Other names.—Mohave Desert Spermophile; Mohave Desert Ground Squirrel, part; Spermophilus mohavensis; Citellus tereticaudus mohavensis, part.
Field characters.—A small-sized, brown-colored ground squirrel, without stripes or special markings whatsoever on the body, but with short broadly haired tail, white underneath; ear a mere rim; length of body alone, about 6½ inches, with tail about 2½ inches more.
Description.—Adult in full winter pelage: General tone of whole upper surface from nose to base of tail cinnamon drab; hairs on back when examined closely are seen to be lead-color at base, then ashy white, then army brown, and tipped with white; mixed with these hairs are a few of solid black color, and on the rump some which are black with a white interval near end. Eyelids white, but cheeks like back; rim of ear and upper sides of feet tinged with light pinkish cinnamon; palms of fore feet naked; soles of hind feet clothed with long buffy hairs; claws black with horn-colored tips. Under surface of body silvery white, but slaty bases of hairs show through making the general effect light gray. Under surface of the flattish stubby tail pure white; upper side like back at base, becoming mixed black and white toward end; extreme end with white fringe. Adult in summer pelage: Coat very much coarser and shorter than in winter; general color tone browner, close to cinnamon, but a grizzling effect is produced by white hair-tippings everywhere on upper surface. Sides of face paler than in winter, and lower surface of body pure white, owing to lack of lead-color at bases of individual hairs.
Color variations.—Specimens of dates May 3 and 12 are in process of molt from winter to summer pelage. Patches of worn and yellowed winter hairs remain on the fore back and rump. The tail is seemingly not included in the spring molt, and the old tail hairs become crinkled and broken at the ends; the white of the under side is dingy, and a dark subterminal band around the end of the tail shows through.
Measurements.—Average and extreme measurements, in millimeters, of seven adult specimens (5 males, 2 females), from the northern part of the Mohave Desert are as follows: Total length, 224 (212–230); tail vertebræ, 62 (42–72); hind foot, 36 (34–37); greatest length of skull, 38.6 (38.1–39.0); zygomatic breadth, 24.3 (23.6–25.3); interorbital width, 8.7 (8.2–9.2).
The two sexes appear to be alike in measurements as well as in coloration.
Weights.—An adult male, not particularly fat, was found to weigh 104 grams (about 3⅔ ounces).
Type locality.—Mohave River, California (Merriam, 1889, p. 15). More exactly, near Rabbit Springs, about 15 miles east of Mohave River at Hesperia, in San Bernardino County (Stephens, in conversation, January 1, 1916).
Distribution area.—Not continuous; western parts of the Mohave Desert, from Haiwee, Inyo County, south to Rabbit Springs, San Bernardino County (see fig. 18). Life-zone, Lower Sonoran, though only in its upper portion apparently. Altitudinal range, 2,500 to nearly 4,000 feet.
Specimens examined.—A total of 8, from the following localities in California: Inyo County: Haiwee Meadows, 3,750 feet alt., about ten miles south of Owens Lake, 2 (in coll. U. S. Biol. Surv.); Little Lake, 3,100 feet, 2 (Mus. Vert. Zool.). San Bernardino County: Salt Wells Valley (eastern edge near Inyo County line), 2,500 feet, 3 (U. S. Biol. Surv.); Rabbit Springs, 2,900 feet, east of Mohave River, 1 (in coll. F. Stephens).
The Mohave Ground Squirrel, although first discovered in 1886 by Mr. Frank Stephens of San Diego, has remained about the least known of all our rodents. Only four rather scattered localities of occurrence are definitely known, as listed above under "Specimens examined." The dates represented are March 22 and 24, May 3 and 12 and June 5.
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