Squirrel, member of one of the largest families, Sciuridae, of rodents. The name commonly refers only to tree squirrels, found in most forested parts of the world. Typically they have long, bushy tails and short muzzles. They are diurnal and feed on seeds, nuts, and leaf buds, with some insect and other animal food. A number of temperate species, while not true hibernators, store food for the winter and enter deep torpor. The family includes the chipmunk, woodchuck, and prairie dog.