Gopher Tortoise

The Gopher Tortoise within the Timucuan Ecological and Historic Preserve:
Diet:
 * The gopher tortoise is a species of reptile that is native to the southeastern United States. i.e. Alabama, Mississippi, Louisiana, South Carolina, Georgia, and Florida.
 * Mature gopher tortoises are typically dark brown to gray-black in colour and when fully grown, can reach 1 foot in length and weigh approximately 30 pounds.
 * Unlike adult gopher tortoises, baby gopher tortoises are bright yellow in colour.
 * Gopher tortoises are able to dig burrows with their front feet.
 * Burrows can be on average 30 feet in length and get up to 20 feet deep.
 * Burrows provide the gopher tortoise protection from predators and bad weather.
 * Gopher tortoises have a long lifespan and can live for more than 40 years.

References:

Diemer, J.E. (1986). The Ecology and Management of the Gopher Tortoise in the Southeastern United States. Herpetologica, 42(1), 125-133.

McRae, W.A., Landers, J.L., Garner, J.A. (1981). Movement Patterns and Home Range of the Gopher Tortoise. The American Midland Naturalist, 106(1), 165-179.

Yager, L.Y., Hinderliter, M.G., Heise, C.D., Epperson, D.M. (2007). Gopher Tortoise Response to Habitat Management by Prescribed Burning. Journal of Wildlife Management, 71(2), 428-434.

Kaczor, S.A. and Hartnett, D.C. (1990). Gopher Tortoise (Gopherus polyphemus) Effects on Soils and Vegetation in a Florida Sandhill Habitat. The American Midland Naturalist, 123(1), 100-111.

MacDonald, L.A. and Mushinsky, H.R. (1988). Foraging Ecology of the Gopher Tortoise, Gopherus Polyphemus, in a Sandhill Habitat. Herpetologica, 44(3), 345-353.

Breininger, D.R., Schmalzer, P.A., and Hinkle, C.R. (1991). Estimating Occupancy of Gopher Tortoise (Gopherus Polyphemus) Burrows in Coastal Scrub and Slash Pine Flatwoods. Journal of Herpetology, 25(3), 317-321.

Hermann, S.M., Guyer, C., Waddle, J.H., and Nelms, M.G. (2002). Sampling on private property to evaluate population status and effects of land use practices on the gopher tortoise, Gopherus Polyphemus. Biological Conservation, (108)289-298.


 * The burrow is a means of escape for many animals during temperature extremes, dessication, and predators.
 * Mounds created from the burrows provide soil areas for germination of seeds.
 * Landscape heterogeneity
 * During fires, burrows act as cool-temperature refugia for plants and seeds
 * Temperatures at the burrow were less than the surrounding area (Kazcor and Hartnett, 1990)
 * Microsuccession occurs on the burrow mounds which contributes toward increasing species diversity in the forest understory
 * Increased nutrient availability?

Reproduction: Ashton KG, Engelhardt BM, Branciforte BS. Gopher Tortoise (Gopherus polyphemus) Abundance and Distribution after Prescribed Fire Reintroduction to Florida Scrub and Sandhill at Archbold Biological Station. Journal of Herpetology. 2008;42(3):523–529.
 * Earl et al (2015): Two sites, high and poor quality. Tortoises avoided dense canopy areas in high quality habitat and exotic weeds in poor quality habitat. Results?
 * However... Florida Fish and Wildlife Conservation Commission
 * Found in Timucuan – native, present, vulnerable, abundance unknown

Catano CP, Stout IJ. Functional relationships reveal keystone effects of the gopher tortoise on vertebrate diversity in a longleaf pine savanna. Biodiversity and Conservation. 2015;24(8):1957–1974.

Mccoy ED, Basiotis KA, Connor KM, Mushinsky HR. Habitat selection increases the isolating effect of habitat fragmentation on the gopher tortoise. Behavioral Ecology and Sociobiology. 2013;67(5):815–821.

Pawelek JC, Kimball ME. Gopher Tortoise Ecology in Coastal Upland and Beach Dune Habitats in Northeast Florida. Chelonian Conservation and Biology. 2014;13(1):27–34.

Tuberville TD, Todd BD, Hermann SM, Michener WK, Guyer C. Survival, demography, and growth of gopher tortoises ( Gopherus polyphemus ) from three study sites with different management histories. The Journal of Wildlife Management. 2014;78(7):1151–1160.
 * Home range of the gopher tortoise is inversely related to amount of herbaceous ground cover (Auffenberg and Iverson, 1979).
 * Mean feeding radius is within 30m of a burrow.
 * As forested habitat quality declines, they will need to travel farther to find food sources and appropriate nesting sites.
 * Human maintained areas - roadsides, agricultural areas
 * Increased exposure to heavy machinery, chemicals, predators
 * An average colony within a year moves over a 4 ha area to search for mates and over-wintering burrows.

Conservation via Relocation?

Gopher Tortoise Effects on Trophic System Thank you! The Gopher Tortoise (Gopherus polyphemus)
 * If relocation were to occur...
 * Study by Pawelek and Kimball (2014) shows burning increases open area for tortoise, increases diversity, and increase forage quality and quantity.

Conservation via Prescribed Burning Simplified Trophic System of Gopher Tortoise in Timucuan
 * The Timucuan Ecological and Historic Preserve is a U.S. National Preserve located in Jacksonville, Florida.
 * It's comprised of several habitats: 46,000 acres of woods, waterways, and marshes.
 * The Preserve was established as a National Park in 1988 and averages over 1 million visitors each year.
 * Currently, the gopher tortoise is one of the oldest species living in the Timucuan Preserve and is the state reptile of Georgia and the state tortoise of Florida.
 * According to the IUCN red list, the gopher tortoise is currently listed as vulnerable.

Simplified Trophic System of Gopher Toroise Burrow in Timucuan

Conservation within Timucuan

Predation: Habitat Destruction: Range: Brief Introduction: Importance of the Gopher Tortoise.
 * Tuberville et al 2014: Male and female tortoises at Conecuh had lower body sizes than Green Cove and Wade Tract.
 * In addition to predation, gopher tortoises are also threatened by habitat destruction and degradation.
 * With regards to Florida, gopher tortoises could potentially lose 700 acres of its habitats if Florida’s population doubles.
 * A growing population = more land development.
 * Land development has been known to increase the competition for water and resources between animals and humans.
 * Due to the low reproductive rate of the gopher tortoise, increased competition makes it more susceptible to population declines in its ecosystem.
 * Removal of the Gopher Tortoise would not cause a trophic system collapse, but the amount of predation would increase.
 * Top predators that frequently feast on the tortoise's eggs and juveniles lose a valuable source of protein and must look for a substitute
 * No new burrows would be created, so there would be a limited number of refugia that are degrading over time.
 * Animals that use the burrows will now have to compete for shelter. Competition increases.
 * Outcompeted animals will have to look for shelter elsewhere and are no longer protected from predators and harsh weather.
 * The Gopher Tortoise has also been noted as a seed disperser for native grasses (Auffenberg, 1969)
 * Less dispersal will lower the species richness and diversity of Timucuan.
 * Overall, the gopher tortoise is seen as a keystone species because it digs burrows that provide shelter for at least 360 other animal species.
 * A few species that use the gopher tortoise burrow in the Timucuan Preserve are:
 * the Southern toad; the Greenhouse frog; the Eastern narrowmouthed toad; the Green treefrog; the Barking treefrog; the Eastern spadefoot; the Green anole; the six-lined racerunner; the Eastern fence lizard; the pygmy rattlesnake; the common garter snake; the Eastern mole; and the Hispid cotton rat.
 * If the gopher tortoise were to go extinct, several species would loose a valuable source of food and there would be no new burrows that species need to occupy for shelter.
 * No new burrows = less shelter.
 * Less shelter = more exposure.
 * Study by Catano and Stout (2015) shows prescribed burning for a 1-7 year period increased species diversity in burrows.
 * Gopher tortoises are herbivore scavengers and their diet is known to contain over 300 species of plants.
 * They consume a very wide range of plants, but mainly eat broad-leaved grass, regular grass, wiregrass, and terrestrial legumes.
 * Gopher tortoises have also been known to eat apples, blackberries, saw palmetto berries, and other fruits.
 * In a study conducted by Landers et al. (1980), the researchers estimated that a successful hatch of gopher tortoise eggs would occur only once every 10 years due to nest predation occuring at a rate of approximately 87%.
 * In addition, it was also estimated that less than 6% of eggs are expected to grow into tortoises that live one year or more after hatching.
 * Several of the common predators that predate on egg clutches and young gopher tortoises that are present at Timucuan include:
 * the common raccoon; the nine-banded armadillo; the common gray fox; the striped skunk; the indigo snake; the red-tailed hawk; the domestic dog; coyotes; and the american alligator.
 * Gopher tortoises are also subject to predation by humans. During the Great Depression (1929-1939), gopher tortoises were known as "Hoover Chicken" because they were eaten by poor people out of work.
 * Although it is now illegal to hunt gopher tortoises or possess their meat or shells, illegal hunting continues to take place at an unsustainable rate, with some colonies being driven to extinction.
 * Exclusion of fire from areas may reduce numbers of gopher tortoises by as much as 60–80% in 8 years (Diemer 1989) or 100% in 16 years (Auffenberg and Franz 1982).
 * Study by Ashton et al (2008) suggests gopher tortoises returned to previously vacated natural areas recently subjected to fire as opposed to fire lanes and ruderal areas, where they commonly are found
 * During the mating season between April and November, female gopher tortoises lay their eggs in open, sunlit areas. If the forest canopy is too dense, they will move to ruderal areas such as roadsides and firelanes to find sunlit nesting sites, but they are also more exposed and vulnerable there.
 * They lay about 1-25 eggs that incubate underground for about 100 days.
 * Eggs are laid only once a year.
 * The sex of the eggs is determined by the temperature where they are incubated in a nest laid below sand.
 * If the sand is over 30°C, it’s a female and if below 30°C, the egg is a male.
 * In the code of federal regulations, Timucuan Ecological Historic Preserve: No managment or conservation principles listed.
 * However... Prescribed burning > relocation

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