More than 250 living species and about 50 genera are known in the squirrel family. They are found in most tropical and temperate regions of the world except Australia, Madagascar, and the major desert regions of Africa . These teeth grow throughout the life of the animal. Some species have cheek pouches where they can temporarily hold food, such as grain, and then deposit it later for storage in a nest or burrow. The tree squirrels bury nuts in the ground for later consumption.
Squirrels have large eyes, a coat of short fur, and bushy tails.
The eyes of the nocturnal flying squirrels are particularly enlarged in order to gather more light for better night vision. Some species in the squirrel family bark or make loud, high-pitched chirping or whistling sounds to communicate among themselves for purposes of courtship, territorial display, or as alarm calls in response to the presence of predators. All squirrels have strong hind legs. Some species are quite dexterous and agile. The various tree-climbing species are especially adept at grasping limbs and other vegetation, making great leaps between branches, and cushioning a fall by flattening their bodies and spreading their tail fur.