Page:Natural History of the Ground Squirrels of California.djvu/68

652 this beginning about July 1st; but we have no specimens of dates between August and May. It is possible that there is an autumn molt leading into a distinct winter coat. Small young are softer-pelaged than adults, but colored just the same.

Measurements.—Average and extreme measurements, in millimeters, of nineteen mature specimens from northeastern California are as follows: Nine males: total length, 275 (260–300); tail vertebræ, 65 (56–80); hind foot, 42 (37–45); ear from crown, 9 (7–11); greatest length of skull, 45.1 (44.2–46.5); zygomatic breadth, 29.1 (27.1–31.0); interorbital width, 10.4 (10.0–11.1). Ten females: total length, 280 (271–292); tail vertebræ, 57 (47–68); hind foot, 43 (41–44); ear from crown, 7.5 (6–8); greatest length of skull, 45.7 (44.9–47.2); zygomatic breadth, 29.7 (29.1–30.4); interorbital width, 10.4 (9.7–10.9).

From the above figures it would seem that, in this ground squirrel, females are larger than males, except for tail and ear. There are chances, however, that measurement of greater numbers would give somewhat different results. It must be kept in mind that the figures taken from the freshly killed animals were supplied by several different people, and method of securing each measurement undoubtedly varies somewhat with the persons doing the measuring. Even with the skulls, all measured by the senior author of this paper, size clearly varies to some degree with age, and the proportions present in our series, of animals of different ages, will naturally affect the average.

Weights.—Average and extreme weights, in grams, of six full grown females are: 302 (267–365.8). This average in ounces is about 10½. The heaviest example was notably fat, the lightest, lean. Adipose tissue thus counts importantly in weight, though probably also weight increases, as does size of skull, with age. The animals would probably weigh most just prior to hibernation, as they are then fattest.

Type locality.—Swan Lake Valley, Klamath Basin [Klamath County], Oregon (Merriam, 1898, p. 69).

Distribution (in California).—Occupies the northeastern corner of the state, comprising the counties of Modoc, Lassen, eastern Siskiyou, and a portion of Plumas (see fig. 18). The metropolis of the species lies in the Upper Sonoran life-zone, but the animals extend through Transition, and even enter the Canadian. In detail: west from the Nevada line as far as the vicinity of Goose Nest Mountain, Siskiyou County, and vicinity of Big Meadows, in extreme northern Plumas County; south from the Oregon line to the last named locality and to the valley of Susan Creek, in Lassen County. Altitudinally, this ground squirrel extends from as low as 3,300 feet, on the Pit River, up to 9,000 feet, on Warren Peak, Warner Mountains (Mus. Vert. Zool.).

Specimens examined.—A total of 51 from the following localities in California: Modoc County: Sugar Hill, 4; Goose Lake near Davis Creek, 2; South Fork Pit River near Alturas, 3; Warner Mts. (Parker Creek and Squaw Peak), 6. Siskiyou County: near head of Little Shasta River, north of Goose Nest Mt., 1; Bull Meadow, northeast of Goose Nest Mt., 1; seven miles south of Macdoel, 24; Grass Lake, 6. Lassen County: Termo, 1; west end of Horse Lake, 1; fifteen miles west of Westwood, 1. Plumas County: ten miles west of Big Meadows, 1.

The Oregon Ground Squirrel occurs in California only in the extreme northeastern counties of the state; but it has a rather wide general range which includes much of Oregon east of the Cascades, and parts of northern Nevada. It is a Great Basin plateau species, and its range ends to the westward in California rather abruptly in the vicinity of Goose Nest Mountain (head of Little Shasta River and Grass Lake) and in the Pit River Valley in the vicinity of Burney, Shasta County. To the southward it extends to Big Meadows, in Plumas County a little southeast of Mount Lassen, and to the valley of Susan River, in Lassen County.

In most of the sagebrush territory thus bounded, the Oregon Ground Squirrel is conspicuously abundant, more so, some people believe, than any other species anywhere in this state. While not so large as the