California Ground Squirrels prefer open, well-drained habitat, and are common along roadsides, on farms, especially where grain is grown, and in grassy fields. Adult squirrels are active only a few months of the year. Males usually retreat underground in early summer and remain there until the following spring. Females follow as soon as they finish nursing their young, usually in late summer or early fall. The aboveground fall and winter populations are composed almost entirely of young squirrels. Litter size correlates with climate: where average temperatures are warmer, litters are larger. In the warmest part of their range, in southern California, they average 8.4 young, whereas in the cooler parts of central Oregon, an average of 5.5 young is born. Predation pressure and time spent aboveground may influence litter size. The longer warm season in southern California allows the squirrels to spend a greater number of days awake and foraging, which likely increases the risk of being killed by a predator.
Links:Mammal Species of the World
Original description: Richardson, J., 1829. Fauna boreali-americana; or the zoology of the northern parts of British America: containing descriptions of the objects of natural history collected on the late northern land expeditions, under command of Captain Sir John Franklin. R.N., p. 170. John Murray, London, 300 pp.