They are most active during mid-morning and late afternoon, especially on warm, sunny days. Ground squirrels may have two periods of dormancy during the year. During winter months most ground squirrels hibernate, but some young may be active at this time, especially in areas where winters are not severe. During the hottest times of the year most adults go into a period of inactivity, called estivation, that may last a few days to a week or more. During these periods, the burrow appears open at the entrance but the squirrel plugs it with soil near the nest.
Ground squirrels breed once a year, averaging seven to eight per litter.
Aboveground activity by adults is at a maximum at the height of the breeding season. The young grow rapidly and by 6 months of age resemble adults. Ground squirrels are primarily vegetarians. Their diet changes with the seasons. After emergence from hibernation, they feed almost exclusively on green grasses and herbaceous plants.