Gopherus polyphemus Photo Fiona Sunquist ©
The gopher tortoise is the only native tortoise living east of the Mississippi River, and it is Florida’s only true tortoise. Adults have a high domed carapace (shell) that can measure 39 cm long, and they may weigh up to 11 kg. Males and females are similar in color and general appearance, but the plastron (shell on underside of body) of males is slightly concave. Females have flat plastrons.
Gopher tortoises dig burrows that can be 30 feet long and 16 feet deep. The sand excavated from the burrow is deposited over a wide apron just outside the burrow entrance. These aprons are the most noticeable sign of the presence of gopher tortoises. Occupied burrows usually have footprints or other signs of activity on the apron, and the width of the hole is a fairly accurate measure of the size of the tortoise living in the burrow.
Tortoises attain their highest densities – as many as 10 per hectare - in grassy, open-canopied plant communities, or fire-adapted savanna-like habitats. These habitats are similar to the steppe and thorn scrub environments of western North America in which the genus is thought to have evolved.
Individual tortoises can live to be 60 years old. Each tortoise digs several burrows throughout its home range, and once ensconced, may occupy the same hole for decades. The burrows are virtually the only shelter available in the sandhills and the tortoise burrow inadvertently provides shelter for an array of other species.
The gopher tortoise is a keystone species in Florida’s xeric (dry) communities, meaning that its presence and behavior affects the survival of many other species. Its burrow not only provides shelter for many other species but the digging returns leached nutrients to the surface. When a lightning fire sweeps through the sandhills, gopher tortoise burrows become a refuge.
Several species are considered commensals - dependent on the gopher tortoise burrow for refuge and microhabitat. These include gopher frogs (Rana capito) crickets, beetles and the Florida mouse (Podomys floridanus).
Indigo snakes (Drymarchon coralis couperi), Florida pine snakes (Pituophis melanoleucus mugitus), eastern coachwhips (Masticophis f. flagellum), and Eastern diamondback rattlesnakes (Crotalus adamanteus) have also been found in burrows.
Mammals also use the burrows as shelters – Old field mice and cotton mice are common residents. Cottontail rabbits use vacant burrows for nesting and escape from predators, while foxes, coyotes, raccoons, opossums and striped skunks have been known to enlarge burrows for dens. More than 300 species of invertebrates have been recorded using tortoise burrows.
Female gopher tortoises do not become sexually mature until they are 10-15 years of age. Each adult female lays about 6 eggs per year in a nest that is 10-20 cm below ground. Nests can be as far as 10 m from the burrow, but many nests are made on the open sandy apron near the burrow entrance. Incubation lasts about 90 days, and the eggs hatch in August and September. Gopher tortoises have the lowest reproductive potential of turtles yet studied.
In addition to a low reproductive potential, gopher tortoises are also threatened by human activities such as mining, citrus, agriculture, roads, and real estate development. However, gopher tortoises can coexist with low-level cattle grazing and timber harvesting.
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