Page:Natural History of the Ground Squirrels of California.djvu/66

650 Rodent Control, of the Davis, Williams, Willows and Orland districts. The reason for this is twofold: The Douglas Squirrels never did have a secure foothold in the Sacramento Valley, such as the Beechey Squirrels have in the San Joaquin Valley; and the former, according to current impression, takes the poisoned grain more readily.

On the other hand, with the clearing of forest lands in the coast district, through lumbering and homesteading, the squirrels are thought to have extended their confines locally. At any rate, they have become numerous where formerly absent altogether or present in such small numbers as to have been overlooked by the average person.

In certain sequestered valleys among the northern coast ranges we have been assured of a loss to grain crops, where no effort at poisoning the squirrels had been made, of from 5 to 25 per cent. In such cases the squirrel population from the wild land immediately adjacent seemed to have moved in en masse, as harvest time approached, to take advantage of the special food supply thus made available. Nevertheless, the Douglas Ground Squirrel, by reason of its relatively sparse population over most of its range, and the ease with which it can be reduced in numbers with reasonable effort, does not rank as of so much economic importance as some other species. We would place it fourth among our ground squirrels, giving precedence to the California, Oregon and Fisher.

Other names.—Plateau Ground Squirrel; Rocky Mountain Ground Squirrel; Citellus grammurus.

Field characters.—As for the Beechey Ground Squirrel, differing in longer tail and grayer general coloration; fore parts of body continuously grayish white, without specially set-off shoulder patches. Length of body alone about 10½ inches, with tail about 8 inches more.

Description.—Summer pelage: Head dull buckthorn brown, grizzled on cheeks and sides of snout; eyelids dull white; whiskers black; backs of ears dull buffy brown, insides of ears pinkish buff. Forward half of upper surface of body light gray, with decided dusky mottling in transverse trend; hinder half of upper surface, of a tawny-olive tone, lighter on sides, and with similar transverse mottling. Whole lower surface of body and upper surfaces of feet, pale pinkish buff, nearly white in some specimens; belly with grayish bases of hairs showing through. Tail considerably bushier than in beecheyi, as well as being longer; length of hairs up to 50 mm. (2 inches); tips of hairs more extensively white, thus nearly as in douglasii; dark and light intervals on individual hairs same as in beecheyi, that is, three dark and four light, the latter including the tipping.

Color variations.—Wear and exposure to intense sunshine evidently accounts for the yellowing of the pelage of one specimen at hand; also the tail of the animal shows a curious crinkling of the hairs as if scorched. An adult of date June 2 has the forward half of the body in fresh new (summer) pelage; this is relatively harsh in texture, without underfur. Young less than half grown are colored almost exactly as described above for adults, but the pelage on the under surface is very scanty, so that the bare skin shows through extensively. No winter specimens are at hand from within the state of California.

Measurements.—Only two adult specimens are available from California. These are from the Providence Mountains, eastern San Bernardino County, and show