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

[Pg 407]

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.

[Pg 408]

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.

[Pg 409]

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[Pg 410]
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.[Pg 411]

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[Pg 412]
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.[Pg 413]

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[Pg 414]
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.

27-7472

Transcriber's Notes

Page 407: Rejoined the remainder of the last paragraph, originally

found on page 409.