A person standing on the North Rim of the Mesa Verde in southwestern
Colorado sees a vast green plain sloping away to the south. The plain
drops 2000 feet in ten miles. On a clear evening, before the sun reaches
the horizon, the rays of the sun are reflected from great sandstone
cliffs forming the walls of deep canyons that appear as crooked yellow
lines in the distance. Canyon after canyon has cut into the sloping
green plain. These canyons are roughly parallel and all open into the
canyon of the Mancos River, which forms the southern boundary of the
Mesa Verde. If the observer turns to the north he sees the arid
Montezuma Valley 2000 feet below. A few green streaks and patches in the
brown and barren low country denote streams and irrigated areas. To the
northeast beyond the low country the towering peaks of the San Miguel
and La Plata mountains rise more than 4000 feet above the vantage point
on the North Rim at 8000 feet. To the northwest, in the hazy distance 90
miles away in Utah, lie the isolated heights of the La Sal Mountains,
and 70 miles away, the Abajo Mountains (see Fig. 1).
In the thirteenth century, harassed by nomadic tribes and beset by years
of drouth, village dwelling Indians left their great cliff dwellings in
the myriad canyons of the Mesa Verde, and thus ended a period of 1300
years of occupancy. The story of those 1300 years, unfolded through
excavation and study of the dwellings along the cliffs and earlier
dwellings on the top of the Mesa, is one of the most fascinating in
ancient America. To stop destructive commercial exploitation of the
ruins, to preserve them for future generations to study and enjoy, and
to make them accessible to the public, more than 51,000 acres, including
approximately half of the Mesa, have been set aside as Mesa Verde
National Park, established in 1906. The policies of the National Park
Service provide protection, not only for the features of major interest
in each park, but for other features as well. Thus the policy in Mesa
Verde National Park is not only to preserve the many ruins, but also the
wildlife and plants.
Five considerations prompted me to undertake a study of the mammals of
Mesa Verde National Park: First, the relative lack of disturbance;
second, the interesting position, zoogeographically, of the Mesa that
extends as a spur of higher land from the mountains of southwestern
Colorado and that is almost surrounded by arid country typical of much
of the Southwest; third, the discovery in the Park of _Microtus
mexicanus_, a species of the Southwest until then not known from
Colorado; fourth, the co-operative spirit of the personnel at the Park
when I visited there in 1955; and finally, the possibility of making a
contribution not only to our knowledge of mammals, but to the
interpretive program of the Park Service.
[Illustration: FIG. 1. Map of the "four corners" region showing the
position of Mesa Verde National Park (in black) relative to the mass of
the Southern Rocky Mountains above 8000 feet elevation (indicated by
stippled border) to the northeast in Colorado, and the positions of
other isolated mountains in the region.]
A Faculty Research Grant from The University of Kansas provided some
secretarial help and field expenses for August and early September,
1956, when my wife, Justine, and I spent our vacation enjoyably
collecting and studying animals in the Park. The co-operation of Dr. E.
Raymond Hall is greatly appreciated; a grant to him from the American
Heart Association provided field expenses for work by Mr. J.R. Alcorn,
collector for The University of Kansas Museum of Natural History, in
1957.
Mr. Harold R. Shepherd of Mancos, Colorado (Senior Game Biologist for
the State of Colorado, Department of Game and Fish), provided advice in
the field, helped in identifying plants, and saved specimens of rodents
(in 1958 and 1959) taken in his studies of the effect of rodents on
browse utilized by deer. Mr. J.D. Hart, Assistant Director of the
Department of Game and Fish, issued a letter of authority to collect in
Colorado; and Superintendent O.W. Carlson approved my appointment as a
collaborator. Mr. "Don" Watson, then Park Archeologist, and Mrs. Jean M.
Pinkley, now Park Archeologist, assisted us in 1956, and since then have
provided advice and assistance, and have reviewed the manuscript of this
report.
Geologically, the Mesa Verde is the northern edge of a Cretaceous,
coal-bearing, sandstone deposit called the Mesaverde group, which dips
beneath the San Juan Basin of New Mexico. An abrupt retreating
escarpment commonly forms on arid plateaus underlain by horizontal rocks
of unequal strength, and characterizes the borders of mesas. Such an
escarpment forms the North Rim of the Mesa Verde. However, the dip of
the rocks has channelled drainage southward and erosion has cut
numerous, deep, parallel-sided canyons rather than a simple, retreating
escarpment. The Mesa Verde therefore is, technically speaking, a cuesta
rather than a mesa. The remnants of the plateau left between the canyons
are also (and again incorrectly in the technical sense) called mesas;
Chapin Mesa and Wetherill Mesa are examples.
Climatically, the Mesa Verde is arid; precipitation averaged 18.41
inches per year for a period of 37 years. Precipitation may be scattered
through the year, and more important, may be erratic from month to month
and from year to year. In addition to low precipitation and periods of
drouth, a great amount of sunshine, and thin, well-drained soils on all
but the more sheltered parts of the Mesa favor vegetation that requires
neither great amounts of, nor a continuous supply of, water.
The vegetation of the Mesa is illustrated in Plates 1 and 2, and
consists predominantly of pinyon pine, _Pinus edulis_ Engelm., and Utah
juniper, _Juniperus osteosperma_ (Torr.) Little. More sheltered areas
along the North Rim and in most of the canyons support scattered small
stands of Douglas fir, _Pseudotsuga menziesii_ (Merb.) Franco. These
are the "spruce trees" of Spruce Tree Canyon. An occasional ponderosa
pine, _Pinus ponderosa_ Laws., represents a vestige of more montane
species of plants and animals in the Park. The dusky grouse,
_Dendragapus obscurus_ (Say), occurs along the North Rim in
oak-chaparral, and is one of the few montane species of birds; several
montane mammals are discussed later. The vegetation of the Mesa Verde
has not changed appreciably in the last thousand years. The tree rings
of 13 centuries show that Douglas fir has grown essentially as it does
now, varying with precipitation from year to year, and periodically
suffering from drouth (Schulman, 1946:18). Surface ruins yield mostly
pinyon and juniper; cave ruins yield more Douglas fir than surface
ruins; and "only rarely does yellow pine [_Pinus ponderosa_] occur in
the ruins, indicating that then, as now, this tree grew only in the
northern and higher parts of the Mesa Verde, remote from most of the
ruins" (Getty, 1935:21).
Not all areas within the Park are undisturbed. The rights of way of
roads are kept clear, as are campgrounds and other facilities in the
area of headquarters. Part of the Mancos Valley within the Park is
privately owned and is still in agricultural use. Cattle from land
belonging to the Ute Indians wander into the Park from the Mancos Canyon
along the floor of the canyon above the mouth of Weber Canyon. In
addition to the pasture near headquarters, Prater Canyon below a fence
across the canyon above Middle Well is used to pasture horses used by
visitors to the Park and belonging to the pack and saddle concessioner.
In 1956, the floor of Long Canyon was grazed by stock belonging to Utes,
and horses ranged freely onto Wetherill Mesa as far as the North Rim.
Occasionally livestock enter the floor of other canyons, for example
Navajo, Soda, Prater, Morfield, and Waters canyons, owing to inadequate
fencing, or no fencing.
[Illustration: FIG. 2. Map of Mesa Verde National Park and vicinity. The
map and this legend provide the names of places mentioned in the
following accounts of mammals. Localities from which specimens have been
preserved are indicated by dots. Localities within 1/2 mile of each
other are not indicated by separate dots. Unnumbered dots designate some
of the places from which specimens were obtained. The numbered dots are:
(1) Prater Grade; (2) Upper Well, Prater Canyon, 7575 ft.; (3) Chickaree
Draw, 8200 ft.; (4) 1/4 mi. N Middle Well, 7500 ft., Prater Canyon; (5)
east side of Morfield Canyon about one mile below the well; (6) Lower
Well, Prater Canyon; (7) Sect. 27, head of east fork Navajo Canyon; (8)
Far View, designated on various specimens as Far View Ruins, Far View
Point, and Far View House, 7700 ft.; (9) localities designated Utility
Area, and Well, "Park Well," or "Old Park Well"; (10) Headquarters,
including the designations 25 mi. [by road] SW Mancos, Museum, Hospital,
head of Spruce Tree Canyon, Spruce Tree House, and Spruce Tree Lodge;
(11) Cliff Palace, across the canyon about 1/4 mile southwest are Sun
Temple and Oak Tree Ruin; (12) Square Tower House; (13) Balcony House;
(14) Indian Cornfield, "Cornfield," or "Garden."]
The first mammals from the Mesa to be preserved for scientific study
were seven specimens in the United States National Museum (designated
USNM in lists of specimens examined) obtained by Merritt Cary in 1907,
and mentioned in his "Biological Survey of Colorado" (Cary, 1911). In
1931 and 1932, R.L. Landberg obtained a few specimens that are in the
Denver Museum of Natural History. In 1935, C.W. Quaintance, Lloyd White,
Harold P. Pratt, and A.E. Borell prepared specimens, some of which
remain in the museum at the Park (all specimens in the museum at the
Park are designated by "MV" for Mesa Verde and by their catalogue
numbers), and some are in the Museum of Vertebrate Zoology at the
University of California at Berkeley (designated "MVZ" in the following
accounts). Specimens in The University of Kansas Museum of Natural
History are referred to by catalogue numbers only. Specimens prepared by
D. Watson bear dates from 1936 until 1955. In 1938, Raymond F. Harlow
prepared some specimens; his Student Technician's Report of 7 typescript
pages, for July 8 to September 9, 1938, is on file at Mesa Verde
National Park. In 1944 and 1945, Dr. D.A. Sutton, then a student at the
University of Colorado, collected chipmunks for his own study, and also
some other specimens that are in the University of Colorado Museum and
the Park Museum. In 1949, Dr. R.B. Finley, then a student at The
University of Kansas, collected in and near the Park and obtained a few
specimens preserved in The University of Kansas Museum of Natural
History. Rodents preserved by Harold R. Shepherd have been mentioned. I
have examined 244 specimens that were collected by the above persons.
Between August 8 and September 4, 1956, and on July 17, 1960, I
collected 216 mammals from Mesa Verde National Park. Between November 3,
and 12, 1957, J.R. Alcorn collected 275 mammals from the Mesa. The total
of specimens examined is 735.
Written reports by C.W. Quaintance, H.P. Pratt, and R. Harlow have been
of considerable use. A typescript report of 13 pages by Wildlife
Technician H.P. Pratt for the period from September 9 to October 15,
1935, and monthly reports comprising 40 typescript pages and 4 pages
with photographs by C.W. Quaintance for the period from February 18
through July 17, 1935, are on file at offices of Region Four, National
Park Service, 180 New Montgomery Street, San Francisco 5, California.
Chief Ranger Wade has kindly made available the files in his office,
including reports of the Superintendent and reports of the Chief Ranger
in earlier years, and Annual or Biennial Animal Census Reports since
1930. Special reports on prairie dogs, porcupines, and deer are in the
files. These reports, and random reports that were regarded as reliable,
are recorded on card files in both the Chief Ranger's office and Park
Archeologist's office. Most of the information reported here on the
larger mammals was gleaned from the above sources. A study of population
fluctuations in porcupines by Donald A. Spencer and perhaps a study of
movements of porcupines by Spencer, Wade and Fitch are to be published
elsewhere. Other studies still in progress are mentioned in the
following accounts.