Mammals of the Grand Mesa, Colorado

Excerpt

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.

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....