Page:Natural History of the Ground Squirrels of California.djvu/102

682 ashy, head less richly coppery, and under surface of body and upper surfaces of feet whiter; under surface of tail medially ochraceous-tawny. Because the lighter colors are paler in tone, the jet black side-stripes stand out with greater sharpness than in the Sierran race.

Color variations.—As in the Sierra Golden-mantled Ground Squirrel. In some specimens in fresh pelage the throat is pure white without a tinge of buff. Half-grown young just out of their nest-burrows show the characteristic paleness of their subspecies to as great a degree as adults in new coat. The pallidness of the adults in old worn breeding dress is greater in degree than in the Sierran race, evidently due to the greater bleaching effects of the more intense sunlight and dryness to which the Inyo animals are exposed. The innate paleness of the Inyo race is thus accentuated by external factors.

Measurements.—Average and extreme measurements, in millimeters, of twenty full-grown specimens from the White Mountains, Mono and Inyo counties, are as follows: Ten males: total length, 268 (260–279); tail vertebræ, 92 (80–105); hind foot, 40 (38–43); ear from crown, 13.4 (11.0–15.0); greatest length of skull, 42.9 (42.0–44.0); zygomatic breadth, 26.2 (25.0–26.9); interorbital width, 10.0 (9.0–11.3). Ten females: total length, 264 (254–286); tail vertebræ, 85 (78–89); hind foot, 38 (36–42); ear from crown, 13.3 (10.0–16.0); greatest length of skull, 41.4 (39.6–42.3); zygomatic breadth, 25.9 (25.0–26.6); interorbital width, 9.8 (9.3–10.2).

As will be seen from the above measurements in comparison with those given for the Sierran race, there are no important size differences between perpallidus and chrysodeirus; indeed it seems likely that, with large enough series, such discrepancies as are here in evidence would disappear altogether. The same variations due to age and sex seem to be present.

Weights.—Average and extreme weights, in grams, of twenty full-grown specimens from the White Mountains, Mono and Inyo counties, are as follows: Ten males, 182 (166.5–199.5); ten females, 160 (141.0–209.1). Averages, in ounces: males, about 6½; females, about 5½.

There were no gravid females in this lot. All were taken before August 10 and so none had become very fat. These facts may account for the lesser weights than shown for the Sierran race.

Type locality.—White Mountains at 10,300 feet altitude, near Big Prospector Meadow, Mono County, California (Grinnell, 1918, p. 429).

Distribution area.—The upper portions of the arid mountain ranges of extreme eastern California lying east and north of Owens Valley, namely the Inyo and White Mountains, and the mountain mass lying southeast of Mono Lake. Northernmost station, Mono Craters, Mono County (Mus. Vert. Zool.); southernmost, summit of Inyo Mountains east of Lone Pine (Elliot, 1904, p. 288). Along this extent of territory the distribution of the animal is not continuous but is interrupted at the lowermost gaps between the Inyo and White Mountains and at the extreme head of Owens Valley. Zonally, this race belongs to Boreal, but it extends down locally as low even as Upper Sonoran (see fig. 23). In other words, it extends from above timberline down to as low as 7,000 feet altitude (lower edge of piñons), the latter level for it being recorded from the bottom of Silver Canyon east of Laws. The highest observed station of occurrence is McAfee Meadow, 11,600 feet, near White Mountain Peak (Mus. Vert. Zool.).

Specimens examined.—A total of 50, from the following localities in California: Mono County: Mono Mills, 4; Mono Craters, 1; McAfee Meadow, White Mts., 7; Big Prospector Meadow, White Mts., 22; Cottonwood Creek, White Mts., 1. Inyo County: Roberts Ranch, Wyman Creek, White Mts., 2; Silver Canyon, White Mts., 4; Black Canyon, White Mts., 5; Mazourka Canyon, Inyo Mts., 4.

This is simply a pale desert-range race of Golden-mantled Ground Squirrel, probably cut off but incompletely from its near relative, chrysodeirus, of the Sierra Nevada. There can hardly be expected to be any decided differences in habits between the two; yet the different "setting" of perpallidus—exceedingly dry, rocky slopes, with only sparse timber at best—has left in our minds an impression of distinctness. This only goes to show that we cannot conveniently, nor should