
SUMMARY
The results of this investigation demonstrate
conclusively that the feral ass (Equus asinus) has a
negative effect on the natural ecosystem of the lower
reaches of the Grand Canyon. The principal impact of
the feral ass is habitat destruction through grazing
and trampling.
On the study area where feral asses occur the
vegetation cover and rodent populations were significantly
reduced when compared to the study area where feral
asses were absent. On the control plot, 28 species of
vascular plants were found compared to 19 on the impact
plot. The total vegetation cover on the control plot
was SO percent, compared to 20 percent on the impact
plot. The mean area (m ) occupied by each individual
cat-claw or mesquite shrub was 27.9m/- on the control
plot and 20.7m" on the impact plot.
The mammal species diversity (H1) was higher on
the control plot (.78652) than it wa.s on the impact
plot (.69022). In addition, the average absolute density
of small mammals from March 1974 to January 1975 on the
control plot was 128 mammals/ acre (51.8/ha.), approximately
four times the 32.6/acre (13.2/ ha.) found on the
impact plot. Thus, differences between the two areas
in mammalian species composition and diversity were
attributed to the depauperate flora, particularly the
forbs and grasses, on the 209 Mile Canyon impact area.

151

REFERENCES CITED
Antonius, O. 1937. On the geographical distribution in
former times and today, of the recent Equidae. Proc.
Zool. Soc. London 107:557-564.
Bailey, N. T. J. 1952.
of recapture data.

Improvement in the interpretation
Jour. Anim. Ecol. 21:120-127.

Blong, B. and W. Pollard. 1968. Summer water requirements
of desert bighorn sheep in the Santa Rosa Mountains,
California in 1965. Calif. Fish and Game 54 (4) :289-296.
Canfield, R. 1941. Application of the line interception
method in sampling range vegetation. Jour. Forestry
39:388-394.
Cottam, G. and J. T. Curtis. 1956. The use of distance
measure in phytoecological sampling. Ecology 37:751-460.
Denniston, A. 1965. Status of bighorn in the River Mountains
of Lake Mead National Recreation Area. Trans, of the
Desert Bighorn Council 9:27-24.
Dixon, J. S. and E. L. Sumner, Jr. 1939. A survey of desert
bighorn in Death Valley National Monument. Calif. Fish
and Game 25:72-95.
Dolan, R. , A. Howard and A. Gallenson. 1974. Man's impact
on the Colorado River in the Grand Canyon. Am. Sci.
62:392-401.
Ferry, P. 1955.
8:18-21.

Burro or bighorn?

Pacific Discovery

Koehler, D. A. 1974. The ecological impact of feral
burros on Bandelier National Monument. Unpub. M. S.
Thesis, Univ. of New Mexico.
Laycock, G. 1974. Dilemma in the desert:
burros? Audubon 76 (5) :116-117.

bighorns or

Lowe, C. H. and D. E. Brown. 1973. The natural vegetation
of Arizona. Ariz. Res. Info. Syst.
MacArthur, R. H. and J. w. MacArthur. 1961.
species diversity. Ecology 42:594-598.

152

On bird

McKnight, T. L. 1958. The feral burro in the United States:
distribution and problems. J. Wildl. Manag. 22 (2) :162-179.
Moehlman, P. D. R.
Death Valley.

1972. Getting to know the wild burros of
Nat. Geogr. 141 (4) :502-517 .

. 1974. Behavior and ecology of feral asses (Equus
asinus). Unpub. Ph.D. Thesis, Univ. of Wisconsin.
Morisita, M. 1959. Measuring of interspecific association
and similarity between communities. Mem. Fac. Sci.
Kyusha Univ. Ser. E. 3:65-80.
Peake, H. J. 1933. Early steps in human progress.
Lowe, Marston and Co. London. 256 pp.

Sampson,

Reichman, O. J. 1975. The relation of desert rodent diets
to available resources. J. Mamm. 56:731-751.
Russo, J. P. 1956. The desert bighorn sheep in Arizona.
Phoenix Ariz. Game and Fish Dept. 152 pp.
Weight, H. and L. Weight.
Calico Print 9:2-4.

1953.

153

A word for brother burro.

Table XI-T.—Boating use between Lees Ferry and Diamond
Creek.
Year
1955
1956
1957
1958
1959
1960
1961
1962
1963*
1964*
1965
1966
1967
1968
1969
1970
1971
1972+
1973
1974
1975

Total Users
70
55
135
80
120
205
255
372
6
38
547
1067
2099
3609
6019
9935
10885
16432
15219
14253
14305

*Lake Powel Filling
+User-day limit set by NFS

15U

CHAPTER XI
CAMPSITE USAGE AND IMPACT
Stewart W. Aitchison
INTRODUCTION
To determine the possible interrelationships
between the river runners and the riparian biota certain
data concerning total use, types of impact, and biological
uniqueness or sensitivity of campsites (termed Biotic
Resource Rating) had to be collected.
METHODS
The National Park Service keeps records of the
total number of people boating from Lees Ferry to
Diamond Creek (Table XI-1). However, these data do
not afford pertinent information as to how many people
were utilizing specific campsites or the location of
these campsites. A visitor usage form (Figure XI-1) was
devised and made available to the various commercial
river running outfitters and to private trips for the
1974 and 1975 seasons (1976 data currently being
collected). These forms were printed as postpaid
postcards to facilitate return of them to the investigators.
They asked for the number of passengers and crew,
beginning date of the trip, camp locations, whether or
not a campfire was made, and whether or not the manditorially
carried portable toilet or equivalent (see NPS River
Regulations, 1974) was dumped (i.e., sewage buried).
Campsite evaluation forms were constructed (Figure
XI-2) and distributed to the various biology investigators.
The forms helped in delineating the various observable
types of human impact and in subjectively quantifying
overall human impact for a specific location. Additionally,
the biotic uniqueness or sensitivity of each campsite
was rated subjectively (see Appendix XI-I for instructions
to this form).
All the above information was computerized for
easy retrival and tabulation.
RESULTS AND DISCUSSION
Although initial return of visitor usage forms was

155

Figure XI-1.—Visitor Usage Form

15b

GRAND CANYON ECOLOGICAL SURVEY 1974
CAMPSITE EVALUATION SHEET - 2
Observer:

Day-

Month

Year

River mile

Side

Profession*

•Profession code:
Biologist
1
Boatman
2
Student
3
Other Scientist 4
Tourist
5
PARAMETER:

RATING:

MAN'S IMPACT
litter
trampling
rock moving
campfire
wildlife
human waste
TOTAL:

COMMENTS :

_______

WILDLIFE AND
HABITAT
habitats
special areas
unicyue combinations
modifications
values and needs
TOTAL:

Figure XI--2. —Campsite Evaluation Form

157

poor, additional cards were received in the fall of
1974. A total of 183 cards (representing, of course,
183 trips) were completed and returned for 1974. This
accounted for 21.1 percent of the total user-days.
In 1975, 196 cards were completed and returned, a
representation of 22.5 percent of the total 1975 userdays.
In 1974, 395 different campsites were reported
between Lees Ferry, river mile 0.0, and Pierce Ferry,
river mile 280.0. Although some of these campsites are
no doubt duplicates due to inaccuracies when filling
out the forms, this number does indicate considerably
more campsites than generally believed. For example,
less than 200 have been noted by investigators using
aerial photo-interpretation techniques (Yates Borden,
pers. comm.).
In 1975, about 350 campsites were used. The
visitor usage data is summarized in Tables XI-2,
XI-3, XI-4. Copies of the complete computer printout are on file with the National Park Service at
Grand Canyon National Park and with Museum of
Northern Arizona at Flagstaff.
Four hundred and twenty-five campsite evaluation
forms were completed. Thirty-three campsites were
evaluated in 1974 and 8 additional ones in 1975. These
41 sites along with their ratings are summarized in
Table XI-5. Through the campsite evaluations forms,
comments from river users and observations by the
Museum of Northern Arizona investigators, the following
types of human impact were revealed:
1.
2.
3.
4.
5.
6.
7.
8.

Fire
Litter
Trampling of vegetation
Porta-potty sewage disposal
Noise
River level fluctuations
Moving of naturally occurring objects
People presence

All of these types overlap to some extent and also
produce direct and indirect effects of either long or
short-term duration. Further discussion of the

153

Table Xl-2.~~Twenty campsite with the most usage.
1974
Rj.ver
Mile

H
VO

19.0
41.0
72.0
81.0
93.0
110.0
114.0
120.0
132.0
133.0
136.0
137.0
148.0
166.0
168.0
212.0
219.0
222.0
279.0
TOTAL

Reported
# of People
L
R
R
L
I,
R
R
L
R
R
L
L
L
L
R
L
R
L
L

1975

Projected
% of Total
# of People of People

380
274
399
343
259
276
3 76
305
279
417
360
585
287
364
326
259
260
321
382

1799
1297
1889
1624
1226
1307
1780
1444
1321
1974
1704
2769
1359
1723
1543
1266
1231
1519
1808

1.62
1.17
1.70
1.46
1.10
1.18
1.60
1.30
1.19
1.78
1.53
2.49
1.22
1.55
1.39
1.10
1.11
1.37
1.63

23,463

111,068

28.65

River
Mile
19.0
19.5
20.0
22.0
29.0
31.0
50.0
66.0
72.0
75.0
81.0
109.0
114.0
136.0
137.0
168.0
178.0
179.0
209.0

Reported
# of People
L
L
L
L
L
R
R
L
R
L
L
R
R
L
L
R
L
L
L

Projected
% of Total
# of People
of People

318
276
383
314
329
277
330
277
610
358
355
310
354
888
764
428
273
426
371

1407
1221
1695
1390
1456
1226
1460
1226
2699
1584
1571
1372
1567
3930
3381
1894
1208
1885
1642

1.24
1.08
1.50
1.23
1.29
1.08
1.29
1.08
2.38
1.40
1.39
1.21
1.38
3.47
2.99
1.67
1.07
1.66
1.45

25,586

113,228

30.95

Table XI-3.—Twenty Campsites with the Most Campfires

River
18.0
19.0
20.0
41.0
72.0
81.0
93.0
110.0
114.0
120.0
132.0
133.0
136.0
137.0
152.0
166.0
168.0
212.0
219.0
279.0

Mile
L
L
L
R
R
L
L
R
R
L
R
R
L
L
R
L
R
L
R
L

1974
Reported Number
11
17
14
13
17
12
11
12
17
11
12
14
19
27
13
14
14
13
12
13

1975
River Mile
Reported Number
19.0 L
11
22.0 L
12
29.0 L
14
50.0 R
13
66.0 L
11
71.0 L
9
72.0 R
18
75.0 L
11
81.0 L
14
108.0 R
14
114.0 R
10
136.0 L
29
137.0 L
23
148.0 L
10
168.0 R
17
178.0 L
10
186.0 L
10
209.0 L
14
219.0 R
10
220.0 R
12

160

Table XI-4.—Campsites with the most
porta-potty dumps
1974
River Mile
Dumps
19.0
20.0
23.0
29.0
41.0
43.0
50.0
53.0
72.0
81.0
108.0
114.0
132.0
136.0
137.0
164.0
166.0
168.0
209.0

L
L
L
L
R
L
R
R
R
L
R
R
R
L
L
R
L
R
L

1975
River Mile
Dumps

11
13
9
13
13
11
9
11
14
15
12
19
17
27
30
11
11
19
10

19.0
20.0
22.0
29.0
31.0
50.0
52.0
53.0
71.0
72.0
75.0
81.0
93.0
108.0
109.0
110.0
114.0
132.0
136.0
137.0
168.0
178.0
179.0
209.0
220.0

l6l

L
L
L
L
R
R
R
R
L
R
L
L
L
R
R
R
R
R
L
L
R
L
L
L
R

15
14
11
19
13
17
11
12
11
24
15
14
11
18
13
12
18
11
42
34
IS
11
12
20
11

Table XI-5.—Summary of campsite evaluations.
River
Mile

Side

17.0
17.5
18.0
29.0
31.5
33.0
35.0
39.0
43.0
47.0
53.0
61.0
64.0
65.5
68.5
71.0
72.0
76.5
84.0
87.0
87.5
103.0
104.0
114.0
120.0
122.0
123.0
133.5
134.0
137.0

R
L
L
L
R
L
L
R
L
R
R
L
R
L
L
L
R
L
R
L
R
R
R
R
R
R
L
R
R
L

Human Impact*
1974
1975
11.2
16.0
15.6

16.0
14.0

15.3
13.6
20.0
10.0
20.6

Biotic Resource Rating**
1974
1975

# of Campers+
1974
1975

11.5
27.0
15.9

232

19.7
13.4
19.0
10.0
22.6

147
66
213
473

34.6
21.7

1013
133

25.7
34.0
30.2

275
175
951

26.0

232

19.4
27.3

450

20.1
15.2

658
1780

25.8
20.3
17.9
35.3
15.2

1046
601

994

10.0
22.7
22.6

239

9.7
18.2
19.0
19.8

876

10.7
20.0

2699

8.0
15.1
21.8

1407
1456

217

7.0
15.4
14.3
9.2
17.7
12.0
12.8
20.2
16.4

11.0

84

601
2769

3381

*The numerical rating scale ranged from 10.0 (no impact) to 22.6
(greater impact) and represents a relative and subjective
evaluation. (See Work Plan, Contract #CX821040079 for elaboration
of the campsite evaluation form insrructions. Also, see Appendix
XI-1.
**The numerical rating scale ranged from 10.0 (no biotic resources)
to 40.2 (greater biotic resources) and represents a relative and
subjective evaluation.
+These data from Visitor Osage Forms - 1974 and 1975.

162

Table XI-5.—cont.

145.5
164.5
166.0
166.5
185.5
188.0
209.0
209.0
242.0

L
R
L
L
R
R
R
L
L

12.0
15.1
18.7
18.3
12.7
16.2
17.0
20.0
17.1

18.0
30.0
17.7
22.4
23.3
26.5
32.8
21.1

8.0

163

497
1723
232
260
57
715
66

1412
752

interrelationships of recreationists and the biota will
be found in Chapter XII.
Quantification of each type becomes the overriding
problem.
Fire
This category includes campfires and also those man-caused
fires that burn uncontrolled. Impact ranges from small
charcoal piles to entire stands of beach vegetation being
consumed in a holocaust. Short-term biological effects
may include elimination of actual or potential nest
sites, forage sites, and display sites through removal
of living or dead vegetation. Large burns may kill or
force movement of certain animals and may encourage the
introduction of nonnative pioneer species.
Litter
Common litter items include:
1.
2.
3.
4.
5.
6.
7.

Paper (namely, toilet paper, feminine napkins,
cigarette butts)
Food scraps
Spilled fluids (e.g., gasoline, oil, lotion,
juices from canned food)
Clothing
Plastic items (e.g., bottles, airmattresses)
Glass (bottles)
Metal products (e.g., cans, nails, motor
parts, pop tops)

Some items may affect vertebrate populations
through increasing the available food supply either
directly by being eaten or indirectly by producing
higher densities of insects. A few litter articles
may be used as nesting material (e.g., paper) or may
present hazards (e.g., broken glass).
Unfortunately most of the litter is practically
indestructible, lasting years before decomposition sets
in,.
Trampling
A very obvious human impact is trampling of vegetation
and disturbance of soil. Some of the riparian ground

164

cover seems to be easily destroyed by a single footstep.
Shrubs and trees suffer from being used as tent poles,
moorings, and being broken back to form paths. Heavy
use of trails can compact the soil to such an extent
that vegetation can no longer grow there (Aitchison and
Theroux, 1973) ._
Ground nesting vertebrates, particularly
lizards, may suffer some nest site destruction from
trampling. Rodent burrows may also be disturbed through
intensive use of an area by humans.
Porta-potty Dumping
This refers to the problem of disposal of sewage.
Since 1971, the NPS has required river parties to carry
portable toilets or equivalent for the containerization
of human waste. Most of these toilets must be emptied
once a day. A hole is dug, the toilet paper is burned
in the hole, and the sewage is poured in and covered.
At least one outfitter carries a large enough holding
tank on the river craft which eliminates the need of
disposing sewage within the Canyon.
The impact of waste disposal on beaches includes
increase in some insects particularly flies and ants,
possible contamination of ground water, smell, and
potential health problems. Also, disturbance of soil
occurs and occasionally destruction of vegetation by
digging the hole.
Noise
Generally manrelated noise in the canyon results
from motors. Few studies have been done on the effects
of noise on wildlife (Douglas and Johnson, 1972);
however, conceivably noise could interfer with certain
songs, calls, or territorial displays of birds. It
appears that airplane noise may be the predominant
type (Schroeder, 1973; Elden Bowman, pers, comm.).
River Level Fluctuation
The most dramatic impact is the controlled fluctuation

1/ Aitchison, S. W. and M„ 3. Theroux. 1973. Ecology of
Oak Creek Canyon, Coconino Co., Arizona. Phase T Report,
unpub. ms. for U., S. Forest Service.

165

of the Colorado River's flow by Glen Canyon Dam. The
discharge may vary 30,000 CFS or more in 24 hours. This
regulation of water quantity and quality (e.g., the silt
load is minimal compared to pre-dam flows) has been a central
factor in the establishment of a new riparian vegetation
community. This new vegetation is in turn encouraging
the proliferation of certain wildlife species. Tamarix
is associated with a high productivity area and correspondingly
an increase in lizard densities. Tamarix and Salix
provide nest sites for Mourning Doves, Lucy's Warblers,
Bell's Vireos, etc. Higher densities of small mammals
occur in the riparian zone. Also, wildlife diversity
is higher in the riparian habitat than adjacent habitats.
(See Chapters I and II for further elaboration of the
vegetational effects of Glen Canyon Dam.)
Moving of Natural Objects
This category includes rock moving for such purposes
as holding down tarps and for making campfire rings.
Also included would be removal of dead or living vegetation
generally used in campfires. Although this type of
impact seems to be minimal, nonetheless, actual or
potential nesting sites, foraging sites, and display posts
are disturbed and may prove detrimental to some species
of wildlife. For instance, Desert Sping Lizards require
elevated objects (e.g., rocks) for establishment of a
functional social system.
People Presence
Heavy visitation of a particular area may cause
stress in certain animals (Dennis S. Tomko, pers.
comm.). This happens because the animals that would
normally be spread out over a given area are forced to
concentrate themselves in order to escape contact
with humans. This artificial crowding may also cause
behavioral changes. For example, usually territorial
species of lizards may be inclined to establish social
hierarchies (Brattstrom, 1974).
Specific experiments should now be devised to
quantify each of the above types. (Studies concerned
with sewage disposal and beach erosion are currently
underway.)
STATISTICAL ANALYSIS
No significant correlation was found between the

166

Figure XI-3.—Number of campers versus the biotic resource
rating for specific campsites - 1974.

Figure X1-4.—Number of campers versus the biotic resource
rating for specific campsites - 1975.

167

Figure XI-5.—Number of campers versus human impact
rating for specific campsites in 1974.

Figure Xl-6.—Number of campers versus human impact
rating for specific campsites - 1975.

168

number of campers and biotic resource rating nor between
the number of visitors and the total amount of impact
(Figure XI-3 through XI-6).
Figures XI-3 and XI-4 may indicate that campsites
were not being chosen for their particular fauna and
flora. This seems reasonable since campsite location
is usually dictated by amount of room for sleeping,
good mooring location, shelter, etc.
The lack of correlation between number of campers
and impact is more difficult to explain. Perhaps, it
is simply too small a sample site.
However, a very good correlation was found between
the impact ratings and biotic resource ratings (Figure
XI-7). Initially one might expect that as the impact
increased the biotic interest would decrease. But just
the opposite was revealed. One might be tempted to say
this is because the more heavily camped at sites are
the more biologically interesting ones; but, we have
already seen there appears to be no correlation (Figures
XI-3 and XI-4). So, what is happening?
By examining specific campsites low and high on
the regression line (Figure XI-7) and reviewing the
campsite evaluation forms, several points become clear
that solve this apparent paradox. First, those areas
that are biologically interesting are also areas
easily damaged by human usage. Additionally, a few
people may cause as much or more impact as a large
group in these areas. (This is supported by Figures
XI-5 and XI-6 if we draw a regression line. Although
not statistically significant, the hypothetical regression
line nonetheless has a slope close t-O zero for both
years.) In other words, if a correlation does exist, it
appears that it would indicate small to large groups of
people can cause the same amounts of impact.
This suggests then that camping and river running
pratices should be closely scrutinized rather than
just thinking of human impact in terms of total usage.
SUMMARY
Basic types of human impact upon the Grand Canyon's
riparian biota have now been delineated. Quantitative
measurement of each type is the next step in eventually

169

Figure XI-7.—Human impact versus the biotic resource
rating for thirty-three campsites.

170

Table XI-6.—Preliminary list of biologically interesting
and/or sensitive areas.
Name
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
3 3.
34.
35.
36.
37.

Paria River
—
Vasey's Paradise
Buck Farm
Saddle Canyon
Nankoweap
Little Colorado
Furnace Flats
Tanner Delta
Cardenas Marsh
Unkar Delta
75-Mile Canyon
Red Canyon
Clear Creek
Phantom Ranch
Shinumo Creek
Elve's Chasm
Blacktail Canyon
122 Mile Creek
Stone Creek
Tapeats Creek
Deer Creek
Matkatamiba
Havasu Canyon
National Canyon
Lava Falls
Granite Park
Juniper Seep
Travertine Canyon
Spencer Canyon
Surprise Canyon
Maxson Canyon
Burnt Canyon
Bat Cave
Emery Falls
Grapevine

River Mile
1.0
17.5
31.9
41.0
43.2
47.0
52.0-53.0
61.5
65.6
69.0
71.0
72.5
75.3
76.6
84.0
87.5
108.6
116.5
120.0
122.0
132.0
133.7
136.2
147.9
156.8
166.5
179.5
208.6
215.0
229.4
246.0
248.4
252.4
259.3
266.4
274.4
279.0

171

Side
R
L
R
R
L
R
R
R
L
L
L
R
L
I,
R
R
R
L
?,
R
R
R
R
L
L
L
L
L
R
L
L
R
L
R
R
L
L

reaching an "ecological carrying capacity." Of course,
social and physical carrying capacties will also have to
be considered.
Overall impact does not seem to be mitigated by the
total number of people but rather a combination of the
sensitivity of the campsite and the specific activities
of the campers.
In the Grand Canyon, biologically unique and/or
important areas should be carefully monitored for
changes due to man's influence. These areas would be
places with high densities and/or diversities of plant
and animal life and/or provide some kind of unique
element required for reproduction and survival of
indigenous populations. Although management should
emphasize ways to minimize biotic damage, temporary
closures may be needed to give these areas a "rest."
A preliminary list of biologically interesting
or sensitive area can be found in Table XI-6.
LITERATURE CITED
Brattstrom, B. H. 1974. Evolution of reptilian
behavior. Am. Zool. 14(1):35-50.
Douglas, C. L. and R. R. Johnson. 1972. Highways and
their impact on the wildlife of the pinyon-juniperoak woodland and grassland in north-central
Arizona. Report prepared for the Ariz. Highway
Dept. Rrescott Col. Ecol. Survey.
Schroeder, J. 1973. Planes upset quiet of Grand Canyon.
Ariz. Republic, 3 March.

172

CHAPTER XII
THE INTERRELATIONSHIPS OF MAN AND THE BIOTA
Steven W. Carothers
Stewart W. Aitchison
Dennis S. Tomko
INTRODUCTION
One of the primary objectives of this study was to
determine the various kinds of human-related impact on
the biota of the riparian zone of the Colorado River.
The impact of man on the biota along the Colorado River
and its tributaries is represented in two forms; (1)
direct impacts of river runners and hikers in heavily used
camping areas (see Chapter XI), and (2) the indirect
impacts brought about by the recent changes in vegetation
downstream from Glen Canyon Dam (see Chapter I ) .
The previous chapters have dealt with the
of baseline data on faunal and floral analysis
riparian habitat and camper usage (i.e., river
of the beach areas. This chapter will discuss
ecological interrelationships as they apply to
of the beach resources of the river.

gathering
of the
runners)
specific
human use

DIRECT IMPACTS OF RIVER RUNNERS AND HIKERS ON HEAVILY USED
RIVER CAMPS
Vegetation
The outstanding direct impact man has on the vegetation
is through disturbance by trampling. In many areas (e.g.,
Saddle Canyon, Nankoweap, and lower Havasu Canyon) multiple
trails,, all with the same ending and beginning place, are
maintained simply through large numbers of people trampling
the vegetation. In many cases, this condition invites
accelerated soil erosion and dramatically changes the flora
of these areas (see Chapter I ) . On the other hand, some
beach areas would probably become uncanpable if the vegetation
were not held in check through this trampling (i.e., general
use). Below Diamond Creek, most of the low use camping
areas are covered by impenetrable stands of salt cedar-

Insects
Several specific problems with regard to man's impact

173

on insect populations are arising along the Colorado River.
Harvester ants (Pogonomyrex californicus), known commonly
as red ants, usually occur in low densities along the
beach/terrace interface near the river. On many of the
heavily used beaches, however, the ant densities are
much higher than they are on relatively unused beach
areas. Preliminary investigations seem to indicate that
this problem is directly related to human activity on
these areas (improper organic garbage disposal). Because
of their great numbers and painful sting this species
represents a minor health hazard (could be a major problem
for toxin-sensitive persons) and a definite source of
discomfort for the many river runners and hikers affected.
The flesh fly (Sarcophagidae) and blow fly (Calliphoridae)
populations also show this increase in density at heavily
used camping areas. Both groups are frequently linked with
sanitation problems, particularly with regard to fecal
and organic waste disposal. These insects could definitely
be the source of some fly-vectored health problems.
Reptiles and Amphibians
Direct impacts on these animals are brought about
through changes in the available food at the heavily
used beach areas. Ants, flies and gnats make up a large
portion of lizard diets (see Chapter III) . These insects
thrive on organic garbage and fecal waste products, and
where these insects are present in unusually high
densities, there is a corresponding increase in lizard
densities.
Many species of lizards utilize the rapidly dwindling
supply of driftwood piles for foraging, display and basking
areas. This is particularly true of the desert spiny
lizard (Sceloporus magister). If the driftwood (particularly
that in very large piles) is eventually removed from the
Canyon, an important resource to the herpetofauna will
be lost. We know of no apparent impacts on the amphibians
and snakes. Most outfitters and private parties have
adopted the policy of not killing rattlesnakes and this practice
should be encouraged.
Birds
In the heavily used camping areas, rhree species of birds,
the StarJ.ing, the Common Raven and the House Sparrow, are

171+

affected by man's activities.
From Lees Ferry to Lake Mead, at every major
campsite, one can usually find at least one pair of
semi-domesticated ravens. In the past, river runners
have fallen into the habit of leaving organic garbage
on the beaches, specifically for the purposes of
feeding the wildlife. Our investigations indicate
that the only bird species influenced by this practice
is the raven. It is amusing to watch this intelligent
and highly adaptable species boldly approach within
a few feet of the commissary area of river camps and
scold the human occupants until they are fed., All
indications are that the ravens are in higher densities
within the inner gorge than they would be if they were
not fed. Feeding animals in a National Park is unlawful
and leaving organic garbage on Grand Canyon beaches
is against the National Park Service river running
regulations.
House Sparrows, an exotic species that is well
known for its preference of areas with heavy concentration
of humans, are found in at least five areas along the
Colorado River and its tributaries. The Phantom Ranch
area contains hundreds of these birds, their concentration
being centered around the corrals and mule barns. They
are also well represented (about 6 pairs each breeding
season) at Indian Gardens and again are found most
frequently around the mule corral. In the main campground
areas along Havasu Creek and the R'avasupai Village area
this species reaches its highest densities in Grand Canyon
riparian habitats. As long as relatively permanent
human/domestic livestock habitation of these areas exist,
this exotic species will continue to proliferate in
these areas.
More alarming, however, is the fact that the House
Sparrow has been found for the first time (1975 breeding
season) occupying the riparian vegetation on some of the
heaviest used beach areas along the river. Our visitor
usage forms (see Chapter XI) nave indicated that the
camp across from Deer Creek, 136.OL, is the heaviest
usee camp along the river. It is precisely this camp
where we first noticed a pair of House Sparrows, giving
all indications that they were nci.ng to nest in the
area. Another heavily used camp, the Granite Park camp,
mile 209.OL, has also yielded observations on House
Sparrows.
Tc stem ar, overall invasion of the House

175

Sparrow in the popular camping areas, it may be necessary to
put some of these camps on a rest rotation basis
and to eliminate these exotics as they are encountered.
The specific factors the House Sparrow keys on before
establishing in an area are unknown, there is little
doubt, that these factors are somehow associated
with man.
Another exotic species, the Starling, has not been
observed along the river as of this writing except the
Phantom Ranch community and the Havasupai Village.
Like the House Sparrow though their presence should be
carefully monitored and when possible eliminated.
Mammals
Four species of mammals (skunks, ringtails, rock
squirrels and mule deer) show direct influences by man.
The mule deer and rock squirrels are not influenced by
river runners, but have reached unnaturally high
population densities in the Phantom Ranch and Indian
Gardens area. These animals are again responding to
finding man as a source of food and in this situation
are suffering for it. Both the deer and rock squirrels
are in poor health and may present a serious health
hazard to man.
Along the river, due to organic garbage accumulation
and in some cases direct feeding, skunks and ringtails
are found in unusually high numbers at heavily used
camping areas. The small rodents (particularly
Peromyscus spp. and Neotoma spp.) are also present in
high densities, but we have found no definite correlation
between use of an area and the densities of these rodents.
INDIRECT IMPACTS AS A RESULT OF GLEN CANYON DAM
There have been significant changes in the riparian
communities along the river below Glen Canyon Dam since
the Dam began functioning in 1962. These changes are
discussed in detail in Chapters I and II, For the mosv,
part, it may be generalized that the Dam has acted to
control high volume, beach scouring floods, and that the
riparian community throughout the study area is increasing
at a rapid rate. The increase in vegetative growth (increase
in available habitat) brings with it a concomitant
increasa in the density and diversity of animal life
alone Colorado River.

176

How this "new" vegetative community has effected
the animal life is discussed in the Chapters dealing
with each faunal group.
Overall, Glen Canyon Dam has produced the most
significant effects on the Grand Canyon biota. The
impacts of river runners are generally concentrated in a.
very small unit area at each major campsite, except
when they are involved in side canyon or special
interest area hikes. Hiking the side canyons (e.g.,
Saddle Canyon, Tapeats Creek, Deer Creek, etc.) and
visiting special interest areas (e.g., Stanton's
Cave, Nankoweap, etc.) probably result in the most
significant impact in terms of vegetation trampling
that we have witnessed thus far in the canyon. With
some minor trail construction and maintenance, this
destruction can be significantly mitigated.

177

CHAPTER XIII
SUMMARY
The scope of this project was designed to cover two
central themes. First, there was an effort to inventory the
biotic resources of the riparian zone of the Colorado River,
and second, there was an attempt to evaluate the ecological
relationships between the biotic resources and Hoover and
Glen Canyon Dams and river runners and other back country
enthusiasts.
The following points have been discussed in the preceding
chapters.
Chapter I.

Vegetational Changes Along the Colorado River

a)

The construction of Hoover Dam flooded out the
existing vegetational belts and established two
distinctive zones below mi. 240. The lower one is
characterized by almost impenetrable thickets of
salt cedar and the upper one is composed of the
typical desert flora which existed there before
Lake Mead.

b)

The construction of Glen Canyon Dam in 1963 and thus
the suppression of annual flooding from Lees Ferry
downstream to mi. 240 has permitted the development
of a new riparian community. This vegetational
community characterized by salt cedar, arrowweed,
coyote willow, desert broom and seep-willow has
become more firmly established in the zone once
subjected to periodic flooding. Variations in
water released from the pov/er plant at Glen Canyon
Dam determine the lower boundary of this new community.
These variations in flooding of the area below this
zone nave prohibited the establishment of any
extensive communities,- however, car-tail and horsetail have become established in some locations
below the new salt cedar belt.

c)

There are four visually distinct vegetation belts
from Lees Ferry to mi. 243. The lowest is
characterized by a salt cedar-willow-seeo-willow
zone; above this is the zone of ephemeral plants
which is heavily utilized dy man, We then find a
mesquite acacia-Apache plume belt and beyond this we
have the communities cf typical desert species on
the talus slopes.

179

Chapter II.

Vascular Flora of the Grand Canyon

a)

Botanical investigations within the riparian and
adjacent habitats of the Colorado River study
area have discerned the presence of 807 species
of vascular plants representing 92 families.

b)

Two species, previously undescribed, Flaveria
mcdougalii and Euphorbia rossii, are presented.

c)

A total of 210 species are new to the local flora,
74 of which resulted from collections during this
project. The remainder are from refined herbaria
and literature searches that took place during the
contract period.

Chapter III.

a)

Dietary Characteristics of Some Grand Canyon
Amphibians and Reptiles

The diets of eight insectivorous reptile and
amphibian species showed considerable variability
temporally and spatially.

Chapter IV„

Demography of Three Species of Grand Canyon Lizards

a)

Male and female reproductive cycles and intensity
of predation display little difference from other
Southwestern areas.

b)

The spring season is the period of greatest
reproductive activity in Grand Canyon lizards.

Chapter. V.

Mammals of the Colorado River

a)

Demographic investigations on the rodent communities
of beach and terrace areas indicate that beach
communities tend to be more complex, less productive
and less stable than those of the terrace areas.

b)

Peromyscus eremicus appears to be the most successful
small mammal in the riparian zone of the Grand
Canyon.

c)

Home range data indicate an inhibitory effect of
high temperature upon rodent movement in at least
twc species.

d)

Survivorship is very low and suggests a nearly
annual population turnover ra.te.

130

e)

Dietary analysis of 5 species of sympatric rodents
indicate that green vegetation and insects are more
important food items than seeds. The relative amounts
of green vegetation and insects vary per species per
area =

f)

Analysis of reproduction in 9 species of rodents
revealed larger mean litter sizes than what has
been reported elsewhere for the same species., Also,
reproduction in the Grand Canyon is generally
confined to the spring and summer months„

Chapter VI.

Birds of the Colorado River

a)

One hundred seventy-eight species of birds utilize
the Colorado River and its riparian habitats. Of
these, only 41 are breeding species.

b)

The majority (74 percent) of breeding species are
primarily restricted to or prefer the narrow band
of vegetation existing from the high water line
to the banks of the river, while the remainder are
restricted to the desert scrub, the talus slopes
or the vertical cliffs of the canyon walls.

c)

Approximately 14 percent of the total breeding bird
community restricted to the "green" vegetation of
the river bank, the vegetation that has proliferated
since the construction cf Glen Canyon Dam.

d)

The breeding season within the area is April through
August, with most activity occurring from April
through June.

e)

The most common breeding birds of the area are
the Lucy's Warbler, accounting for almost 20 percent
of the total population, folio-wed by the Rouse Finch
(15 percent) and the Canyon Wren (11.5 percent).

f)

The total population density of the 2.25 mile breeding
bird study area was decermined to be 3.93 pairs/mile,
bird species diversity (Kc) was 2.69 and the eveness
of ais'cributior, of the species (Jv) was .76.

g)

Exotic bird species, r.he House Sparrow and Starling
are only found in areas of heavy7 human concentration.

181

Chapter VII.
a)

Over twelve thousand insect specimens in 20 orders
and 247 families have been prepared and identified.

Chapter VIII.

a)

An Insect Inventory of Grand Canyon

Insect Production of Native and Introduced
Dominant Plant Species

Tamarix chinensis is not evenly incorporated into the
riparian ecosystem. Within its cycles T. chinensis'
insect production fluctuates dramatically in comparison
to the more harmonious shifts noted on dominant
native plant species.

Chapter IX.

Distribution of Feral Asses

a)

The areas occupied by feral asses in the Grand Canyon
are from Tanner Canyon to Crystal Creek on the
south side of the river. From Crystal Creek to
Tapeats Creek, asses inhabit both sides of the river.
This area between Crystal Creek and Tapeats Creek is
the only area where feral asses appear above the
Redwall of the canyon in any numbers. Havasupai
Point and Pasture Wash on the South Rim have resident
ass populations. On the north side of the river, asses
occasionally go above the Redwall on Point Sublime
and Swamp Point.

b)

From Tapeats Creek to Havasupai Creek, asses inhabit
only the south side of the river. From Whitmore
Canyon to 220 Mile Canyon, asses occur on the north
side of the river. From 215 mile to Lake Mead, asses
inhabit the south side of the river.

c)

Areas of highest feral ass densities appear to be
from Red Canyon to Hermit Canyon on the south side
of the river, the Shinumo Amphitheater, Parashant
Canyon to 220 Mile Canyon on the north side of
the river, and mile 215 to Bridge Canyon on the south
side of the river.

d)

The area from mile 215 to Lake Mead is part of the
Hualapai Indian Reservation and is not included in Grand'
Canyon National Park. However, this area appears to
contain extremely large populations of feral asses.

182

Chapter X.

Feral Asses on Public Lands:
Biotic Impact

An Analysis of

a)

The results of this investigation demonstrate
conclusively that the feral ass has a
negative effect on the natural ecosystem of the lower
reaches of the Grand Canyon. The principal irapact
of the feral ass is habitat destruction through grazing
and trampling.

b)

On the study area where feral asses occur the
vegetation cover and rodent populations were
significantly reduced when compared to the study area
where feral asses were absent. On the control plot,
28 species of vascular plants were found compared
to 19 on the impact plot. The total vegetation cover
on the control plot was 80 percent, compared to 20
percent on the impact plot. The mean area (m~) occupied
by each individual catclaw or mesquite shrub 'was
5
2
•
27.9m'' on the control plot and 20.7m on the .impact
plot.
The mammal species diversity (H1) was higher on the
control plot (.78652) than it was on the impact
plot (.69022). In addition, the average absolute density
of small mammals from March 1974 to January 1975 on the
control plot was 128 mammals/acre (51.8/ha.)
approximately four times the 32.6/acra (13.2/ha.)
found on the impact plot. Thus, differences between
the two areas in mammalian species composition and
diversity were attributed to the depauperate flora,
particularly the forbs and grasses, on the 209 Mile
Canyon impact area.

c)

Chapter XI.
a)

Campsite Usage and Impact

Human impact on the riverine ecosystem seems to be
a function of visitor activities (e.g. campfires,
sewage disposal, etc.) and the specific biotic
sensitivity of the use area rather than a function of
the total number of users. Therefore,
management to minimize impact should be resource
and education oriented instead of simply stressing a
carrying capacity figure for the entire Colorado River
within the Grand Canyon.

183

b)

In 1974, 395 different campsites were reported between
Lees Ferry and Pierce Ferry, in 1975 350 different
campsites were used.

c)

The following types of human impact on the beach
ecosystem have been identified: fire, litter,
trampling of vegetation, sewage disposal, noise, moving
of naturally occurring objects and the presence
of people. An indirectly related impact to man's
activities, that of the fluctuation river level
due to differing water releases from Glen Canyon Dam
are also discussed.

Chapter XII.

Interrelations of Man and the Biota

a)

The primary impact of river runners has been
determined to be excessive trampling of vegetation
at special interest areas and many popular
tributaries.

b)

Other negative impacts include the feeding of
some wildlife species by improper organic
garbage disposal that has resulted in an
increase in population densities of Common
Ravens and House Sparrows.

c)

Flies and red ants are positively correlated
with human densities at major campsites and are
probably a result of improper organic garbage
disposal and possibly an accumulation of human
waste products.
General Summary Statement

Although the inventories and descriptions of the biotic
resources of the riparian zone of the Colorado River from
Lees Ferry to the Grand Wash Cliffs will never be completed,
the results of this study have greatly added to the "state of
knowledge" regarding these resources.
As outlined in this report, the negative impacts on the
ecology of the riparian resources resulting from the annual
invasion of over 15,000 river-runners is relatively small.
The greatest impacts result from off river vegetation destruction
at special interest areas and frequently visited tributaries
of the Colorado River, and the accumulation of fecal waste
products on the heavily used beach areas.

18^

It is our belief that these impacts may be significantly
mitigated by (a) construction and maintenance of an adequate
trail system in the areas of heavy vegetation impact, (b)
the future removal of all fecal waste material from the
beach areas of the river, and (c) the initiation of an
education program for both private and commercial outfitters
and boatmen (particularly the latter) regarding current
and future National Park Service river-running regulations
and general conservation practices and behavior.
Finally, it must be stressed that this project surveyed
the impact of man only after a relatively short period
of heavy Colorado River use. The impacts of man on the
riverine ecosystem over the next several years should be
carefully monitored for an evaluation of the long-term
effects of man on this valuable resource.

185

APPENDICES

187

APPENDIX 1
Publications and related manuscripts resulting from this study.

Aitchison, S. W. 1976. Human impact in the Grand Canyon.
River, April, 3(4):18-19.

Down

Aitchison, S. W., S. W. Carothers, M. M. Karpiscak, M. E. Theroux
and D. S. Tomko. 1975. An ecological survey of the
Colorado River and its tributaries between Lees Ferry
and the Grand Wash Cliffs, Phase I. National Park Service,
Grand Canyon National Park, unpubl. ms.
Carothers, S. W. 1976. Canyons, commitments, and experiences:
a naturalist reflects. Plateau 49(1):16-25„
Carothers, S. W. and R. R. Johnson. 1975. Recent observations
on the status and distribution of some birds of the
Grand Canyon region. Plateau 47(4):140-153.
Carothers, S. W., R. R. Johnson, and M. E. Stitt. In press.
Feral asses on public lands: an analysis of biotic impact.
Transactions of the North American Wildlife Conference,
Washington, D. C.
Carothers, S. W., J. H. Overturf, D. S. Tomko, D. B. Wertheimer,
W. W. Wilson, and R. R. Johnson. 1974. History and
bibliography of biological research in the Grand Canyon
region with emphasis on the riparian zone. Unpub. National
Park Service Report.
Johnson, R.. R. , S. W. Carothers, and N. J. Shaxber. 1976.
Grand Canyon birds, field checklist. Grand Canyon Natural
History Association, Grand Canyon, Arizona.
Ruffner;, G. A. and S. W. Carothers. 1975. Recent, notes on the
distribution of some mammals of the Grand Canyon region.
Plateau 47 (4):154-160.
Shoemaker', P. L. 1976.
Canyon SAMA.

The darker side of Brighty.

Grand

Shoemaker, P. L. and S. W. Carothers. 1976. Burro? threaten
parts of Grand Canyon. Nan. Park Service Newletter 11(8):l-2.
Tomko, D. S.
Canyon.

1975. The reptiles and amphibians of the Grand
Plateau 47(4):161-166.

139

Tomko, D. S. 1976a. Rana pipiens (Ranidae) in the Grand Canyon
of the Colorado River, Arizona. S. W. Naturalist 21(1):131.
Tomko, D. s. 1976b. Grand Canyon amphibians and reptiles, field
checklist. Grand Canyon Natural History
Canyon, Arizona.
Wertheimer, D. B. and J. H. Overturf. 1975. A history of
biological research in the Grand Canyon region.
Plateau 47 (4):123-139.

190

APPENDIX 2
Professional papers presented and/or abstracted.
Aitchison, S. W. 1974. Campsite evaluation forms and
visitor usage forms. Grand Canyon Research Symposium,
Flagstaff.
Aitchison, S. W. 1975. Human impact on wildlife.
Academy of Science, Tempe.
Aitchison, S. W. 1975. River-running and wildlife.
Canyon Research Sympsoium, Grand Canyon,
Carothers,
small
along
Grand

Arizona

Grand

S. W. 1974a. Wild Burros, vegetation cover and
mammal populations. their interrelationships
the Colorado River. Grand Canyon Research Symposium,
Canyon.

Carothers, S. W. 1974b. MNA Ecological Survey: an overview
and progress report. Grand Canyon Research Symposium,
Flagstaff.
Carothers, S. W. and R. R. Johnson. 1974. Recent observations
on the status and distribution of some birds of the
Grand Canyon region. Grand Canyon Research Symposium,
Flagstaff.
Carothers, S. W., R. R. Johnson, and M. E. Sritt. 1976.
Feral asses on public lands: an analysis of biotic impact.
4.1st Annual North American Wildlife and Natural Resource
Conference, Washington, D. C.
Carothers, £. W. and G. A, Ruffner. 1975. Feral asses,
vegetation, and small mammals: their interrelationships
in the Grand Canyon. 55th Annual State Meeting of the
American Society of Mammalogxsts, Missoula, Montana.
Carothers. S. W. , M. E. T'neroux, D. S. Tomteo, and G A. Ruffner,
1975. Feral asses, vegetation, and small mammals:
their interrelationships in Grand Canyon. Arizona Academy
of Science, Tempe.
Ruffner, G, A. and S. W. Carothers. 1974. Recent notes on
the distribution cf some mammals of the Grand Canyon
region. Grand Canyon Research Symposium.

191

Shoemaker, P. L. 1975. Distribution of feral asses in the
Grand Canyon, Grand Canyon Research Symposium, Grand Canyon.
Theroux, M. E. 1975. Vegetative community structure within
the Grand Canyon: unique problems of classification
and mapping. Arizona Academy of Science, Tempe.
Theroux, M. E. 1975. A question of timing: man's impact
on the vegetation of the Grand Canyon. Grand Canyon
Research Symposium, Grand Canyon.
Tomko, D. S. 1974. The amphibian and reptile species of the
Grand Canyon. Grand Canyon Research Symposium, Flagstaff.
Tomko, D. S. 1975. Population dynamics of small mammals
in the Grand Canyon. Arizona Academy of Science, Tempe.
Tomko, D. S. 1975. Population characteristics of Nankoweap
small mammals. Grand Canyon Research Symposium, Grand
Canyon.
Tomko, D. S. 1975. Diet characteristics of Grand Canyon
lizards. Grand Canyon Research Sympsoium, Grand Canyon.
Turner, R. and M. M. Karpiscak. 1975. Vegetational changes
in the Grand Canyon. Journal of Arizona Academy of
Science, Tempe.

192

.APPENDIX VI-1
A checklist of the birds occurring along the Colorado Pdver from Lee s Ferry (mile 0.0)
to the Grand Wash Cliffs of Lake Mead (mile 279.0).
Species marked with an asterisk (*) indicate those not included in recently revised
checklist of birds of the Grand Canyon (see Johnson et al., 1976).

H
CO

Abundance: C - Common; easily found in proper habitat in right season.
F -• Fairly common; may be found in low numbers or scattered through the orooer
habitat in right season.
u - Uncommon; may or may not be found with difficulty in oroper habitat in
right season.
R - Rare., not to be expected, occurrence unpredictable.
A = Accidental; completely out of normal range
[J = Hypotheticai; alledged occurrence in area not substantiated.
Status;
PR - Permanent Resident
SR = Summer Resident
W = Winter Visitant
J ~ Irregular
T « Transient (Migrant)
SPECIES
Abundance/Status Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
GREBES
Eared Grebe
Western Grebe
Pied-billed Grebe

u
R
R

PELICANS
Brown Pelican
white Po]ican*

A
A

CORMORANTS
Double-crested Cormorant

R

T
T
T

x
x

x
x:

x

x
x

x
X

T

x

x

SPECIES
HERONS & BITTERNS
Great Blue Heron
Green Heron
Common Egret
Snowy Egret
Black-crowned Night Heron
[American Bittern]

H
VO

Abundance/Status
F
R
R
U
U

T
T
T
T
SR

Jan Feb Mar Apr May Jun Jul Aug See Oct Nov Dec
x

x
x

x

x

IBISES
White-faced Ibis

U

T

SWANS, GEESE & DUCKS
Canada Goose
Mallard
Gadwali
Pintail

U
F
R
U

T
T
T
T

x
x

Green-winged Teal
Blue-winged Teal
Cinnamon T e a l

U
U
F

T
T
T

x

American Widgeon
Shoveler
Canvasback
Common Goldeneye*
Redhead
Ring-neck Duck
Lesser Scaup
Bufflehead

R
U
R
R
R
R
R
U

T
T
T
T
T
T
T
T

Common M e r g a n s e r
Ruddy Duck

F
R

T
T

x

x

x

x

x

x
x
x

x

x

x
-s

x

x

x
x

x

x

[x]

x
x
x
x x
x
x

x

x
x

x
x
x

x

x x

x
x

x

x

x

x

x

x

x

x

x

x

x
x

x

x

x

x
x
x

x
x

x
x

x
x
x
x
x

x

x

x

x

x

x
x
x
x

x
x
x
x

x

x

x
x

x

x

x

x
x

x

x

x

x

SPECIES

H
rO

Abundance/Status

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

AMERICAN VULTURES
Turkey Vulture

F

SR

HAWKS
Sharp-shinned Hawk
C o o p e r ' s Hawk
Red-tailed Hawk
Swainson's Hawk
Golden E a g l e
Raid Eagle
Marsh Hawk
Osprey

U
U
F
U
U
R
R
R

T
SR
PR
T
PR
T
T
T

FALCONS
Prairie Falcon
Peregrine Falcon
Kestrel

R
R
C

PR
PR
PR

COOTS
American Coot

U

T

x

x

KILLDEER
Killdeer

U

T

x

x

SNIPE S SANDPIPERS
W i l s o n ' s Snipe
Spotted Sandpiper
Willet
long-billed Curlew
Greater1 Yellowlegs
Least Sandpiper

U
F
R
R
R
R

T
SR
T
T
T
T

x

x
x

x
x
x
x

x
x
x

x
x

x

x

x

x

x
x

x

x

x
x

x
x

x
x

x
x

x
x
x
x

x
x
x

x

x
x

x
x

x
x

x
x

x
x

x
x

x

x
x

x
x

x
x

x

x

x

x

x

x
x

x
x

x
x

x

x

x
x

x
x
x

x

x
x
x

x
x
x

x

x

x

x
x
x

x

x

x

x

x

x

x

x

x

x
x
x

x
x

x

x

x
x
x

x

x

x

x

SPECIES

H
cr.

Abundance/Status

AVOCETS AND STILTS
American Avocet
Black-necked Stilt

U
R

T
T

PHALAROPES
Wilson's Phalarope

R

T

GULLS & TERNS
California Gull
Bonapart's Gull*
Herring Gull*
Ring-billed Gull
Black Tern
Forster's Tern*

R
R
R
R
R
R

T
T
T
T
T
T

PIGEONS AND DOVES
band-tailed Pigeon

R

T

Mourning Dove

F

SR

ROADRUNNER
Roadrunner

R

PR

OWLS
Screech Owl

R

T

G r e a t - h o r n e d Owl

U

PR

Long-eared Owl
Flammulated Owl

R
R

T
T

GOATSUCKERS
Poorwill
Lesser Nighthawk*

R
R

T
T

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

x

x
x

x
x

x

x
x
x

x
x

x

x
x

x
x

x

x

x

x

x

x

x
x
x

x

x
x

x
x

x

x

x

x
x

x

x

x

x
x

x

x
x

x

x

x

SPECIES

g

Abundance/Status

SWIFTS
Vaux's Swift
White-throated Swift

R
C

T
SR

HUMMINGBIRDS
Black-chinned Hummingbird
Costa's Hummingbird
Broad-tailed Hunaningbird

F
R
U

SR
T
T

KINGFISHERS & WOODPECKERS
Belted Kingfisher
Flicker
Yellow-bellied Sapsucker
Fairy Woodpecker
ladder-backed Woodpecker

U
U
U
0
R

T
W
T
T
SR

TxRANT FLYCATCHERS
Eastern Kingbird
Western Kingbird
Casein's Kingbird
Ash-throated Flycatcher
Weid'sCrested Flycatcher
Black Phoebe
Say5 s Phoebe
Western Flycatcher
Western Wood Pewee

R
U
U
F
u
C
FC
U
U

T
SR
SR
SR
T
BR
T & SR
T
T

SWALLOWS
Violet-green Swallow
Tree. Swallow
Bank Swallow
Rough-wing Swallow
Barn Swallow
Cliff Swa]low

C
R
R
R
R
U

?
T
T
T
T
T S SR

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

x
x x
x
x

x

x
x

x
x

x
x

x

x
x
x
x

x

x

x

x

x

x
x

x
x
x
x

x
x
x
x
x x

x
x

x
x

x
x
x

x
x
x

x

x

x

x

x

x
x
x
x
x
x
x

x
x

x
x

x
x
x
x
x

x
x
x
x
x

x
x
x

x
x

x
x

x
x

x
x
X
x
x
x

x

x

x
X
x
x

x

x
x
x
x
x
x

x
x

x

x
x

x

x

x

x

x

x

x
x
x

x

SPECIES

Abundance/Status

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

CROWS & JAYS
Steller's Jay
Scrub Jay
Raven
Pinyon Jay

R
U
C
U

T
T
PR
T
x

CHICKADEES & BUSHTITS
Mountain Chickadee
Common Bushtit

U
F

T
W

Dipper

F

PR

WRENS
House Wren
Winter Wren

U
R

T
'i'

B e w i c k ' s Wren
C a c t u s Wren
l o n g - b i l l e d Marsh Wren
Canyon Wren
Rock Wren

U
R
R
C
C

T
T
PR
PR

MOCKINGBIRDS S THRASHERS
Mockingbird

U

T

ROBINS & THRUSHES
Robin
Hermit Thrush
Western Bluebird
Mountain Bluebird
Townsend's Solitaire

U
R
U
U
U

T
T
T
T
T

x
x

x

x

x
x x

x
x
x
x
x

x
x
x

x

x

x
x

x
x

x

x
x

x

x

x

x

x

x

x

x

DIPPERS

so
oo

x

x

x

x

x
x
x

x

x

x

x

x

x

x

x
x

x

x

x

x

x
T

x
x
x

x
x
x

x
x

x
x
x
x

x
x
x
x
x

x
x
x

x
x

x

x
x
x

x

x
x

x

x
x

x
x

x
x

x
x

x

x

x

x
x
x

x
x

x
x

SPECIES

VO

Abundance/Status

Jan Feb Mar. Apr May Jun Jul Aug Sep Oct Nov Dec

GNATCATCHERS AND KINGLETS
Blue-gray Gnatcatcher
Golden-crowned Kinglet
Ruby-crowned Kinglet

F
K
U

PR
T
T

x

x

x

x

X

x

PIPITS
Water Pipit

R

T

x

SILKY FLYCATCHERS
Fhainopepla

U

SHRIKES
Loggerhead Shrike
Northern Shrike

U
R

T
T

Local

SR

x

x

x

x

V1RE0S
Bell's Vireo
Gray Vireo
Solitary" Vireo
Warbling Vireo

C
R
U
U

SR
T
T
T

x

x
x
x

x

x

WOOD WARBLERS
Orange-crowned Warbler
[Blackburrian Warbler]*
Virginia's Warbler
Lucy's Warbler
Yellow Warbler
Vellow-rumped Warbler

UJ
A
P
C
F
U

T

STARLINGS
Starling

I SB. & T

x

x

x

x

x
x
x

x

x
x

x

x
x

x

x

x

x

x

x

x

x

x

x

x

x
x

x

x

[x]
T
SR
SR
T

x

x
x

x
x
x

x
x

x
x

x
x

x
x
x
x

x

SPECIES

Abundance/Status

WOOD W A R B L E R S (cont.)
Black-throated Gray Warbler
Ovenbird
Northern Waterthrush
MacGillivray's Warbler

0
A
U
U

T
T

Yellowtbroat

F

SR

Yellow-breasted Chat
Wilson's Warbler
American Redstart

F
U
R

SR
T
T

Local

PR

BLACKBIRDS a ORIOLES
Yellow-headed Blackbird
Redwing Blackbird
Hooded Oriole
Scott's Oriole
Northern Oriole
Brewer's Blackbird
Great-tailed Grackle
Brown-headed Cowb.i rd

U
Ll
U
U
U
U
R
F

T
T
T
T
SR
T
T
SR

TANAGERS
Western Tanager
Summer Tanager

F
R

T
T

GROSBEAKS, FINCHES, SPARROWS
Rose-breasted Grosbeak
Black-headed Grosbeak
Blue Grosbeak

& BUNTINGS
R
T
U
T
F
SR

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

T

x
x

x
x

x
x
x

x
x

x

x
x
x

x

x

x

x

x

x

x
x

x

x

x

x
x

WEAVER FINCHES
House S p a r r o w

ro
o
o

x

x

x

x

x

x

x
x
x
x
x
x
x

x

x

x
x
x
x
x
x

x
x

x
x

x
x

x
x

x
x

x

x

x

x
x
x

x
x

x

x

x

x

x

x
x
x
x

x

x
x

x

x

x
x

x

x

x
x

x

SPECIES

o
H

Abundance/Status

GRGOBFAI..S, F I N C H E S , SPARROWS
Indigo Bunting
Lazuli Bunting
House Finch
Pine Siskin
Lesser Goldfinch
Green-tailed Towhee
Rufous-sided Towhee
Brown Towhee
Savannah Sparrow
Vesper Sparrow
hark Sparrow
Rufous-crowned Sparrow
Black- throated Sparrow
Sage Sparrov;
Oregon Junco
Gray-headed Junco
Chipping Sparrow
Brewer; s Sparrow
Black-chinned Sparrow
Fox Sparrow
Lincoln's Sparrow
Song Sparrow
Harrd s Sparrow
White-crowned Sparrov.'
White-throated Sparrow

Jjan Fjio M a r A p r M a y J u n J u l Aug Sep Oct Nov Dec

& BUNTINGS (cont.)
U
SP.
V
SR
C
PR
x
R
T
I
SR
0
T
U
T
R
T
R
T
R
T
R
T
R
T
F
PR
R
T
U
WT
x
0
W
U
T
11
T
R
T
R
T
x
U
T
x
U
T
x
A
F
T
x
A

x

x

x

x

x

x
x
x

x
x
x

x
x
x

x
x
x

x

x
x

x
x

x

x

x
x
x

x

x
x
x
x
x
x
x

x

x

x
x

x

x

x
x
x

x

x

x

x

x
X
x

x
x

X

x

x

x

x

X

X

x

x

x
x
X

x

x
x

x

APPENDIX VI-2
Annotated list of breeding species found along the Colorado
River from Lees Ferry (mile 0.0) to Diamond Creek (mile 225.0).
Turkey Vulture
The Turkey Vulture is rarely seen at river level. The
preferred habitat for this species is the high cliff areas of
the rim, usually in the Kaibab and Toroweap limestone
formations. We have sufficient records in the lower canyon
area (mile 180-225) during the breeding season that would
possibly indicate some breeding activity by isolated pairs
far below the rim. Observation dates are from March through
September.
Cooper's Hawk
Individual Cooper's Hawks have been recorded throughout
the canyon from March to November, suggesting that this species
may occasionally winter in the area. The preferred breeding
habitat for this species consists of any area with large trees,
from the desert to the boreal forests. The only positive
breeding record we have for the inner canyon, is upper Deer
Creek, mile 136, where a pair of this species nested in the
large cottonwood trees in every year from 1973 to 1976.
Preliminary searches along Havasu Creek and Tapeats Creek
have failed to produce any additional breeding pairs.
Red-tailed Hawk
The Red-tailed Hawk is rarely seen at river level, however,
it is the most common large hawk, seen soaring high above
the river as one traverses the canyon by boat. The preferred
nesting habitat for this species consists of large trees,
from the deserts to the high mountains, but it will utilize
cliffs and ledges in the absence of trees. Our surveys
indicate that the Red-tail is a permanent resident in the
canyon, and is observed with regularity during float trips.
Our data indicate that there are about 10 locations within
the study area where this species is repeatedly seen.
Golden Eagle
The Golden Eagle is similar in distribution to the
Red-tailed Hawk, occurring throughout the study area, rarely
seen at river level, and preferring to nest on the high
cliffs of the canyon country.
The eagle is a permanent

202

resident in the canyon and is repeatedly seen from several
specific locations within the canyon.
Prairie Falcon
Throughout the United States, populations of the Prairie
Falcon have been on the decline in recent years (Carothers
and Johnson, 1975). For this reason, this species is officially
listed in the compendium of "threatened" wildlife of the United
States, that has been compiled by the Department of Interior
(U.S.F. and W.S. Resource Publication, 114). During our
investigation we have observed this falcon several times within
the inner gorge of the Grand Canyon. Our observations indicate
the possible presence of two eyrie sites along the Colorado
River in Marble Canyon. The preferred haJoitat of this species
consist of high cliffs for nesting sites and an abundant
supply of small diurnal mammals nearby for food. Clearly,
the canyon country contains an abundance of high cliffs, but
compared to other desert areas, small diurnal mammals are
present in relatively low densities (pers. observations).
Peregrine Falcon
The Peregrine Falcon is currently on the U.S.F. and W.S.
"endangered" species list. The Grand Canyon may represent one
of the few areas in the state, if not the entire Southwest,
where active Peregrine Falcon eyries occur.
American Kestrel
Also known as the Sparrow Hawk, this is the most common and
regularly distributed falcon along the Colorado River.
Although we have evidence that the Sparrow Hawk will occasionally
rash in potholes or crevices alone cliff faces, its preferred
nest sites consist: of cavities in trees. This species is a permanent
resident in the canyon, however some migrants also pass
through the area during April and September. Our censusing
data indicate that there are at least 7 or 3 pairs of these
small falcons nesting along the 225 mile study area,.
Spotted Sandpiper
Although Spotted Sandpipers may be cossrved along the
upper Colorado River any month of the year, we have determined
that the: ones that breed during: June are most, likely
summe: residents only. During January and March, there are
fewer than 5 or 6 of these birds observed on the entire 225 mile
section of river with which we are concerned., By mid April,

103

however, their densities increase to about 15 individuals
observed and by early May, they are present in densities that
average 1 bird per 2 miles of river. These high densities
are maintained until mid September when the majority of the
birds migrate out. The Spotted Sandpiper lays its eggs
in a nest placed on the ground, usually in grassy clumps, and
most often very close to the water.
Mourning Dove
The Mourning Dove is a common summer resident of the
heavily vegetated areas of the Colorado River and its tributaries.
It is one of the few species that is capable of utilizing the
tamarix or salt cedar for nesting habitat. This species begins
to appear in early April in flocks consisting of 5-15 individuals.
Although a few pairs will break from the flocks and begin
breeding in late April, or early May, the general flocking pattern
persists until the end of May. The highest densities of the
dove are reached in April and May, then their numbers decline
steadily through September when they disappear, not to be
seen again until the following April. The high densities
recorded in April and May, reflect not only the arrival of
the summer resident birds, but the migration of others that
continue moving through the canyon to their northern breeding
grounds. It is interesting, that this is probably a one-way
migration, as our data do not indicate that the doves returning
from their breeding grounds in the fall utilize the canyon for
southward migration.
Roadrunner
Our observation records do net provide sufficent
information on this species to draw any definite conclusions.
The Roadrunner is known to live in the Sonoran zones throughout
the Southwest, but its occurrence within the Grand Canyon area
is very sporadic and rare. Although it is known to breed in
the desert around Lake Mead, the Roadrunner has not penetrated
the upper reaches of the canyon to any extent. Our observation
records are as follows: 13 July 1973, scats seen at mile 74.0;
16 July 1973, scats seen at mile 123.8; 13 November 1975; 1 adult
seen at mile 260.0;September 1575, one adult seen at mile 209.0.
Great-horned Owl
This owl is a permanent resident of the inner canyon,
preferring the mors heavily wooded areas, usually in tributaries
of the main river, for its nesting area. Although it is almost

20k

never seen, this owl may be heard almost any summer night
near Cardenas Creek, Bright Angel Creek, Indian Gardens or
Spencer Canyon. The nest of this species is usually placed.
on a high cliff, frequently overlooking its favorite hunting
areas, such as the marsh area near Cardenas Creek.
White-throated Swift
Although this species is probably the single most
common bird in all of the canyon country, its behavior and
distribution patterns are very enigmatic. Our records
indicate that it can be seen in large flocks foraging above
the Colorado River, and occasionally dropping down to water
level to drink or forage, from early March through September.
We have not observed this species in the inner canyon from
September to March, yet there are sporadic sightings during the
winter on the rim of the canyon. For the most part, this
species is a summer resident, nesting in deep crevices in the
high cliffs of the rim and inner canyon. It will frequently
forage in close association with the Violet-green Swallows.
Black-chinned Hummingbird
The Black-chinned Hummingbird is the only hummingbird
we have found nesting along the Colorado River from Lees
Ferry to Lake Mead. It arrives in early March, is seen all
spring and summer and then departs for the warmer south by
mid September. We have never found a nest of this species
along the main Colorado River, but they are commonly
found in the tributary canyons. The nests, placed on
either rock shelfs or in vegetation, usually contain
eggs by late April and the young are hatched and
off the nest by early May.
Ladder-backed Woodpecker
This woodpecker is a rare summer resident of the inner
canyon, found only occasionally along the Colorado River
(Cardenas Creek, Mankoweap). Our only verified breeding
records for this species are from Indian Gardens and UpperDeer Creek. It prefers the larger cottonwood. trees for
nest sites, and these trees are usually only found in the
tributary canyons. Our records are net sufficiently complete
to determine the arrival and departure dates for this species.
Ash-throated Flycatcher
The Ash-throated Flycatcher is a summer resident.

205

preferring to construct its nest in abandoned woodpecker
holes in large and small trees. In the Grand Canyon area,
it may also nest in cavities in rocks. This flycatcher
arrives on the breeding grounds in early April, and departs by
late August. Although this species may be found along the
entire length of the study area, it reaches its greatest
densities in the areas of heavy concentration of woody
vegetation, particularly the vegetated tributaries. Thus,
it is almost never seen in the Marble Canyon area, and
only a few may be found from Nankoweap (mile 52.0) to
Red Canyon (mile 76.0), and almost none in the Precambrian
rocks from Red Canyon to the area just below Deer Creek
(mile 136.0). In the area from Kanab Creek (mile 143.0)
to Diamond Ceek (mile 225.0) the Ash-throated Flycatchers
are frequently ecountered and evenly distributed. They
reach their highest densities in these areas primarily
because of the proliferation of woody vegetation that
may be found in this lower section of the canyon.
Black Phoebe
This flycatcher is a permanent resident of the inner gorge
of the Grand Canyon. It is exclusively restricted to
breeding areas where there is running water and moderate to
extensive amounts of riparian vegetation. The Black Phoebe
may be found in every side canyon that contains water from
Lees Ferry to Lake Mead. For some unknown reason, it does
not prefer to nest along the main part of the Colorado River
even when it appears all the nesting and feeding requirements
have been met. The one exception to this, is that in 1974
a pair of Phoebes constructed their nest on the north side of
the large boulder chat forms Boulder Narrows (mile 18,5).
Also, they will nest along the Colorado River when there
is a spring dripping or running directly into the river; e.g.,
springs in Marble Canyon {ca. mile 36.0) and the spring dripping
into the river from the north side of the canyon at mile
155.0.
Sayls Phoebe
Most of the Say's Phoebes we have observed along the
Colorado River are migrants, utilizing the Grand Canyon
corridor as a migratory route to their northern breeding
grounds. During January, one may see fewer than 5-6 Say's
Phoebes on a complete traverse of the 225 mile study area.
These few birds are probably some eccentric winter residents.
By early March, the migration is on. All through March and
tc a. somewhat lesser extent in April, Say's Phoebes are in
extremely high densities all along the Colorado-River. During mid

206

March of 1975, this phoebe was seen in densities as high as
1 or 2 individuals per mile. During their migration, they
frequently appear to be in pairs, and by mid April we have
observed definite courtship behavior. The densities drop
off dramatically by May, and remain relatively low for
the remainder of the year, until the heavy migration begins
again in early March. The birds that remain to breed in
the Grand Canyon area build their nests on ledges above the
river and in permanently flowing side canyons. They do not
need vegetation to the extent other flycathers do, but may
frequently construct their nests in areas completely lacking
in vegetation. Our breeding bird census data indicate that
approximately 24 pairs of Say's Phoebes nest from Lees Ferry
to Diamond Creek. This figure is probably an over
estimation as it is based on observed courtship behavior which may
not reflect breeding activity within the study area.
Willow Flycatcher
This Willow Flycatcher is the only member of the genus
Empidonax known to breed along the upper Colorado River and
its tributaries. It is a rare summer resident, arriving
sometime in May and leaving by late September. The only
areas from which we have verified breeding records are
Cardenas Creek Marsh (mile 71.0), Upper Deer Creek (mile 136.0)
and Havasu Creek (mile 157.0). We have previously published
additional information on the status of this species in the
Grand Canyon region (see Carothers and Johnson, 1975).
Violet-green Swallow
Although the Violet-green Swallow is seen from March
through September along the Colorado River, we know surprisingly
little about its breeding habits in the canyon country.
Typically, this species prefers to nest in cavities in trees
in the ponderosa pine and spruce-fir forests of both the north
and south rims of the Grand Canyon and surrounding boreal
forest areas. We have no positive evidence that it does
breed within the inner canyon, yet they are present in large
numbers throughout the breeding season and we have on occasion
observed pairs copulating in mid flight above the river. They
reach their greatest densities in April and May, often
occurring in mixed flocks with White-throated Swifts, Cliff,
Fern. Tree, Rough-wing and Bank Swallows. By late May,
their densities are noticeably lower, but large flocks are
still commonly seen throughout the remainder of the spring
and summer. Our feeling is that some of these birds do breed
in rock crevices in the ir.ner canyon, but this conjecture
awaits verification.
20?

Cliff Swallow
This swallow is an uncommon migrant during April and
May and September when it is seen in mixed flocks with other
swallows. It is also an irregular and rare summer resident
in the Marble canyon area. We have records of one small
breeding colony near mile 28 in 1975. With all the available
nesting sites and apparently abundant supply of food we are at
a loss to explain why this species is not more common as a
breeding resident along the Colorado River.
Common Raven
The Raven, a permanent resident in the canyon country
of the Southwest, prefers to build its nest of large and
small sticks on north facing rock ledges 100 to several
hundred feet above the river. The Raven has learned to
frequent the areas camped in by river parties along the
Colorado River. In the past, it was common for river
groups to leave quantities of organic garbage on the beaches,
specifically for the ravens. Present National Park Service
regulations forbid this practice, but the ravens still
remain at the periphery of major campsites, waiting for a
handout. If river parties have not contributed to increasing
the densities of ravens in the canyon, they have certainly
caused these birds to select nest sites based on areas of "nigh human
concentrations. Nest building begins in late March and
continues into April The young are usually off the nest
by early June.
Dipper
This bird, also known as the Water Ouzel, is a permanent
resident of the flowing tributaries of the Colorado River.
During the winter months of November through February it may
be frequently seen along the main portion of the Colorado
River, and we suspect that these winter birds are the same
ones that will nest in the tributaries during the spring.
Nest building begins as early as late February, as by late March,
the young are already off trie nest. The nest is usually
constructed under a small or large waterfall and consists
of a mossy acme, The highest densities of these birds during
the breeding season may be round along Bright Angel Creek.
Canyon Wren
The distinctive laughing or mocking song of the Canyon
Wren may be heard at any time of the year along the upper

208

Colorado River, This wren prefers the vertical cliff
areas for its permanent residency, thus the highest densities
are found in the Marble Canyon area and from Red Canyon
(mile 76.0) to Kanab Creek (mile 143.0). Although the
Canyon Wren occurs sympatrically with the Rock Wren,
there seems to be no direct competition, the Rock wren
preferring the loose talus slope areas to the vertical
cliffs. The nests of the Canyon "Wren are placed deep
into rock crevices and the young are usually off
the nest by early June. Due to its inaccessible nesting habitat
very little is known about the behavior and. natural history of
this species.
Rock Wren
The breeding activities of the Rock Wren closely correspond
with those of the Canyon Wren, with the exception of the
specific preference of breeding habitat. Like the Canyon Wren,
they also sing all year, but the frequency of their songs
increase dramatically in March and continue at a high level
until mid June. The Rock Wren is slightly less common than
the Canyon Wren.
Blue-gray Gnatcatcher
The Blue-gray Gnatcaitcher occurs only along the
Colorado River and in the tributary canyons that contain
large numbers of mesquite and/or acacia trees and some running
water. We have never observed a nest .in the Grand Canyon
area that was placed in any other type of vegetation. This
characterisoic then clearly limits the overall distj:ibution
of the gnatcatcher along the upper Colorado River. The
gnatca'cchers arrive on the breeding grounds in mid March, nest
construction begins in early April and most young are
fledged by mid April Both young and adults remain ir.
the canyon area until late September when the fall migration
begins.
Phainopepia
The distribution, breeding activities and migration
patterns of this species are extremely confusing throughout.
its range (see Phillips et ai., J.964) . In the Grand Canyon
area, we have two positive breeding records, both ir. mid March,
22 Marc:; 1975,. Mohawk Canyon (mile 174.0) and 28 March 1975,
2CS Mile Canyon. Other than those nesting dates, the Phainopepia
has fc&an bur rarely observed in along the upper Colorado River.
The only ether observation records are in May, when a few

20Q

scattered individuals have been seen at a variety of locations
within the canyon.
Phainopeplas are drawn to mistletoe, as a primary item
in their diet consists of mistletoe berries. In areas that
have been heavily overgrazed by wild burros, we find
abundant mistletoe infestation in the mesquite and acacia
shrubs, and it is in these areas where the Phainopeplas
are seen.
Starling
The Starling was introduced into the United States from
Europe in the very late 1800's. Although it was introduced
on the east coast, it had reached the west coast by the
early 1960's. Our research in the Grand Canyon and other
areas of the Southwest, confirm that the Starling will
only nest in close association with man. To this date,
its breeding activities have been confined to Lees Ferry,
Phantom Ranch, Indian Gardens, and Havasu Creek, particularly
in the vicinity of the campground and village. The migratory
periods for this species are confusing, but it begins
breeding as early as late February in Havasu Canyon and
then forms flocks and remains in the area often throughout
the winter.
Bell's Vireo
This species is evidencally a relative newcomer to the
avifauna of the Grand Canyon region. In their treatment
of the birds of Arizona, Phillips et al. (1964) state that
the Bell's Vireo was not present in the bottom of the Grand
Canyon, but that it. was present throughout the rest of the
state, occupying low shrubby vegetation, particularly mesquite
and acacia. Our data indicate that the Bell's Vireo is a
common summer resident within the lower section of the study
area (from mile 143.0 to Lake Mead), and that its preferred
habitat consists of the true phrear.ophytic vegetation such
as Salix, Baccharis, and to some extent the tamarisk, that
grows on the banks of the Colorado River.. The vireo arrives
in mid April, begins nesting in Kay and by early June the
young are fledged. The fall migration begins in August and
by late September, almost ail the vireos have departed south.
The distribution of the Sell's Vireo in the Grand Canyon
region is enigmatic. Although it is possible to find the
vireos in mid summer in almost any location within the canyon's
riparian system, they don't occur in high densities until

210

the area just above Kanab Creek (143.0). From that point downstream to Lake Mead, one may find a pair of Bell's Vireos spaced
no more than 100 meters apart in areas where green
vegetation proliferates.
Lucy's Warbler
This small gray warbler is the most common breeding
bird of the riparian habitat of the Colorado River from
Lees Ferry to Lake Mead. Although it characteristically
places its nests in cavities in trees, in the Grand Canyon
area it will also utilize crevices and cavities in rocks,
and will also occasionally weave a nest in riparian vegetaion.
The Lucy's Warbler arrives on the breeding ground in
early March and the fall migration begins in late July.
By September, most of the Lucy's have left the Grand
Canyon region. As with the Blue-gray gnatcatcher, the
distribution of the Lucy's Warbler is very closely associated
with the distribution of the mesquite and acacia trees and
shrubs. This warbler is usually not in evidence as one
travels Marble Canyon, until about mile 39.0 where the
mesquite/acacia association begins. Unlike the
gnatcatcher, however, the Lucy's Warbler will nest in other
reparian areas that are lacking the mesquite and acacia.
Yellow Warbler
The western race of the Yellow Warbler possesses a
breeding song there is very similar to that of the Lucy's Warbler.
To even the most experienced observer, these two species are
difficult to distinguish based on song alone. A genere.l rule
of thumb is that the Yellow Warbler song is shorter and
louder than that of the Lucy's. in the riparian hafbitats
of the Grand Canyon there are some subtle differences in
nabicau select.ion between tnese two species as well.
Basically, the Yellow Warbler prefers the. dense, ta.ll green
vegetation that may be found at the Cardenas Creek marsh
area, one marshy area at Mohawk canyon etc.- but not the
dry mesquite/acacia. areas that are preferred by the Lucy's.
The Lucy's Warbler will also inhabit the areas preferred by
the Yellow warbler, but the reciprocal! is rare.
The Yellow Warbler arrives on the breeding ground in mid
April, and remains until mid September. The nest is graced
near the top of the highest branch of green vegetation the
bird can find. They occur vary irregularly'' along the banks
of the Colorado River until just below Kanab Creek (mile
?.43.0) vnere the increasing amounts of green riparian grov/th

211

provide them with nesting habitat. From this point
downstream to Lake Mead, they occur in regular intervals
wherever the vegetation is bushy and thick.
Yellowthroat
This bright and noisy warbler is limited in distribution
in the Grand Canyon area to the marshy areas of the upper
canyon (Cardenas Creek, mile 71.0, north end of Nankoweap
Delta, mile 52.0) and the very dense growths of Baccharis,
Salix and Tamarix near the lower end. The Yellowthroat
arrives in late April and has usually departed by late
September, although we have scattered observations from
as late as November.
Yellow-breasted Chat
The habitat requirements for this large, raucous warbler
are identical to those of the Yellowthroat, thus their
distribution patterns in the Grand Canyon are similar. The
chat does not arrive on the breeding grounds until late
April or early May and by mid September, most birds have
already begun their journey south.
House Sparrow
Like the Starling, this sparrow is an introduced
species that does not fare well in the wild without the
presence of man. Where it does occur in the Grand Canyon
area, it is a permanent resident, raising up to three broods
of young per year. Areas of heavy House Sparrow concentrations
are the same as those listed for the Starling, Lees Ferry,
Phantom Ranch, Indian Gardens and Havasu campground and
village. In addition, we have recently discovered a pair
of House Sparrows building a nest in the large group of
tamarisk trees in the camping area across from Deer Creek
Falls (mile 136.0). It is probably net coincidental that our
visitor usage forms (see Chaper XI, "chis report) indicate
that this camping area receives more river groups per
year than any other campsite along the Colorado River.
Northern Oriole
The Cardenas Creek marsh id the only locale along the
Colorado River where this species may be found regularly during
the breeding season. This oriole prefers to breed in the
heavily vegetated side canyons {Clear Creek, Tapeats, Deer Creek,
Havasu etc.) where large cottonv/ood trees provide- the favored
nesting sites. The Northern Oriole arrives on its breeding

212

grounds in late May and remains until late August.
Brown-headed Cowbird
This member of the blackbird family is a nest parasite.
They do not build a nest of their own, but lay their eggs
in the nest of another species (very commonly the Yellow
Warbler and Bell's Vireo). The result is usually that the
young of the host bird die while the host parents raise
the young cowbird. Cowbirds are present along the
Colorado River from May? through September. Our data
indicate that they are more commonly? found in the vegetated
tributaries than on the main part of the Colorado River.
Blue Grosbeak
The Blue Grosbeak is a late arriving summer resident
that breeds along the full length of the Colorado River and to
a lesser extent, the vegetated tributaries. It does not
arrive on the breeding grounds until late May? or early June.
Nesting is not underway until July and the birds remain on
the breading grounds until late September. They are one of the
few species that seem to be adapting to using the tamarisk tree.
Indigo Bunting and Lazuli Bunting
These two species are treated together here because
they? are identical in distribution, abundance and habitat
preferences. They are summer resident species, rarely
occuring along the Colorado River and definitely not breeding
there. They seem to prefer almost exclusively? the vegetation
in upper Tapeats Creek, for it is here that they both reach
their highest densities. Further work needs to be done on
the interactions of these two birds.
House Finch
Although it is not uncommon to fend House Finches in
and along the Colorado River during the winter, there is a
heavy? influx of spring migrants moving into the preferred
breeding areas in early? April. Very? high breeding densities
are mar ntained until early July then the low densities
remain until following April. For this reason then, we
consider the House Finch to be a simmer .resident. This
species is the second most abundant of all the breeding species.
It will nest in a variety of habitat types, ranging from
rocky talus slopes to heavily vegetated tributaries.

213

The preferred habitat seems to be the areas that support
large mesquite, acacia or hackberry trees.
Lesser Goldfinch
The Lesser Goldfinch is an uncommon and irregular
member of the breeding avifauna of the Grand Canyon region.
As with the House Finch, it is not uncommon for some of these
birds to appear along the Colorado River during the winter.
During the spring however,(early April) a few birds, usually
in small local flocks, will move into some of the tributary
areas and breed. Our records are not sufficiently complete
to delineate the full migratory-breeding cycle in the Canyon,
but we do have breeding records from the following localities:
Cardenas Creek marsh, Phantom Ranch, Deer Creek and Tapeats
Creek.
Black-throated

Sparrow

This species is probably one of the most common breeding
birds of the desert environments adjacent to the Colorado River
riparian habitats (e.g., Tonto Platform).
Occasionally,
a few individuals will nest close enough to the riparian
habitat that they are detected in our breeding bird censuses.
We have a few records of nesting activity in the Granite Park
(mile 209.0) area, and a few scattered localities eisev/here.
The Black-throated Sparrow is a parmanent resident in the
Grand Canvon desert communities.

2ll4

KEY TO APPENDICES VT.I-1 and VIT-2 •
1.
2.

3.

4.
5.
6.

Location Range -- River miles between which specimens were
collected.
Distribution (from field observation as well as specimen
data)
U — Upper section of Grand Canyon, Lees Ferry (mile
0.0R) to Phantom Ranch (mile 37.8R).
M -- Middle section of Grand Canyon, Phantom Ranch
(mile 87.8R) to Diamond Creek (mile 225.9L).
L — Lower section of Grand Canyon- Diamond Creek
(mile 225.9L) to Pierce Ferry (mile 280.0L).
G — Entire length of Colorado River.
Relative Abundance of Insects (estimated from field
observation as well as specimen data)
R — Rare
N — Uncommon
C — Common
A — Abundant
Date Range -- Dates between which specimens were collected
(includes both adult and larval insect data).
Elevation Range — Elevations between which specimens were
collected.
Habitat.
a -- General Beach Habitat
b — Terrace (Bench)
c -- Talis Slope
d -- Burned Area
a ~ Marsh Area
f — In or Under Driftwood
g — Near Colorado River
h — In Colorado River
i -- Under Stones
j — Near a Side-Stream
k -- In a Side-Stream
1 - - Near a Seep or Spring
m — In a Pool (Lentic Situation)
n — In Mule Dung
o -- In Equus asinus Dung
p — Parasitic on .Anas plat.yrhyr.chos
q — Parasitic on Aeronautes saxatalrs
r — Parasitic on Plecotus townsendii
s -- Parasitic on Antrozous pallidus
t ••- Parasitic on Peromyscus eremicus
u -- Parasitic on Peromyscus manicuiatus
v -- Parasitic on Peromyscus crinitus
w -•- Parasitic on Neotoma lepida
x — Parasitic on Neotom.a albigula
y -- Parasitic on Bassariscus astutus

215

7.

Vegetation Associations of Insects (if any were noted):
1 — Equisetum spp.
2 — Juniperus osteosperma
3 — Ephedra spp.
4 — Typha spp.
5 — Bromus spp.
6 — Sporobolus airoides
7 — Oryzopsis hymenoides
8 — GRAMINEAE
9 — Yucca angustissima
10 — Agave utahensis
11 — Populus fremontii
12 — Salix exigua
13 — Salix gooddingii
14 — Salix spp.
15 — Atriplex canescens
16 — Abronia nana
17 — Lepidium montanum
18 — Rorippa nasturtium-aquaticum
19 — Stanleya pinnata
20 — CRUCIFERAE
21 — Cercis occidentalis
22 — Acacia greggii
23 — Prosopis juliflora
24 — Astragalus lentiginosus
25 — Alhagi camelorum
26 — Melilotus albus
27 — Larrea divaricata
28 — Ptelea pallida
29 -- Sphaeralcea spp.
30 — Tamarix chinensis
31 — Opuntia phaeacantha
32 — Sarcostemma cynanchoides
33 — Datura meteloides
34 -- Lycium spp.
35 — Mimulus cardinalis
36 — Franseria acanthicarps
37 --- Aster spp.
38 — Baccharis sergilcides
39 — Baccharis sarothroides
40 — Baccharis glucinosa and emoryi
41 — Baccharis spp.
42 — Brickellia longifolia
43 — Encelia spp.
44 — Erigeron spp.
45 — Gutierrezia spp.
46 — Haplopappus heterophyllus
47 -- Pluchea sericea
48 — Senecio spp.

216

8.

49 — Xanthium strummarium
Collection Methods:
A -- General Collection
B — Sweeping with Canvas and Mesh Collecting Nets
C — Malaise Trap on Ground
D — 15 Watt Ultra-Violet Light Trap
E — White Light Trap
F — Carrion Trap
G — Parasite Removed from Host Species
H -- Bufo punctatus Stomach Contents Analysis
I — Sceloporus magister Stomach Contents Analysis
J -- Urosaurus ornatus Stomach Contents Analysis
K
— u t a stansburiana Stomach Contents Analysis

cl [

A
Appendix VII-1.—Families, of Insects Collected in Grand Canyon National Park
LOCATION 1 R E L A T I V E 3 DATE 4 ELEVATION 5 HABITAT 6
RANGE
ABUNDANCE RANGE RANGE
DISTRIBUTION 2
(FT.)

TAXON

THYSANURA
Lepismatidae

71.0R-136.2R
C
4-V
2500
(U,M)
27-VII
2700
COIiLEMBOLA (After Braes,. Melander and Carpenter, 1954)
Arthropleona
Entomobryidae 0.9R-116.4L
N
24-1
2140

ro

VEGETATION 7
COLLECTION 3
ASSOCIATION(S)
METHOD

b,c,i

A

a,i,l,m

A

Isotomidae

34.9L-145.5L
(U,M)

N

26-1
1850
13-VIII 2850

c

4

A,B

Poduridae

34.9L-65.2R
(U)

N

13-VIII 2680
18-1
2850

e,g

4,12

A,B,D,

34.9L -246.0L
(G)

C

11-V
12-XI

1100
2850

e

1,4,6,27,34

A,B

N

23-IV
1980
17-VIII 2870

m

31.9R-246.0L
(G)

C

17-1
13-XI

1100
2890

i,k,m

0. 9R-246. ll.R
(G)

C

5-VIII
8-IX

1100
4000

m

Symphypleona
Sminthuiidae

CO

EPHEMKROPTERA (After ""singer, 1956)
Heptageniidae
31.9R-133.8R
(U.M)
Baetidae

ODONATA
Anisoptera
Aeshn.idae

B

4,40

*see Key
A- Phylogenetic order based on Borror and Delong (1964) unless otherwise indicated.
For text used in identification of insects see Appendix VII-3.

A,B,C,D,

A,E

Gorapbidae

203.6T,
(M)

Idbellulidae

1500

1090
2390

A

A

19-V
2250
16-VITI 2300

j

A

N

10-IX
24-IX

3600
3600

j

A

A

17-1
22-IX

1090
2890

j,k,l,m

A,B

53.0R-208.6L
(G?)

N

24-V
1510
31-VIII 2800

j,l

B,D

Tetrigidae

223-8L-246.0L
(L)

N

7-X
21-XI

1100
1330

Acrididae

0.9R-208.6L
(G)

C

6-III
5-X

1500
3200

124.0L-208.6L
(G?)

N

22-V
16-VII

31.9R-269.5R
(G)

C

29-1
14-XI

Lestidae

31.9R-248.4R
(G)

C

4-IT.I
26-IX

116.41,
(M)

R

0.9R-47.OR
(U)

Coenagrionidas 31.8R-248.4R
(G)
ro
H

6-VII1

a,m

Zygoptera
Agrionidae

vo

N
N

ORTHOPTERA
Cae]ifera
Tridactylidae

Ensifera
Tettigoniidae

Gryllidae

1,6,12,40

B

a,b,c,e

5,6,8,14,15
25,30,43

A,B,D,E,

1510
2100

a

11,12,23,27

A,B

1000
2880

a,e,f,i,j,l

13,35,40

A,B,D,K

'hasmatodea
Phasmatidae

87.8R

N

fall'74

2450

observation by M. Langdon

0.9R-187.0L
(U,M,L?)

R

28--IX
5-X

1610
3100

276.0L

N

31-1

1000

f

A

R

11-VII

2620

b

A

N

2-VII
14-VII

2050
2800

1

A,I,K

C

8-III
19-IX

1400
3100

a,f

R

7-X

1420

a

A

R

16.1
8-III

2140
2890

j

A

N

15-VII
1-X
10-111

1980
3600
2500

i,j,k

A

k

A

(M)
Mantodea
Mantidae

Blattaria
Blattellidae

47

A,E

(L)
undet. Blattaria

70.8L

ISOPTERA
Ka.lotermitidae 52.5R-124.0L
(U,M)
ro
ro
o

Rhinotermitidae 0.7R-218.0
(U,M)
DERMAPTERA
Forficulina
Labiidao

214.2R
(M)

PLECOPTERA (After Osinger, 1956)
Fil.ipalpia
Nemouridae
29.0L--116.4L
(U,M)
Setipalp.ia
Perlodidae
Perlidae

133.8R K.
Thunder R.
136.2R
(M)

(M)
R

20

A

PSOCOPTERA
Ty09iomorpha
Psyllipsocidae 120.OR
(M)
undet. Family

133.8R-171.4R
(M)

N

31-VII

2100

N

6-V1
4-X

1710
1980

D

—

C,D

MALLOPHAGA (After Brues, Melander and Carpenter, 1951)
Aitiblycera
Menoponidae
166.0
N
18-VIII 1750 q
Laemobothriidae 39.0

to
to
H

N

17-1

2840

p

THYSANOPTERA (After Brues, Melander and Carpenter, 1951)
Terebrantia
Aeolothripidae 0.9R-174.3L
C
16-IV
1730 —
(G?)
4-X
3100
Thripidae

0.9R-246.0L
(G)

HETEROPTERA (HEMIPTERA)
Hydrocorizae
Corixidae
34.9L-246.0L
(G)
Notonectidae

34.9L-208.5L
(U,M)

Belostomatidae 246.0L
(L)

1100
3200

G

a,j

G

3,21,37,43,46
48

B

A

26-1
12-XI

13,19,21,23,25 B,C,D
27,30,31,40,43
46,47,48

N

29-1
6-VIII

1120
2870

k,m

A

C

8-III
22-IX

1200
3000

l,m

A,D

N

21-111
8-VIII

1100
1130

k

A

Gelastocoridae

0.8R-246.0L

C

(G)

9-III

1100

15-IX

3100

e,j,k,l

A

m

A

(Ochteridae, reported by J.T. Polhemus, 1976)
Amph ibicor iz ae
Gerridae

34.9L-124.0L

C

5-III

1930

(Macrovel.iid.ae, recorded by J.T. Polhemus, 1976)
VelAidae

1100
2890
1900

i,j,k,m

A

R

17-1
23-IX
17-VII

j

A

C
"

23-V
23-IX

1750
2890

e,l,j

4

0.9R-246.0L
(C)

C

27-1
4-X

1100
3100

a,l

2,8,12,13,17
B,D
19,21,22,25,
30,39,40,44,46,47

Miridae

0.0R-246.0L
(G)

A
""

2 3-IV
12-XI

1000
3600

a,j

1,3,7,8,11,12, A,B,C,D,F,
13,14,15,16,17,
18,19,22,23,27,
30,33,34,35,36,
39,40,44,46,47,48

Nabidae

0.0R-208.GL
(U,M)

C
"

12-111
28-IX

1500
3100

a,d,j

5,25,30

Hebridae
Ealdidae
IO

ro
ro

Geocorizae
Anthocoridae

31.9R-246.0L
(G)
156.81.
(M)
31.9R-171.4L
(UfM)

C

A,E

A,B,D,E

Reduv.iidae

0.9R-274.4L
(G)

C
"

5-III
5-X

1000
3600

a,c,j

5,8,14,19,25
30,36,39,40,
43,47

A,B,C,D

Phymatidae

166.5L-246.0L
(M,L)

C
'

5-VIII
12-XI

1100
1750

a

40

A

Tingidae

0-9R-198.5R
(U,M)

C
'"'

23-V
25-IX

1530
3200

a

14,36,39,46,49 A

Lygaeidae

0.9R-269.5R
(G)

A
'"

11-V
12-XI

1000
3100

a,j

1,5,6,15,22,
30,39,40,44,
46,47

A,B,C,D,E

Berytidae

72.5R-208.6L
(U,M)

N
""

11-V
5-X

1510
2600

a,c,j

30

A,B,D

Largidae

198.511
(M,L)

N

25-IX

1530

39

A

Pyrrhocoridae

246.0L
(L)

N

12-XI

1100

j

Coreidae
0.9R-208.6L
(incl. Coris(G)
cidae K Corizidae)

C

10-V
28-IX

1100
3200

a,j,l

Pentatomidae

C
"

13-111
12-XI

1100
2610

C
"'

24-IV
18-VIII

1100
3000

ro
IX)
LO

72.5R-246.0L
(G)

Cydnidae
41.0R-269.5R
(incl.
(G)
Corime].aenidae)

a

B

13,30,31,36
40,43,47,39

A,B,D

1,6,7,8,15
27,39,40

A,B

A,D,E

(HOMOPTERA)
Auchenorrhyncha
Cicadidae

r.j

0.9R-248.4R
(G)

C

10-VII
4-X

1090
3100

a,e

Merabracidae

0.9R-151.6R
(U,M)

N
"

22-IX
28-IX

1850
3100

a,l

Cicadellidae

0.0R-269.5R
(G)

A

29-1
13-XI

1000
3200

a,c,g,j

Cercopidae

17i.4L-274.4L
(M,L)

N

22-Y
15-XI

1000
1730

Delphacidoe

35.0L-246.0L
(G)

C

19-V
28-IX

1100
2850

CJ.xij.dae

0.9R-269.5E
(G)

C

13-V
1-X

1000
3100

Kinnaridae?

18.1L-61.5L
(0)

N

7-VII
22-IX

2170
3000

undet. Fulgor- 0.9R-259.5R
oidea
(G)

N

5-V
14-XI

1010
3100

e.f.i

A

9-V
1-X

1510
3100

j,l

ro

Sternorrhyncha
Psyllidae

0.0R-203.6L
(G?)

22,39,40

A,D,E,I

B

1,3,5,6,7,8,
12,13,14,15,
16,19,22,24,
26,27,30,33,
34,35,36,39,
40,42,47

A,B,C,D

40

A

e.j

1,4,6,8,40

A,B,

a,j

11,12,13,14,
B.C.D.
23,25,30,39,47
C,D

A

11,12,13,22,
23,25,26,30,
34,39,42,47

A,B,C,D

Apbididae

0.0R-274.4L
(G)

A
~

16-IV
15--XI

1000
3600

a

Margarodidae

4,4L

N

11-VIII 3080

N

27-1

1800

C
~"

11-VI
2-X

1750
2850

a,e

Carabidae
0.0R-274.4R
(incl. Omophronidae)(G)

C

24-1
14-XI

1000
3700

a,c,e,f,i,j

Haliplidae

94.9L-246.0L
(M,L)

N

16-IV
8-VIII

1100
2340

k

Dytiscidae

34.9L-259.5R
(G)

C
"

19-1
14-XI

1010
2870

e,i,k,m

Tloteridae

116.4L-246.0L
(M,L)

N

29-1
7-X

1100
2140

k,m,

1.0R

R

15-IX

3200

3,8,12,13,18
19,25,26,30,
32,33,38,40,
42,43,44

A,B,C,D

A

(U)
undet. Coccoidea 214.5R
(M)

ro
ro
\J1

COLEOPTERA (After Arnett, 1960)
Adephaga
Cicindellidae 40.9R-L66.5L
(G)

Myxophaga
Sphaeriidae

(U)

2

A

A,D,K

12,13,30

A,B,D,E,F,

A

13

A

A

8

B

'olyphaga
Hydrophilidae

31.8R-259.5R
(G)

C

17-1

1010

~~

14-XI

3600

a,h,i,j,k,l,m

Staphylinidae

18.1L-269.7R
(G)

A

18-1
14-XI

1000
3600

a,c,e,f,i,j,
n,o

Pselaphidae

124.0L-208.4L
(M)

N

14-VII

1800

m

Scydmaenidae

20.1L

R

16-IX

2990

A,B

10,30

A,B,D,F,I

A,D

D

(u)

IV)

ro
c

Histeridae

53.0R-219.2R
(G)

C

17-V
6-X

1420
2700

a,o

12

A,F

Scarabaeidae

18.1L-274.6L
(G)

C

19-111
6-X

1000
3000

a,f,i,j,o

11,30

A,D,E

Dascillidae

65.2R-208.6L
(U,M)

C

4-V
18-IX

1500
2700

c

22,31

A,B

Byrrhidae?

34.91,
(U)

R

23-IX

2850

Psephenidac

136.2R
(M)

R

10-111

2500

Heteroceridae

246.0L
(M,L)

R

12-XI

1100

Elmidae

Thunder R.
(M)

N

15-VII

3600

D

i,k

A

1,6

i,k

B

A

Fuprestidae

34.9L-133.8P,
(G?)

C

24-IV
15-VIII

2020
3200

a,d

22,31

A,B,C

Elateridae

49.8R-274.4L
(G)

C

25-IV
19-IX

1000
3000

a,i

Throscidae

49.9L-208.61,
(M)

N

16-IV
5-VIII

1500
2340

a

Eucnemidae

124.0L
(M)

R

14-VII

2060

D

Phengodidae

72.OR

R

11-VII

2610

D

A,D,E

41

A,B

(U)
ro
ro

Lampyridae

O.OR-333.8R
(U,M)

N

7-VII

1960

Dexraestidae

72.6R-246.0L
(G)

C
~"

9-V
21-VII

Anobiidae?

19.1L-208.6L
(U,M)

N

Ptinidae

2.8R-166.5I
(U,M)

Bostrichidae

33.OR

-J

j

26

A,B

1100
3600

13,19,30

A,B,F,

23-IV
5-VI

1500
3600

21,22,30,31,37 A,B,

N

17-VII
16-IX

1750
3100

a

45

B,D

N

26-VI

2810

b,d

23

A

R

17-IV

2340

a

N

22-IV
11-VII

1750
3050

a

(U)
Ostomidae

94.91.

F

(M)
Cleridae

12.OL-171.4L
(U,M)

19,28,31

A,B,D

ro
ro

Melyridae

0.9R-246.OL
(G)

A

15-IV
12-XI

1000
3600

a,b,c,i,j

1,3,5,8,9,10,
11,13,15,17,
19,21,22,23,
28,29,31,34,
37,40,44,46,47

Meloidae

70.9R-269.5R
(G)

C
""

27-IV
29-IX

1010
2630

a

47,48

Mordellidae

0.9R-269.5R
(G)

C
"

11-V
5-X

1000
3600

a

8,12,15,30,
40,46

A,B,C,D

Tenebrionidae

0.9R-274.4L
(G)

C

29-1
7-X

1000
3400

a,b,c,d,f,g,i

14,23

A,D

Alieculidae

18.1L-274.4L
(G)

C
"

2-V1
21-IX

1000
3000

a,e

4

A,C,D

Melandryidae

75.3L-Thunder
R.
fU,M)

N

15-V
30-IX

2590
3600

j

Oedemeridae

70-5L-274.4L
(G)

C

5-V
8-VIII

1000
2700

a,b,m

30,31

Anthicidae

34.9L-269.5R
(G)

C

9-III
22-IX

1000
2850

a,e,j

4

Nitldulidae

25.5L-208.6L
(G)

C

24-IV
20-IX

1500
2950

a,b,c

19,31,41

C\:icjidae

133.8R
(M)

R

2-VI

1980

00

A,B,C,D

A,B,H

B,D

A,C,D

A,C,D,E

A,B,C

B

Coccinellidae

0.0R-246.0L
(G)

A

12-111
12-XI

1100
3600

Phalacridae

222.1L-269.5R
(M,L)

N

21-VII
26-IX

1000
1360

D

Lathridiidae

269.5R
(L)

R

21-VII

1000

D

Colydiidae?

190.4L
(M)

N

19-VIII

1800

F

Cerambycidae

18.1L-156.8L
(U,M)

N

25-VI
23-IX

1850
3000

A,C,D

Chrysomelidae

0.9R-246.0L
(G)

A

23-IV
12-XI

1000
3600

a,b,d,e ,f,j,1

1,3,4,6,8,9
12,13,14,17
19,27,39,40,
41,42,46

A,B,C,D,E,

Bruchidae

12.0L-208.6L
(G?)

C

16-IV
5-X

1500
3040

a

17,20,21,24,
30,40

A,B

Anthribidae

49.8R

R

24-IV

2800

a

A

R

24-VII

2700

j

A

A

7-III
12-XI

1100
3700

a,b,c,di,j

ro
ro
X3

a,c,l

1,3,8,13,14
15,23,25,26,
30,39,40,41,
44,45,47

A,B,C,D,E

(M)
Brentidae

52. 5R
(M)

Curculionidae

0.9R-246.0L
(G)

5,8,17,22,23,
29,40,41,46

A,B,C,K

Scolytidae

56.1R

R

2I-IX

2750

C

52.5R-248.4R
(G)

C
""

29-1
8-VIII

1100
3200

i,j,k

56.1R-246.0L
(G)

C

23-1
13-XI

1100
2850

a

30,46

C,D

0.9R-246.0L
(G)

C
"

23-1
5-X

1100
3500

a,j

3,5,8,13,17,
25,30,46,47

A,B,D,C,E

C

24-IV
28-IX

1010
3770

a

A,D,E

C
~

11-V
24-IX

1930
3200

k

A,D

C

2-VI
30-IX

1980
3600

j

B,C,D

Hydropsychicae 87.8R-133.8R
(M)

N

21-1
16-VII

1980
2470

k

A

Hydroptilidae

R

18-IX

2680

C

29-1
30-IX

1100
3600

(M)
NEUROPTERA
Megaloptera
Corydalidae

Planipennia
Hemerobiidae

Chrysopidae

Myrmeleontidae 0.0R-269.5R
(G)
ro
o

TRICHOPTERA (After Usinger, 1956)
Philopotamidae 65.2R-136.2R
(U,M)
Psychomyiidae

109.0R-133.8R
(M)

65.2R

A,E

D

(U)
Limnephilidae

41.0R-246.0L
(G)

j,k,m

A,B

u e p i d o s t o m a t i d a e T h u n d e r R.
(M)

N

30-IX

3600

j

B

Brachycentridae

N

15-VII

3600

j

B

Thunder R.
(M)

(Heliopsychidae, recorded by D. Kubly, 1976, pers. comm.)
LEPIDOPTERA
Frenatae
Papilionidae

no
u>

52.5R-109.0R
(G)

C

10-VII
30-VII

2100
3000

a

30

A

Pieridae

40.9R-246.0L
(G)

C

12-111
24-IX

1110
2850

a

39

A

Danaidae

87.0L-209.0L
(G)

C
"

17-V
28-IX

1500
2430

a

30,40

A

Satyridae

122.8L
(U?,M)

N

30-IX

2080

a

Nymphalidae

49.8R-209.0L
(G?)

C

5-III
28-VII

1500
2810

a

40

A,E

Libytheidae

166.5L-252.4L
(M,L)

C

4-X
13-XI

102 0
1750

j

39,43

A

Riodinidae

174. 3R-181.5R
(M)

N

24-IX

1600
1700

a

39

A

Lycaenidae

0.9R-2 52.4L
(G)

C

24-V
13-XI

1010
3100

a

22,29,37,39

A

H

A

Hesperiidae

40.9R-246.0L

C

(G)

9-VI1

1110

4-X

2800
(2200)
3600

a,l

Megathymidae

75.4L(-108.5R) N
(U,M)

15-V
(22-IX)

Sphingidae

75.3L(-208.6L) C
(G?)
"

15-V
(1510) a
(5-VIII)
2580

Saturnidae

40.9R

39

(a),c

A

A

16

A,D,E

11

A

N

9-VII

2840

Ctenuchidae
19.1L-198.5R
(incl. Amatidae)
(G)

C

15-V
4-X

1710
3000

a

A,D

Arctiidae

53.0R-208.61,
(G?)

C
~

15-V
24-IX

1510
2800

a

D

Noctu.idae

0.OR-274.4L
(G)

A

16-IV
4-X

1000
3100

a

Liparidae?

174.3R
(M)

N

4-X

1710

a

Geometridae

18.1L-274.4L
(G)

C
"

5-III
4-XI

1000
3000

a,l

Limacodidae?

73.4R-246.0L
(G)

C

8-V
13-XI

1100
2850

a,c

C,D

Thyrididae?

80.6L

R

27-VII

2600

a

E

(U,M)

ro
ro

(U)

30

A,C,D,E

A

12,14,23,30,39 A,B,C,D,E

Pyralidae

18.1L-274.4L
(G)

A
""

6-V
4-X

1000
3000

a,j

25

A,C,D,E

Pterophoridae

0.0R-20.0L
(U,M?)

C
""

16-IX
28-IX

2990
3100

a

A,D,E

Olethreutidae

65.2R-222.1L
(G?)

C

4-VI
26-IX

1400
2700

a

C,D

Tortricidae

20.0L-274.4L
(G)

C
"'

2-VI

1000
2990

a

C,D,E

Cossidae?

93. 4L

N

28-VII

2400

a

E

a,b

(M)
Gelechiidae

34.9L-246.0L
(G)

A

7-V
13-XI

1100
3200

Yponomeutidae

18.1L

N

7-VII

3000

D

Gracilariidae

47.0R-274.4L
(G)

C

18-1
26-IX

1000
2820

C,D,E

Opostegidae

166.51,
(M)

N

17-Vii

1750

a

D

Lyonetidae?

147.9L
(M)

N

1-X

1900

j

A

Psychidae?

19.1L-34.9L
(U)

N

22-IX
23-IX

2850
3000

ro

'

3,8

A,B,C,D

D

incurvariidae? 246.OL
(L)

N

13-XI

1100

C

17-1
13-XI

1100
3600

a,c,j,k,l

116.4L-Thunder N
R.
(M)

8-III
30-IX

2140
3600

j

B

R

12-VIII

2880

1

B

C

21-1
27-VII

1110
2610

l,m

30

A,E

Ceratopogonidae 19.1L-274.4L
(G)

A

18-1
4-X

1000
3020

a,j

3,13,30,46

B,D,E

Chironomidae

0.0R-246.0L
(G)

A

17-1
12-XI

1100
3600

a,b,h,j,l,m

3,5,7,8,12,13 A,B,C,D,E
14,17,19,22,
23,25,26,30
33,39,40,42,47

Sinvuliidae

34.9L-225.9L
(G)

A

22-1
6-X

1330
2850

a,b,j

13,23,25,27,
30,39,40,47

A,B,C,D,E

Mycetophilidae? 34.91,
(U)

R

9-V1I

2850

30

B

Sciaridae

A
"

7-V
12-XI

1100
2950

17,30,42

A,B,C,D

DIPTERA (After Cole, 1969)
Nematocera
Tipulidae
16.5R-246.0L
(G)
Psychodidae

Ptychopteridae 31.9R

C

12,39

A,B,C,D,E

(U)
Culicidae

ro
-p-

71.0L-239.0L
(G)

25.5L-246.0L
(G)

a,j,l

Oecidomyiidae

0.0R-274.4L
(G)

A
"

18-1
4-X

1000
3600

a,l

145.5L
(M)

R

10-111

1850

g

Stratiomyidae

84.1R--246.0L
(G)

C
"

23-V
12-XI

1100
3200

a,j

Tabanidae

0.0R-246.0L
(G)

N

21-VII
10-IX

1110
3600

a,j

Therevidae

61.5L-171.3L
(G?)

C

11-V
22-IX

1720
2780

a

Mydidae

243.0

N

21-VII

1050

g

A

A,J,L

Brachycera
Goenomyiidae?

26,27,30,47

A,B,C,D,E

A

13,39,40

A,B,C

A

13,23,39

A,B,C

(L)
Asilidae

18.1L-208.6L
(G)

C

8-VI
25-IX

1500
3000

a,j,l

Bombyliidae

0.0R-208.6L
(G)

A
'

13-111
26-LX

1500
3600

a,j

5,7,8.16,19
22,26,30,37,
39,46,47

A,B,C,D

Empididae

31.9R-208.6L
(U,M)

C

9-III
4-X

1500
3600

g,j

13,15,30

A,B,C

C
' '

29-1
4-X

1120
3600

a,g,j,k

5,12,14,26,30
40

A,B,C,D

R

17-VIII 1980

Dolichopodidae 0.0R-246.0L
(G)
Cyclorrhapha
Lonchopteridae 133.8R
(M)

j

B

ro

Phoridae

71.0L-166.5L
(U,M)

N

5-V
31-VII

1750
2610

D,F

Platypezidae

133.8R
(M)

R

17-VIII

1980

j

Pipanculidae

49.8R-246.0L
(G)

N
""

25-IV
12-XI

1100
2810

d

1,5,6,8

B

Syrphidae

19.1L-246.0L
(G)

C

9-III
13-XI

1100
2880

a,c,d

5,12,30,39,
40,43

A,B,C

Conopidae

0.0R-166.5L
(U,M)

N

7-VII
4-X

1750
3100

Otitidae?

72.6R-222.1L
(U,M)

N
"'

12-V
26-IX

1360
2610

a

Tephritidae

0.0R-252.4L
(G)

A
"

16-IV
13-XI

1000
3600

a,e,j

Sepsidae

72.5R-208.6L
(U,M)

C

11-V
24-V

1500
3600

Sciomyzidae?

34.9L

R

13-VIII

2850

N
'"

19-V
21-IX

1980
3100

R

11-V

2600

B

26,40

.B

A,C

4,5,12,13,18,
A,B,C
22,23,25,26,
27,30,39,43,47
13,19,30

A,B

e

4

A

j

26,39

B,C

13

B

(U)
Lauxaniidae

0.0R-133.8R
(U,M)

Chamaemyiidae? 72.5R
(U)

Piophilidae

72.5R-208.6L
(U,M)

N

12-V
26-V

1500
2620

3,13

B

Lonchaeidae

0.0R-171.4L
(U,M)

N

22-V
7-VII

1720
3100

26,43,47

B

Sphaeroceridae 19.1L-]74.3R
(U,M)

N
"

12-VIII
4-X

1750
3000

1

Tethinidae

19.1L-171.4L
(U,M)

C

7-V
16-VIII

1750
2990

c

Milichiddae

72.0R-208.6L
(U,M)

N
"

11-VII
5-VIII

1500
2610

Ephydridae

0.0R-208.6L
(G?)

A

24-LV
5-X

1500
3600

a,b,c,j

8,17,19,25,26, A,B,C,D
30,42

Drosophilidae

0.0L-208.6L
(G?)

A
~

15-V
5-X

1500
3600

a,b,j,l

8,26,30,33,40, A,B,D
42,45

Diastatidae?

208.6L
(M)

R

26-V

1500

Chloropidae

0.0R-208.6L
(G?)

C
'

24-IV
28-IX

1500
3100

j

8,13,19,22,26, A,B,C,D
30

Agromyzidae

0.0R-208.6L
(G?)

C

16-IV
30-IX

1500
3600

j

7,12,13,19,26, A,B,C,D
30,33,43

Heleomyzidae

56.1R-171.4L
(G?)

C

22-V
21-IX

1720
2750

-—

47

-4

B,D

20

A,B,D

30

B,D

22

B

B,C

Trizoscelidae

0.0R-208.6L
(G?)

C
"

9-v
7-VII

1500
3100

13,22,26,30,
40

B,C,F

Anthomyzidae?

208.6L
(M)

R

26-V

1510

Qpomyzidae

18.2L-174.3R
(G?)

C
"

9-V
4-X

1710
3020

11,13,30

A,B,D

Chyromyidae?

72.5R

R

12-V

2620

3

B

F

(U)
Asteiidae

0.0R-171.4L
(U,M)

N

23-V
7-VII

1750
3100

26

A,B

Scatophagidae

0.0R-133.8R
(U,M)

N

15-V
19-IX

1980
3100

26

A,B,C,D

Anthomyiidae

0.0R-246.0L
(G)

A
"

29-1
13-XI

1100
3600

a,b,g,i

8,13,18,26,30, A,B,C,D,F
36,40

Muscidae

0.0R-208.6L
(G?)

C

6-VI
4-X

1500
3100

a

26,30,39,40

Nycteribiidae

35.3L-166.5L
(G)

N
"

9-VII
29-VII

1750
2920

r,s

Calliphoridae

71.0L-246.0L
(G)

A

22-1
12-XI

1100
3600

a,g

12,30,40

Sarcophagidae

0.0R-246.0L
(G)

A
""

16-IV
12-XI

1100
3600

a,b,c,i,j

12,26,30,40,46 A,B,C,D,F

ro
OO

A,B,C,D

G

A,B,F

Tachinidae

0.9R-274.4L

A

4-V
13-XI

1000
3600

a,b,c,i,j

Cuferebridae

40.9R-274.4R
(G)

N
"

20-1
18-IX

1000
2830

j,t,u,w

18.0L-274.4R
(G)

C
"'

18-1
12-IX

1000 f ,t,u,v,w,x,y
2990

0.0R

R

28-IX

3200

47

1.0R-246.0L
(G)

A
"

8-III
12-XI

1100 a,1
3600

1,5,8,11,12,13 A,B,C,D
13,17,23,27,30
39,40,46,47

Ichneumonidae

1.0R-246.0L
(G)

C

24-IV
13-XI

1100 a,m
3200

5,8,19,23,30,
40

A,B,C,D,E,I

Mymaridae

34.9L

R

9-viI

2850

30

B

SIPHONAPTERA
Pulicidae

HYMENOPTERA
Symphyta
Siricidae

12,13,14,26,
30,39,40

A,B,C,D,E,F

A,G

A,G,

A

(U)
Apocrita
Braconidae
VA

(u)
Eulophidae

49.8R-208.6L
(U,M)

N

24-IV
26-V

1510
2800

8,23,27,30,40

B

Encyrtidae

34.9L-246.0L
(G)

C

15-V
12-XI

1100 a
2850

13,19,30,40

A,B

Eupelmidae

222.1L
(M)

N

26-IX

1360

23

B

ro
•fr
G

•forymidae

61.5L-94.9L
(U,M)

N

15-V
23-IX

2330
2720

Pteromalidae

18.2L-246.0L
(G)

A

25-IV
12-XI

1100
3600

a

Eurytomidae

71.0L-208.6L
(U,M)

N

24-V
26-IX

1510
2610

a

Chalcididae

49.9R-198.5R
(G?)

C

24-IV
25-IX

1530
2800

a

13,19,23,30,
39,46

B

Leucospidae

75.4L-181.5R
(G?)

N

15-V
24-IX

1700
2580

a

30,39

A

Figitidae

72.6R-208.6L
(G?)

N

12-V
26-V

1500
2700

12,13,19

B,C

Platygasteridae 181.5R
(M)

R

24-IX

1650

39

A

Diapriidae

R

15-V

2800

42

B

7,30,39,47

A,B,

15

B

12,30,39,40

A,B,C,D,E

75.3L

12,19,24,30

B,C

5,8,12,13,15,
19,22,27,30,
40,43

A,B,D

B

(U)
Chrysididae

34.9L-246.0L
(G)

N

15-V

1530

Trigonalidae

72.5R

R

11-V

2610

A

15-V

1000

a,l

(M)
Tiphiidae

18.1L-269.5R
(G)

a

no
H

Sierolomorphidae 93.4L-171.4L N
(U,M)
""

22-V
2-VIII

1730
2400

9,14,30

B

Mutillidae

53.0R-222.1L
(G)

C

24-VII
26-IX

1350
2800

a

Scoliidae

52.5R-180.0R
(G)

C

31-VI
13-VIII

1660
2800

a

Sapygidae?

208.6L
(M)

N

4-VIII

1500

a

Formicidae

0.0R-259.4R
(G)

A

8-III
4-X

1010
3100

a,b,c,f,i,l

4,5,14,23,26,
A,B,C,D,F
30,32,40,42,46

Vespidae

41.9R-246.0L
(G)

C

24-IV
5-X

1100
2840

a

19,30,39,40

A,B

Pompilidae

0.9R-225.9L
(G)

C

11-V
6-X

1330
3400

a,e

30,39,40

A,C

Sphecidae

0.0R-246.0L
(G)

C
"~

8-V
6-X

1100
3100

a,c

8,13,25,26,
30,39,40

A,B,C,D,K

Colletidae

75.4L-246.0L
(G)

C

24-IV
12-XI

1100
3600

a,l

1,30,39,40

A,B

Andrenidae

49.8R-208.6L
(G)

C

11-V
26-IX

1500
3600

a

12,13,30,39,40 A,B

Halictidae

0.0R-208.6L
(G)

A

18-1
28-IX

1010
3600

a,c,l

8,12,19,24,25, A,B,C,D
26,30,39,40,
46

A

30,40

A

A

ro
ro

-p-

Melittidae?

133.8R-171.4L
(M)

N

22-V
8-VI

1730
3600

7,30

B,C

Megachilidae

53.0R-109.0R
(U,M)

C

5-V
30-VII

2200
3600

a

23,24,25,30,31 A,B

Apidae

0.9R-208.6L
(G)

C

16-IV
6-X

1600
3100

a,l

19,21,24,30,
31,39,40

A,B

Appendix

VII-2.—SomeArachrud^^h^ol^doRrverR^
in Grand Canyon National Park
LOCATION 1 RELATIVE 3 DATE 4 ELEVATION HABITAT 6
RANGE
ABUNDANCE RANGE RANGE
DISTRIBUTION 2
(FT.)

TAXON

VEGETATION 7
COLLECTION
ASSOCIATION(S)
METHOD

SCORPIONIDA (After Williams, 1967 and Francke, 1973).
Specimens identified by Oscar F. Francke.
Buthidae
1.0R-246.0R
C
5-V
1100
a,c,i,k
A
(G)
12-IX
3100
Centruroides sculpturatus sculpturatus Ewing
Vaejovidae
to
4="

1.0R-71.0R
(U,M?)

N

4-V
19-IX

2610
3100

a,b,c,f

A

Vaejovis confusus Stahnke
Serradigitus wupatkiensis Stahnke
Paruroctonus sp.
Hadrurus spadix Stahnke
SOLPUGIDA (After Kaston, 1 9 7 2 ) .
Eremobatidae
0.0R
ARANEIDA (After Kaston, 1 9 7 2 ) .
Orthognatha
Dipluridae
31.6R

Specimens identified by Maryclaire Maltese.
N
3100
Specimens identified by Maryclaire Maltese.
N

17-IX

2800

N

5-V

2650

A

(U)
Brachythele
Labidognatha
Filistatidae

longitarsus

75.3L
(U,M?)

Filistata arizonica

c

A

Phlocidae

87.0L-171.4L

N

(G?)

17-V

1740

22-V

2450

a,f

A

A

Psilochorus sp.
17.5L-208.6L
(G)
Latrodectus hesperus
Latrodectus mactans

ro
•p•p-

Theridiidae

N

13-V
1550
5-VIII 3400

c,l

Micryphantidae 0.0R-190.0R
(G?)

N

24-V
1700
12-VIII 3100

a,e,i

4

Araneidae

N
"

9-V
21-IX

1510
3250

a,c

3,22,27,30,35, A,B,C
39,47

C

24-IV

2830

j

17,35,49

A,B

a,f,j

23,30,39

A,D

1.0R-208.6L
(G?)

A

Eustala rosea
Eustala sp.
Neoscona oazacensis
Tetragnathidae 31.9R-Thunder R.
(U,M)

12-VIII 3600

Tetragnatha versicolor
Lycosidae

17.5L-190.0R
(G)

Paradosa distincta
Paradosa sp.

A

14-V
24-V

1450
3400

Clubionidae

49.8R-81.2L
(U,M?)

C

Anyphaenidae

81.0L-246.0L

N

(G)

15-V
16-V

2550
2880

a

1100

a,j

22,41

A

C

13-XI

2460

A

24-IV
15-IX

1510
3600

a,i,j

7,12,15,17
18,22,23,25,
27,30,47

A
""

12-V
15-V

1510
3100

a,j,l

3,12,13,26,
A,B
30,35,41,46,47

Anyphaena sp.
Thomisidae

18.2L-208.6L
(G)

A,B,C

Misumenops sp.
Philodromus sp.

ro

Salticidae

18.2L-208.6L
(G)

Appendix VII-3.—Texts used in identification of insects.
Arnett, R. H., Jr. 1960. The beetles of the United States.
The Catholic Univ. of Am. Press, Wash., D.C.
Borror, D. J. and DeLong, D. M. 1971. An introduction to
the study of insects, 3rd ed. Holt, Rinehart and
Winston, New York.
Brues, C. T., Melander, A. L., and Carpenter, F. M. 1954.
Classification of insects. Bull. Mus. Comm. Zoo. at
Harvard Col. Vol. 108, Cambridge.
Cole, A. C , Jr. 1968. Pogonomyrex harvester ants: a study
of the genus in North America. U. of Tenn. Press, Knoxville.
Cole, F. R. 1969. The flies of western North America. U. of
Calif. Press, Berkeley and Los Angeles.
Comstock, J. H. 1967.
Ithica, N.Y.

The spider book.

Comstock Publ. Asso.,

Crowson, R. A. 1967. The natural classification of the
families of Coleoptera. E. W. Classey Ltd., Middlesex
(England).
Emerton, J. H. 1961. The common spiders of the United States.
Dover Publ., Inc., N.Y.
Froeschner, R. C. 1960. Cydnidae of the western hemisphere.
Proc. U.S.N.M. 111:337-680
Hodges, R. W. 1971. The moths of America north of Mexico:
Fascicle 21, Sphingoidea. E. W. Classey Ltd. and R. B. D. Publ.
Inc., London (England).
Hubbard, C. A. 1947. Fleas of western North America.
State Col. Press, Ames.

Iowa

Hungerford, H. B. 1948. The Corixidae of the western hemisphere.
(Hemiptera). U. of Kansas Sci. Bull. 31:1-827.
Hunt, J. R. and Snelling, R. R. 1975. A checklist of the ants of
Arizona. J. of the Ariz. Acad, of Sci. 10(l):20-23.
Kaston, B. J. 1972. How to know the spiders.
Publ., Dubuque, Iowa.

247

WM. C. Brown Co.

Kissinger, D. C. 1964. Curculionidae of America north of
Mexico. Taxonomic Publ., South Lancaster, Mass.
Linsley, E. G. 1961 - 1964. The Cerambycidae of North America
(in 5 parts). U. of Calif. Publ. Ent.
Muesebeck, C. F. W., Krombein, K. V., Townes, H. K., et. al.
1951. Hymenoptera of America north of Mexico, synoptic
catalogue. U.S.D.A Agr. Mono. No. 2, U. S. Govt. Prin.
Off., Wash., D.C.
Munroe, E. 1972. The moths of America north of Mexico;
Fascicles 13.1A, B and C, Pyraloidea: Pyralidae. E. W.
Classey Ltd. and R. B. D. Publ., INc., London (England).
Needham, J. G., and Westfall, M. J., Jr. 1955. A manual of
the dragonflies of North America (Anisoptera). U. of
Calif. Press, Berkeley and Los Angeles.
Pennak, R. W. 1953. Fresh-water invertebrates of the United
States. The Ronald Press, New York.
Usinger, R. L. (Ed.). 1956. Aquatic insects of California.
U. of Calif. Press, Berkeley and Los Angeles.

248

APPENDIX XI-I
DIRECTIONS FOR CAMPSITE EVALUATION SHEET-2
1.

Fill in your name, date, river mile, side of river
(N or S), and profession.

2.

The rating scale used for the following parameters
ranges from 1 to 5 on an integer basis. Although
descriptions are given only for ratings of 1, 3,
and 5, intermediate values of 2 and 4 are
permissible.
Man's Impact:
Litter
1 - No litter
3 - Apparent upon inspection
5 - Litter obvious
Trampling
1 - None
3 - Apparent upon inspection
5 - Obvious paths and/or trampled vegetation
Rock moving

(this includes rock walls, cairns;
does not include campfire sites)

1 - None
3 - Apparent upon inspection
5 - Obvious rock structures
Campfire sites
1 - None
3 - Campfire sites or rings but no or little
charcoal
5 - Campifire sites and/or charcoal present
Wildlfire
1 - None
3 - Partial burn or ground fire
5 - ENtire area burned or crown fire
Human waste
1 - None present nor any smell
3 - Evidence such as chemical stain, smell,
toilet paper
5 - Feces exposed, strong offensive odor

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Wildlife and Habitat Criteria:
Habitats
1 - Homogeneous habitat types with no
more than one of the habitat types
in the immediate vicinity so that it
has little or no influence on increasing
species diversity. The habitat supports
low densities.
3 - Homogeneous habitats with only moderate
to low amounts of interspersion of different
life forms, and intermediate species
density and diversity.
5 - a. Three or more different habitat types
in close proximity which provide for
maximum species diversity, or
b. Homogeneous habitat types with high
density and low to moderate diversity.
Special areas
1 - Habitats and broad geographic areas which
contain general, non-specific requisites
for wildlife. Non-critical needs are
provided in these areas (as opposed to
the criteria under 5a, b and c).
3 - Critical wildlife habitat requisites (food,
cover, water, space, etc.) may be present
but are either in low amounts or are widely
scattered. The critical requisites provide
for only a few species.
5 - Habitats and geographic areas where special
requisites (food, cover, water, space) occur
that are needed by the species to complete
their life cycle.
a. Habitats which provide the specific items
required for successful reproduction of
each species. Examples include fawning
areas, nesting areas, rearing areas,
courtship areas.
b. Habitats which provide for the energy
demands of the species during the harsh
periods of the year.
c. Habitats which provide for the needs of
migrating animals.
Unique combinations
1 - Habitats of broad homogeneous geographic
distribution supporting what is generally

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considered as "common organisms." No
unique species interactions occur within
the communities nor do they support rare or
endangered species.
3 - Habitats of either small geographic
area containing unique combinations of
plants and animals or habitats of broad
geographic area that contain few unique
combinations.
5 - Areas of "unique combinations" of plants
and wildlife. Criteria for defining
uniqueness should include the following:
a. Areas that support rare or endangered
species.
b. Areas that have not been modified to
any great areas are in dynamic
equilibrium.
c. Plants and animals that are existing at
or near the edges of their geographic
ranges.
d. Plants and animals that are restricted
to specific geographic areas of the
region.
e. Areas where unusual interactions
of species occur. The species are usually
spearated in their geographic distribution
or by local habitat conditions.
Modifications
1 - Habitats significantly modified by man's
activities, resulting in low animal species
density and diversity.
3 - Habitats showing only limited modifications
by man. These areas, if left to their own
dynamic interactions, will return to natural
conditions.
5 - No modification of habitat by man.
Value and needs
1 - Habitats that provide minimal wildlife
related experiences or products for man.
3 - Areas that support a moderate number of
organisms which satisfy human needs and
values.
5 - Habitats which support plants and animals
that satisfy various human needs (i.e.,
esthetic, scientific, hunting, long range
stability of the ecosystem).

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