Gerbil , common name for any of several small, burrowing rodents that have soft, sand-colored fur, a mouselike face, and long hind legs that enable them to leap about like rodents such as jerboas and kangaroo rats. Gerbils are 5 to 20 cm (2 to 8 in) long, excluding the tufted tail, which is 4 to 24 cm (1.6 to 9 in) in length. Sometimes called sand rats or desert rats, gerbils are found in the dry, sandy areas and grasslands of western Asia and Africa. Colonies usually live together in a tunnel that varies from a single short burrow to multiple intersecting tunnels. The animals plug the entrance of the tunnel with earth to retain moisture. Most species are active at night and feed on seeds, grasses, nuts, insects, and roots. They require little water. Gerbils may live four to eight years in captivity, depending on the species. Litters of 1 to 14 young are born as often as once a month during the first two years. About 12 genera and more than 70 species are known. The Mongolian gerbil became a popular pet after it was introduced as a laboratory animal. It is clean, active, and friendly .