Gopher Tortoise: Gopherus polyphemus
The gopher tortoise is a moderate-sized, terrestrial turtle, averaging 23–28 cm (9–11 in) in length. The species is identified by its stumpy, elephantine hind feet and flattened, shovel-like forelimbs adapted for digging. The shell is oblong and generally tan, brown, or gray in coloration. Gopher tortoises can live 40 to 60 years in the wild.
Gopher tortoises are ancient: their ancestors are a species of land tortoise that originated in western North America some 60 million years ago. They are members of the Class Reptilia, Order Testudines, and Family Testudinidae. Of five North American tortoise species (genusGopherus), the gopher tortoise is the only one that occurs east of the Mississippi River.
Gopher tortoises live in well-drained sandy areas with a sparse tree canopy and abundant low growing vegetation. They are commonly found in habitats such as sandhill, pine flatwoods, scrub, scrubby flatwoods, dry prairies, xeric hammock, pine-mixed hardwoods, and coastal dunes which have historically been maintained by periodic wild fires. When fire is suppressed in gopher tortoise habitat, small trees, shrubs, and brambles begin to grow making it difficult for the gopher tortoise to move around and eventually shade out the low growing plants that gopher tortoises eat.
During winter, tortoises are much less active; although on warm afternoons some individuals trudge to the earth's surface to bask on the sandy aprons of their burrows. A superb earth-mover, it lives in long burrows that offer refuge from cold, heat, drought, forest fires and predators. The record length for a burrow is over 47 feet long, however, the burrows average 15 feet long and 6.5 feet deep. The burrows maintain a fairly constant temperature and humidity throughout the year and protect the gopher tortoise and other species from heat, cold, drought, and predators. Burrows also act as a refuge from the periodic, regenerative fires that are required to maintain the quality of their habitat.
Gopher tortoises have adapted to living in dry habitats with frequent fire occurrence by digging burrows deep into the sandy soil. The absence of natural cycles of burning in pine forests spells hardship for tortoises. The dense vegetation (shrubs, brambles, small trees) that grows in a forest in the absence of fire shades out the tender herbs tortoises like to eat, and limits their food supplies. Fire is vital in maintaining many native ecosystems, like longleaf pine sandhills, where gophers live.
Gopher tortoises are slow to reach sexual maturity, have a low fecundity, and a long life span. Females reach sexual maturity at 9–21 years of age, depending on local resource abundance and latitude; males mature at a slightly younger age. The breeding season is generally April–November. Nests are constructed (often in burrow mounds) from mid-May to mid-June, and only one clutch is produced annually. Clutch size is usually five to nine eggs, with an average of six. Predation on nests and hatchlings is heavy.
These reptiles feed on low-growing plants like wiregrass, broadleaf grasses, and legumes (bean family plants). They also eat prickly pear cactus, blackberries, paw-paws, and other seasonal fruits. In addition to needing open areas with abundant food, gopher tortoises require relatively deep, sandy soils for burrowing and sunny spots for laying eggs.
An amazing trait of the gopher tortoise is that it shares its burrow with more than 350 other species, including burrowing owls, Florida mice, indigo snakes, opossums, rabbits, gopher frog, eastern diamondback rattlesnakes and gopher crickets. For this reason it is called a keystone species, so named because the upper stone in an arch, the keystone, supports the other stones to hold them in place. Animals which utilize the gopher tortoise burrows are known as commensal species. Since many commensal species depend on the burrows for survival, decreases in gopher tortoise populations result in a decline of other species.
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Image Credit: Cliff Leonard