Page:Natural History of the Ground Squirrels of California.djvu/115

Rh the last week of May are numerous. The latest date is September 4 (1908) for half-grown young at Vallevista, San Jacinto Valley. From all the facts at hand we would estimate the usual date of birth for this species to be close to May 10.

By the time they are half grown the young seem to be well able to forage for food by themselves. No solicitude has been observed on the part of the parent. The young show themselves to be less shy than adults, and for this reason it is probable that a large toll is taken by their enemies during early summer, until the young get sophisticated.

The Antelope Ground Squirrel, according to the data above given, is the most prolific of all our species of ground squirrels. It can be inferred from this that existence on the desert, in the mode followed



by this squirrel, is the most precarious. The factor of high mortality must therefore be provided against by high birth rate. The category of predaceous animals which occupy the same territory and which are sure to prey habitually upon the Antelope Squirrel includes "snakes, weasels, foxes, coyotes, badgers, bobcats, and many kinds of hawks" (Nelson, 1918, p. 443).

At all the lower elevations, where the winters are not especially cold, Antelope Ground Squirrels are to be seen abroad at all seasons. For instance, around Victorville in December and January, 1904–05, and at Palm Springs in December, 1904, they were to be seen nearly every day, though they did not seem to be foraging far and wide actively then as is their wont in March and later. At the former locality on the coldest windy days none was seen. It is very likely that at higher places, altitudinally, especially where there is some snow, as at the head of Owens Valley, these animals hibernate through the coldest months.