||Gopherus polyphemus Daudin, 1802
||Testudo polyphemus Daudin, 1802
Other Taxonomic Groupings
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).
HABITAT AND DISTRIBUTION
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.
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.
LIFE HISTORY AND POPULATION BIOLOGY
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).
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,
Gopher tortoises walk and burrow.
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.
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.
Gopher tortoises are cold sensitive (Auffenberg and Franz 1982; Diemer 1986).
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 1991at 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
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.
Predators of gopher tortoises include various
snakes, fire ants (Solenopsis saevissima), accipiter hawks, buteo hawks,
raccoons, opossums, armadillos, skunks, dogs, foxes, feral cats and man all prey
on gopher tortoises. Generally, eggs and hatchling tortoises are significantly
more at risk for predation than older animals.
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.
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), the pine snake (Pituophis melanoleucus)
the indigo snake (Dymarchon corais), the 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).
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.
Auffenberg, W., R. Franz. 1982. The status and distribution of the
gopher tortoise (Gopherus polyphemus). In: Bury, R.B., ed.
North American Tortoises: conservation and ecology. Wildlife Research
Report 12. U.S. Department of the Interior, Fish and Wildlife Service,
Washington, D.C. pp. 95-126.
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
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
Breininger, D.R., P.A. Schmalzer, and C.R. Hinkle.
1994. Gopher tortoise (Gopherus polyphemus) densities in coastal
scrub and slash pine flatwoods. Journal of Herpetology 28:60-65.
Burke, R.L. and J. Cox. 1988. Evaluation and review of
field techniques used to study and manage gopher tortoises. 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. 205-215.
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.
Diemer, J.E. 1986. The ecology and management of the
gopher tortoise in the southeastern United States. Herpetologica. 42(1):
Ernst C.H. and R.W. Barbour. 1972. Turtles of the
United States. The University Press of Kentucky, Lexington, KY. 347 pp.
Landers, J.L, J.A. Garner, W.A. McRae, and W. Alan.
1980. Reproduction of gopher tortoises (Gopherus polyphemus) in
southwestern Georgia. Herpetologica. 36(4): 353-361.
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: http://www.fs.fed.us/database/feis/ [accessed
U.S. Fish and Wildlife Service. 1990. Gopher tortoise (Gopherus
polyphemus) recovery plan. Prepared by Wendell A. Neal, U.S.
Fish and Wildlife Service, Jackson, MI. 28 pp.
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.
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.
Report by: K. Hill, Smithsonian Marine Station
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Page last updated: Oct. 23, 2001