Gopherus polyphemus - (Daudin, 1802)
Gopher Tortoise
Other English Common Names: gopher tortoise
Taxonomic Status: Accepted
Related ITIS Name(s): Gopherus polyphemus (Daudin, 1802) (TSN 173858)
Unique Identifier: ELEMENT_GLOBAL.2.105196
Element Code: ARAAF01030
Informal Taxonomy: Animals, Vertebrates - Turtles
Image 11541

© Larry Master

 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Chelonia Cryptodeira Testudinidae Gopherus
Genus Size: B - Very small genus (2-5 species)
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Concept Reference
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Concept Reference: King, F. W., and R. L. Burke, editors. 1989. Crocodilian, tuatara, and turtle species of the world: a taxonomic and geographic reference. Association of Systematics Collections, Washington, D.C. 216 pp.
Concept Reference Code: B89KIN01NAUS
Name Used in Concept Reference: Gopherus polyphemus
Taxonomic Comments: Auffenberg (1976), Bramble (1982), Crumly (1987, 1994), and Lamb and Lydeard (1994) provided information on phylogenetic relationships among tortoises of the genus Gopherus, which comprises four living species and nine fossil taxa. A recent study of phylogeny based on mtDNA variation identified the four living North American tortoises as a monophyletic group consisting of two well-defined clades, the agassizii clade and the polyphemus clade (Lamb and Lydeard 1994). MtDNA and osteological data indicate that G. polyphemus is more closely related to G. flavomarginatus of Mexico than it is to the other two species of Gopherus. Gopherus polyphemus is only slightly distinct from G. flavomarginatus based on allozymes (Morafka et al. 1994).

Using mtDNA, Osentoski (1993) assessed rangewide genetic variation and found three major assemblages: (1) a western assemblage consisting of seven haplotypes (Louisiana eastward to Taylor County, Florida, and along the Chattahoochee River drainage north to Talbot County, Georgia); (2) an eastern assemblage containing the two most common haplotypes (South Carolina through peninsular Florida) and (3) a mid-Florida assemblage consisting of seven haplotypes (along the Gulf coast from southern Levy County north to Pinellas County, then east to north of the Hillsborough River, and northeast into Orange/Oseola counties).
Conservation Status
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NatureServe Status

Global Status: G3
Global Status Last Reviewed: 25Feb2014
Global Status Last Changed: 20Mar1996
Rounded Global Status: G3 - Vulnerable
Reasons: Occurs in the southeastern U.S. from South Carolina to Louisiana; still common in some parts of range though rare in others; population has undergone 80% decline in last 100 years; decline is expected to continue with ongoing habitat loss; multiple threats to habitat plus direct human exploitation.
Nation: United States
National Status: N3 (05Oct1996)

U.S. & Canada State/Province Status
United States Alabama (S3), Florida (S3), Georgia (S2), Louisiana (S1), Mississippi (S2), South Carolina (S1)

Other Statuses

Implied Status under the U.S. Endangered Species Act (USESA): PS:LT, C
Comments on USESA: Listed by USFWS as Threatened west of the Mobile and Tombigbee rivers in Alabama, Mississippi, and Louisiana. Populations east of the Mobile and Tombigbee rivers are included on the Candidate list of species (USFWS 2011).

USFWS (July 27, 2011) announced a 12-month finding on a petition to list the gopher tortoise as threatened in the eastern part of its range (east of the Mobile and Tombigbee rivers).

In a 90-day finding, USFWS (September 9, 2009) found a petition to list the eastern population of the gopher tortoise as threatened under the ESA and to designate critical habitat may be warranted and have initiated a status review.

U.S. Fish & Wildlife Service Lead Region: R4 - Southeast
IUCN Red List Category: VU - Vulnerable
Convention on International Trade in Endangered Species Protection Status (CITES): Appendix II

NatureServe Global Conservation Status Factors

Range Extent Comments: Southeastern United States from southern South Carolina (Clark et al. 2001) through southern Georgia to southern Florida (excluding most of inland southern Florida), west through southern Alabama and southeastern Mississippi to eastern Louisiana (Diemer 1989). Occurs on islands off the Gulf coast of Florida as far south as Cape Sable (Logan 1981, Kushlan and Mazzotti 1984, Mushinsky and McCoy 1994). Most common in southern Georgia and northern and central Florida (Diemer 1989). At the northern end of the range in South Carolina, four disjunct populations remain in Jasper County and a few tortoises occur in southern Hampton County (Wright 1982); recently found in Aiken County (Clark et al. 2001). In Georgia, large populations occur in the western Fall Line Sand Hills and the central Tifton Uplands (Landers and Garner 1981); severely fragmented populations occur in the Coastal Plain. The largest remaining population in Mississippi is in Desoto National Forest (Lohoefener and Lohmeier 1984). A few populations remain at the western edge of the range in eastern Louisiana. For a detailed range map, see Iverson (1992).

Number of Occurrences: 81 to >300
Number of Occurrences Comments: Several hundred EOs of varying quality in Florida and southern Georgia; nearly extirpated in South Carolina and Louisiana; relatively rare in Mississippi and Alabama.

Population Size: 10,000 to >1,000,000 individuals
Population Size Comments: Large numbers still exist, but see trend comments.

Overall Threat Impact Comments: Urban development and agricultural conversion (including commercial forestry) are the primary threats; also mining in some areas. Though illegal, hunting for human consumption still exists. Road kills are a minor problem.

Area reduction (habitat loss and fragmentation) and habitat degradation are two of the greatest threats. As either increases, the probability of local extirpation also increases. In combination, the effects of area reduction and habitat degradation likely increase the probability of extirpation in a synergistic fashion. Any development that fragments a population and/or creates a barrier to the natural movement of gopher tortoises likely will negatively impact that population.

Negative impacts also include predation on eggs and young by raccoons (e.g., Butler and Sowell 1996) and other predators and predation by humans. Intensive and/or sustained harvest by humans has seriously impacted some local populations (Diemer 1989). Fortunately, because of prohibition or regulation of harvest throughout most of the range, collecting for food has declined.

Exposure to and/or active signs of Upper Respiratory Tract Disease (URTD) have been recorded in Florida and Mississippi; the significance of this is not yet known, but the situation warrants monitoring (Smith et al. 1998). Diemer Berish et al. (2000) documented the presence of URTD in several locations in Florida. Seigel et al. (2003) reviewed available data on the disease and recent tortoise mortality and concluded that URTD may have a substantial negative impact on tortoise populations. Thomas and Blankenship (2002) sampled a Mississippi population and found no evidence of URTD.

In Florida, major causes of the decline include increased urbanization, incompatible silvicultural practices (chiefly conversion to densely planted sand pine or slash pine; the dense canopy of closely packed pine trees shades the understory, preventing the growth of grasses and herbaceous plants that provide food for gopher tortoises; Landers and Buckner 1981), phosphate mining, unmanaged habitats, and citrus production. Widespread development and destruction of upland habitats have fragmented large tortoise populations and pushed individuals into unsuitable habitats and onto highways (Diemer 1989). In the Florida panhandle, human predation on tortoises has drastically reduced populations (Auffenberg and Franz 1982, Taylor 1982, Diemer 1986); this was most severe during the Depression (Hutt 1967). Poor habitat management also is a serious threat. As the habitat becomes increasingly overgrown, large sexually mature adults leave the population in search of better forage with the result of a decrease in the recruitment of young into the population.

In Georgia, large populations of tortoises have been fragmented by extensive agricultural and urban development, the construction of dams (inundating upland habitat), and sand extraction (Landers and Garner 1981, Diemer 1989). Many populations in Georgia have been depleted because of overharvesting (Landers and Garner 1981, Auffenberg and Franz 1982). Large-scale rattlesnake roundups are a threat to many tortoise populations throughout the Georgia Coastal Plain.

In Mississippi, habitat loss to crops and pasturage is the primary reason for the decline; most remaining populations are on protected lands (Lohoefener and Lohmeier 1984). Alabama populations are reported to be recovering from past exploitation, but these populations are threatened by habitat degradation as a result of fire exclusion (Lohoefener and Lohmeier 1984). The few tortoise populations in South Carolina are threatened by human predation and slash pine monocultures (Auffenberg and Franz 1982). In Louisiana, most of the tortoise habitat has been converted into pine plantations (Lohoefener and Lohmeier 1984, Auffenberg and Franz 1982).

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: Formerly common in upland ecosystems throughout the southeastern United States; now threatened with extirpation in many areas and in serious decline in others. There has been an approximately 80% decline in the number of gopher tortoises in the last 100 years (Auffenberg and Franz 1982). Decline is predicted to continue to at least the year 2000.

Other NatureServe Conservation Status Information

Inventory Needs: Determine current distribution and status of occurrences in all states. Inventory for highest quality (largest, most natural) occurrences in Florida and Georgia. Inventory lands adjacent to all managed areas region-wide.

Protection Needs: Secure permanent legal protection (e.g., by acquisition or easement) for as much private land as possible within the habitable range of this species.

Management: Many of the pine-dominated upland habitats utilized by this species require periodic fire to retard succession to more hardwood-dominated forests. Enforce state prohibitions on hunting and collecting.

Distribution
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Global Range: Southeastern United States from southern South Carolina (Clark et al. 2001) through southern Georgia to southern Florida (excluding most of inland southern Florida), west through southern Alabama and southeastern Mississippi to eastern Louisiana (Diemer 1989). Occurs on islands off the Gulf coast of Florida as far south as Cape Sable (Logan 1981, Kushlan and Mazzotti 1984, Mushinsky and McCoy 1994). Most common in southern Georgia and northern and central Florida (Diemer 1989). At the northern end of the range in South Carolina, four disjunct populations remain in Jasper County and a few tortoises occur in southern Hampton County (Wright 1982); recently found in Aiken County (Clark et al. 2001). In Georgia, large populations occur in the western Fall Line Sand Hills and the central Tifton Uplands (Landers and Garner 1981); severely fragmented populations occur in the Coastal Plain. The largest remaining population in Mississippi is in Desoto National Forest (Lohoefener and Lohmeier 1984). A few populations remain at the western edge of the range in eastern Louisiana. For a detailed range map, see Iverson (1992).

U.S. States and Canadian Provinces
Color legend for Distribution Map
Endemism: endemic to a single nation

U.S. & Canada State/Province Distribution
United States AL, FL, GA, LA, MS, SC

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. For information on how to obtain shapefiles of species ranges see our Species Mapping pages at www.natureserve.org/conservation-tools/data-maps-tools.

Range Map Compilers: NatureServe 2008


U.S. Distribution by County Help
State County Name (FIPS Code)
AL Baldwin (01003), Bullock (01011), Clarke (01025), Coffee (01031), Conecuh (01035), Covington (01039), Crenshaw (01041), Dale (01045), Escambia (01053), Geneva (01061), Henry (01067), Houston (01069), Lowndes (01085), Mobile (01097), Montgomery (01101), Pike (01109), Russell (01113), Washington (01129)
FL Alachua (12001), Baker (12003), Bay (12005), Bradford (12007), Brevard (12009), Broward (12011), Calhoun (12013), Charlotte (12015), Citrus (12017), Clay (12019), Collier (12021), Columbia (12023), DeSoto (12027), Dixie (12029), Duval (12031), Escambia (12033), Flagler (12035), Franklin (12037), Gadsden (12039), Gilchrist (12041), Glades (12043), Gulf (12045), Hamilton (12047), Hardee (12049), Hendry (12051), Hernando (12053), Highlands (12055), Hillsborough (12057), Holmes (12059), Indian River (12061), Jackson (12063), Jefferson (12065), Lafayette (12067), Lake (12069), Lee (12071), Leon (12073), Levy (12075), Liberty (12077), Madison (12079), Manatee (12081), Marion (12083), Martin (12085), Miami-Dade (12086), Monroe (12087), Nassau (12089), Okaloosa (12091), Okeechobee (12093), Orange (12095), Osceola (12097), Palm Beach (12099), Pasco (12101), Pinellas (12103), Polk (12105), Putnam (12107), Santa Rosa (12113), Sarasota (12115), Seminole (12117), St. Johns (12109), St. Lucie (12111), Sumter (12119), Suwannee (12121), Taylor (12123), Union (12125), Volusia (12127), Wakulla (12129), Walton (12131), Washington (12133)
GA Appling (13001), Atkinson (13003), Baker (13007), Ben Hill (13017), Berrien (13019), Bibb (13021), Brantley (13025), Brooks (13027), Bryan (13029), Bulloch (13031), Burke (13033), Calhoun (13037), Camden (13039), Candler (13043), Charlton (13049), Chatham (13051)*, Chattahoochee (13053), Clay (13061), Coffee (13069), Colquitt (13071), Cook (13075), Crisp (13081), Decatur (13087), Dodge (13091), Dooly (13093), Dougherty (13095), Early (13099), Echols (13101), Effingham (13103), Emanuel (13107), Evans (13109), Glascock (13125), Glynn (13127), Grady (13131), Irwin (13155), Jeff Davis (13161), Jefferson (13163), Lanier (13173), Laurens (13175), Lee (13177), Liberty (13179), Long (13183), Lowndes (13185), Marion (13197), Mcduffie (13189), Mcintosh (13191), Miller (13201), Mitchell (13205), Montgomery (13209), Muscogee (13215), Peach (13225), Pierce (13229), Richmond (13245), Screven (13251)*, Seminole (13253), Stewart (13259), Sumter (13261), Talbot (13263), Tattnall (13267), Taylor (13269), Telfair (13271), Terrell (13273), Thomas (13275), Tift (13277), Toombs (13279), Ware (13299), Washington (13303), Wayne (13305), Webster (13307), Wheeler (13309), Wilcox (13315)*, Worth (13321)
LA St. Tammany (22103), Tangipahoa (22105), Washington (22117)
MS Clarke (28023), Covington (28031), Forrest (28035), George (28039), Greene (28041), Hancock (28045), Harrison (28047), Jackson (28059), Jasper (28061), Jefferson Davis (28065), Jones (28067), Lamar (28073), Lauderdale (28075), Marion (28091), Pearl River (28109), Perry (28111), Stone (28131), Walthall (28147), Wayne (28153)
SC Aiken (45003), Allendale (45005), Colleton (45029), Dorchester (45035), Hampton (45049), Jasper (45053)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
03 South Fork Edisto (03050204)+, Edisto (03050205)+, Salkehatchie (03050207)+, Broad-St. Helena (03050208)+, Middle Savannah (03060106)+, Brier (03060108)+, Lower Savannah (03060109)+, Upper Ogeechee (03060201)+, Lower Ogeechee (03060202)+, Canoochee (03060203)+, Ogeechee Coastal (03060204)+, Lower Oconee (03070102)+, Upper Ocmulgee (03070103)+, Lower Ocmulgee (03070104)+, Little Ocmulgee (03070105)+, Altamaha (03070106)+, Ohoopee (03070107)+, Satilla (03070201)+, Little Satilla (03070202)+, Cumberland-St. Simons (03070203)+, St. Marys (03070204)+, Nassau (03070205)+, Upper St. Johns (03080101)+, Oklawaha (03080102)+, Lower St. Johns (03080103)+, Daytona - St. Augustine (03080201)+, Cape Canaveral (03080202)+, Vero Beach (03080203)+, Kissimmee (03090101)+, Northern Okeechobee Inflow (03090102)+, Western Okeechobee Inflow (03090103)+, Everglades (03090202)+, Big Cypress Swamp (03090204)+, Caloosahatchee (03090205)+, Florida Southeast Coast (03090206)+, Peace (03100101)+, Myakka (03100102)+, Charlotte Harbor (03100103)+, Sarasota Bay (03100201)+, Manatee (03100202)+, Little Manatee (03100203)+, Alafia (03100204)+, Hillsborough (03100205)+, Tampa Bay (03100206)+, Crystal-Pithlachascotee (03100207)+, Withlacoochee (03100208)+, Waccasassa (03110101)+, Econfina-Steinhatchee (03110102)+, Aucilla (03110103)+, Upper Suwannee (03110201)+, Alapaha (03110202)+, withlacoochee (03110203)+, Little (03110204)+, Lower Suwannee (03110205)+, Santa Fe (03110206)+, Apalachee Bay-St. Marks (03120001)+, Upper Ochlockonee (03120002)+, Lower Ochlockonee (03120003)+, Middle Chattahoochee-Walter F. George Reservoir (03130003)+, Lower Chattahoochee (03130004)+, Upper Flint (03130005)+, Middle Flint (03130006)+, Kinchafoonee-Muckalee (03130007)+, Lower Flint (03130008)+, Ichawaynochaway (03130009)+, Spring (03130010)+, Apalachicola (03130011)+, Chipola (03130012)+, New (03130013)+, Apalachicola Bay (03130014)+, St. Andrew-St. Joseph Bays (03140101)+, Choctawhatchee Bay (03140102)+, Yellow (03140103)+, Blackwater (03140104)+, Pensacola Bay (03140105)+, Perdido (03140106)+, Perdido Bay (03140107)+, Upper Choctawhatchee (03140201)+, Pea (03140202)+, Lower Choctawhatchee (03140203)+, Upper Conecuh (03140301)+, Patsaliga (03140302)+, Sepulga (03140303)+, Lower Conecuh (03140304)+*, Escambia (03140305)+, Lower Alabama (03150204)+, Lower Tambigbee (03160203)+, Mobile - Tensaw (03160204)+, Mobile Bay (03160205)+, Chunky-Okatibbee (03170001)+, Upper Chickasawhay (03170002)+, Lower Chickasawhay (03170003)+, Upper Leaf (03170004)+, Lower Leaf (03170005)+, Pascagoula (03170006)+, Black (03170007)+, Escatawpa (03170008)+, Mississippi Coastal (03170009)+, Middle Pearl-Silver (03180003)+, Lower Pearl. Mississippi (03180004)+, Bogue Chitto (03180005)+
08 Tangipahoa (08070205)+, Liberty Bayou-Tchefuncta (08090201)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: Gopher tortoise, Testudinidae.
General Description: The gopher tortoise is a relatively large (carapace length often 15-28 cm, but up to 38 cm) terrestrial turtle with a domed carapace, short elephantine hindlimbs, shovellike forelimbs, a gular projection from the anterior plastron, and a short tail. The anterior surface of the flattened forelimb is covered with 7-8 rows of large scales. Often the surface of the carapace is quite smooth in adults, reflecting the abrasion it receives as an individual enters or exits its burrow. The carapace is keelless and oblong, with the greatest width just anterior to the well-developed bridge (connecting the carapace to the plastron), and the greatest height in the sacral region. The carapace drops off abruptly to the rear of the highest region (Ernst and Barbour 1972). The carapace of an adult varies from dark- brown to grayish-black. In Florida, individuals from coastal areas are generally darker than those from central populations. The gular scutes of the robust, hingeless plastron project below the chin. Males often have longer gular projections than do females. However, because both sexes use their projections during agonistic encounters, the gular projections are often broken and may not be an accurate diagnostic feature of the sex of an individual (Mushinsky et al. 1994). Most gopher tortoises have well defined "growth rings" on the scutes of the yellowish plastron. Use of the growth rings to age individuals must be done with caution, as there is much variation in the number of "false" growth rings throughout the range of this taxon.

Female gopher tortoises become sexually mature at a carapace length of about 23-24 cm. Males are somewhat smaller at maturity and do not obtain the large body size of females. The best indicator of the sex of an adult gopher tortoise is the depth of the plastral concavity (Mushinsky et al. 1994). Mature males have a shallow depression in the posterior, central portion of the plastron to facilitate mounting a female for copulation. Large females may have a shallow plastral concavity (2-4 mm) compared to the deeper concavity found on mature males (5-8 mm). Males often have larger integumentary glands under the chin than do females (Ernst and Barbour 1989), but the size of these integumentary glands varies seasonally. Based upon numerous anatomical measurements, McRae et al. (1981a) developed a discriminant function that accurately identified the sex of adult individuals. Using a stepwise multiple regression on numerous morphological measurements, Burke et al. (1994) developed a non-invasive sex identification technique for determining the sex of hatchling and juvenile gopher tortoises.

Hatchlings emerge from their eggs at a carapace length of generally about 3-5 cm. Coloration of the vertebral and costal scutes of the carapace of hatchlings is yellowish to yellowish-orange, and each scute is bordered by brownish coloration (Allen and Neill 1953). The skin on the head and limbs is likewise brightly colored yellow to yellowish-orange. The bright coloration of hatchlings darkens during the first year or two of life. The gular scutes of young tortoises do not project forward as in the adult tortoises, and the claws of young tortoises are long and sharp (Allen and Neill 1953). Hatchlings dig their own burrows, often just a few meters away from the nest from which they emerged. Hatchlings and juveniles, up to an age of 5-7 years, have relatively soft shells and are highly vulnerable to predation (Wilson 1991).

Eggs are white, nearly spherical, and brittle-shelled. For photographs of eggs see Allen and Neil (1951) and Pope (1939). Iverson (1980) reported an average maximum egg diameter of 42-43 mm and an average wet mass of 40.9 g (also see Arata 1958, Landers et al. 1980).

Diagnostic Characteristics: This is the only terrestrial tortoise east of the Mississippi River. The only other terrestrial turtle within the geographic range of the gopher tortoise is the eastern box turtle. Box turtles are smaller than gopher tortoises, have a high domed carapace, and a hinged plastron. Box turtles can close their shells completely so that neither the head nor any appendage is visible when retracted completely. Gopher tortoises cannot withdraw completely into their shells. A startled gopher tortoise will withdraw its limbs into the shell, but the limbs are visible when retracted.

Gopher tortoise differs from the desert, Texas, and bolson tortoises (none of which occur in the range of the gopher tortoise) in having relatively smaller hind feet. In the desert, Texas, and bolson tortoises, the distance from the base of the first claw to the base of the fourth claw on the forefoot is approximately equal to the same measurement on the hind foot; in the gopher tortoise, the measurement is smaller on the hind foot (Ernst and Barbour 1989).

Reproduction Comments: Male tortoises seek females for mating from May to July. There is some evidence that dominant males breed with several females (Douglass 1990). When seeking a female, a male moves to the mouth of a burrow occupied by a female and displays a head bobbing behavior (Auffenberg 1966, Wright 1982). If the female exits her burrow the courting male walks in a circle around the female, periodically stopping and performing the head bobbing behavior. When the female approaches the courting male, he bobs his head violently, and bites her on the forelegs, head, anterior edge of the carapace, and gular projection. The female then backs in a semicircle, stops, and extends her hindlimbs. Thereafter, she rotates her body about 180 degrees, so that her posterior end is near the male's head. The courting male then attempts to mount the female; if unsuccessful, he repeats the courting behavior (Auffenberg 1966, Ernst and Barbour 1972).

Nesting occurs from late April to mid-July (mainly mid-May to mid-June) (Iverson 1980, Landers et al. 1980, Wright 1982, Epperson and Heise 2003)). Clutch size usually is 5-9, averages 3.8 in South Carolina, 5-6 in Florida (e.g., Butler and Hull 1996), 7 in Georgia (see Diemer and Moore 1994), 4.8 in Mississippi (Epperson and Heise 2003). A large female from central Florida produced an unusually large clutch of 25 eggs (Godley 1989). Clutch size increases with increasing female size (Landers et al. 1980, Diemer and Moore 1994). Adult females produce one clutch/year (but some adults do not nest every year). The ovarian cycle was described by Iverson (1980) and Palmer and Guillette (1988). Incubation lasts about 110 days in South Carolina, 80-90 days in northern Florida (Iverson 1980, Landers et al. 1980), mean of 105 days in northeastern Florida (Butler and Hull 1996), mean of 88 dyas in Mississippi (Epperson and Heise 2003). Hatching occurs from August through September. In northeastern Florida, hatchlings emerged from the nest from late August through early October (Butler and Hull 1996). At hatching, and about 24-48 hours prior to emergence, hatchlings exhibit a large external yolk sac (Linley and Mushinsky 1994). The external yolk sac is absorbed as the hatchlings remain in the nest cavity prior to emergence. Just after emergence a deep transverse groove across the plastron is visible; it disappears two to three days after emergence as the anterior- posterior axis of the body becomes straight and the plastron flattens (Ernst and Barbour 1972). This species exhibits temperature-dependent sex determination (Burke et al. 1996, Chelonian Conservation and Biology 2:86-88).

In Georgia, Landers and coworkers (1982) found that pronounced growth occurred through the age of 11 years, after which growth rate gradually decreased. In central Florida, Mushinsky and coworkers (1994) reported an average increase of 18.9 mm/year for ages 1-11, after which time growth slowed to approximately 3%/year until age 20.

Females become sexually mature at a carapace length of 23-24 cm. Body size, rather than age, seems to determine sexual maturity in gopher tortoises. In southern Georgia, it may take from 19-21 years for females to become sexually mature (Landers et al. 1982), while in central Florida females may mature in 9-11 years (Mushinsky et al. 1994). In part, this variation reflects the long activity season available to tortoises in central Florida. In addition to geographic location, however, local conditions also influence the number of years required to achieve sexual maturity. For example, one study of gopher tortoises in central Florida (Godley 1989) found that females attain sexual maturity in 14-16 years, while another study in the same county found that females attain sexual maturity in 9-11 years (Mushinsky et al. 1994). The study area occupied by the faster maturing females was a frequently burned sandhill habitat, whereas the other study area was a mosaic of habitats including pine flatwoods and mixed mesic forests. Males likely mature at a smaller size than females. In north Florida, Diemer and Moore (1994) reported males that were apparently mature at a carapace length of about 18 cm. Potential longevity is several decades.

The level of predation on eggs and young is high. For example, over a two- year period in South Carolina, 17 of 24 (74%) nests were destroyed (Wright 1982). In Georgia, an average female is estimated to produce a successful clutch of eggs (eggs are not destroyed prior to hatching) once a decade (Landers et al. 1980), because about 90% of their nests are destroyed annually. Common predators of eggs are armadillos (DASYPUS NOVEMCINCTUS), raccoons (PROCYON LOTOR), grey foxes (UROCYON CINEREOARGENTEUS), striped skunks (MEPHITIS MEPHITIS), and opossums (DIDELPHIS VIRGINIANUS) (Hallinan 1923, Ernst and Barbour 1972, Douglass and Winegarner 1977, Landers et al. 1980). Hatchling gopher tortoises (individuals in their first year of life) also are subjected to high levels of predation. From egg laying to one year of age, gopher tortoises in northern Florida were estimated to have a mortality rate of 94.2% (Alford 1980). Results from another study in central Florida, which also combined mortality of eggs and hatchlings, suggested an annual mortality rate of 92.3% (Witz et al. 1992). Estimated rates of survivorship of juvenile gopher tortoises (age 1 to 4 years) have been reported from one location in central Florida (Wilson 1991). Wilson (1991) found that predation of juvenile tortoises was higher in October-November and April-May than any other two month interval of the year. Juvenile tortoises are known to bask at the mouths of their burrows more often in the spring and fall of the year than during the summer or winter months (Wilson et al. 1994). It appears that a juvenile tortoise, when positioned at the mouth of the burrow to thermoregulate during the cool months of the year may be quite vulnerable to predation by avian and mammalian predators (Wilson 1991, see also Fitzpatrick and Woolfenden 1978).

Ecology Comments: BURROWING AND BURROW ECOLOGY: Gopher tortoises excavate deep burrows that provide shelter from climatic extremes and refuge from predation. Adult burrows average approximately 4.5 m in length and about 2 m deep (Diemer 1989; see Guyer and Hermann 1997 for information on burrow size and longevity at sites in Georgia and Alabama). Burrows have been found to be significantly shorter in clayey soils than sandy soils which may be a result of respiratory limitations (Ultsch and Anderson 1986); oxygen decrements and carbon dioxide increments were greatest in clayey soils and were positively correlated with burrow length. The high humidity associated with the burrow may offer the tortoise protection from desiccation (Auffenberg and Weaver 1969, Means 1982). At the mouth of each burrow is a mound of subsoil excavated by the burrow resident. Kaczor and Hartnett (1990) found that these soil mounds undergo microsuccession and contribute toward increased plant species diversity in the surrounding habitat.

In northern Florida, Diemer (1992c) found that, on average, adult male tortoises use 5.5 burrows and adult female tortoises use 2.7 burrows per activity season (April-December). In Georgia, tortoises were reported to use 7 and 4 burrows for males and females, respectively (McRae et al. 1981b). Average number of burrows used annually by juvenile tortoises was 1.1 by 0-1- year-olds, 2.2 by 2-year-olds, and 1.7 by 4-5-year-olds in a southern Georgia population (McRae et al. 1981b) and 4.4 by 1-4-year-olds in a central Florida population (Wilson et al. 1994). At the Kennedy Space Center in Florida, Smith et al. (1997) documented the use of individual burrows by several tortoises at different times and occupation of individual burrows by two tortoises at the same time. Suggested reasons for differences in burrow use between populations include differences in ground cover, soil composition, temperature extremes at different latitudes, and number of disturbances to burrows.

Although juvenile tortoises use several burrows they spend most of their time in a primary burrow. Annual use of the primary burrow for juvenile tortoises in a central Florida population was 75% of the use of all burrows (Wilson et al. 1994). The data for estimated use of the primary burrow for adult gopher tortoises are not available. Hatchlings dig burrows (Epperson and Heise 2003) and, in their first year, use multiple burrows (Butler et al. 1995). Several studies have noted that gopher tortoises sometimes use shallow depressions, possibly as resting sites when traveling far from their burrows (Fucigna and Nickerson 1989, Godley 1989, Stout et al. 1989, Diemer 1992c), and windrows, possibly for protection from cattle and machinery (Diemer 1992c). On pine plantations in Alabama, most burrows of juveniles were associated with stumps, fallen logs or tree limbs, or shrub stems, which could interfere with excavation attempts by predators (Aresco 1999). Ashton and Ashton (2001) documented the use of apparently abandoned burrows by juveniles in Citrus County, Florida.

In Northern Florida, Diemer (1992b) studied tortoise populations for several years. She found that the number of burrows showing signs of recent activity increased in April, peaked in July, and remained high through October. The burrow surveys showed a continuous cycle of burrow creation and abandonment. The ratio of captured tortoises to burrows (active and inactive) varied among sites and years; the ratio of burrows to tortoises ranged from 0.45-0.69. Percentages of adult individuals in the three populations studied ranged from 40-62%.

Gopher tortoises desiccate more rapidly when deprived of a burrow than any other member of the genus GOPHERUS (Auffenberg and Weaver 1969). They may withstand relatively high body temperatures (Bogert and Cowles 1947) but froth at the mouth and breathe rapidly when heat stressed. Critical thermal maximum is reported as 43.9 C (Hutchinson et al. 1966).

Many vertebrate and invertebrate species have been recorded from gopher tortoise burrows (Young and Goff 1939, Brode 1959, Hansen 1963, Franz 1986, Jackson and Milstrey 1989, Lips 1991, Witz et al. 1991), including protected species such as the eastern indigo snake (DRYMARCHON CORAIS COUPERI) and the gopher frog (RANA CAPITO) (Auffenberg 1969, 1978; Diemer 1986). Some burrow associates prefer active burrows over inactive or abandoned ones (Lips 1991); these can be distinguished by characteristics of the burrow entrance (Auffenberg and Franz 1982, Cox et al. 1987). Eisenberg (1983) found that 73.7% of gopher frogs censused were found in active tortoise burrows. Witz and coworkers (1991) excavated 1019 burrows and found that of the vertebrate symbionts captured only lizards were found significantly more often in active burrows than in either inactive or abandoned burrows. Fecal material and other organic debris in the enlarged area at the bottom of the burrow serves as an important food source for some burrow associates (Milstrey 1986).

POPULATION ECOLOGY:

Often occurs in more or less isolated colonies of up to about 57 individuals; population density within a colony was estimated at 3-27/ha in Florida (Auffenberg and Franz 1982). Folk (1993) estimated density at about 1-2/ha, 3-5/ha, and 16-25/ha on 3 TNC preserves in Florida. At the Kennedy Space Center, Florida, fall densities ranged from a mean of 2.7/ha in disturbed habitat to 0.0/ha in saw palmetto habitat; spring densities ranged from a mean of 2.5/ha in saw palmetto habitat to 0.7/ha in oak-palmetto habitat (Breininger et al. 1994).

A comprehensive study of about 50 populations of gopher tortoises in Florida (McCoy and Mushinsky 1988) found several trends. Gopher tortoise populations residing on sites that had experienced severe area reduction (greater than 25% reduction over the past 20 years), or occurred on sites with greater than 50% tree canopy, or occurred on sites of small size (< 2 ha), tended to have truncated demographic profiles. A truncated profile suggests little recruitment of individuals into the population and abandonment of the site by larger, mature individuals. In contrast, tortoise populations on sites with no or limited area reduction, or sites with less than 50% tree canopy, or relatively large sites (> 2 ha) tended to have a high proportion of large, mature individuals and evidence of recruitment of young into the population (McCoy and Mushinsky 1988).

Comparisons of tortoise populations on true islands with populations on the mainland suggested that tortoises do respond to relatively small, isolated habitats (Mushinsky and McCoy 1994). Both island and mainland tortoise populations show a positive relationship between the number of active and inactive burrows and the area of habitat. Density of burrows, however, decreased as area increased on the mainland, but density of burrows was not related to area on the islands. Also, on the mainland, the ratio of inactive to active burrows (a measure of the tendency of individuals to construct new burrows) increased with area of habitat, and burrow density increased with increasing herbaceous vegetation, but neither of these relations could be demonstrated on islands. Collectively, these findings suggest that tortoises have a greater selection of habitats on the mainland than on islands. Tortoises on islands are confined and may be forced to live in less than ideal conditions. The implications of these findings are profound for tortoises living in small, fragmented "habitat islands" on the mainland. In time, perhaps a few decades, as the quality of their habitat island is degraded, mature adults may be forced to abandon a site in search of better habitat quality. Such individuals, which may be forced to abandon isolated patches of habitat in areas surrounded by human dwellings seem doomed to perish. From a practical perspective, prior to this study (Mushinsky and McCoy 1994), observation of large numbers of active and inactive gopher tortoise burrows in a confined area likely would have been viewed as indicators of a "healthy" population; however, these findings suggest just the opposite. Rather than a signal of a healthy population, large numbers of active and inactive gopher tortoise burrows, relative to the actual number of tortoises, may signal a stressed population (see also Stewart et al. 1993).

Habitat Type: Terrestrial
Non-Migrant: Y
Locally Migrant: N
Long Distance Migrant: N
Mobility and Migration Comments: Individuals generally maintain a well-defined home (activity) range. A large one may encompass up to 6+ hectares over several years (Douglass 1990). Available information indicates that home range size generally is less than 5.3 hectares and averages less than 1.9 hectares, with the largest sizes in adult males and the smallest in juveniles (Auffenberg and Iverson 1979McRae et al. 1981b, Doonan 1986, Diemer 1992c, Wilson et al. 1994, Smith et al. 1997, Eubanks et al. 2003, Riedl 2006, Beauman 2008). Reported movements between and from burrows generally average less than 80 meters and often much less than that (mean of 20 meters or less) (McCrae et al. 1981b, Diemer 1992c, Wilson et al. 1994, Mushinsky et al. 2003). However, in southwestern Georgia, Beauman (2008) recorded multiple movements of around 200-400 meters between successive locations.

Movements of hatchlings tend to be limited but sometimes can be extensive. In east-central Florida, home range size (minimum convex polygon) of hatchlings averaged 1.95 hectares and two hatchlings had home ranges of 4.8 hectares (Pike 2006). Hatchlings moved farther from the nest over time; by the spring following hatching, hatchlings were an average of around 70-80 meters from the nest (Pike 2006). In Mississippi, 7 hatchlings surviving 41-736 days dispersed 17.5 to 458 m (mean about 130-160 m) from their nest (Epperson and Heise 2003). In northern Florida, mean home range of hatchlings during the active period was 363 sq m; mean annual range of nine individuals surviving a year was 2,032 sq m, and their mean total range after about two years was 2,554 +/- 1382 sq m (Butler et al. 1995).

Tortoises sometimes make long distance movements. Using radio-telemetry, Diemer (1992c) found that of her radio-tagged animals the longest movement made was 0.74 km by an emigrating subadult. Juveniles also may make long distance movements, usually following some type of disturbance to the resident burrow (Diemer 1992c, Wilson et al. 1994). Two adult males in Georgia dispersed 1.2 km and 1.5 km (straight-line distance to final known location) (Eubanks et al 2003). An adult female resided in two adjacent burrows for 11 months, then moved 2.1 km to a new location, where it resided for at least 9 months (Ashton, unpublished, in Mushinsky et al. 2006).

Size of home range has been shown to decrease with an increase in the amount of herbaceous ground cover (Auffenberg and Iverson 1979, Mushinsky and Gibson 1991). Management of habitat by controlled burning increases the amount of herbaceous ground cover, such that tortoises do not have to travel far from their burrows to find ample food. Thus, home ranges for this species may vary among populations depending on the quality of the habitat (Diemer 1992c, Mushinsky and McCoy 1994).

Terrestrial Habitat(s): Grassland/herbaceous, Old field, Savanna, Woodland - Conifer, Woodland - Hardwood, Woodland - Mixed
Special Habitat Factors: Burrowing in or using soil
Habitat Comments: Commonly occupies habitats with a well-drained sandy substrate, ample herbaceous vegetation for food, and sunlit areas for nesting (Hallinan 1923, Landers 1980, Landers et al. 1980, Diemer 1989). These habitat types include sandhill (pine-turkey oak), sand pine scrub, xeric hammock, pine flatwoods, dry prairie, coastal grasslands and dunes, and mixed hardwood-pine communities (Landers and Speake 1980, Auffenberg and Franz 1982, Kushlan and Mazzotti 1984, Diemer 1986, 1992a). Prefers open habitats that support a wide variety of herbaceous ground cover vegetation for forage; usually abandons densely canopied areas and frequently can be found in disturbed habitats such as roadsides, fence-rows, old fields, and the edges of overgrown (unburned) uplands (see Diemer 1989, Stewart et al. 1993, Breininger et al. 1994). Upland habitats with extensive canopies reduce the amount of direct sunlight on the ground which may hamper tortoises from reaching minimum thermal requirements for normal daily activities. Also, excessive shade decreases herbaceous vegetation essential for growth, development, and reproduction (Mushinsky and McCoy 1994).

Temporarily abandons marginal habitats during periods of drought; increasing habitat isolation eventually may result in marginal habitats being completely abandoned (Matthews and Moseley 1990). In Georgia, adults congregated on droughty sites in early spring, and many moved to more mesic soils for autumn-winter (McRae et al. 1981).

Densities of gopher tortoises are known to be relatively high in sandhill communities, however, high densities may not be indicative of a healthy population (Mushinsky and McCoy 1994). Mushinsky and McCoy (1994) reported that high densities of some tortoise populations may be the result of tortoises confined to a true or "habitat" island. Tortoises in this situation are unable to move freely to new locations as the quality of the habitat degenerates. More research is needed on the demography of tortoises in confined areas.

Gopher tortoises are highly fossorial and construct extensive burrow systems. They spend much of the time underground. See ecology section for further information on burrows.

Eggs are deposited in a typical flask-shaped nest cavity excavated by the hindlimbs of the female to a depth of about 10-15 cm. Nests may be located in any open sunny area near the burrow of the female, but most often, nests are placed in the spoil mound immediately outside the female's burrow (e.g., Hallinan 1923, Allen and Neil 1951, Arata 1958, Mount 1975, Landers et al. 1980, Butler and Hull 1996).

Adult Food Habits: Herbivore
Immature Food Habits: Herbivore
Food Comments: Gopher tortoises feed primarily on grasses and other herbaceous plants (Carr 1952, Garner and Landers 1981). Sometimes eats insects, carrion, and fruits.

Macdonald and Mushinsky (1988) identified 26 families of plants from 68 genera in scat analyses and foraging observations of gopher tortoises. The most common families of plants ingested were the Poaceae, Asteraceae, Fabaceae, Pinaceae and Fagaceae. The most common genus of plants ingested was Aristida (see also Wright 1982). Insects were found in 75% of scats and charcoal in 67% suggesting intentional ingestion of these items. Compared to adults, young tortoises tend to ingest fewer plants of the family Poaceae and plants with external defense mechanisms and more forbs such as legumes; they may negatively select Aristida even if it is abundant (Garner and Landers 1981, Macdonald and Mushinsky 1988, Mushinsky et al. 2003).

Macdonald and Mushinsky (1988) concluded that gopher tortoises tend to fall somewhere between a generalist and a specialist forager and prefer some plants over others with respect to their availability in the habitat. Rocks may be intentionally ingested as a source of minerals. During a study on the reproduction of adult female gopher tortoises in central Florida, radiography revealed that a large proportion of the females contained rocks in their digestive tracts (Mushinsky and Wilson, unpublished data). Digestive efficiencies of the gopher tortoise have been studied by Bjorndal (1987). Feeding occurs usually within 50 m of the burrow (Diemer 1992).

Adult Phenology: Diurnal
Immature Phenology: Diurnal
Phenology Comments: Spends a limited amount of time above ground outside of the burrow. With a device that automatically recorded activity, Auffenberg and Iverson (1979) calculated that an adult tortoise was active 9.2% of its time. Juveniles have been reported to spend 90% of their time underground inside their burrows (Wilson et al. 1994).

Active all year except during cold spells (Ernst and Barbour 1972). Activity away from the burrow tends to peak in the late spring and summer. In northern Florida, the number of burrows showing active sign increased in April, peaked in July, and remained high through October (Diemer 1992). In southern Florida, activity peaked May-August (Douglass and Layne 1978). In southwestern Georgia, activity was severely restricted in winter (McRae et al. 1981). For juveniles, Wilson and coworkers (1994) found that 80% of observed activity in fall, winter and spring consisted of basking on the burrow mound; juveniles moved away from their burrows significantly more during the summer months. During the winter months, tortoises have been observed basking at the mouths of their burrows on warm days throughout their range (Douglas and Layne 1978, McRae et al. 1981b, Wilson et al. 1994). Thus, the activities of gopher tortoises away from their burrows are limited in the winter months and increase as seasonal temperatures increase.

Daily activity has been reported as unimodal in the spring and bimodal in the summer in a Georgia population (McRae et al. 1981b). These investigators suggested that adult tortoises may be active in the late morning and late afternoon in summer to avoid the hottest part of the day. In contrast, Douglass and Layne (1978) and Wilson et al. (1994) found that juvenile tortoises were more active in mid-afternoon and did not display a bimodal activity pattern in the summer. Activity patterns of juvenile tortoises may be influenced by the risk of predation and thermoregulatory behavior (see Wilson et al. 1994 and Wilson 1991). No evidence of nocturnal activity has been reported for the gopher tortoise.

Length: 28 centimeters
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: The gopher tortoise, Gopherus polyphemus, is a large, herbivorous terrestrial turtle that is found in six states in the southeastern United States. Gopher tortoises most commonly are found in upland areas that are characterized by a deep, well-drained, sandy substrate suitable for construction of their extensive burrows. The gopher tortoise prefers relatively open-canopied habitats that provide sunlit areas for nesting and thermoregulation, and ample herbaceous ground vegetation for forage. Because the gopher tortoise is seldom found above ground outside of its burrow, it is often necessary to use tortoise burrows as a means of assessing populations. Burrows within a defined area are designated a status or condition based on time since occupancy. The width of a burrow can be measured to estimate the size of the current resident tortoise. With these survey data, population counts and size class distributions can be determined for populations under study.

Historically, gopher tortoises were considered common in upland habitats throughout their range, however, this species now faces numerous threats to its continued survival in many areas. Overharvesting by humans, as well as habitat destruction, degradation, and fragmentation have contributed to the decline of this species. Because the gopher tortoise is long-lived with delayed sexual maturity and a low reproductive potential, it is essential to develop management schemes that offer the tortoise adequate protection. Management schemes must be formulated to address the needs of the specific population under consideration. Along with current conservation measures of habitat protection and restrictions on harvesting by humans, public awareness through comprehensive public education is imperative for the continued persistence of this species.

Species Impacts: Gopher tortoises compact soil and alter vegetation composition near their burrows (Boglioli et al. 2000).
Restoration Potential: At Camp Shelby in Mississippi, low hatching success and high hatchling mortality may limit recruitment and inhibit recovery of the population from previous declines (Epperson and Heise 2003).
Preserve Selection & Design Considerations: Landers and Speake (1980) recognized that gopher tortoises can be maintained on small management units, but they proposed that larger units (up to several hundred hectares) would lessen the impact of emigration and mortality. Similarly, Cox et al. (1987) suggested that areas of 10-25 ha (25- 70 acres) of favorable, managed habitat should be set aside for populations occupying lands slated for development. Perhaps the most extensive study of gopher tortoise populations was that conducted by McCoy and Mushinsky (1988). They surveyed a wide variety of sites for tortoises, including some of the largest federal lands in Florida as well as numerous, relatively-small, largely unprotected populations of tortoises. They recognized the importance of protecting, if possible, large areas (tens to hundreds of hectares) of gopher tortoise habitat, but emphasized the value of the numerous small isolated populations that exist throughout the range of the tortoise. McCoy and Mushinsky (1988) pointed out that gopher tortoises function as "keystone species" (Campbell and Christman 1982, Jackson and Milstrey 1989), and therefore merit special consideration in ranking conservation priorities.

Conservation of large areas of land has the potential side-effect of creating false security about the future of resident tortoises. Continuous management is critical to these populations; but tortoises occupying extant large conservation areas typically have not been so managed (McCoy and Mushinsky 1992b). Development patterns throughout peninsular Florida are such that it is not practical to set aside even 10 ha of land in many places. McCoy and Mushinsky (1988) believed it unwise to place full emphasis upon the single large area notion of conservation. Rather they proposed that greater emphasis be placed upon alternate conservation strategies for the gopher tortoise in Florida. They proposed a two-pronged approach. Whenever feasible, large areas of land should be secured, with the stipulation that rigorous management practices are to be employed to monitor continuously the demographic health of the resident population. In parallel with the securing of large areas, they recognized a need to secure large numbers of small areas. Such small areas allow "banking" of genetic diversity, as well as of individuals, for decades or perhaps longer. Management practices tailored to these small areas might even be able to perpetuate a metapopulation for tens of decades or longer.

Dichotomies created between apparently suitable and less-than-suitable gopher tortoise habitats may be misleading, and cause some small sites to be dismissed too quickly as unworthy of conservation effort. It seems imperative to view tortoise habitat quality as a dynamic gradient. Area reduction and habitat degradation are two of the greatest threats to the future of tortoise populations: as either increases, the probability of extinction also increases. In combination, the effects of area reduction and habitat degradation likely increase the probability in a synergistic fashion. Hence, while tortoises on large areas of land are in need of continuous monitoring, tortoises on small areas are likely in need of continuous management as well. Each state in which the gopher tortoise resides should serve as steward over these small areas of land, to coordinate research efforts designed to address critical questions regarding tortoise management on them, and to serve as a clearing house for all translocations of individuals among them. Research priorities concerning management of small areas should include delineation of the potential consequences of tortoise translocation and derivation of methods of increasing site tenacity.

Management Requirements: Recommendations for specific management procedures for gopher tortoises have been made by Landers and Speak (1980) for Georgia, Wright (1982) for South Carolina, Lohoefener and Lohmeier (1984) for Louisiana, Mississippi, and Alabama, and Auffenberg and Franz (1982) and Diemer (1986, 1994) for Florida. Conservation measures include habitat management, establishment of preserves, protection from overharvest, and public education (Landers 1980, Diemer 1986, Diemer-Berish 1994).

Maintenance of gopher tortoises populations generally requires active habitat management, even on seemingly "protected" lands owned by states or the federal government (McCoy and Mushinsky 1992b). Active management of upland habitats increases food abundance and nest site availability for gopher tortoises (Landers and Speak 1980). Gopher tortoises prefer, and attain their highest densities, in grassy, open-canopied sites (Auffenberg and Franz 1982, Mushinsky and McCoy 1994). Prescribed burning is the preferred method for managing gopher tortoise habitats (Landers 1980, Mushinsky and Gibson 1991).

The details of any habitat management program aimed at maintaining or increasing the number of gopher tortoises present in an area must be site specific. However, the goal should be to produce a mosaic of vegetation density by altering the frequency and timing of controlled burns (Diemer-Berish 1994). Habitat management that reduces excessive canopy cover and promotes a lush herbaceous ground cover (burning or stand thinning) is desirable. Optimal conditions include multi-aged forest, ranging from treeless areas with high diversities and abundances of grasses and herbaceous plants to areas with tree canopies that cover about 30-50% of the area. Summer burning mimics the natural fire cycle, promotes flowering of annual herbaceous plants, and facilitates the production of seeds by many of the grasses. Sandhill habitat responds well to summer burns on a 2-7 year periodicity. Pine flatwoods also should be subjected to summer burns on a 2-5 year cycle to encourage the production of the plants used as forage by gopher tortoises. Sand pine scrub habitat should be burned less frequently, perhaps every 15-30 years. A highly overgrown site may be first burned during the winter months to reduce the risk of a very hot fire and to thin the canopy prior to implementing a cycle of summer burns which promote vegetative regrowth. Activities that involve root-raking and windrowing should be avoided.

Because predation on tortoise eggs and hatchlings is great, protection of these stages of their life history has been recommended (Wright 1982). Nests can be protected by predator-proof enclosures, and predators can be removed by hunting or trapping (Landers 1980).

Restocking of all ages of tortoises to sites they formerly occupied has been attempted. Over the years, these relocations have involved thousands of individuals, particularly in Florida. However, the fate of most relocated tortoises is unknown (Diemer 1986). In south Georgia, about 40% of the tortoises introduced into an area remained in that area three years after their introduction (Landers 1981). In north Florida, Diemer (1987b) recaptured about 30% of relocated tortoises five years after their release. These studies suggest that most tortoises quickly abandon sites to which they have been relocated (or that mortality rate is high).

See Burke (1989) and Dodd and Seigel (1991) for a discussion of, and references pertaining to, tortoise relocations.

See Kpoeny (1991) for information on Florida's proposed incidental take rule.

Monitoring Requirements: Determining population size directly by use of underground cameras (Spillers and Speake 1988) or bucket trapping of burrows can be expensive and time consuming. More commonly, estimates of the number of tortoises in a population have been based on surveys of tortoise burrows (Carr 1952, Alford 1980, Cox et al. 1987). Because not all burrows in a population are occupied, this indirect method requires the calculation of a correction factor that relates number of tortoises to the number of burrows. Burrows are classified as active or inactive. Based on the results of a long-term study (Auffenberg and Franz 1982), a "standard correction factor" of 0.614 was adopted by the Florida Game and Fresh Water Fish Commission. Counts of active and inactive burrows are multiplied by the correction factor to determine the number of tortoises present relative to the number of burrows in an area. Several authors have suggested that accurate correction factors must be site specific (Burke 1989, Godley 1989, Stout et al. 1989, Breininger et al. 1991, Diemer 1992b). A study of 26 populations of gopher tortoises showed that the "standard correction factor" overestimated the number of tortoises present in a population in 22 of the 26 populations. With proper caution, an accurate estimate of tortoises present in a population can be made by an accurate assessment of active burrows in a population (see McCoy and Mushinsky 1992a). However, it should be noted that Brandt et al. (1993, Herpetol. Rev. 24:149) found no tortoises in 59 excavated burrows, of which 78% had been classified as active.

Because burrow size (width) is related to the size (carapace length) of the resident tortoise (Alford 1980, Martin and Layne 1987, Wilson et al. 1991, Doonan and Stout 1994), demographic profiles can be constructed by evaluating the size distributions of burrows. Burrow size is measured normally at a depth of 50 cm because the mouth of the burrow is frequently enlarged or eroded (Martin and Layne 1987). To measure the width of a burrow, calipers are constructed from two meter sticks hinged together at the 50 cm mark. The calipers are inserted into the burrow and the width is measured across the open arms.

Repeated surveys, perhaps spaced over a period of 5-10 years, could provide information about population trends. One can use population profiles derived from burrow surveys to evaluate the relative demographic "health" of populations (Mushinsky and McCoy 1994). A healthy population should have some very large (old) tortoises and show signs of recent recruitment (see Cox et al. 1987).

See Blankenship et al. (1990) for information on a tracking method using fluorescent powder.

See Bryan et al. (1991) for information on a method of capturing tortoises using snare traps at burrow entrances.

See Carthy et al. (2005) for an anlysis of population estimation techniques. See Smith et al. (2009) for a handbook of survey methods.

Management Research Needs: Three recent reports summarize topics in need of further study for North American tortoises (Burke and Cox 1988, Germano and Bury 1994, McCoy 1994). Below is a selected summary of those recommendations that are particularly pertinent to management needs.

1. Quantification of habitat use.

2. Definition of habitat requirements.

3. Determination of what constitutes "quality" habitat.

4. Improving methods to determine tortoise density.

5. Long-term studies to determine temporal variability.

6. Studies on egg and hatchling survivorship.

7. Behavioral studies to determine social interactions and hierarchies.

8. Genetic studies of parentage and selective mate assortment.

9. Genetic studies to determine gene exchange among neighboring populations.

10. Studies on homing and orientation.

11. Studies of the long-term success of relocated tortoises.

12. Studies of diseases and disease transmission among populations.

13. Studies of nutritional requirements and foraging preferences of free ranging tortoises.

14. Long-term studies designed to understand natural population trends.

15. Identification of factors that contribute to local extinctions of small populations.

16. Estimates of minimum viable population size.

17. Genetic studies to determine variation and heterozygosity of populations of tortoises throughout their range.

18. More studies concerning alternate habitat management techniques in areas where burning is not feasible.

Population/Occurrence Delineation
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Use Class: Not applicable
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a given location. Such evidence includes reliable observation and documentation of one or more individuals (including burrows) in or near appropriate habitat where the species is (or was) presumed to be established.
Mapping Guidance: As a general rule, extant (E) or A-D-ranked occurrences generally should be mapped as polygons that encompass known occupied habitat patches, including suitable habitat within at least 20 meters of known active or inactive (but not abandoned) burrows. An active burrow is a burrow that shows evidence of recent tortoise activity. An inactive burrow lacks evidence of recent tortoise activity but retains general structure near the entrance. An abandoned burrow is one that needs to be excavated before use is possible. These definitions are slightly modified from McCoy et al. (2006).

Single occurrences may comprise multiple polygons as long as the distance between the polygons does not exceed the separation distance for suitable or unsuitable habitat, as appropriate.

Depending on the particular evidence, a single location in a small patch of suitable habitat may be sufficient to justify mapping the entire patch as the occurrence, although alternatively it may be mapped as a point. For any occupied patch that is smaller than 0.5 hectare (individual home ranges generally are larger than this), the entire patch may be mapped as the occurrence.

The appropriate size and boundaries of an occurrence become ambiguous in situations characterized by just one or a few locations in a small portion of a large patch of contiguous suitable habitat (substantially larger than the typical or average home range size). In such cases, the occurrence should be mapped as a polygon that minimally includes all locations that are not separated by a gap larger than the separation distance for suitable habitat (4 km). In addition, this polygon may also include suitable habitat outside a minimum convex polygon defined by available observation locations; this area may extend up to 20 meters from known active and inactive burrows. However, if the area of the mapped feature includes more than 70 percent of the total contiguous area of suitable habitat, then one may include the entire patch of suitable habitat in the occurrence, using unsuitable habitat to define the boundary. [Note: The value of 70 percent serves as an arbitrary threshold deemed appropriate as an indicator that, for all practical purposes, the entire patch likely is occupied.]

The boundaries of patches of suitable habitat sometimes can be readily identified by their abrupt transitions into adjacent areas of unsuitable habitat. In other situations, suitable habitat may grade gradually into unsuitable habitat. In these latter circumstances, occurrences should include only suitable habitat and contiguous marginally suitable habitat.

Suitable habitat may be interrupted by narrow or wide areas of unsuitable habitat that are smaller than the separation distance. Whether or not to include these areas in the occurrence is a subjective determination that should take into consideration the relative size and nature of the suitable and unsuitable habitats. Narrow habitat interruptions should be ignored if those areas are relatively inconsequential discontinuities in an otherwise continuous tract of suitable habitat.

Separation Barriers: Unsuitable habitat or structure of such extent that tortoises rarely if ever cross or circumnavigate successfully. Examples include: busy highway or highway with obstructions such that individuals rarely if ever cross successfully; untraversable topography; stream, lake, marsh, or floodplain that completely separates suitable upland habitats and is unlikely to be traversed at any time; developed area dominated by buildings and pavement; large, intensively managed agricultural areas.
Separation Distance for Unsuitable Habitat: 1 km
Separation Distance for Suitable Habitat: 4 km
Separation Justification: Multiple movements of a few to several hundred meters have been documented for this species (see Migration/Mobility comments), and in a one-year study in high quality habitat in Georgia, Eubanks et al. (2003) found that two adult males emigrated 1.2 km and 1.5 km. An adult female moved 2.1 km between two locations, each of which was occupied for at least several months (Ashton, in Mushinsky et al. 2006). In Mississippi, hatchlings dispersed up to 458 meters from their nest (Epperson and Heise 2003). Hence, nomadic or emigration movements may unite populations over fairly large distances. The gopher tortoise recovery plan (USFWS 1990) defined a "colony" of tortoises on Camp Shelby, Mississippi, as "three or more active adult burrows...within 300 feet of each other." This concept was thought to distinguish groups of interacting individuals from other such isolates, but currently available data indicate that tortoises could readily cross this distance through suitable habitat. It seems unlikely that two locations separated by a gap of less than several kilometers of suitable habitat would represent independent occurrences over the long term.
Date: 27May2011
Author: Hammerson, G., D. Jackson, M. Barbour, M. Elliot, J. Jensen, and T. Mann
Population/Occurrence Viability
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Excellent Viability: Occurrence exhibits optimal or at least highly favorable characteristics with respect to population size and/or quality and quantity of occupied habitat; and, if current conditions prevail, the occurrence is very likely to persist for the foreseeable future (i.e., at least 20-30 years) in its current condition or better. These occurrences have characteristics (e.g., size, condition, landscape context) that make them relatively invulnerable to extirpation or sustained population declines, assuming that habitat conditions are maintained or improved, even if they have declined somewhat relative to historical levels. Occurrences of this rank typically include at least 250 mature individuals (assuming that the population is not strongly male-biased). Occurrences of this size have a very high probability of long-term persistence (e.g., Tuberville et al. 2009). However, occurrences may be ranked A even if population size is not definitely known (e.g., the population is clearly very large but it is not known how large; the area of occupied habitat is exceptionally large [at least 100 hectares] and the tortoise population appears to exhibit at least average density). Occurrences with excellent estimated viability are ranked A even if one or more other occurrences have a much larger population size and/or much greater quantity of occupied habitat. In most cases, occurrences ranked A will occupy natural habitats. However, "natural" is an ambiguous concept, and occurrences that have been somewhat modified by human actions may still be assigned a rank of A if they otherwise meet the criteria. Occurrences that have significant populations of invasive plants or red imported fire ants (Solenopsis invicta) such that negative impacts on tortoises are expected should be ranked B if they otherwise meet the A criteria. Occurrences that meet the population size criteria for A but show little or no evidence of recruitment over the past 10-15 years (based on adequate information on population structure) may be ranked B, BC, or C, depending on the severity of the recruitment limitation (rationale: demographic models indicate that gopher tortoise population viability depends importantly on relatively high levels of hatchling survivorship; Tuberville et al. 2009). An occurrence rank may be down-ranked (e.g., from A to AB, or from A to B, etc.) as deemed appropriate if the tortoise population is known to be strongly male-biased; this ranking policy applies also to occurrences that otherwise meet the B or C criteria.
Good Viability: Occurrence exhibits favorable but not optimal characteristics with respect to population size and/or quality and quantity of occupied habitat; and, if current conditions prevail, the occurrence is likely to persist for the foreseeable future (i.e., at least 20-30 years) in its current condition or better. B-ranked occurrences have good estimated viability and, if protected, contribute importantly to maintaining or improving the conservation status of the species. Occurrences of this rank typically should include at least 100 mature individuals (e.g., see Tuberville et al. 2009). However, occurrences can be ranked B even if population size is not known or is less than 100 mature individuals as long as the occurrence meets the qualitative conceptual guidelines for this rank. Occurrences that show little or no evidence of recruitment over the past 10-15 years but otherwise meet the B criteria should be ranked C.
Fair Viability: Occurrence characteristics (size, condition, and landscape context) are non-optimal such that occurrence persistence is uncertain under current conditions, or the occurrence does not meet A or B criteria but may persist for the foreseeable future (i.e., at least 20-30 years) with appropriate protection or management, or the occurrence is likely to persist but not necessarily maintain current or historical levels of population size or genetic variability. This rank may be applied to relatively low-quality occurrences with respect to size, condition, and/or landscape context if they still appear to have reasonable prospects for persistence for the foreseeable future. Occurrences of this rank typically should include at least 20-25 mature individuals. Demographic models indicate that even small populations (20-50 individuals) of gopher tortoises have a high probability of persistence for at least several decades (Cox et al. 1987, Cox 1989, Miller et al. 2001, Tuberville et al. 2009).
Poor Viability: If current conditions prevail, occurrence has a high risk of extirpation (because of small population size or area of occupancy, deteriorated habitat, poor conditions for reproduction, ongoing inappropriate management that is unlikely to change, unusually high adult mortality, or other factors). Questionably viable occurrences that could be restored to at least fair viability should not be ranked D if restoration is deemed feasible and plausible; in most such cases CD should be used. Very small occurrences that may be vulnerable to deleterious stochastic events may be ranked as follows: If the stochastic event is highly theoretical or of very low probability in the appropriate time frame (e.g., 20-30 years), then a C or CD rank may be appropriate. If a minority of other similar occurrences have disappeared as a result of, say, disease or inbreeding, then perhaps CD is best. If most of these small occurrences have been extirpated or are disappearing due to such events, then D is probably appropriate.
Date: 27May2011
Author: Hammerson, G., D. Jackson, M. Barbour, M. Elliot, J. Jensen, and T. Mann
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 10Mar2011
NatureServe Conservation Status Factors Author: Jackson, D. R., D. Wilson, H. Mushinsky, and G. Hammerson
Management Information Edition Date: 02Mar1995
Management Information Edition Author: Dawn S. Wilson and Henry R. Mushinsky, Department of Biology, University of South Florida, Tampa, FL 33620. Edited for BCD by G. Hammerson.
Element Ecology & Life History Edition Date: 25Apr2011
Element Ecology & Life History Author(s): WILSON, D., H. MUSHINSKY, AND G. HAMMERSON

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

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