Mammals of the Grand Mesa, Colorado

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UNIVERSITY OF KANSAS PUBLICATIONS
MUSEUM OF NATURAL HISTORY


Volume 9, No. 16, pp. 405-414, 1 fig.
May 20, 1959



Mammals of the Grand Mesa, Colorado

BY

SYDNEY ANDERSON



UNIVERSITY OF KANSAS
LAWRENCE
1959




UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Robert W. Wilson


Volume 9, No. 16, pp. 405-414, 1 fig.
Published May 20, 1959


UNIVERSITY OF KANSAS
Lawrence, Kansas


PRINTED IN
THE STATE PRINTING PLANT
TOPEKA, KANSAS
1959

27-7472




Mammals of the Grand Mesa, Colorado

BY

SYDNEY ANDERSON


The Grand Mesa of Colorado is a westward extension of the mountains of
central Colorado, standing more than five thousand feet above the
valleys of the Colorado and the Gunnison rivers. To certain montane
mammals the mesa is a peninsula of cool, moist, forest surrounded by
inhospitable, hot, dry, barren lowland.

Few mammals previously have been preserved or reported from the Grand
Mesa. Of the species here reported, Warren (1942, The Mammals of
Colorado, Univ. Oklahoma Press) mentioned only four from the counties
in which the Grand Mesa is located. Twenty-two species are here
recorded from the Grand Mesa, and two localities below the rim of the
Mesa on the north slope, on the basis of specimens preserved, and five
additional species on the basis of observations. Many of these species
are limited to a montane habitat or find their optimum conditions
there. The known geographic ranges of some subspecies are extended
westward.

Specimens and notes were obtained by members of a field party from the
Museum of Natural History led by Dr. Harrison B. Tordoff. The party,
including also R. Gordon Cliffgard, John M. Legler, Olin L. Webb, and
Glen E. Woolfenden, was in the area from June 17 to July 5, 1954, and
obtained all of the specimens listed excepting those from 28 miles east
of Grand Junction (Sect. 29, T. 11S, R. 95W), Mesa County, that were
obtained from June 13 to July 2, 1956, by Phillip M. Youngman, and
those from Land's End Road that were obtained on May 13 and 14, and on
October 1, 1948, by D. A. Sutton.

Localities designated by numbers in the accounts to follow are listed
in the legend for Figure 1. Localities 1 and 3 lie below the rim of the
Mesa on the north side. Catalogue numbers are of the Museum of Natural
History of the University of Kansas, unless noted otherwise.

=_Sorex cinereus cinereus_= Kerr.--Two male (59642-59643) Masked Shrews
weighing 4.8 and 4.9 grams were trapped on June 17 at locality 10, and
a nonpregnant female (59644) was trapped on June 26 at locality 6.
_Sorex cinereus_ seemed to be less abundant on the Mesa than _Sorex
vagrans_; more individuals of _S. vagrans_ than of _S. cinereus_ were
trapped on June 17 at locality 10 and on June 26 at locality 6, and _S.
vagrans_ was trapped at three localities where no _S. cinereus_ was
obtained.

[Illustration: FIG. 1. Map of the Grand Mesa (for purposes of this
paper the area above 7500 feet on each side of the northern boundary of
Delta County). The inset of the western three-fourths of Colorado shows
the Grand Mesa in relation to the larger areas of mountains in the
state (areas above 9000 feet are stippled). The following collecting
localities are indicated by numbered, black dots:

 (1) 2 mi. N, 9 mi. E Collbran, 7000 ft., Mesa County.
 (2) Land's End Road to Grand Mesa, 6800 to 8050 ft., Mesa County.
 (3) 3 mi. E, 4 mi. S Collbran, 6800 ft., Mesa County.
 (4) 3 mi. E, 9 mi. S Collbran, 10,200 ft., Mesa County.
 (5) 5-1/2 mi. E, 11-1/2 mi. S Collbran, _in_ Delta County.
 (6) 5-1/2 mi. E, 12 mi. S Collbran, 9600 to 10,400 ft., _in_ Delta County.
 (7) 28 mi. E Grand Junction (Sec. 29, T. 11S, R. 95W), Mesa County.
 (8) 6 mi. E Skyway, 10,000 to 10,500 ft., _in_ Delta County.
 (9) 7 mi. E Skyway, _in_ Delta County.
(10) 8 mi. E, 1/2 mi. S Skyway, 9500 to 10,200 ft., _in_ Delta County.
(11) 8 mi. E, 3/4 mi. S Skyway, 10,200 ft., _in_ Delta County.
(12) 8 mi. E, 1 mi. S Skyway, 10,000 to 10,200 ft., _in_ Delta County.
(13) 8 mi. E, 1-1/2 mi. S Skyway, 8500 to 9600 ft., _in_ Delta County.
(14) 8 mi. E, 2 mi. S Skyway, 9000 ft., _in_ Delta County.
(15) 8 mi. E, 2-1/2 mi. S Skyway, 9600 ft., _in_ Delta County.
(16) 1 mi. S, 4 mi. W Skyway, 10,200 ft., Mesa County.]

=_Sorex vagrans obscurus_= Merriam.--Fifteen specimens of the Vagrant
Shrew (59645-59655, 59665-59668) were trapped in Delta County from
localities 6, 10, 12, 13, and 14. The fourteen specimens having skulls
fell into two distinct age-classes based on wear of the teeth as
described by Findley (1955, Univ. Kansas Publ., Mus. Nat. Hist., 9:8);
5 were in the younger group and 9 in the older group. Weights in grams
of the younger shrews were 4.6, 5.5, 5.7, 5.8, and 6.4; weights of the
older shrews were 6.4, 6.8, 7.3, 7.4, 7.5, 8.0, 8.3, and 8.8. One of
the seven females was lactating; none contained embryos.

=_Sorex palustris navigator_= (Baird).--Six Water Shrews (59633-59638)
were trapped in Delta County at localities 10, 13, 14, and 15. The one
specimen from locality 10 was trapped on June 17; all others were taken
on June 21. None was pregnant or lactating. Two are young, weighing
11.0 and 12.9 grams; the other four are older, weighing 16.6, 17.0,
19.2, and 21.5 grams.

=_Myotis evotis evotis_= (H. Allen).--One female Long-eared Myotis
(59671), containing no embryos, was shot at dusk on July 2, at locality
3, which is below the rim of the Mesa.

=_Myotis volans interior_= Miller.--One female Long-legged Myotis
(70016), containing no embryos, was shot at locality 7 on July 1, 1956.

=_Ochotona princeps figginsi_= J. A. Allen.--Six specimens of the Pika
(59672-59675, 70018-70019) from localities 5, 6, 7, 8, and 9 extend the
known range of the subspecies approximately 55 miles to the westward
from Irwin in Gunnison County. Each of two females taken on June 18 and
26 contained three embryos, which measured 20 millimeters in the
latter; a third female on June 29 contained two embryos 35 millimeters
in length.

=_Lepus americanus bairdii_= Hayden.--No Snowshoe Rabbit was taken, but
one individual was observed by H. B. Tordoff on June 18, 1954, at
locality 8. Droppings of a large lagomorph were seen in the woods, and
tracks were seen in the snow.

=_Marmota flaviventris luteola_= A. H. Howell.--The seven specimens of
the Yellow-bellied Marmot (59731-6, 70022, four adult and two young,
each a skin and skull, and one skull only of an adult) are referable on
the basis of size, color, and locality as discussed by Warren (1936,
Jour. Mamm., 17:394) to _M. f. luteola_. The total lengths in
millimeters are as follows: young male 582; adult males 640, 655; young
females 460, 520; adult female 630. The color and condition of the
pelage is the same in all the specimens except that the two largest
males are much more worn and show irregular patches of new hair on the
back, and the two young females are paler especially on the back and
tail. These marmots were taken at localities 4, 7, 8, 10, and 16.

=_Spermophilus lateralis lateralis_= (Say).--Eleven specimens of the
Golden-mantled Ground Squirrel (59748-59756, 59763-59764) were taken at
localities 1, 3, and 4. Young were born before late June; three young
of the year were taken at locality 3 on June 29 and 30, and none of the
adult females taken at locality 1 (1 female) and at locality 4 (3
females) was pregnant. Most adults of both sexes at all elevations
represented (6800 to 10,200 ft.) showed molt in progress and proceeding
from anterior to posterior. All specimens were obtained from June 25 to
July 4.

=_Spermophilus variegatus grammurus_= (Say).--Three Rock Squirrels
(59738-59739, 59742) were obtained at locality 3. One of these
specimens was a skull found near a wood rat nest. The other two were
nonpregnant females; the adult measured 485 millimeters in total
length, and the younger individual measured 413 millimeters. The two
skins are characteristic of _S. v. grammurus_ in their paleness.

=_Eutamias minimus consobrinus_= (J. A. Allen).--The 63 specimens of
the Least Chipmunk (59770-59824, 60105-60108, 70024-70025, and nos.
5194 and 5196 in Univ. of Colorado Museum) were taken at localities 2,
3, 4, 6, 7, 8, 10, 13, and 15. The reproductive condition at time of
death had been noted for 20 females obtained from June 17 to July 2 at
elevations from 9500 to 10,400 feet. Eleven of these had no embryos,
but six have mammae that are still prominent on the dried skins and may
have had litters prior to their capture. Nine females contained
embryos, numbering 3 in two specimens, 5 in four specimens, 6 in two
specimens, and 7 in one specimen.

=_Eutamias quadrivittatus hopiensis_= Merriam.--Four specimens of the
Colorado Chipmunk were obtained by D. A. Sutton at locality 2, at 6800,
6900, 7175, and 8050 feet elevation. All are males taken on May 13 and
14, 1949; the specimens bear numbers 5197, 5198, 5199, and 5201 in the
collection of the University of Colorado Museum.

=_Thomomys talpoides fossor_= J. A. Allen.--The 27 specimens of the
Northern Pocket Gopher (59840-59849, 70086-70102) were trapped at
localities 3, 6, 7, 10, 11, and 13. The eight skins from locality 7
differ from those from the other localities on the Mesa in being
uniformly duller in color dorsally. No significant difference in size
or cranial characters was observed. Specimens assigned to _T. t.
fossor_, in the collection of the Museum of Natural History, from other
localities in Colorado differ in color from any of the specimens from
the Grand Mesa. Until larger numbers of _Thomomys talpoides_ from other
localities in Colorado and from the type locality of _T. t. fossor_,
stated to be at Florida, in southern Colorado, have been studied, the
specimens from the Grand Mesa seem best referred to _T. t. fossor_.
Three females from localities 7, 10, and 11 contained embryos (2, 4,
and 5 in number), and seven other females from localities 6 and 7 show
distinct mammae on the dried skins or were recorded by the collectors
as lactating.

=_Castor canadensis concisor_= Warren and Hall.--Dams constructed by
beavers were seen at locality 4 on June 23, 1954. No specimen was
taken.

=_Peromyscus maniculatus rufinus_= (Merriam).--The 36 specimens of the
Deer Mouse (59921-59956) are from seven localities (3, 4, 6, 10, 12,
14, and 15). The mice vary considerably in color; most of them are like
mice of the highlands of Colorado and unlike the paler mice inhabiting
the lower areas immediately to the west of the Grand Mesa. Young
individuals trapped on June 20, 21, and 22 and judged to range from a
month through two months in age, and females containing embryos, attest
to a somewhat protracted breeding season on the Grand Mesa.

=_Neotoma cinerea arizonae_= Merriam.--Two immature Bushy-tailed Wood
Rats (60000-60001) were obtained at locality 3 on July 3.

=_Clethrionomys gapperi galei_= (Merriam).--The 22 specimens
(60005-60025, 70133) of Gapper's Red-backed Vole were taken at
localities 6, 7, and 10, and are clearly referable to _C. g. galei_,
rather than to _Clethrionomys gapperi gauti_ to the south, on the basis
of generally dark dorsal pelage, indistinctly bordered broad dorsal
stripe, and cranial features. _C. g. gauti_ was described by Cockrum
and Fitch (1952, Univ. Kansas Publ., Mus. Nat. Hist., 5:289) on the
basis of 14 specimens from southern Colorado and northern New Mexico.
Twenty-one additional specimens from five miles south and one mile
west of Cucharas Camps, Huerfano County, were obtained from the seventh
to the fourteenth of July by the field party led by Tordoff after the
party left the Grand Mesa. These specimens substantiate the subspecific
distinctness of _C. g. gauti_ in that they agree in external and in
cranial appearance with the description of typical _C. g. gauti_, and
are distinct in appearance from specimens of _C. g. galei_ from the
Grand Mesa and from other localities in northern Colorado. The six
specimens from two localities in Colorado available to Cockrum and
Fitch exhibited evidence of intergradation at one locality, and
atypical smallness at the other locality. A specimen (70134) taken on
June 26, 1956, by Phillip M. Youngman on the Black Mesa, nine miles WNW
of Sapinero, 9500 ft., Gunnison County, Colorado, is almost identical
in color to the two specimens from Saguache County regarded by Cockrum
and Fitch as intergrades between _C. g. galei_ and _C. g. gauti_, but
in small size of auditory bullae and narrowness of braincase resembles
_C. g. galei_, to which it seems best referred. The specimens from the
Grand Mesa extend the known range of _C. g. galei_ approximately 50
miles westward in central Colorado from Gothic. Three females were
pregnant; two trapped on June 17 and June 25 contained 6 embryos each,
and one trapped on June 25 contained 5 embryos. Four of the females
taken in Huerfano County were pregnant; one contained 3 embryos, two
contained 5 embryos, and one contained 7 embryos. Immature individuals
are present in the sample from Huerfano County also.

=_Phenacomys intermedius intermedius_= Merriam.--Three Heather Voles
(60048, 60049, 70135) were trapped at localities 6, 7, and 10. All were
adult females; one, taken on June 25 at locality 6, contained seven
embryos five millimeters in length, and one, taken on July 2 at
locality 7, contained seven embryos nine millimeters in length. These
specimens extend the known range of the species approximately 55 miles
west from Gothic (Pruitt, Jour. Mamm., 35:450, 1954).

=_Microtus longicaudus mordax_= (Merriam).--Ten Long-tailed Voles
(60070-60079) represent localities 3, 6, 12, 13, 14, and 15.

=_Microtus montanus fusus_= Hall.--Ten Montane Voles (60060-60068,
70145) represent localities 3, 6, 7, and 15.

=_Ondatra zibethicus osoyoosensis_= (Lord).--Muskrats were seen daily
from June 17 to June 23 in a lake at locality 13. No specimen was
obtained.

=_Zapus princeps princeps_= J. A. Allen.--Nineteen Western Jumping Mice
(60109-60126, 60137) were trapped at localities 6, 10, 12, 14, and 15.

=_Erethizon dorsatum epixanthum_= Brandt.--A Porcupine skull was seen
in the nest of a wood rat by John M. Legler at locality 3 on July 2. On
June 20 a porcupine was seen at locality 12. No specimen was obtained.

=_Mustela frenata nevadensis_= Hall.--Seven Long-tailed Weasels
(60138-60143, 70152) were taken at localities 1, 4, 7, 8, 13, and 14.
Four are males and three are females. Some of these were attracted by
"squeaking" noises and then shot.

=_Taxidea taxus taxus_= (Schreber).--One adult male Badger (60144) was
found dead; the skull and baculum were saved. The subspecific
identification is on geographic grounds, and is tentative. In this area
_T. t. taxus_ and _T. t. fippsi_ may intergrade.

=_Mephitis mephitis estor_= Merriam.--One Striped Skunk (60145) of
unknown sex was found dead in the cellar of a cabin at locality 10.

=_Odocoileus hemionus hemionus_= (Rafinesque).--Mule Deer were observed
at locality 15; no specimen was obtained.


DISCUSSION

The species here reported from the Grand Mesa may be placed according
to their geographic ranges and their restriction to certain habitats in
two groups:

BOREAL.--Each of the 12 species listed below is of northern
distribution, is dependent, at the latitude of Colorado, upon the
habitat provided by areas of high altitudes, and is near its southern
zonal limit on the Grand Mesa. The 12 species are: _Sorex cinereus_,
_Sorex palustris_, _Sorex vagrans_, _Ochotona princeps_, _Lepus
americanus_, _Marmota flaviventris_, _Spermophilus lateralis_,
_Clethrionomys gapperi_, _Phenacomys intermedius_, _Microtus
longicaudus_, _Microtus montanus_, and _Zapus princeps_. _Thomomys
talpoides_ may be considered in this category also, although it is less
restricted in range and habitat than most of the other species listed
as boreal. These thirteen species make up almost half of the
twenty-seven species known from the Grand Mesa.

WIDE-SPREAD.--Species in this category are those that are widely
distributed in the western United States and that occur in Colorado in
both the mountains and the lower more arid intermontane areas. Some of
these species are differentiated into subspecies, one of which
inhabits the mountains and another the lowlands. Wide-spread species
that do not have subspecies in the lowlands different than the
subspecies in the mountains or that are represented by too little
material from the Grand Mesa to be evaluated critically are _Myotis
evotis_, _Myotis volans_, _Spermophilus variegatus_, _Eutamias
quadrivittatus_, _Castor canadensis_, _Ondatra zibethicus_, _Erethizon
dorsatum_, _Mustela frenata_, _Taxidea taxus_, _Mephitis mephitis_, and
_Odocoileus hemionus_. Three other wide-spread species are
differentiated into lowland and highland subspecies; two of these
species, _Eutamias minimus_ and _Peromyscus maniculatus_, are
represented on the Grand Mesa by the darker subspecies of the
mountains. The third species, _Neotoma cinerea_, is represented by two
individuals from below the actual rim of the mesa; they are intergrades
between the lowland and highland subspecies.

Species of southern distribution, that are dependent at the latitude of
Colorado upon the habitat provided by areas of lower altitudes, and
that are here in Colorado near their northern limit comprise a third
category that is not represented in the list of mammals from the Grand
Mesa although such characteristic species as _Ammospermophilus
leucurus_, _Perognathus apache_, and _Dipodomys ordii_ occur as near as
Grand Junction.

Approximately 55 per cent of the species of the mammalian fauna are
boreal; no species of Sonoran affinities finds haven on the Grand Mesa.

Transmitted January 22, 1959.


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Transcriber's Notes:

Italicized text is shown within _underscores_.

Bold italicized text is shown within =_equal signs and underscores_=.

Page 407: Rejoined the remainder of the last paragraph, originally
found on page 409.