Species Description: The gopher tortoise, Gopherus polyphemus, is a large terrestrial turtle having forefeet well adapted for burrowing, and elephantine hind feet. The front legs have scales to protect the tortoise while burrowing. Body length averages approximately 25 cm (10 inches), with the shell ranging in height from 15 - 37 cm (6 - 15 inches). Body mass averages approximately 4 kg (9 pounds). Color is a dark brown to gray-black, with a yellow plastron (bottom shell). A gular projection is evident on the anterior plastron where the head projects out from the shell. Sexual dimorphism is evident, with male gopher tortoises having concave plastrons, while those of females are flat. In addition, the gular projection on male plastrons is generally longer than in females (Ernst and Barbour 1972).
Gopher tortoises dig burrows for cover and for nesting. These can be extensive, measuring approximately 4.7 - 11 m (14 - 40 feet) in length (Witz et al. 1991). Burrow depth is heavily dependent on depth of the local water table (Diemer 1986; Burke and Cox 1988).
Regional Occurrence: The distribution of gopher tortoise is generally correlated with the original range of longleaf pine forests, according to U.S. Fish and Wildlife Service estimates (USFWS 1990). Along the Atlantic coast, G. polyphemus occurs from southern South Carolina, through Georgia and Florida. Beyond this area of the range, disjunct populations occur westward through southeastern Louisiana. The segment of the population that occurs westward from the Tombigbee and Mobile rivers in Alabama is federally listed as threatened.
IRL Distribution: Gopher tortoises are found in all counties in Florida and utilize many habitat types, from beach dunes to scrub and pine flatwoods. Though it is generally agreed that typical gopher tortoise habitats are sandy and well-drained, Breininger et al. (1991) observed that in Brevard County, Florida, gopher tortoises often inhabit poorly drained scrub and slash pine areas. The Breininger et al. (1991) study reported higher overall tortoise densities in poorly drained areas than in well-drained, sandy areas.
Age, Size, Lifespan: Body length averages 25 cm (10 inches); shell height ranges from 15 - 37 cm (6 - 15 inches); body mass averages 4 kg (9 pounds). G. polyphemus can be long-lived. Age estimates for tortoises in the wild ranges from 40 - 60 years; however, captive tortoises can live more than 100 years (Landers et al. 1980).
Abundance: The gopher tortoise is listed in Florida as a Species of Special Concern (SSC). Auffenberg and Franz (1982) have estimated that historical population densities of this species had been reduced 70% by the year 2000, and could be extirpated from all but protected land areas by 2025. Merritt Island Wildlife Refuge at Kennedy Space Center (KSC) in Florida is the largest protected area of gopher tortoise habitat along the Atlantic coast. Overall tortoise density at KSC is estimated at approximately 18,000 animals, with tortoise density highest in areas where herbaceous cover dominates. Tortoise density decreases in areas where cover of shrubs, oak trees and pines dominates (Breininger et al. 1988, 1991, 1994).
Locomotion: Gopher tortoises walk and burrow.
Reproduction: Maturity is reached at 19 - 21 years of age in Georgia, 10 - 15 years in Florida. The reproductive season extends from February through September, with a peak throughout May and June (Diemer 1986). Females excavate nests in open, sandy areas. One clutch of eggs is laid per year, with an average of 6 eggs laid each season. However, clutch size varies depending on body size, and ranges anywhere between 3 - 14 eggs. Females may have only one successful brood every ten years, as most eggs do not survive to hatching. Mammalian predators such as foxes, raccoons, feral cats, and armadillos prey upon eggs. Landers et al. (1980) estimated that only 1 - 3 eggs of every 100 eggs survives to maturity.
Embryology: Incubation time is approximately 100 days in Georgia, and 80 - 90 days in Florida. Sex of hatchlings is dependent on the temperature of the sand where the nest is sited. In gopher tortoises, average sand temperatures above 30°C (approximately 85° F) produce females, while those below 30° C produce males.
Hatchlings measure approximately 3 - 5 cm (1.5 - 2 in.) long and are vulnerable to predation due to their soft shells. Growth rates in gopher tortoises are extremely slow, estimated to be less than 2.5 cm (1 in.) per year.
Temperature: Gopher tortoises are cold sensitive (Auffenberg and Franz 1982; Diemer 1986).
Physical Tolerances: Disease: Gopher tortoises are susceptible to a disease called Upper Respiratory Tract Disease (URTD). This disease is caused by the bacterium Mycoplasma agassizii and is not only extremely contagious, but generally fatal once contracted. URTD was first discovered in 1991 at Sanibel Island, Florida, and has subsequently been found throughout the tortoise's range. URTD inflames the respiratory tract of tortoises, causing wheezing, swollen eyelids, and excessive mucous. Infected animals, unable to find food or eat, eventually die. The disease is spread by introduction of sick animals into healthy populations. Urban development and habitat fragmentation contribute to infection by forcing tortoise populations closer together in suitable habitats.
Trophic Mode: Gopher tortoises are primarily herbivorous, with the bulk of the diet consisting of low-growing herbs and grasses. Foods most common in the diet are grasses and legume fruits. They are also known to consume pine needles and seeds, oak mast, prickly pear cactus, asters, palm tree fruits, raspberries, black cherry, and gopher apples (Landers et al. 1980; Auffenberg and Franz 1982; Diemer 1986). Gopher tortoises have also been observed to eat mollusk shells and the bones of dead animals, possibly to supplement their diets with additional calcium.
Competitors: Predators of gopher tortoises include various snakes, fire ants (Solenopsis saevissima), accipiter and buteo hawks, raccoons, opossums, armadillos, skunks, dogs, foxes, feral cats and humans all prey on gopher tortoises. Generally, eggs and hatchling tortoises are significantly more at risk for predation than older animals.
Habitats: Gopher tortoises use a variety of habitats, including beach dunes, scrub, and pine flatwoods. In all habitat types, soils are generally dry, sandy and well-drained. While generally avoiding swampy areas, gopher tortoises in Brevard County, Florida have been observed to inhabit poorly drained scrub and slash pine flatwoods (Breininger et al., 1991). In this county, higher densities of gopher tortoises were found in poorly-drained sites than in well-drained sites.
Individuals occupy distinct home ranges, with male home ranges typically being larger than those of females. In east-central Florida, home ranges of male tortoises averaged 1.9 ha (4.7 ac), while those of females averaged only 0.65 ha (1.6 ac). A tortoise excavates several burrows for its use within the home range. Burrows typically are dug at a 30° angle from the surface. In Florida studies, male tortoises dug between 8 - 35 burrows. Females tended not to use as many burrows as males, averaging between 3 - 17 burrows (Breininger et al., 1988).
Tortoise densities tend to be higher in fire-adapted communities (Auffenberg and Franz 1982; Diemer 1986). In the absence of fire, canopy trees grow large and shade out the herbaceous vegetation that gopher tortoises rely on as their primary food source.
Associated Species: Gopherus polyphemus is considered a keystone species in that more than 80 different species live in their burrows, or are dependent on their burrows for protection. Some of these species, such as the gopher frog (Rana areolata), pine snake (Pituophis melanoleucus), indigo snake (Dymarchon corais), and scrub jay (Aphelocoma coerulescens), and in inland prairies, the burrowing owl (Athene cunicularia floridana) are rare (Burke and Cox 1988; Spillers and Speake 1988; Stout et al. 1988; Witz et al. 1991).
Special Status: Gopher tortoises play an important role in structuring the habitats within ecosystems. They are Federally listed as threatened in Louisiana, Mississippi, and Alabama. In Florida, they are listed as a Species of Special Concern (SSC).
Benefit in IRL: Gopher tortoises play an important role in ecosystem ecology for two reasons. First, by consuming grasses, herbs, and the fruits of trees, the gopher tortoise aids in seed dispersal. Second, its burrows provide important habitat for more than 80 different species of invertebrates and vertebrates, some of which are rare.
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Breininger, D.R., P.A. Schmalzer, D.A. Rydene, and C.R. Hinkle. 1988. Burrow and habitat relationships of the gopher tortoise in coastal scrub and slash pine flatwoods on Merritt Island, Florida. Final Report, Project No. GFC 84-016. Florida Game and Fresh Water Fish Commission, Division of Wildlife, Non-game Wildlife Section, Tallahassee, FL. 238 pp.
Breininger, D.R., P.A. Schmalzer, and C.R. Hinkle. 1991. Estimating the occupancy of gopher tortoise (Gopherus polyphemus) burrows in coastal scrub and slash pine. Journal of Herpetology 25:317-321.
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Cox, J., D. Inkley, and R. Kautz. 1987. Ecology and habitat needs of gopher tortoise (Gopherus polyphemus) populations found on lands slated for large-scale development in Florida. Technical Report No. 4. Florida Game and Fresh Water Fish Commission, Division of Wildlife, Non-game Wildlife Section, Tallahassee, FL. 69 pp.
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Ernst C.H. and R.W. Barbour. 1972. Turtles of the United States. The University Press of Kentucky, Lexington, KY. 347 pp.
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Snyder, S. A. 1991. Gopherus polyphemus. In: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (2001, July). Fire Effects Information System, [Online]. Available at https://www.feis-crs.org/feis/ [accessed Sept. 2020].
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Spillers, D.M., and D.W. Speake. 1988. A survey method for measuring gopher tortoise density and habitat distribution. In: Szaro, R.C., K.E. Severson, and D.R. Patton, technical coordinators. Management of amphibians, reptiles and small mammals in North America: proceedings of the symposium, July 19 - 21, 1988, Flagstaff, AZ. Gen. Tech. Rep. RM-166. U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO. pp. 199-204.
Stout, I.J., D.R. Richardson, and R.E. Roberts. 1988. Management of amphibians, reptiles and small mammals in xeric pinelands of peninsular Florida. In: Szaro, R.C., K.E. Severson, and D.R. Patton, technical coordinators. Management of amphibians, reptiles and small mammals in North America: proceedings of the symposium, July 19 - 21, 1988, Flagstaff, AZ. Gen. Tech. Rep. RM-166. U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO. pp. 98-108.
Witz, B.W., D.S. Wilson, and M.D. Palmer. 1991. Distribution of Gopherus polyphemus and its vertebrate symbionts in three burrow categories. American Midland Naturalist. 126(1): 152-158.