The gopher tortoise (Gopherus polyphemus) is a species of tortoise in the family Testudinidae. The species is native to the southeastern United States. The gopher tortoise is seen as a keystone species because it digs burrows that provide shelter for at least 360 other animal species. G. polyphemus is threatened by predation and habitat destruction. The gopher tortoise is a representative of the genus Gopherus, which contains the only tortoises native to North America. The gopher tortoise is the state reptile of Georgia and the state tortoise of Florida. The specific name, polyphemus, refers to the cave-dwelling giant, Polyphemus, of Greek mythology. Gopher tortoises are so named because of some species' habit of digging large, deep burrows like the rodent of that name. The gopher tortoise is a fairly large terrestrial reptile which possesses forefeet well adapted for burrowing, and elephantine hind feet. These features are common to most tortoises. The front legs have scales to protect the tortoise while burrowing. G. polyphemus is dark brown to gray-black in overall color, with a yellow plastron (bottom shell). A gular projection is evident on the anterior plastron where the head projects from the shell. Sexual dimorphism is evident, with the male gopher tortoise having a concave plastron, while that of the female is flat. In addition, the gular projection of a male plastron is generally longer than that of a female. Straight carapace length of adults usually ranges from 6 to 9.5 in (15 to 24 cm), with a maximum of 16 in (41 cm). The carapace is at least twice as long as it is high. Body mass averages 4 kg (8.8 lb), with a range of 2–6 kg (4.4–13.2 lb). It has been suggested that gopher tortoises, more than other tortoise species, exhibit social behaviour. While primarily solitary creatures, gopher tortoises live in well-defined colonies which are similar to those of highly social animals such as the Prairie dog. The distribution and proximity of burrows might be the consequence of social relationships between tortoises. Some females have been observed visiting the burrows of a particular female repeatedly, even if there are other tortoises closerby. This may be a sort of 'friendship', but such terms are not normally used to describe the relationships between animals.