Page:Natural History of the Ground Squirrels of California.djvu/83

Rh The enemies of this species of squirrel probably include most of the carnivores of the high mountains. A Mountain Weasel (Mustela arizonensis) has been seen to kill one by biting it through the back of the neck (C. L. Camp, MS).

The Belding Ground Squirrel bears no decided economic importance, save as might be involved in the grass it eats. Its habitat falls only within the summer range of sheep and cattle, and its numbers are nowhere so great as to be likely to reduce the crop of pasture grass to any material extent.

Other names.—Stephens Spermophile; Picket-pin, part; Stephens Ground Squirrel; Spermophilus mollis stephensi.

Field characters.—Small size combined with very short and slender tail and gray coloration (no stripes or special markings); ear small; length of body alone about 6¼ inches, with tail about 2 inches more.

Description.—Nearly full-grown young in summer pelage (June): General tone of coloration on upper surface of body, buffy gray; top of head from nose to hind neck, pale cinnamon-buff, deepest on nose, and changing into color of back on shoulder; cheek to shoulder, olive-buff; eyelids white; whiskers black; back light drab with a faint effect of fine dappling; the hairs on the back lead-colored at extreme bases, then gray, then bister, and tipped with buffy white. Upper surfaces of feet dull white; palms naked; soles of hind feet clothed with dull whitish hairs to about halfway forward from heel; claws blackish, with horn-colored tips. Tail flat-haired, but narrowly so, and tapering from base to tip; upper surface buffy drab; beneath dull white at base, becoming dusky pinkish buff toward end. Lower surface of body silvery white, faintly buff tinged, particularly as forming a band along each side, and with much of the leaden-hued bases of the hairs showing through.

We have at hand but two specimens of this ground squirrel, and these are both immature.

Color variations.—A considerable series of specimens of Citellus mollis (subspecies?) at hand from northern Nevada make it seem likely that stephensi varies in color but little from the coloration as here described; probably old adults are grayer, with little or none of the cinnamon-buff about the head. The summer pelage at all ages is notably soft and silky as compared with that of most other species of ground squirrels at the same season. There is possibly a distinct winter pelage, with regular molts in spring and fall; but we have no specimens to indicate this.

One of our two specimens has the tail much flatter, and broader ended, than the other; but this we think is due to the way the tail was wired when the skin was prepared. The usual thing is for the tail to taper from base to tip, thus quite unlike the condition found in the Mohave Ground Squirrel.

Measurements.—Nine specimens from the head of Owens Valley, in California, average, in millimeters as follows: total length, 212; tail vertebræ, 50; hind foot, 32.4 (Merriam, 1898, p. 70).

The two immature specimens in the Museum of Vertebrate Zoology, from near Mono Lake, measure as follows, the first figures given being for the male, the second for the female: total length, 195, 185; tail vertebræ, 45, 45; hind foot, 32, 32; ear from crown, 4, 4; greatest length of skull,, 35.6; zygomatic breadth, 21.8, 22.0; interorbital width, 7.4,

Weights.—Our two specimens weigh, in grams, as follows: male, 83.6; female, 78.0 (in ounces, about 3 and 2¾, respectively).

Type locality.—Queen Station, near head of Owens Valley, Nevada [in Esmeralda County, just across California boundary] (Merriam, 1898, p. 69).