The gopher tortoise has a vital community role and is known as a keystone species because of the wide use of their burrows by other animals (such as burrowing owls, raccoons, opossums, gopher frogs, snakes, etc.). Because they are a keystone species, the protection of the gopher tortoise is crucial for the whole ecosystem in which it lives. In some states the gopher tortoise is being protected by state agencies that are enforcing conservation laws and controlling illegal harvest. Besides protecting the tortoise against poaching other methods of conservation are being used. Relocation of gopher tortoises has been used, with success, to protect tortoises on land that is being developed. Reintroduction into areas from which the tortoises were driven has also been used. Protection of gopher tortoise habitat, such as sand dunes and longleaf pine forests, is also an alternative that can help keep populations high.
IUCN Red List of Threatened Species: vulnerable
Adult gopher tortoises require 16-21 years to mature, and can live 40 years or longer.
Average lifespan
Status: captivity: 8.5 years.
The upper shell is brown or tan, with growth rings evident on younger individuals, but these are worn away on adults. The under shell is unhinged, dull yellowish in color, with the soft parts being grayish brown. The upper shell can range in length from 107 mm to 240 mm. The feet of this tortoise are stumpy and without webs, and their heads are large and blunt. Compared to the other species in the genus Gopherus, the gopher tortoise's head is broad, hind feet small, and shell elongate.
Range length: 170 to 240 mm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Average mass: 5500 g.
Average basal metabolic rate: 0.579 W.
Tortoises are known in legend and folklore for their leisurely ways and slow pace. The Florida gopher tortoise follows this legend well with a slow pace of between .27 and .5 miles per hour.
There are few negative aspects of the gopher tortoise. The occasional damage of crops by hungry tortoises and the relocation costs of developers needing to relocate tortoises from areas being built are the only negative aspects.
Ancient Indians had a monetary system that used gopher tortoises in the place of money. Shells of the tortoises have served as baskets, pots and even sun helmets. Even today, they are a source of food for poorer rural people of Florida and south Georgia.
Overall, the gopher tortoise is an herbivore that enjoys low vegetation. The gopher tortoise spends most of its foraging time grazing in areas with a good supply of grasses and low herbs. Its food primarily consists of grasses and leaves with the occasional wild fruits and berries. In captivity gopher tortoises have been known to be fond of watermelon and cantaloupe rinds.
The gopher tortoise is found in the southeastern part of the United States. Its range includes southwestern South Carolina, south almost to the tip of the Florida peninsula; west through southern Georgia, Alabama, and Mississippi, to Louisiana and the edge of southeastern Texas and Arkansas
Biogeographic Regions: nearctic (Native )
The habitat of the gopher tortoise is in sandy ridge and sand dune areas where the water table never comes near the surface. The forests of longleaf pine, Pinus palustris, are also prime areas for gopher tortoise habitation.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: desert or dune ; savanna or grassland ; forest
The mating behavior of the gopher tortoise is not well documented because of its secretive nature. Male gopher tortoises have been known to utter short rasping calls, to attract females. Fights between male and female gopher tortoises are also sometime seen, which could be related to courtship and mating. Males have a pair of glands under their chin that may function to attract females. The eggs of the gopher tortoise are laid in late April to July. They are deposited, five or six eggs at a time, in holes dug in the ground so that they are protected from the blazing sun. Once in the nest cavity the eggs incubate for approximately 100 days.
Breeding interval: Gopher tortoises breed once per year.
Breeding season: April through July
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Average gestation period: 90 days.
Average number of offspring: 8.
Average age at sexual or reproductive maturity (male)
Sex: male: 3650 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 3650 days.
Like its daily activity, the annual activity of the gopher tortoise is highly reliant upon environmental conditions. Annual activity patterns of gopher tortoises vary geographically, depending upon the severity of winter weather. Researchers divided the gopher tortoise's range into 2 subranges based upon annual activity patterns caused by latitudinal differences in weather. The northern subrange included gopher tortoises that were typically inactive through most of the winter months (January-March). This subrange included gopher tortoises occurring from southern South Carolina southwest to eastern Louisiana and east through northern Florida. The southern subrange included gopher tortoises that were typically active year-round and included those occurring south of the Santa Fe River in Florida [7]. During winter, gopher tortoises bask at the mouths of their burrows on warm days throughout their range [156], and gopher tortoises in all regions may be inactive for long periods (weeks to months) during cold or very hot and dry weather [7]. Even in places where gopher tortoises are active year-round, gopher tortoise activity is not uniformly distributed temporally. A peak in activity typically occurs during April through October, but particularly from April to June and September to October [10,55,152]. For more information on this topic, see Home range and movement.
Time of breeding and nesting vary throughout the gopher tortoise's range, depending upon latitude. Variations in air and soil temperature, forage availability, rainfall, and average number of sunny days affect gopher tortoise phenology [7]. Courtship behavior occurs principally in spring (April-early June), but also in late winter (February-March) and fall (October-November), particularly in the South [7,42,54,85]. Nesting generally occurs in spring through summer (late April-mid-July), with peak nesting activity occurring from mid-June to mid-July [54]. Nesting occurs only on warm, sunny days [85]. Hatching and emergence of young from the nest typically occur from August through October [7].
A gopher tortoise may spend as much as 80% of its time (or about 19 hours/day) in its burrow [7]. In mesic longleaf pine/pineland threeawn habitat at Ichauway in Baker County, Georgia, female and male gopher tortoises monitored during the day (when gopher tortoises are most active) were observed aboveground only 0.8% of the time [55]. Fourteen adult female gopher tortoises in pine-oak sandhills and old fields at the Katharine Ordway Preserve in north-central Florida were monitored during the day for up to 505 days. Female gopher tortoises were above ground <2% of the time. When active above ground, they spent most of their time basking at or near the apron (i.e., the mound of soil outside the burrow mouth formed during burrow excavation) (76%), walking (17%), and feeding (4%). Mating and nesting comprised 2% of their activities [135]. In pine-oak/saw-palmetto/pineland threeawn sandhills in Hillsborough County, Florida, juvenile gopher tortoises monitored during the day were active above ground 10% of the time [152].
Gopher tortoises occur in a variety of plant communities, including pine-oak (Pinus-Quercus spp.) sandhills, pine flatwoods, pine plantations, sand pine (P. clausa) scrubs, coastal strands, coastal prairie grasslands, hammocks, and a variety of ruderal communities ([80], reviews by [39,54]). Ecotones between communities are also used ([47,59], reviews by [7,9]). Gopher tortoises prefer open habitats that support a variety of herbaceous ground cover vegetation for forage (see Diet) and usually abandon densely canopied areas (see Preferred Habitat). According to a review, the gopher tortoise is associated with the following forested and nonforested plant communities throughout its range [7]:
This review subjectively ranked the "level of suitability" of forested and nonforested habitats for gopher tortoises based upon information available in literature, unpublished data, and expert opinion. Because herbaceous plant species composition is highly variable within and across habitats and dependent upon current and historic management practices, the "potential for forage" occurrence within each habitat was also ranked. Data from numerous published and unpublished studies were compiled to estimate gopher tortoise densities in each habitat presented in the above table [7].
According to the State of Florida Game and Fresh Water Fish Commission, gopher tortoises occupy the following habitats in Florida [15]:
Gopher tortoise habitats in Florida using 3 habitat classification systems [15]. Additional habitats listed by Cox and others [39] are highlighted in bold. US Soil Conservation Service Florida Land-Use and Cover Florida Natural Areas Inventory Florida coastal strand (north and south) Grassland Coastal strand Sand other than beaches Overwash plainBeach dune
Maritime hammocks Coastal berm Shell mound Florida flatwoods (north and south) Palmetto (e.g., saw-palmetto and scrub palmetto (Sabal etonia)) prairies Mesic flatwoods Pine flatwoods Scrubby flatwoods Coniferous planted forests Dry prairie Wet flatwoods Wet prairie Prairie hammock Sand pine scrub Coastal scrub Scrub Other scrub and brush Xeric hammock Sand pine scrub Coniferous planted forests Longleaf pine-turkey oak hills Longleaf pine-xeric oak Sandhill Coniferous planted forests Mixed hardwoods and pine Mixed forest Upland pine forest Coniferous planted forests Upland mixed forest Hardwood planted forests Xeric hammocks Upland hardwood hammocks Other hardwood Upland hardwood forest Hardwood planted forests Xeric hammocks Oak hammocks Xeric oak forest Xeric hammocks Ruderal Recreational Mixed Open land and other Cropland and pastureland Orchards, groves (except citrus) Citrus groves Grassland Clearcut areas Altered lands Other barren landsForested habitats: Although gopher tortoises occur in many plant communities, longleaf pine ecosystems, which are divided into 2 general types—pine-oak sandhills and pine flatwoods—comprise about 80% of the habitats associated with the gopher tortoise (review by [7]). Longleaf pine and threeawn (Aristida spp.) are characteristic species of "virtually all" longleaf pine ecosystems associated with gopher tortoises [119]. Gopher tortoises occur at high densities in midsuccessional stages of longleaf pine ecosystems maintained by fire and are less abundant in more advanced successional stages such as hammocks [9]. Historically, large areas of longleaf pine ecosystems were converted to plantations with slash pine, sand pine, or loblolly pine. Gopher tortoises may occur at moderate to high densities in early-successional stages of pine plantations but tend to occur at lower densities in late stages with closed canopies [7].
Pine-oak sandhills: Gopher tortoises occur at high densities in pine-oak sandhills. These plant communities extend over a large portion of the Atlantic Coastal Plain in the southeastern United States. Widely spaced longleaf pine typically dominates the overstory of pine-oak sandhills [58]. Less frequently, slash pine dominates the overstory [117,140]. The understory is typically sparse and consists of a mixture of deciduous oaks, including turkey, blackjack, bluejack, and post oak, and a variety of shrubs (e.g., blueberry (Vaccinium spp.), lyonia (Lyonia spp.), and gallberry) [7,31,58,117,140,151]. The ground layer is typically dense and consists of diverse herbaceous plants [58]. The understory and herbaceous ground cover associated with pine-oak sandhills vary across the gopher tortoise's range [21]. In the eastern part of the gopher tortoise's range, the gopher tortoise is primarily associated with the longleaf pine/turkey oak/threeawn (e.g., pineland threeawn (Aristida stricta) and Beyrich threeawn (A. beyrichiana)) plant association. This plant association is the "most typical" plant association in pine-oak sandhills [31,58,117]. In the western part of the gopher tortoise's range, threeawn is replaced by bluestem grasses (e.g., Schizachyrium scoparium and Andropogon spp.) in the ground layer [21,117]. Pine-oak sandhills occur on ridgetops and slopes of gently rolling hills, and their soils are deep, well-drained, and sandy. Pine-oak sandhills are fire-maintained communities that succeed to xeric hardwood hammock communities in the absence of fire or other disturbance. Xeric hardwood hammock communities are characterized as either scrubby, dense, low-canopied forests with little understory other than saw-palmetto, or multistoried forests of tall trees (e.g., pignut hickory (Carya glabra), sweetgum, and southern red oak) with variable canopy closure and an understory dominated by deciduous scrub oaks [2,58,117]. The ground layer of xeric hardwood hammocks is typically sparse and thus supports smaller gopher tortoise populations, particularly when the canopy cover is >60% [7]. The scarcity of herbaceous plants and the relatively incombustible oak litter preclude most fires in xeric hammock communities. When fire does occur, it is nearly always stand replacing (see FIRE REGIMES) [21,58,140].
Pine flatwoods: Gopher tortoises occur at high densities in pine flatwoods. These plant communities are characterized by an open canopy of widely spaced longleaf and/or slash pine with a sparse understory and a dense ground cover. Pine flatwoods occur on flat topography, and their soils are moderately to poorly drained, consisting of 1 to 3 feet (0.3-0.9 m) of sand overlying an organic hardpan or "clayey" subsoil [2,58,140]. Because pine flatwoods are more mesic than pine-oak sandhills, they typically support a more well-developed shrub layer [119] and relatively fewer grasses and forbs [20,140] than pine-oak sandhills. Oaks (e.g., sand live, laurel, water, and running (Q. pumila) oak), saw-palmetto, gallberry (e.g., inkberry (Ilex glabra) and large gallberry (I. coriacea)), lyonia (coastal plain staggerbush (Lyonia fruticosa) and fetterbush lyonia (L. lucida)), and wax-myrtle (Myrica cerifera) are common in the understory [2,119]. Like pine-oak sandhills, the understory and herbaceous ground cover associated with pine flatwoods vary across the gopher tortoise's range [68,140], but gopher tortoises frequently occupy pine flatwoods with a threeawn understory. Pine flatwoods are fire-maintained communities that succeed to mesic hardwood hammocks and other communities (e.g., bayheads) in the absence of fire or other disturbance (see FIRE REGIMES) [2,140]. Mesic hammock communities are dominated by evergreen oaks, saw-palmetto, gallberry, and ericaceous (Ericaceae) shrubs [2].
Scrub: Gopher tortoises occur at moderate densities in scrub, often in ecotonal or disturbed, open areas [9,16,31,60]. Scrub is dominated by various evergreen oaks (e.g., sandhill oak (Q. inopina), Chapman oak (Q. chapmanii), sand live oak, and myrtle oak (Q. myrtifolia)). Saw-palmetto, scrub palmetto, lyonia, and Florida rosemary occur in the understory [117]. Sand pine may or may not be present in the overstory. The tree and shrub canopies vary from sparse to dense depending upon the frequency of fire. The ground cover is "always sparse", species poor, and distributed in scattered open areas [117,140]. Soils of scrub are sandy and well drained [31,140]. Without fire or other disturbance, scrub may succeed to xeric hammock communities [2,132,140].
Nonforested habitats: Gopher tortoises may reach high densities in ruderal or heavily disturbed habitats. High gopher tortoise densities (8.9-9.9/acre) were reported in "remnants of natural habitat and had in every case a 20% to 60% cover of (nonnative) bahia grasses as well as a high diversity of broadleaf forage of over 160 species" [7]. Auffenberg and Franz [9] reported that "ruderal habitats may contain higher gopher tortoise population densities than original ones if grasses and forbs are abundant". In Orange County, Florida, gopher tortoises were absent from orange (Citrus à sinensis) groves that were annually disced, but were relatively abundant in old fields (range: 1.1-2.5 gopher tortoise burrows/ha) and abandoned orange groves with dense herbaceous ground cover (range: 0.3-2.3 gopher tortoise burrows/ha) [74]. Across 24 counties in southern Alabama, mean gopher tortoise densities were highest in old fields compared to 7 other habitats [137]:
Average gopher tortoise densities in 8 habitats in 24 counties in southern Alabama [137] Habitat Mean gopher tortoises/ha Old fields 1.53 Pastures 0.50 Agricultural lands 0 Edges 0.64 Clearcuts 0 Pine plantations 0.72 Burned pine/scrub oak 0.64 Unburned pine/scrub oak 0Among 7 habitat types at the Kennedy Space Center in Florida, gopher tortoise densities were highest in disturbed habitats. In this study, disturbed habitats were historically scrub habitats that were clearcut ≥20 years before the study [16,18]. The authors suggested that gopher tortoises might benefit from disturbed areas in scrub and slash pine flatwoods [16]. For more information on this study, see Population density.
Gopher tortoises may benefit from having a variety of plant communities in close proximity to each other. Wetland habitats (e.g., ephemeral ponds, freshwater marshes, and wet prairies) adjacent to other habitats may be used for feeding when seasonally dry or during drought years [7]. At the Kennedy Space Center, gopher tortoises preferred coastal scrub oak habitat to 6 other habitats for burrowing. No or few burrows occurred in swales; however, swales were used for feeding and many burrows were located adjacent to swales. These results suggested that gopher tortoises may require a range of well-drained to poorly drained sites for feeding and burrowing [16]. Other researchers report that pastures or mowed sites may be used for feeding when adjacent to other habitats. At the Kennedy Space Center, gopher tortoises rarely burrowed in disturbed areas, such as periodically mowed grassy areas, pastures, citrus groves, and firebreaks, but used these sites for foraging and burrowed along their ecotones [16,136].Burrows are an important aspect of gopher tortoise ecology. The burrow is a defendable refuge that protects the gopher tortoise from daily and seasonal temperature extremes, fire, and predators [7]. A gopher tortoise may spend up to 80% of its time in its burrow (see Annual activity), where it rests and defecates [54]. When active above ground, its activities (e.g., basking, foraging, and nesting) are centered around its burrow [103,135]. The temperature and humidity within the burrow remain relatively constant throughout the year, providing a consistent, suitable microclimate where temperature is moderated and humidity is held relatively high; thus, the burrow protects the gopher tortoise from lethal temperatures and prevents desiccation [7,39,51,54].
Burrow description: All age classes use burrows, although some hatchlings and juveniles may bury themselves in sandy soil or push under litter to create a depression or excavation directly below the soil surface called a "pallet". Gopher tortoises excavate new burrows, use the abandoned burrows of other gopher tortoises, or reconstruct damaged burrows [7,54].
The burrow is typically a single-channeled tunnel [105] that gradually slopes downward from the soil surface and levels off under ground [36]. The deepest part of the burrow is typically enlarged into a chamber [54]. The chamber is commonly placed close to the groundwater table and may be in soils different from the overburden (see Burrow sites). Burrows may be as long as 35 feet (10 m) and as deep as 10 feet (3 m) below the soil surface [7]. The length and depth of the burrow vary with the depth of sand and depth of the water table (Hallinan 1923 cited in [39]). Burrows of juvenile gopher tortoises are typically narrower, shorter, and shallower than those of adults, possibly making juveniles more vulnerable to predators [39]. Burrows are wide enough so that the gopher tortoise can turn around at any point along its length [36]. During burrow construction, excavated soil is deposited in a "half-moon shape" outside the burrow mouth to form the apron, which may be up to 7 feet (2 m) in diameter [7]. Its size and shape may be influenced by microtopography, gopher tortoise movements, and vegetation (Kaczor 1988 cited in [77]). The apron is often used as a basking site [8] and as a nesting site for female gopher tortoises (see Nests) [51].
Burrow sites: Where available, gopher tortoise burrows are typically located on well drained (rapid to moderate percolation rate), sandy soils where the groundwater table or impermeable clay or rock layer is at least 2 feet (0.5 m) below the soil surface. However, burrows may be dug in a variety of soils such as "shallow shelly soils", "heavy periodically flooded soils", and "rich loamy soils" [7]. In Louisiana, availability of sandy soils is "limited". In this region, most burrows are excavated in loamy soils with a "rather high" clay content, and the aprons are "usually compacted into a hard cement" [9]. The burrow may extend into different soils throughout its profile. The burrow's end chamber is often in soils "much less pervious than the overburden" [7]. Burrows dug in sandy soils are typically longer than those in clay soils, and hypoxia and hypercarbia may be more pronounced in burrows dug in clay soils (Ultsch and Anderson 1986, 1988, cited in [54]). In general, soils with high clay content do not support large gopher tortoise populations [9].
According to Ashton and Ashton [7], the most important soil characteristic in burrow site selection by gopher tortoises may be the distance between the soil surface and the groundwater table, with gopher tortoises typically placing the burrow chamber close to the groundwater table and at least 2 feet (0.5 m) below the soil surface [7]. The close proximity of the burrow chamber to the groundwater table may provide a suitable microclimate by keeping the humidity in the burrow high (>60%) year-round [7], but may subject the burrow to flooding when the water table moves upward during wet periods, particularly in winter [16,104]. In Leon County, Florida, and Thomas County, Georgia, water was observed in >100 burrows for periods lasting as long as 48 consecutive days, and several occupied burrows contained ground water at least once every year of the 4-year study [104]. In coastal scrub and slash pine flatwoods at the Kennedy Space Center, most burrows were flooded in winter. However, gopher tortoises still used them and "it was obvious that in winter gopher tortoises did not select for well-drained areas and that use of flooded burrows was common" [16]. Conversely, on Cape Sable, gopher tortoises commonly located burrows on upland ridges, but few burrows were located on beaches or swales. Beaches and swales were frequently used for foraging, however, suggesting that gopher tortoises "avoided digging burrows in areas subject to flooding" [80]. Mitchell [110] suggested that burrow flooding prompted gopher tortoises to abandon burrows in longleaf pine/turkey oak/pineland threeawn habitat at the Fort Stewart Army Reserve. It is unclear whether gopher tortoises prefer burrows that flood, but gopher tortoises apparently tolerate water in their burrows. In flooded burrows, gopher tortoises were found partially or completely immersed in water even when water levels were low enough in the burrow to avoid immersion, suggesting that gopher tortoises may prefer immersion and gain some thermoregulatory advantages from it [16,47,104].
Burrow site selection by gopher tortoises may be more heavily influenced by physical characteristics (i.e., soil type and proximity of the groundwater table) of the habitat than plant associations [7]. However, vegetation characteristics, including species composition and structure, apparently influence burrow site selection at least in part. Gopher tortoises may place burrows at sites where herbaceous ground cover, especially preferred herbaceous forage, is abundant [130,144]. A review states that gopher tortoises consistently select burrow sites where herbaceous ground cover is moderate to very dense (35-80%) [7]. In longleaf pine/turkey oak/pineland threeawn sandhills at George L. Smith State Park and Fort Stewart Army Reserve in Georgia, gopher tortoises selected burrow sites where percent cover of herbaceous plants was significantly greater than that available (burrow sites: 36-40%, random sites: 12-29%; P≤0.05) [130]. However, because selective foraging close to burrows may result in decreased abundance of herbaceous ground cover close to burrows, studies of the relationship of burrow sites to ground cover are confounded. In longleaf pine/pineland threeawn habitat at Ichauway, the abundance of some preferred forage (e.g., fleshy-fruited plants and nonthreeawn graminoids) was significantly lower near active gopher tortoise burrows than random sites (P≤0.05), whereas the abundance of other preferred forage (e.g., legumes) was more abundant near active burrows compared with random sites (P≤0.05). This author attributed the reduced abundance of some forage items next to burrows to selective foraging. Greater abundance of other forage items was attributed to gopher tortoise activities (i.e., creation of openings during burrow excavation and seed dispersal) that encouraged greater reproduction and growth of these plants near gopher tortoise burrows [13].
Gopher tortoises consistently select burrow sites where tree and shrub cover is low to moderate (range: 0-60%, "optimum": 20-30%) [7]. In longleaf pine/pineland threeawn habitat at Ichauway, average canopy cover at burrows (30%) was lower than at random points (60%; P=0.0001) [13]. In slash pine flatwoods and scrub habitats at the Kennedy Space Center, gopher tortoise burrows were associated with less canopy cover and lower shrub height than average conditions across the study sites [16]. At George L. Smith State Park, longleaf pine/turkey oak/pineland threeawn habitat that had not burned for >20 years had significantly lower canopy cover at active gopher tortoise burrows (26%) than at random points (76%; P≤0.05). In the same habitat, maintained by prescribed fire on 3- to 5-year intervals at Fort Stewart Army Reserve, canopy cover was also lower (26%) at active gopher tortoise burrows than at random points (40%; P≤0.05) [130]. Also in longleaf pine/turkey oak/pineland threeawn habitat at Fort Stewart Army Reserve, Mitchell [110] found low canopy cover both at burrows (23%) and at random points (22%), a result attributed to the uniformity of the habitat at her sites. Some researchers suggested that an open canopy near the burrow may provide basking and nesting sites, and may also provide sites for growth and reproduction of herbaceous forage [6,39,44,86,98,130,156]. However, gopher tortoise burrows are sometimes found in dense vegetation. Active gopher tortoise burrows were found in dense cogon grass (Imperata cylindrica) on the edge of sandhill habitat at the Withlacoochee State Forest in Florida [92]. Burke and Cox [28] located burrows in "extremely dense vegetation" in northern Florida, and Ashton and Ashton [7] located over 30 young gopher tortoises in burrows and pallets in a dense thicket of greenbriar (Smilax sp.), blackberry (Rubus sp.), blueberry, and grape (Vitis sp.) at another location in northern Florida.
Obstacles may also influence burrow site selection. Burrows are frequently located at the base of natural or manmade obstacles such as logs, rocks, plant roots, fences, and buildings [7].
Burrow use: The gopher tortoise uses one or more burrows within its home range. The number of burrows used by an individual varies geographically, seasonally, with the age and sex of the individual, and with habitat type, quality, and size [29,47,103,115]. Juvenile gopher tortoises typically use fewer burrows than adults, and adult males often use more burrows than adult females. In longleaf pine-oak habitat at the Southlands Experiment Forest, 2-year-olds used the greatest number of burrows [103]:
Mean number of burrows used from April to November by different age classes of gopher tortoise [103] Age class (years) Burrows used Neonate-1 1.1 2 2.2 4-5 1.7 6-9 2.0In pine-oak/saw-palmetto/pineland threeawn sandhills in Hillsborough County, Florida, juvenile gopher tortoises used 4.4 burrows annually [152]. In several habitats at the Lochloosa Wildlife Management Area, juveniles used an average of 2.1 burrows from April to December, while subadults used 2.9 burrows, adult females used 2.7 burrows, and adult males used 5.5 burrows [47]. In 7 habitat types at the Kennedy Space Center, adult female gopher tortoises used an average of 8.8 burrows and adult males used an average of 16.6 burrows for 8 to 16 months. In this study, the number of burrows used by adult males was larger but not significantly different from that of adult females [136]. In longleaf pine/pineland threeawn habitat at Ichauway, male gopher tortoises used significantly more burrows (x =10.0 burrows) than females (x =5.2 burrows) during a 13-month period (P<0.0001) [55].
Although gopher tortoises may use multiple burrows, many burrows are consistently occupied by the same individual for months to years; others are used only briefly, abandoned, and then reopened by the same or another individual [7]. In pine-oak/saw-palmetto/pineland threeawn sandhills in Hillsborough County, Florida, juvenile gopher tortoises used an average of 4 burrows annually but used a single burrow 75% of the time [152]. There are typically more burrows in a given area than are used by gopher tortoises. A review states that "typical" occupancy rates of gopher tortoise burrows in Florida were between 47% to 49% in pine-oak sandhills and 32% to 67% in pine flatwoods [7]. Mushinsky and McCoy [115] found 55% of burrows were active at 19 sites located throughout Florida. To differentiate between burrows experiencing different use, many researchers classify gopher tortoise burrows as "active", "inactive", or "abandoned" [9,16,39,115,156]. Patterns of burrow occupancy are not thoroughly understood, but periodic occupation and abandonment of burrows often occurs seasonally [100]. In 7 habitats at the Kennedy Space Center, the average number of burrows used by adult gopher tortoises was highest for both sexes in March, August, and September. Burrow use decreased greatly during winter (December-February) [136]. In longleaf pine/pineland threeawn habitat at Ichauway, females used an average of 2 burrows each month from May through October and an average of 1 burrow in all other months. Males used increasingly more burrows each month from May (about 2 burrows) though September (about 5 burrows), followed by a decline in number of burrows used in October (about 3 burrows) and thereafter. Males used an average of 1 burrow from November to April [55]. In longleaf pine-turkey oak sandhills in Mobile County, Alabama, burrows used in spring and early summer were not used in late summer and vice versa [100]. In longleaf pine-oak habitat at the Southlands Experiment Forest, adult male and female gopher tortoises moved less and used fewer burrows during the spring breeding season than at any other time except late fall [103].
Seasonal patterns in burrow occupancy and abandonment may be influenced by environmental factors. In longleaf pine-oak habitat at the Southlands Experiment Forest, food depletion in spring breeding areas may have triggered burrow abandonment by adult gopher tortoises in late fall [103]. At the Katharine Ordway Preserve, adult female gopher tortoises moved between burrows 2 to 3 times more frequently from June to August in pine-oak sandhills than in old fields. Infrequent interburrow movements in old fields were attributed to more abundant, evenly distributed forage [135]. Other suggested reasons for differences in burrow use among populations were differences in ground cover, soil composition, temperature extremes at different latitudes, and number of disturbances to burrows [156]. For more information, see Home range and movement.
The gopher tortoise is typically solitary (see Social interactions); however, 2 or more gopher tortoises may occupancy a single burrow. In several habitats at the Lochloosa Wildlife Management Area, cooccupancy by 1 or more adult male gopher tortoises and an adult female gopher tortoise occurred at least 14 times from mid-May to mid-November, and cooccupancy of 1 burrow by 2 adult males or by 2 immature gopher tortoises occurred several times [47]. Cooccupancy occurred on 10 occasions at the Kennedy Space Center from March through November; a majority of dyads sharing the same burrow were the same sex [136]. Gopher tortoises may cooccupy burrows at night [47], but cooccupancy during the day may be more common [47,103]. Where burrow sites are limited, burrows may be more closely distributed and cohabitation may occur at higher rates. Young gopher tortoises appear to tolerate cohabitation of burrows more readily than adults and are sometimes found clustered together in small areas outside burrows [7]. At the Kennedy Space Center, 42% of burrows were used by more than one gopher tortoise at the same or different times during the course of a 16-month study conducted in 7 habitats [136].
Burrow distribution: Gopher tortoise burrow distribution within available habitat varies across sites and is poorly understood [39]. Many authors describe clusters of gopher tortoise burrows [3,9,10,103], while others demonstrate a random or regular distribution of burrows throughout an area [3,80]. In ruderal and pine-oak sandhills habitats in northern peninsular Florida, the burrow distribution varied from widely scattered, approximately uniform dispersion to distinctly clumped aggregations [3]. A review speculated that varying degrees of aggregation may reflect historical, sociological, or environmental differences among the areas surveyed or may simply reflect random variation in burrow placement [39]. Gopher tortoise burrows in longleaf pine-oak habitat at the Southlands Experiment
Forest were aggregated. At this site, gopher tortoise movements were concentrated on a small area (about 2.5 acres (1 ha)) during the breeding season, when a few dominant males occupied the burrows closest to female burrows and excluded juvenile males from the immediate colony area. After the breeding season, gopher tortoises were more widely dispersed, shifting activity from the interior to the periphery of the colony [103]. In longleaf pine/pineland threeawn habitat at Ichauway, all burrows were clumped (Z=2.602, P<0.05), possibly reflecting the use of multiple burrows by a single individual. Active burrows were randomly dispersed (Z=1.225, P>0.05), possibly "related to the distribution of optimal habitat patches", which also appeared randomly dispersed. This researcher expected to find reproductive advantages for females in aggregations, but found no difference in the frequency of interactions, courts, or mounts between aggregated and isolated individuals [13]. She suggested that burrow distribution may be more closely associated with open canopy cover than with any particular social advantage. In habitats where gopher tortoises are forced into marginal areas or where suitable habitat patches are small and isolated, burrows may be clumped due to increased gopher tortoise density, a pattern noted for an island population in south Florida [80] and other sites throughout Florida [102]. A gopher tortoise burrow in "fire-maintained" longleaf pine forest in Georgia. Photo courtesy of Pete Pattavina, US Fish and Wildlife Service.No cases of direct mortality of gopher tortoises caused by fire had been reported as of this writing (2009). Since fire generally only heats the top 2 inches (10 cm) of the soil during fire [134] and gopher tortoise burrows may be as deep as 10 feet (3 m) below the soil surface (see Burrow description), burrows likely shelter gopher tortoises from fire [33,104]. However, active gopher tortoises located away from their burrows may be killed by fire, particularly if the fire is fast-moving [82] or occurs during cold weather when gopher tortoises move slowly (Means 1988 unpublished letter cited in [129]). Because their higher surface area to volume ratios make them more sensitive to heating, young gopher tortoises may be more susceptible to direct mortality caused by fire (see Daily activity). Also, young gopher tortoises may use shallow pallets or burrows (see Burrow description) that may provide inadequate protection from the heat of fire [16], particularly if these shelters are under or near heavy fuel loads and fire is of high intensity or severity. Although no information is available on gopher tortoises, desert tortoises (Gopherus agassizii) located in shallow burrows were killed by fire (see FEIS review of the desert tortoise).
Since active gopher tortoises are susceptible to fire, the timing of fire likely affects the extent of fire-caused mortality and the age and gender classes most affected. Gopher tortoises may be most affected by early spring, late summer, and fall fires, when they are most active and thus more likely to be away from their burrows, without protective cover. Spring is a time of recovery from winter dormancy and increased reproductive activity (i.e., nesting and mating), and late summer and fall (September-October) is a time when food plants have become fibrous and less available, so gopher tortoises may travel long distances in search of food (see Home range and movement and Foraging activity). In late summer and fall, gopher tortoises may be particularly susceptible to the indirect effects of fire, since fire at this time may reduce already limited available forage prior to winter dormancy, a potentially critical time for gopher tortoises. Also, during August through October, gopher tortoises are hatching from their nests (see Annual activity) [7]. Fire occurring during summer, but prior to emergence of hatchlings from their nests (i.e., late June and July), may be best suited to gopher tortoise conservation [7,39,103,156]. For additional information on timing of fire, see Habitat management and Indirect Fire Effects.
Several studies report fire having a positive effect on gopher tortoises. However, most studies are anecdotal, use small sample sizes, or include no controls and/or replicates, so results should be interpreted with caution. General observations at the Ashton Biological Preserve indicated that gopher tortoises in pine-oak sandhills used formerly abandoned burrows after fire, perhaps due to reduced vegetation cover over the burrows [7]. On the Ocala National Forest in Florida, a gopher tortoise excavated a new burrow approximately 30 days after a stand-replacing February prescribed fire in sand pine scrub [41]. On a 2.5-acre (1 ha) site at the St Marks National Wildlife Refuge in Florida, gopher tortoise burrow abundance increased from 2 to 13 burrows over 2 years after a prescribed fire in March 1983. The width of 4 of the 11 new burrows indicated that adult gopher tortoises had immigrated to the site following fire. The remaining 7 new burrows contained recently hatched gopher tortoises, indicating successful postfire reproduction (Means unpublished data cited in [105]). In Hillsborough County, Florida, richness and abundance of reptiles and amphibians were consistently higher on 2.5-acre (1-ha) plots of slash pine-oak/saw-palmetto/pineland threeawn sandhills burned in late spring (late May-early June) at 3 fire-return intervals (1-, 2-, and 7-year intervals) than on a "control" plot protected from fire for 20 years. After 6 years of treatment, the plot subjected to annual prescribed fires had few standing mature trees and sparse herb cover, with many areas of exposed sand. The plot subjected to 3 fires at 2-year intervals had dense herb cover with few standing trees and no exposed sandy areas. The plot subjected to fire at a 7-year interval had many fire-damaged understory trees. In the year after its second burn, this plot had much exposed sand and moderate grass and herb cover. The following year, "more complete" herb cover had reduced the sand cover in the plot. The control plot had a well-established tree canopy and dense understory of saw-palmettos, with herb density intermediate to that of plots burned at 1- and 2-year intervals. Gopher tortoise numbers were higher in annually burned plots than other plots, but no statistical tests were performed. The authors described gopher tortoises as "very abundant" and gopher tortoise numbers "relatively constant year to year" throughout the plots [114]:
Gopher tortoise densities on prescribed burned plots in slash pine-oak/saw-palmetto/pineland threeawn sandhills in southern Florida [114] Fire-return interval (years burned) Study year 1983 1984 Gopher tortoises/acre 1-year intervals (1979-1984) 15.4 13.8 2-year intervals (1979, 1981, & 1983) 8.5 10.5 7-year intervals (1976 & 1983) 11.7 10.5 Control* 8.1 5.7 *Burned in 1965.Across 24 counties in southern Alabama, gopher tortoise densities were not found in unburned pine-scrub oak habitat, while their density averaged 0.64/ha in burned pine/scrub oak habitat [137]. In 7 counties in southern Georgia, gopher tortoise burrows were denser on "frequently burned", open-canopied longleaf pine stands with a "robust" herbaceous ground cover than on agricultural lands (i.e., cropland, field edges, and grazed or mowed pasture), pine plantations (mostly densely stocked with a sparse herbaceous understory), and unburned areas that had succeeded to dense hardwoods with sparse herbaceous ground cover [72]. In southern Georgia, gopher tortoise density and herbaceous biomass were greater in habitat burned at 1- to 2-year intervals than in habitat not burned in 8 years [86]:
Management history, habitat composition, and gopher tortoise density at 4 sites in southern Georgia [86] Site 1 Site 2 Site 3 Site 4 Plant community 16-year-old slash pine plantation with a "sparse tree canopy" harvested longleaf pine-scrub oak 16-year-old slash pine plantation with a "sparse tree canopy" "natural" longleaf pine-scrub oak Management history Site preparation anchor chained and debris windrowed none double-chopped and debris burned none Harvest history clearcut and planted to slash pine "much" of the longleaf pine had been harvested from the overstory clearcut and planted to slash pine none Fire interval dormant-season fire every 2 years for an unknown period prior to the study devoid of fire for 8 years prior to the study dormant-season fire annually for 8 years prior to the study dormant-season fire annually for approximately 20 years prior to the study, but carried fire every 2-4 years Habitat composition Herbaceous plantsHigh gopher tortoise densities at sites 1, 3, and 4 were attributed in part to frequent prescribed fire, which reduced oaks and litter and increased herbaceous biomass production. These data suggest that pine plantations managed similarly to longleaf pine-scrub oak habitat may benefit gopher tortoises [86].
Some gopher tortoise research indicates little or no effect of fire on gopher tortoise abundance. On the Ocala National Forest, gopher tortoises were surveyed in mature sand pine forest (≥55 years old) and in sand pine forest 5 to 7 years after the following treatments: 1) severe wildfire, salvage logging, and natural regeneration, 2) clearcutting, roller chopping, and seeding, and 3) clearcutting and seeding. Reptile species richness, diversity, and evenness did not differ among the 3 treatments or the mature forest control site. Although predisturbance data were not available, gopher tortoises were found only at treated sites, and the rate of detection of gopher tortoises was high enough to estimate gopher tortoise density only at the severe-fire site [66]. At the Kennedy Space Center, gopher tortoises were more abundant at sites burned within the previous 3 years than at sites burned at longer intervals. Data were combined across disturbed, oak-palmetto, and palmetto habitats. However, the relationship between time-since-fire and gopher tortoise densities was marginal and explained only a small amount of variation in gopher tortoise density, a result attributed to an abundance of gopher tortoise forage near plots that were not recently burned. In this study, herbaceous cover decreased and shrub height increased with time-since-fire (P<0.01 for all variables) [18]. In Orange and Osceola counties, Florida, gopher tortoise abundance in sand pine scrub was frequently higher at clearcut and roller chopped sites than burned and control sites, but this pattern was not consistent [60]:
Number of active gopher tortoise burrows on control and treated sites in sand pine scrub of Orange and Osceola counties, Florida [60] Site 1 Site 2 Site 3 Treatment Gopher tortoise age class Adult Juvenile Adult Juvenile Adult Juvenile Prescribed fire 4 0 6 0 3 1 Clearcut and roller chopped 7 1 10 1 3 1 Control 0 1 1 6 3 0Prescribed fire is generally considered favorable and often recommended for management of gopher tortoise habitats [9,81,86,113]. Several researchers recommend maintaining presettlement annual and seasonal periodicity of fire within habitats occupied by gopher tortoises [105,107,129,156]. Recommended fire-return intervals for gopher tortoise management in pine flatwoods vary from 1 to 3 years [7,156]. Recommended fire-return intervals for gopher tortoise management in pine-oak sandhills are 1 to 3 years [6], 2 to 4 years [86], 2 to 6 years [7], and 2 to 5 years [156]. Because herbaceous ground cover and longleaf pine needles help carry fire, retaining longleaf pine in the overstory and herbs in the ground layer is important in maintaining this forest type [83,86]. Since longleaf pine seedlings <1 year old are susceptible to fire mortality, several researchers recommend that annual fires be avoided in longleaf pine forests [105]. A review states that the potential benefits for gopher tortoises in maintaining a fire regime of periodic, low-severity fire in longleaf pine ecosystems include maintaining the physiognomic character of longleaf pine-bunchgrass ecosystems by excluding plants that are poorly adapted to fire; preparing a seedbed favorable to longleaf pine regeneration; reducing the density of understory vegetation and thus providing microsites for herbaceous plants and gopher tortoise nesting and burrow sites; stimulating increased seed production by native grasses; and releasing nutrients to the soil for uptake by plants [21].
To maintain sand pine scrub habitat in conditions suitable for gopher tortoises, researchers recommend fire-return intervals of 15 to 30 years [7,156]. In sand pine scrub communities, fire stimulates flowering and seed production of many species, enhances regeneration by exposing bare mineral soil, reduces shading from woody understory species, reduces fuel loads, releases nutrients to the soil, accelerates growth in the herbaceous layer, and increases fruit and forage production [41]. Some researchers have speculated that clearcutting may "mimic the natural situation of infrequent crown fires to which the scrub fauna is adapted" [31]. However, other researchers demonstrated that timber harvesting in Florida sand pine scrub had a negative effect or mixed results on herpetofaunal species richness and diversity compared with prescribed fire [60,128], and that the 2 treatments resulted in different herpetofaunal assemblages [66,128]. On the Ocala National Forest, Custer and Thorsen [41] found that stand-replacing prescribed fire could be used in sand pine scrub habitat to stimulate regeneration of sand pines in gopher tortoise habitats. For more information on this topic, see these reviews: [65,117].
Growing-season fires are often recommended for management of gopher tortoise habitats because plant responses to growing-season fires benefit gopher tortoise survival and recruitment much more than plant responses to fire during other seasons (see Indirect Fire Effects) [86,105]. However, because higher fuel loads in fire-excluded longleaf pine forests may allow stand-replacing fires [149] and make it difficult to control prescribed fire [43], alternative management strategies are often suggested for gopher tortoise habitats to avoid killing overstory trees [21,43,105,131]. Several researchers recommend that if too much fuel has accumulated to make summer prescribed fire practical, one or more consecutive winter fires "may provide a way to begin a fire program" [43]. Once fuels are reduced, prescribed fire may be conducted during the growing season [21,43,86,105,148,156]. Landers and Speakes [86] found that longleaf pine-scrub oak habitats winter-burned at 2- to 4-year intervals sustained high gopher tortoise densities (15.8/ha). Nonetheless, the authors recommended summer fires every 5 to 10 years for management of gopher tortoises in longleaf pine-scrub oak habitats to control hardwoods and increase canopy openness. For more information on this study, see Direct Fire Effects. Brockway and Lewis [20] acknowledged the importance of growing-season fires in longleaf pine flatwoods but reported that frequent, winter prescribed fires maintained high grass cover in this community. Frequent (every 2 years) dormant-season prescribed fires conducted over 17 years in longleaf pine flatwoods in Berrien County, Georgia, resulted in increased cover of some understory shrubs (shiny blueberry (Vaccinium myrsinites)), decreased cover in other shrubs (e.g., inkberry), and increased cover of graminoids (e.g., bluestem grasses, pineland threeawn, and Curtis' dropseed (Sporobolus curtissii)) compared with an unburned control site. However, dormant-season fire resulted in no difference in forb cover among sites, a result attributed to high residual cover of gallberry and other shrubs on fire-treated plots [20]. At the Camp Shelby Training Site in Mississippi, prescribed fire was implemented in previously fire-excluded longleaf pine forests at 4 sites during January and February 2002 to reduce fuel loads and dense shrub understories. Prescribed fire was conducted at these sites again during April 2003. One cycle of "dormant-and-growing-season prescribed fire" did not restore desired habitat conditions for gopher tortoises. Although understory shrub biomass was reduced in the short term, herbaceous forage and canopy openness did not increase. Reintroduction of fire in this 4-year study did not result in large shifts of habitat use by gopher tortoises from adjacent habitats to burned areas, although 3 gopher tortoises used burrows in postfire habitat. These authors suggested that repeated application of dormant- and/or growing-season prescribed fires may increase gopher tortoise use of these forests in the long term [159]. At the Escambia Experimental Forest in Alabama, winter burning at 3-year intervals for about 40 years led to a "significant and increasing hardwood component". The authors indicated a "need to resort to a temporary series of spring burns to bring the hardwoods back under control". Because of safety and logistical concerns, the authors suggested that "winter burning should be the operational norm" [57]. Several researchers suggested that, at sites where hardwoods are too large to be controlled by winter prescribed fire, selective cutting or herbicide treatments prior to winter prescribed fire may be effective [21,57]. Other researchers report that it is necessary to reintroduce summer fire to restore longleaf pine ecosystems [129].
In general, results from seasonal fire experiments indicate that effects of prescribed fire season on vegetation may be minor relative to the effects of long-term fire exclusion [19,83,105]. Ultimately, using prescribed fire to restore longleaf pine habitat will vary with local site conditions and degree of ecological succession [21]. For more information on this topic, see these reviews: [21,129]. For details on employing prescribed fire in longleaf pine ecosystems, see reviews by Landers and others [84] and Robbins and Myers [129].
Fire historically provided a mosaic of habitat types in a variety of seral stages and fuel conditions over the landscape [21,84,147], thus several researchers suggested that longleaf pine ecosystems be managed for a variety of seral stages [7,84]. Ashton and Ashton [7] suggested that prescribed fire conducted in a mosaic pattern over large areas may be beneficial for gopher tortoises. However, the effects of patch mosaic burning and different burning patterns (shape and size) on gopher tortoises have not been tested and remain largely unknown [124].Gopher tortoises occur in a wide variety of habitats (see Plant Communities), and the periodicity of fires is thought to have varied considerably among these habitats [9,118]. Under presettlement conditions, low-severity, summer surface fires occurred in longleaf pine forests of the southeastern Coastal Plain at intervals of 1 to 10 years, resulting in savannas with widely spaced overstories, minimal midstories of scattered hardwoods, and diverse herbaceous ground cover dominated by perennial bunchgrasses (i.e., threeawn or bluestem) [11,21,35,39,44,87,106,117,127,140]. These conditions provided the diverse herbaceous ground cover gopher tortoises needed for foraging and the open-canopy conditions needed for thermoregulation and nesting [149]. Because fire-return intervals were short in longleaf pine ecosystems, fuels did not accumulate to levels that would allow stand-replacing fires [149]. Among longleaf pine ecosystems, pine flatwoods are more mesic than pine-oak sandhills, so fuels accumulated at greater rates, and fires were more frequent (1-3 years) [21,87]. Dry conditions in pine-oak sandhills typically resulted in sparse fuel accumulations that could carry fire about every 2 to 4 years [83,84]. Without relatively frequent fires, dense understory and midstory oaks develop in pine-oak sandhills and pine flatwoods, and these communities may succeed to hardwood hammocks [2,9,20,44,65,86,131]. Development of dense understory and midstory oaks degrades habitat for gopher tortoises. Oak shade suppresses herbaceous ground cover; leachates from oak litter retard ground cover growth and reduce gopher tortoise forage; oak litter is often so dense that it may discourage burrow initiation; and oak leaf litter is relatively nonflammable and retards fire [105]. The scarcity of herbs, the relatively incombustible accumulation of oak litter and other fuels, and the expansion of understory shrubs and hardwoods preclude most fires from invading hardwood hammock communities. When fire does occur, it is nearly always stand replacing [21,58]. Depending upon site conditions, threeawn may persist in the understory for 20 to 40 years after fire exclusion; however, other herbaceous plants often only bloom the year following fire and decline during postfire years 2 and 3, becoming rare thereafter [35]. Conversely, fires that are too frequent or severe may eliminate longleaf pine recruitment [21,35,43,57,105,126] and may eventually transform longleaf pine forests into other plant communities where gopher tortoises are less abundant [58].
Sand pine scrub communities are adapted to and maintained by severe, infrequent fires and other disturbance, such as windthrow during storms [44,117]. Stand-replacing crown fires historically occurred on average every 20 to 40 years (range: 10-100 years) in sand pine scrub [31,39,41,44,132]. At less productive sites, where fuel accumulation was slow, fire-return intervals may have been longer [117]. Scrub communities lack fine-textured, flashy fuels and require high wind, low humidity, and low fuel moisture for fire to start and spread. When fire occurs in sand pine scrub, mature sand pines are typically killed and the aboveground vegetation consumed. However, because scrub vegetation is dominated by species that sprout (e.g., oaks) or seed (e.g., sand pine and rosemary) after fire, recovery is relatively rapid. Fire in sand pine scrub typically results in little change in species composition or richness, although dominance may shift to more rapidly growing species after fire [66,117,128,132,140]. Unlike pine-oak sandhills and pine flatwoods, a flush of annuals does not typically occur in sand pine scrub the year following fire, so herbaceous ground cover remains sparse [117]. However, fire creates a low, open habitat structure and large areas of exposed mineral soil beneficial to gopher tortoises for burrowing [66]. This is particularly beneficial if such areas are adjacent to other habitats with greater herbaceous forage [16,18]. Gap colonization and closure of open canopies in sand pine scrub is slow, thus suitable gopher tortoise habitat is maintained "for several years" after fire [66,117]. Over time, however, shrubs, lichens, and leaf litter increase as the canopy closes, and gopher tortoises become less abundant [66]. Sand pine is fire-adapted. If fire is excluded from sand pine scrub for long periods (>75 years), sand pines may eventually be eliminated, and sand pine scrub may succeed to xeric hardwood hammock. Frequent fire can also eliminate sand pine from the overstory [31,39,41,44,132,140].
Historically, fires in gopher tortoise habitats were ignited by lightning and indigenous peoples, primarily during the growing season but also during other times of year [39,87,117]. Lightning-caused fires occurred mostly from May through August; the number of fires and burned area peaked in May and June [129]. Many plant species in gopher tortoise habitats are adapted to growing-season fires but not necessarily to dormant-season fires [4,14,34,35,105]. Thus, changes in the seasonality of fires could change the structure and plant composition of gopher tortoise habitats [7,39,86]. Growing-season fires generally reduce hardwoods, maintain the threeawn-dominated herbaceous layer, promote flowering of annual herbs, facilitate seed production of grasses, and increase the abundance and species richness of understory vegetation more effectively than dormant-season fires [129]. Threeawn and associated species are generally denser and bloom more prolifically after a growing-season than a dormant-season fire [35]. On Lake Wales Ridge, Abrahamson [1] reported "vigorous flowering" by pineland threeawn, cutthroat grass (Panicum abscissum), and beardgrasses (Andropogon spp.) after May, June, and July fires; however, these species grew but showed little or no flowering after January fire. Because of weather and plant physiology, growing-season fires may lead to greater mortality of hardwoods [57,63,96,126], whereas dormant-season fires are more likely to encourage the growth of hardwood trees and a dense shrub midstory [39,86,96,106,113,129]. Because the moisture content of deciduous hardwoods is lowest in early spring, early growing-season fires are the most detrimental to their growth, whereas evergreens may be most affected by late growing-season fires [129].
The Fire Regime Table summarizes characteristics of FIRE REGIMES for vegetation communities in which gopher tortoise may occur. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES". Other information regarding FIRE REGIMES in gopher tortoise habitats is available in these sources: [59,17,125,183,134,164,195,208].
Diet: The gopher tortoise is an herbivore [54]. The bulk of its food is grasses (70-80% of total intake by volume). The young shoots, stems, and roots of herbaceous plants, and seasonally available forage from woody plants such as flowers, fruits, and leaves from vines, shrubs, and trees, comprise much of the remainder [7]. Gopher tortoises may consume dry grasses, pine needles, and broadleaf tree leaves (MacDonald 1986 cited in [39]). Lichens, mosses, fungi, insects, carrion, rocks, bones, charcoal, and feces of other animals may also be consumed; these foods typically do not make up a substantial portion of the gopher tortoise's diet [7] but may be an important resource, especially for conditioning females prior to and shortly after egg laying [59]. Gopher tortoises may obtain some water from food [59] but drink water when it is available [54].
Gopher tortoises eat many herbaceous plants. A review states that throughout the gopher tortoise's range, >1,100 plant species are known to serve as forage. Forage availability differs throughout the gopher tortoise's range and depends upon environmental conditions. An individual gopher tortoise may consume up to 160 to 400 plant species. Forty-five of the 83 families of plants consumed by gopher tortoise were identified in a review as providing "critical" forage for the gopher tortoise throughout its range [7]:
Important gopher tortoise forage [7] Common name Family Some genera used as forage Important most of the year Carrot Apiaceae Apium, Daucus, Eryngium, Hydrocotyle, Centella, Ptilimnium Palm Arecaceae Serenoa, Sabal Aster Asteraceae Ambrosia, Artemisia, Krigia, Lactuca, Hieracium, Helenium, Solidago, Bidens, Conyza, Aster, Gnaphalium, Liatris, Carphephorus, Chrysopsis, Coreopsis, Circium, Eupatorium, Emilia, Erechtites, Elephantopus, Helianthus, Heterotheca, Hieracium, Hypochaeris Midsorus fern Blechnaceae Belchnum, Woodwardia Cactus Cactaceae Opuntia, Cereus, Hylocereus Manosteen Clusiaceae Hypericum Sedge Cyperaceae Bulbostylis, Cyperus, Fimbristylis, Kyllinga, Rhynchospora, Scleria Fern Dennstaedtiaceae Pteridium Pea Fabaceae Acacia, Aeschynomene, Amphicarpaea, Apios, Arachis, Astragalus, Baptisia, Canavalia, Cassia, Centrosema, Chamaecrista, Chapmannia, Clitoria, Crotalaria, Dalea, Desmodium, Galactia, Indigofera, Lespedeza, Lupinus, Macroptilium, Medicago, Melilotus, Mimosa, Phaseolus, Pisum, Pueraria, Rhynchosia, Senna, Stylosanthes, Tephrosia, Trifolim, Vicia, Vigna, Zornia Grass Poaceae Amphicarpum, Andropogon, Axonopus, Bouteloua, Bromus, Cenchrus, Chloris, Cynodon, Dactylis, Digitaria, Dichanthelium, Echinochloa, Eragostis, Eremochloa, Eustachys, Muhlenbergia, Panicum, Paspalum, Poa, Schizachyrium, Setaria, Stenotaphrum, Sporobolus, Tridens Purselane Portulacaceae Portulaca Rose Rosaceae Agrimony, Amelanchier, Crataegus, Eriobotrya, Photinia, Potentilla, Prunus, Rubus Madder Rubiaceae Diodia, Ernodea, Galium, Hedyotis, Richardia, Spermacoce Secondary or seasonal importance Agave Agavaceae Polianthes, Nolina, Yucca, Sansevieria Amaranth Amaranthaceae Amaranthus, Iresine, Froelichia, Alternanthera, Blutaparon, Gomphrena Sumac Anacardiaceae Schinus, Rhus, Mangifera, Toxicodendron Custard apple Annonaceae Asimina, Annona Mustard Brassicaceae Lepidium, Brassica, Raphanus, Descurainia, Capsella, Draba, Polanisia, Warea Butterfly bush Buddlejaceae Polypremum Goosefoot Chenopodiaceae Atriplex, Chenopodium, Salicornia, Salsola Coco plum Chrysobalanaceae Chrysobalanus, Licania Spiderwort Commelinaceae Commelina, Cuthbertia, Murdannia, Tradescantia Gourd Cucurbitaceae Coccinia, Cucurbita, Melothria, Momordica Yam Dioscoreaceae Dioscorea Heath Ericaceae Vaccinium, Gaylussacia Spurge Euphorbiaceae Acalypha, Chamaesyce, Cnidoscolus, Croton, Euphorbia, Phyllanthus, Stillingia Beech Fagaceae Quercus Mallow Malavaceae Abutilon, Alcea, Hibiscus, Malva, Modiola, Sida Meadow beauty Melastomataceae Rhexia Mulberry Moraceae Morus Primrose Onagraceae Gaura, Oenothera, Ludwigia Woodsorrel Oxalidaceae Oxalis Passion flower Passifloraceae Passiflora Plantain Plantaginaceae Plantago Buckwheat Polygonaceae Antigonon, Coccoloba, Eriogonum, Polygonella, Polygonum, Rumex Figwort Scrophulariaceae Agalinis, Aureolaria, Buchnera, Gratiola, Linaria, Penstemon, Seymeria, Verbascum, Veronica Smilaz Smilacaceae Smilax Nightshade Solanaceae Solanum, Lycopersicon, Petunia, Physalis Vervain Verbenaceae Stachytarpheta, Lantana, Lippia, Phyla, Stylodon, Verbena, Callicarpa Grape Vitaceae Ampleopsis, Cissus, Parthenocissus, Vitis Important but of low biomass Acanthus Acanthaceae Ruellia, Dyschoriste, Elytraria, Stenandrium Borage Boraginaceae Heliotropium, Lithospermum, Myosotis, Onosmodium Morning glory Convolvulaceae Cuscuta, Dichondra, Stylisma, Convolvulus, Ipomoea, Evolvulus Turnerna Turneraceae Piriqueta Violet Violaceae ViolaGrasses and legumes appear particularly important in the gopher tortoise's diet ([59], MacDonald 1986 cited in [39]). In longleaf pine-slash pine/oak sandhills in Hillsborough County, Florida, 68 genera and 26 families of plants were identified in the scats of gopher tortoises of mixed ages and genders. The most frequent components in the diet were: Poaceae (particularly threeawn, 98% of scats), Pinaceae (particularly pine (Pinus sp.), 84% of scats), Fagaceae (79% of scats), Fabaceae (65% of scats), and Asteraceae (60% of scats). Gopher tortoises in this study did not exclude any common plant genus from their diet [98]. The most common genus ingested was Aristida, but when compared with availability, gopher tortoises randomly selected or avoided it. Dominant plants in the Poaceae and Asteraceae families and the Pityopsis genus were also randomly selected or avoided [98]. In young slash pine/bluestem and mature longleaf pine/bluestem habitats on the Desoto National Forest, gopher tortoises of unknown age and gender ate mostly grasses (Poaceae), particularly crabgrass (Digitaria sanguinalis) and panic grass (Panicum sp.) [94]. In slash pine-oak sandhills in Jasper County, South Carolina, gopher tortoises of mixed ages and genders commonly consumed threeawn, prickly-pear (Opuntia sp.), broom sedge (Andropogon sp.), and fennel (Eupatorium sp.) [158]. In longleaf pine-oak habitats at the Southlands Experiment Forest, plants in the Poaceae, Cyperaceae, and Asteraceae families were the principal foods of adult gopher tortoises throughout the active season (80% of fecal contents). Adult gopher tortoises ate pineland threeawn, particularly in the early spring and late fall when forbs such as Florida pusley (Richardia scabra) and poorjoe (Diodia teres) were least available. Legumes (e.g., sensitive brier (Schrankia microphylla), hoary pea (Tehrosia spp.), milk pea (Galactia spp.), and butterfly pea (Clioria mariana)) were used extensively, especially by juveniles [59]. Ashton and Ashton [7] speculated that a diverse diet appears critical for the overall health of gopher tortoises. These authors suggested that "moderately suitable" and "very suitable" gopher tortoise habitats were those that had at least 100 species of native plants, of which >50% were available to gopher tortoises as forage throughout the active season [7]. See Preferred Habitat for additional information.
Legumes appear particularly important in the diet of juveniles [10,59,81,103]. Compared to adults, young gopher tortoises tend to ingest more legumes and other forbs, fewer Poaceae, and fewer plants with thorns or other external defense mechanisms (e.g., Rubus and Cnidoscolus) [59,98]. In longleaf pine-oak habitats at the Southlands Experiment Forest, legumes were used extensively by juveniles [59]. In pine-oak/saw-palmetto/pineland threeawn sandhills in Hillsborough County, Florida, juvenile gopher tortoises avoided Aristida and other Poaceae and selected Liatris and Dyschoriste when compared with availability. Grasses were generally consumed during months when forbs were not readily available (October-December) [116]. Young gopher tortoises, particularly neonates, have higher metabolic rates, protein demands, and evaporative losses than adults [112], so they may ingest plants accordingly. However, nitrogen content of ingested genera was not correlated with the probability of a plant being ingested by juvenile gopher tortoises in pine-oak/saw-palmetto/pineland threeawn sandhills in Hillsborough County, Florida [116].
Threeawn may be seasonally or irregularly consumed [7]. Gopher tortoises frequently select threeawn right after fire, when it is one of the first grasses available. However, threeawn is apparently not selected as forage when legumes and other forbs are available. In longleaf pine-oak habitats at the Southlands Experiment Forest, consumption of threeawn was highest in the early spring and late fall when other species were unavailable [59]. In longleaf pine-slash pine/oak sandhills in Hillsborough County, Florida, young gopher tortoises did not ingest threeawn [98]. In slash pine-oak sandhills in Jasper County, South Carolina, threeawn comprised the greatest biomass available to gopher tortoises and also formed the largest portion of their diet [158], but no statistical comparison between use and availability was provided. Mushinsky and others [116] indicated that in a study of juvenile foraging, pineland threeawn was avoided when compared with its availability. Threeawn is an important component of gopher tortoise habitats (see FIRE REGIMES) [12,35], but threeawn presence alone may be a poor indicator of habitat suitability for gopher tortoises. In Florida, a population decline of 30% occurred when threeawn ground cover went from 40% to nearly 95% [7]. For an annotated list of 83 families, 376 genera, and 1,103 species of plants used as gopher tortoise forage, see Ashton and Ashton [7].
Foraging activity: Gopher tortoises select forage species seasonally and according to plant phenology [7,116]. Although gopher tortoises may consume plants in all growth stages, most forage is selected when it is actively growing. Gopher tortoises may consume dry grasses, pine needles, and broadleaf tree leaves from late fall through early spring, when most plants are senesced and other foods are unavailable [7]. Critical periods for gopher tortoises are early spring—a time of recovery from winter dormancy and when nutrients are needed for egg formation—and fall, when food plants are fibrous and less available and gopher tortoises are preparing for winter dormancy. Seasonal shifts in forage help maintain protein and mineral intake. As grasses became more fibrous in summer and fall than in spring, gopher tortoises tend to shift to higher-quality forage such as legumes and ripe fallen fruits [59].
Gopher tortoises are restricted to foraging near the ground. Adults can typically access forage items up to 12 inches (30 cm) above the ground; forage items <4 inches (10 cm) above the ground are typically accessible to hatchling and juvenile gopher tortoises [7,105]. Many species of groundcover plants grow out of reach of gopher tortoises as the growing season advances [105].
Gopher tortoises typically feed close to their burrows. In Alachua County, Florida, they usually fed <160 feet (50 m) from their burrows [10]. In longleaf pine-oak habitat at the Southlands Experiment Forest, mean feeding radius of adult gopher tortoises was 43 feet (13 m) from their burrows. Mean feeding radius of juvenile gopher tortoises was 25.6 feet (7.8 m) [103]. All feeding activity of adult female gopher tortoises in pine-oak sandhills and old fields at the Katharine Ordway Preserve occurred within 56 feet (17 m) of their burrows [135]. Mean feeding radius of juveniles in pine-oak/saw-palmetto/pineland threeawn sandhills in Hillsborough County, Florida, was 26.2 feet (8.0 m) [154]. However, gopher tortoises may travel long distances to forage. Some gopher tortoises at the Ashton Biological Preserve traveled 2 miles (3 km) to feed on legumes [7]. Ashton and Ashton [7] state that grasses, which make up a bulk of the gopher tortoise's diet, are normally near the gopher tortoise's burrow (i.e., within 328 feet (100 m) diameter of the burrow), whereas forbs, which make up much of the remainder of the gopher tortoise's diet and are often only seasonally available, are often much farther from the burrow (i.e., as far as 3,281 feet (1,000 m)). See Home range and movement for additional information on this topic.
Foraging sites: Mesic and xeric habitats and their ecotones, including all of the sites associated with burrows (see Burrow sites), serve as foraging sites [7]. Additional sites include wetlands [16], annually tilled fields, periodically mowed grassy areas [16,60], dense thickets [7], and firebreaks [16]. Because foraging sites may differ from burrow sites, "solely protecting gopher tortoise burrow habitat may not preserve adequate resources needed to support a population" [136]. For more information on this topic, see Plant Communities.
The gopher tortoise's home range is considered "well-defined" [7,10], and gopher tortoise movements are described as "extremely habitual" [54]. In general, older and larger individuals have larger home ranges than younger and smaller individuals [54]. Although females are often larger than males (see Reproduction and development), males tend to have larger home ranges [47,103], perhaps due to reproductive activity and dominance behaviors (see Social interactions). Adult female gopher tortoises typically travel less frequently and move shorter distances than adult males, and young gopher tortoises travel less frequently and move shorter distances than adults [10,55]. Home range of individual gopher tortoises tends to overlap greatly within and between sexes [42,103]. In coastal sand pine scrub at Savannas Preserve State Park, gopher tortoises overlapped home ranges but did not overlap core areas (i.e., areas of concentrated use) [42], suggesting that core areas may be defended from conspecifics.
There is considerable variation among individuals with respect to home range size and movements. Home range sizes range from less than 0.01 acre (0.004 ha) to more than 8 acres (3.2 ha). In longleaf pine-oak habitat at the Southlands Experiment Forest, home ranges of males were larger than those of females (P<0.01). Males had home ranges from 1.5 to 3.6 acres (0.6-1.44 ha), and females had home ranges from 0.1 to 0.2 acres (0.04-0.14 ha) [103]. In several habitats (i.e., mature slash pine plantation, grassy roadside strip, clearcut, and pasture) at the Lochloosa Wildlife Management Area, mean home range sizes were 2.17 acres (0.88 ha) for adult males, 0.77 acre (0.31 ha) for adult females, 0.12 acre (0.05 ha) for subadults, and 0.02 acre (0.01 ha) for juveniles [47]. In coastal sand pine scrub at Savannas Preserve State Park, male gopher tortoises had significantly larger home ranges than females (P<0.01); home ranges of male gopher tortoises ranged from 1.5 to 1.6 acres (0.62-0.64 ha), and home ranges of female gopher tortoises ranged from 0.8 to 0.9 acre (0.34-0.35 ha) [42]. In longleaf pine/pineland threeawn habitat at Ichauway, the average male home range was 2.7 acres (1.1 ha), and the average female home range was 1.0 acre (0.4 ha). Females in this study had significantly smaller home ranges than males (P<0.0001) [55]. At the Kennedy Space Center, home ranges of adult gopher tortoises encompassed 7 habitat types (i.e., oak scrub; oak palmetto scrub; palmetto/lyonia/wax-myrtle; mesic woody; swales; forest; and open, disturbed habitats). Males tended to have larger home ranges (x = 4.7 acres (1.9 ha)) than females (x =1.5 acres (0.6 ha)), though not significantly larger (P>0.05). Habitat use within gopher tortoises' home ranges was generally in proportion to the amounts of habitat available, except that gopher tortoises used swales and disturbed areas (e.g., grassy, mowed road shoulders, pastures, citrus groves, and firebreaks) less than expected based on availability [136]. Although gopher tortoise densities were low in swales and disturbed habitats, they were "heavily used by gopher tortoises for feeding" (Smith and Breininger personal observation cited in [136]). In pine-oak/saw-palmetto/pineland threeawn sandhills in Hillsborough County, Florida, the mean annual home range of juvenile gopher tortoises was 0.18 acre (0.072 ha) [152].
In general, home range sizes and distance of movements of gopher tortoises increase as forage quality and/or quantity decrease [7,10,45,103,113]. At the Katharine Ordway Preserve, home ranges of adult females ranged from 0.287 to 3.55 acres (0.116-1.435 ha) in pine-oak sandhills and 0.005 to 1.18 acres (0.002-0.479 ha) in old fields; differences between these habitats were attributed to more abundant and evenly distributed forage in old fields than sandhills [135]. In Florida, mean recapture radius (an estimate of home range size) of gopher tortoises in 3 habitats increased as the percent ground cover of herbaceous plants decreased (r²=0.83, P=0.012; [10,16]), an indication that gopher tortoises had to move farther to find food in habitats with fewer herbaceous plants [10]:
Mean herbaceous groundcover (%) and recapture radii (m) of gopher tortoises at 6 sites in Florida [10] Habitat Site Ground cover* Mean recapture radius** Longleaf pine-turkey oak sandhills A 92 17.8 B 43 23.6 Xeric live oak hammock A 68 18.2 B 31 36.3 Sand pine scrub A 13 53.5 B 3 65.4 *All plant species combined. **Sexes combined; n=312.Reproductive behavior and seasonal availability of preferred forage may influence gopher tortoise movements and home range sizes. Although differences in methodology among studies make it difficult to compare results, in general, movements of adult gopher tortoises peak in spring (April-June), when gopher tortoises are reproductively active [10,103]. A secondary peak in movements occurs in late summer and fall (September-October), when local food supplies are reduced [103]. In slash pine-oak sandhills in Jasper County, South Carolina, adult gopher tortoises foraged at the greatest distances from their burrows and spent proportionately more time foraging during spring (April and May) and fall (October) than other times of the year [158]. In Alachua County, Florida, movements of adult males and females peaked during spring (May and June). Movement distances of adult males during this time were greater than those of adult females, presumably because adult male gopher tortoises moved farther to access the activity ranges of several females [10]:
Average monthly movements (m) of gopher tortoises in Alachua County, Florida from 1963 to 1969 (n=383) [10] Carapace length (mm) Gender Jan-Feb Mar-Apr May-June Jul-Aug Sept-Oct Nov-Dec 100 Male 3.5 5.0 7.7 5.8 5.0 5.4 Female 4.3 4.7 6.5 5.9 4.7 5.6 101-200 Male 6.3 7.9 13.3 21.6 26.6 15.3 Female 9.2 8.8 15.2 18.9 27.1 17.8 201-300 Male 11.2 31.4 78.6 48.8 43.7 21.6 Female 13.1 22.5 61.5 44.2 51.8 38.1 >301 Male 10.6 41.3 69.3 46.7 45.5 32.3 Female 12.3 38.2 56.1 53.3 56.2 21.8Herbaceous ground cover, an important food source for gopher tortoises, is typically less abundant in late summer and fall; home range sizes and movements may increase during this time [10,103,154]. In longleaf pine-oak habitat at the Southlands Experiment Forest, mean feeding radius of adult gopher tortoises for summer and fall (after 15 June) was larger than that for spring (before 15 June; P<0.10). The authors suggested that some preferred forage, such as legumes (Fabaceae), may be depleted around gopher tortoise burrows by this time [103]. Juvenile gopher tortoises in sandhills in Florida spent significantly more time foraging, traveled farther, and ate more plants as the number of seasonally available plants increased [116] (P<0.02 for all variables), indicating that juveniles moved farther to access preferred seasonal forage. For more information on this topic, see Foraging activity.
Seasonal movements of juvenile gopher tortoises may or may not be as pronounced as that of adults [10,103,154]. In Alachua County, Florida, young gopher tortoises typically moved shorter distances than adults and exhibited no consistent seasonal pattern. Gopher tortoises <3.9 inches (10.0 cm) in carapace length moved relatively small distances throughout the year and exhibited a small peak during May and June, and movements of gopher tortoises 4.0 to 7.9 inches (10.1-20.0 cm) in carapace length peaked in September and October [10]. In pine-oak/saw-palmetto/pineland threeawn sandhills at the University of South Florida Ecological Research Area in Hillsborough County, Florida, home ranges of juvenile (1-4 years old) gopher tortoises were significantly larger in summer (June-September) than in other seasons (P<0.05), and 89% of long-distance movements (>200 feet (61 m)) by juveniles were made during this time [154].
Because environmental conditions influencing gopher tortoises may not remain constant over many seasons and years, the area required for an individual over its lifetime is likely considerably larger than the area required over a single year. In longleaf pine/turkey oak/pineland threeawn habitat at the Fort Stewart Army Reserve in southeastern Georgia, Mitchell [110] found a significant positive correlation between average monthly rainfall and average monthly movements of gopher tortoises (r²=0.350, P=0.01), perhaps because burrow flooding prompted increased movements. Douglas (1986 cited in [47]) reported home ranges of 10.4 acres (4.2 ha) for a male gopher tortoise observed occasionally over a 5-year period in south Florida slash pine-turkey oak habitat and 16.6 acres (6.3 ha) for a male gopher tortoise observed over a 6-year period in an old field. In longleaf pine/turkey oak/pineland threeawn habitat at the Fort Stewart Army Reserve, average home range of adult female gopher tortoises was 1.94 acres (0.79 ha) in 2002 and 3.02 acres (1.22 ha) in 2003. The multiyear home range (2002-2004) was larger (5.60 acres (1.86 ha)) [110].
Long-distance movement: Gopher tortoises typically travel short distances within their home ranges but may infrequently travel long distances [7]. In several habitats at the Lochloosa Wildlife Management Area, adult male gopher tortoises moved 10 to 1,555 feet (3-474 m) between recaptures, adult females moved 0 to 610 feet (0-186 m), subadults moved 20 to 2,441 feet (6-744 m), and juveniles moved 10 to 325 feet (3-99 m) [47]. In longleaf pine/pineland threeawn habitat at Ichauway, the longest distance between subsequent locations was 1,942 feet (592 m) and 2,093 feet (638 m) by a female and male gopher tortoise, respectively, although the average distance traveled by female gopher tortoises was 177.4 feet (54.0 m)/move and that of males was 279.5 feet (85.2 m)/move [55]. Exploratory (i.e., nondispersal) movements as far as 5 miles (8 km) were recorded at the Ashton Biological Preserve in Florida [7]. Because of their "considerable mobility" [112], gopher tortoises may respond quickly to changes in local environmental conditions [121]. Gopher tortoises "rapidly colonized" an abandoned orange grove adjacent to gopher tortoise habitat in Orange County, Florida [74]. On the Ocala National Forest, gopher tortoises immigrated to burned longleaf pine-turkey oak within postfire year 1 [121]. For additional information on this study, see Fire Management Considerations. Large movements may occur over suitable or "apparently unsuitable" habitats (Diemer personal communication cited in [39]). Suggested reasons for large movements were foraging for seasonally available food resources (e.g., fruits, flowers, and seeds), breeding activity of males, nesting forays of females, seasonal migrations to and from overwintering sites, and departure from unsuitable habitat due to extremely dry or wet conditions, physical disturbance of burrows, or plant succession [7,9,10,83].
Dispersal by gopher tortoises is largely unstudied, and information is mostly based upon anecdotal observations. Dispersal apparently occurs within all age classes, although adults appear to disperse at a "proportionately much higher rate" than hatchlings. Hatchlings may or may not disperse from their natal areas. If dispersal occurs, movements away from the natal area may not take place for several years after hatching, and movements may be slow. In northern Florida, "the entire process leading to dispersal of at least 2 neonates from their natal areas took several years" [10]. In longleaf pine-oak habitat at the Southlands Experiment Forest, juvenile gopher tortoises rarely dispersed more than 49 feet (15 m) from the nest during the first year of life [103]. When hatchlings disperse from their natal areas, movements away from the natal area appear random. Dispersal movements of adults are apparently "more directed" and farther than that of hatchlings. Dispersal of adults, particularly males, is most likely to occur during the beginning of the reproductive period [10]. Total distance traveled by 2 dispersing, adult male gopher tortoises in longleaf pine/pineland threeawn habitat at Ichauway was 3 and 4 miles (5 and 6 km) [55]. In southwestern Georgia, 5 adult males emigrated >0.6 mile (1 km) from their colonies [86]. In several habitats at the Lochloosa Wildlife Management Area, the longest movement (0.56 mile (0.74 km)) of 22 adult, subadult, and juvenile gopher tortoises was made by an emigrating subadult [47]. McRae and others [103] suggested that subadult male gopher tortoises were more likely to disperse or be forced to the periphery of breeding areas than other age and gender groups; however, Eubanks and others [55] found no evidence that dispersal movements were tied to competition among males for mating opportunities.
Barriers to movement: Physical features such as cliffs, fissures, caverns, and sink holes [7,10], human infrastructure (e.g., roads, urbanized areas, and railroad tracks) [7,10,42], water (e.g., major rivers, lakes, ponds, and deep marshes), wind-erosion features [7], coarse woody debris [25], and dense vegetation [94,105] may be barriers to gopher tortoise movements. In young slash pine plantations on the Desoto National Forest in southern Mississippi, unburned windrows and associated stands of dense deciduous woody plants were barriers to gopher tortoise movements (see Windrows) [94]. Means [105] suggested that especially dense groundcover vegetation may impede gopher tortoise movements. Gopher tortoises at the Southlands Experiment Forest modified foraging movements near roads. Foraging areas were typically elliptical areas centered around the burrow entrance, but when a gopher tortoise was located along a road edge its foraging area was typically linear [103], perhaps avoiding the road. Bryant and Boykin [25] speculated that on the Desoto National Forest following Hurricane Katrina in 2005, "the amount of timber blown down could have restricted gopher tortoise movements for foraging and reproduction".
Gopher tortoises reach their highest densities in fire-adapted habitats, such as pine-oak sandhills, pine flatwoods, and sand pine-oak scrub, indicating that fire in those habitats is likely to benefit gopher tortoises [9,44]. Without fire or under altered FIRE REGIMES, gopher tortoise numbers are typically reduced (see Succession). Fire favors growth and reproduction of herbaceous gopher tortoise forage by maintaining an open-canopy structure, reducing woody plants and litter, and exposing mineral soil [2,9,13,26,43,96,105,151]. In gopher tortoise habitats, species diversity in the groundlayer vegetation increases after fire and is greater on frequently burned than infrequently burned sites [86,91]. Legume species (see Diet) were abundant in longleaf pine/pineland threeawn habitat occupied by gopher tortoises at Ichauway, which had been winter-burned at 1- to 3-year intervals for about 70 years. At this site, legumes were present in all months of the year, but abundance peaked in June immediately following a March prescribed fire and declined thereafter [69]. Nutrient content of preferred forage species may increase after fire [26]. Fire consumes parts of plants that are less digestible for gopher tortoises and stimulates new, more accessible plant growth [7,39,43,103]. Fire may also benefit gopher tortoises by exposing mineral soil and reducing root density, thus facilitating burrowing and nesting [9,32,65,105].
Winter prescribed fire may aid in restoring pineland threeawn and forbs important as gopher tortoise forage on sites where fire has been excluded for long periods [4]. Several fire-dependent herbs often consumed by gopher tortoises (e.g., pineland threeawn, narrowleaf silkgrass (Pityopsis graminifolia), and shortleaf blazing star (Liatris tenuifolia)) "responded positively" to the conditions following a prescribed fire at the Archbold Biological Station by "sprouting, rapid vegetative growth, and abundant flowering and fruiting". The prescribed fire was conducted in February on a pine-oak sandhill site that had succeeded to dense scrub species including evergreen oaks (Chapman, myrtle, and sand live oaks) and palmettos (e.g., scrub and saw-palmettos). Prior to the prescribed fire, the site had not been burned for over 60 years, and only small remnant patches of slash pine, sand pine, turkey oak, and pineland threeawn were present. Approximately 85% of the ground surface was burned using a series of strip head fires 7 to 33 feet (2-10 m) wide. For shortleaf blazing star and narrowleaf silkgrass, measures of reproductive effort were higher on burned plots than unburned plots (P<0.01 for all variables). Pineland threeawn flowering was not observed in unburned plots or prefire plots, but flowering was common in postfire plots [4]. Additional information on the fire and its effects on herbaceous plants is available in Anderson and Menges [4].
Fire could reduce the diversity and/or availability of some gopher tortoise forage in the short term [114]. Abrahamson [1] reported responses of 5 habitats to 2 fires. A lightning-caused May fire reduced total vegetation cover in swales and gallberry-lyonia flatwoods on Lake Wales Ridge, Florida, to 0% cover. However, total vegetation cover had returned to 94% in swales and 95% in gallberry-lyonia flatwoods 232 days after the fire, and complete recovery to prefire levels occurred within 2 years. After a January prescribed fire, total vegetation cover in pine-oak/palmetto flatwoods recovered to prefire levels in 1 year, slash pine/pineland threeawn flatwoods recovered to prefire levels in 3 years, and slash pine/oak-scrub hickory (Carya floridana)/pineland threeawn-palmetto sandhills did not recover to prefire levels during the 5 year study period. The author noted a lack of change in plant species composition following fire in these habitats [1].
Some nonnative invasive plants that occur in gopher tortoise habitats may proliferate after fire [139]. Because nonnative invasive plants may threaten gopher tortoise habitats by displacing native species, disrupting nutrient and fire cycles, and altering plant succession [24,92], fire could degrade habitat for gopher tortoises by creating conditions favorable to invasive species. Since many native herbaceous groundcover plants are adapted to fire and help carry fire, sites with remnant native groundcover may burn more easily and recover more quickly after prescribed fire than sites where the ground cover has been substantially altered by mechanical site treatments, invasive species, or other alterations [21]. For additional information on the effects of fire on gopher tortoise forage, see Fire Management Considerations.
Since gopher tortoise densities are directly related to herbaceous biomass (see Population density), the effect of fire in gopher tortoise habitats depends largely on its effect on herbaceous ground cover, which varies with fire frequency, severity, and season [109]. During late summer and fall, gopher tortoises may be stressed because of limited forage, and gopher tortoises may move over large areas in search of food. Fire occurring during late summer and fall may reduce this already limited forage, subjecting gopher tortoises, particularly hatchlings, to starvation [39,103,105]. Conversely, fires occurring during summer—when herbaceous plants are still growing—may stimulate late-season growth in many plants and provide additional forage for gopher tortoises prior to winter dormancy [105]. Fires during transitions from spring to summer—when intervals between successive rainfalls are increasing and fires may be more intense—may result in flowering of many groundcover species, greater mortality of hardwoods, and more open canopies than fires at other times [126]. Summer fire may create an open vegetation structure, which Cox and others [39] suggested may make it easier for neonates hatching in subsequent months (August-October) to move about, initiate burrows, and find food. In longleaf pine-turkey oak sandhills on the Ocala National Forest, greater numbers of gopher tortoise burrows were recorded on summer-burned plots than on winter-burned plots (P=0.0001). The authors suggested that gopher tortoises may have immigrated to the summer-burned plots in postfire year 1 [121]. However, inference is limited in this study because prefire data on gopher tortoise burrow densities were not available, and no information regarding habitat differences leading to such differences were provided.
Status and threats: From the late 1800s to the late 1990s, the gopher tortoise's range contracted, and populations declined an estimated 80% [9]. Gopher tortoise population decline is attributed to habitat destruction, habitat degradation, and human predation. Habitat destruction affecting the gopher tortoise includes urbanization, phosphate strip-mining, sand extraction, road building, and dam construction. Conversion of longleaf pine forests to other habitats, fire exclusion from longleaf pine habitats, establishment and spread of invasive species, and increased predation have contributed to habitat degradation for the gopher tortoise. Collection of gopher tortoises for food and pets, vehicular mortality, removal as "pests" from fields with livestock or agricultural crops, and gassing during rattlesnake (Crotalus and Sistrurus) round-ups have also contributed to a reduction in gopher tortoise numbers [7,9,44,45,48,81,86,151,156].
Perhaps the single largest contributor to gopher tortoise population decline was the historical reduction in the extent and quality of longleaf pine ecosystems (reviewed by [13]). As of 1985, area of longleaf pine-dominated forests was reduced by approximately 86% [106]. Those forests that remained were often fragmented or of poor quality for gopher tortoises, largely as a result of forest management such as conversion of large areas to pine plantations and fire exclusion [9,21,58,151]. Habitat loss and degradation have fragmented many gopher tortoise habitats, resulting in small and discontinuous gopher tortoise populations in some areas (see General Distribution). Habitat fragmentation may limit the gopher tortoise's ability to immigrate into or emigrate away from isolated areas, thereby potentially restricting the expansion of colonies, limiting the establishment of new colonies, or reducing a colony's ability to replenish its numbers or diversify its gene pool [100]. Fragmentation may also increase gopher tortoise predation by humans, domestic dogs and cats, and urban-associated wildlife (e.g., northern raccoons), or force individual gopher tortoises into unsuitable habitats and onto roads [100,156]. Low reproductive rates, delayed maturation (see Reproduction and development), and high mortality (see Survival) may make it difficult for gopher tortoises to recover from population declines and habitat changes [39,44,59,81,85,93].
Ecological significance: Because gopher tortoises may increase local animal and plant diversity, the gopher tortoise has been characterized as a keystone species [52,67]. Gopher tortoises excavate burrows and build aprons; burrows may be large (see Burrow description) and last as long as 10 years following abandonment [68,71]. Burrow creation produces small gaps in the understory vegetation, which may increase habitat heterogeneity and promote plant species richness and diversity by exposing mineral soil favorable for germination of early-successional species [77,144]. Gopher tortoises may affect the flora around their burrows and the surrounding habitat by ingesting and subsequently dispersing seeds ([138], Boglioli and others. 2000, Birkhead 2001, cited in [12]). In pine-oak/saw-palmetto/pineland threeawn sandhills in Hillsborough County, Florida, gopher tortoise aprons had lower concentrations of some soil nutrients and organic matter, higher pH and light intensities, and greater daily temperature fluctuations than adjacent undisturbed areas. Temperature maxima during prescribed fires were significantly lower on aprons than in surrounding undisturbed vegetation at sites burned annually and at sites burned every 5 years (P≤0.05 for all variables), suggesting that gopher tortoise aprons "may function as cool-temperature refugia during fire for seeds, perennating organs, or established plants" [77].
Because gopher tortoise burrows provide habitat for other species, gopher tortoise presence may increase local animal diversity. Many other animals seek temporary shelter or live permanently in gopher tortoise burrows. Jackson [75] reported over 60 vertebrate and 300 invertebrate species found in gopher tortoise burrows. Some commensals, including beetles (Coleoptera), crickets (Orthoptera), and mites (Arachnida), have not been found in habitats other than active gopher tortoise burrows, where they feed on gopher tortoise feces (see [157] and [75] for annotated lists). Other commensals, such as the Florida mouse (Podomys floridana) and gopher frog (Rana capito), may utilize gopher tortoise burrows whether a gopher tortoise is present or not. Foxes, skunks, bobcats, coyotes, nine-banded armadillo, and Florida burrowing owls (Athene cunicularia floridana) may use abandoned gopher tortoise burrows to rear their young or as hibernation dens [7,10]. Several species associated with gopher tortoise burrows are listed as endangered, threatened, or species of special concern by the US Fish and Wildlife Service, including the gopher frog, eastern indigo snake, Florida pine snake, and Florida mouse [39]. Some researchers speculated that a decline in gopher tortoise populations could trigger declines in other animal species in the same ecosystem [120]. Several reviews covering this topic are available: [7,39,54].
Succession: Gopher tortoises tend to occur at high densities in midsuccessional stages of fire-maintained longleaf pine ecosystems, which have a "savanna-like" structure, early-successional stages of sand pine scrub, and ruderal habitats. Low gopher tortoise densities tend to occur in advanced successional stages such as hardwood hammocks with dense canopies (see Plant Communities) [9]. Habitats associated with the gopher tortoise are subject to frequent disturbance by fire, tropical storms, insects, and pathogens [21,87,126]. At the Kennedy Space Center, disturbed habitats had nearly twice as many gopher tortoises as 6 other habitats, partially because disturbed sites generally had less oak and shrub cover but higher nonthreeawn herbaceous cover [16]. Without disturbance, open habitats become more shaded as tree and shrub canopies close, and gopher tortoise forage becomes less available [9,31,58,144]. Lemon [91] recognized over 35 plant species found in longleaf pine forests that are abundant during the first few years following fire but decline after 8 years. Edmisten (1963 cited in [16]) found that herb frequency declined as canopy cover increased after fire in pine flatwoods in northern Florida. While threeawn declined at an even rate, several forbs declined earlier and more rapidly. In addition to reducing herbaceous forage cover, excessive shade may prevent gopher tortoises from reaching minimum thermal requirements for daily activities (see Daily activity) [115]. As shade increases and foraging, nesting, and basking sites decrease, gopher tortoises become less common [9]. Without frequent disturbance, plant succession may cause gopher tortoises to emigrate from an area within 3 to 8 years [6,9,45,86]. In Lake County, Florida, gopher tortoises declined 1,800% over 11 years as abandoned agricultural land succeeded to mature sand pine scrub. These authors provided the following account of this time period [9]:
"During the first year the flora of the habitat is predominantly composed of annuals; the specific composition varies considerably due to the importance of chance colonization. Though gopher tortoises occur in these pioneer communities, colonies are never formed, and population densities are generally very low. During the second and third years, dog fennels (Eupatorium capillifolium) gradually increase and tortoise population densities remain low; by the third year, broom sedges (a common food of gopher tortoise) become a conspicuous element. Population density increases and tortoise colonies become established from the 4th to the 10th years, and young trees of species commonly associated with disturbed situations (such as persimmon (Diospyros spp.), hawthorn (Crataegus), and chickasaw plum (Prunus angustifolia)) are abundant. Tortoise nests often become common for the first time, and populations usually prosper for several years. Populations will remain at high levels if the area is subjected to recurrent fire, pasturing, or any other factor that tends to reduce the growth and density of taller tree species in the succeeding years. Without such modification, the period after 11 years is one during which larger native trees begin to shade out and otherwise compete with ruderal species, and tortoise densities are generally reduced in accordance with the rate and patterns of shade production."
In Covington County, Alabama, Aresco and Guyer [6] found a relationship between level of permanent abandonment of burrows and increase in midstory and overstory canopy closure in slash pine plantations that were winter-burned every 3 to 4 years. In this study, active burrows were located in areas with the most open canopy, and abandoned burrows were associated with a dense midstory of young hardwoods (e.g., oaks, dogwoods, and gallberry). Burrows were abandoned at a rate of 22%/year over 5 years. Potential long-term effects of fire exclusion that may adversely affect the gopher tortoise include increased canopy closure due to the expansion of understory and midstory hardwoods, reduced cover and richness of herbaceous plant species used as forage, changes in composition of the dominant species from fire-adapted to less fire-tolerant species, and increased litter [20,62,79]. Changes in forest structure and buildup of litter may increase fuel loads and support a more homogeneous, "hotter" fire, which may have a detrimental effect on gopher tortoises [62,113]. For more information on this topic, see Fire Effects and Management.
Habitat management: Habitat management for the gopher tortoise is largely focused on reducing overstory trees and understory shrubs to increase the amount of light reaching the forest floor and on improving the quality and quantity of herbaceous forage [6,7,44,86,98,116,130,141,156]. Management to reduce canopy closure and woody understory vegetation in habitats associated with gopher tortoises include prescribed fire, tree harvest, mechanically treating understory shrubs, grazing, mowing, and herbicides [21]. Depending upon ecological conditions, a combination of treatments is sometimes recommended (e.g., [6,43,73]). Because fire provides many ecosystem services that other management methods may not, fire is frequently cited as being "more beneficial" to gopher tortoises than other methods [39]. For example, fire may release nutrients, scarify seeds for germination, reduce litter, and increase sunlight on the ground by removing groundlayer, understory, and overstory vegetation (see Indirect Fire Effects) [19,39]. However, because of concerns for safety and air quality, fire may be impractical in some areas [19,131], and mechanical methods may be used to keep habitat open and sustain plant species diversity [7,21]. Intensive mechanical site preparation and chemical treatments may be detrimental to gopher tortoises, and some researchers recommend that these techniques be avoided [43] or that lower-impact alternatives be selected [21,83,86].
Many undesirable effects of management activities on gopher tortoises and their habitats may be overcome by timing treatments so gopher tortoises are in their burrows and removal of seasonally important foods is avoided [82]. Depending on local and regional weather patterns, gopher tortoises may exhibit a unimodal or bimodal daily activity pattern (see Daily activity) [51,103,154]. In spring, gopher tortoises typically forage in midday and afternoon. At this time, gopher tortoises eat young growth from a diversity of species including grasses. In summer, gopher tortoises tend to bask and forage in early morning and in late evening, while staying in their burrows during the hottest part of the day. During summer, plants may be stressed due to dry, hot conditions and gopher tortoises may travel to low, moist areas to forage (see Foraging sites and Home range and movement). In fall, gopher tortoises often forage in midday and afternoon and stay in their burrows on cool days. At this time, gopher tortoises often forage upon ripe fallen fruits and legumes. In winter, gopher tortoises forage only at midday if the weather is sunny and warm, but during periods of cold weather gopher tortoises may stay in their burrows for several days or weeks. Gopher tortoise feed on legumes and cool-season herbaceous plants in winter [7]. Because gopher tortoises are relatively inactive, winter is often the "best" time for management activities [7]:
Best and worst times for management activities for the gopher tortoise based upon gopher tortoise's daily and annual activity patterns in areas south of the Suwannee River, Georgia [7] Activity Best Dates Best Time of Day Worst Dates Worst Time of Day Prescribed fire June-July or December-January any time September-October*, November-December, or February-April none Tree harvesting December-February any time March-November midday Mowing December-August before 10 AM in summer, before 10 AM and after 4 PM in winter, or on cool cloudy days September-November* after 10 AM in summer and between 10 AM and 4 PM in winter Mechanical site preparation (e.g., plowing and fireline cutting) December-February before 10 AM March-November 10 AM to 4 PM Plant surveys April-October any time November-March after dark Burrow surveys after fire**, September-November, or April-June 1 hr after sunrise to 1 hr before sunset December-March or July-August when visibility is low or during fog or rain *Hatching occurs during these months. **Burrows are often highly visible after fire.Because gopher tortoise diet and activity patterns differ throughout its range, these authors caution that timing of management activities is likely different throughout the species' range, and that management activities should take into account local site conditions and characteristics of local gopher tortoise populations. The authors recommended monitoring habitat and populations before and after treatments to determine whether management objectives, such as improving gopher tortoise forage, are met [7,16].
Fire: For information on the effects of fire on the gopher tortoise, see Fire Management Considerations.
Silviculture: A wide variety of silvicultural techniques may be compatible with maintaining or increasing gopher tortoise populations when applied at appropriate times and at intensities, scales, and frequencies that gopher tortoises can tolerate. Silvicultural practices favorable to gopher tortoises in longleaf pine forest include uneven-aged forest management involving selective thinning of overstory and midstory trees [7,9,43,83,85,93,94,156,158]. Uneven-aged management is often promoted for gopher tortoise habitats because it allows much of the forest structure to be retained between harvests [149]. Because longleaf pine regeneration is largely confined to canopy gaps (Wahlenberg 1946 cited in [21]), selective group thinning that creates canopy gaps may facilitate its regeneration [43,57,149]. Wilson and others [156] recommended natural regeneration of longleaf pine over planting because planting and associated soil disturbance may adversely impact the groundlayer vegetation and thereby negatively impact gopher tortoises. In longleaf pine forest, group selection may be compatible with gopher tortoise management by reducing canopy cover, thinning dense oaks in the understory, stimulating productivity of herbaceous forage, and creating suitable nesting and burrowing sites [7,9,44,72,83,86]. However, selective timber harvesting may be detrimental to gopher tortoises if tree and shrub cover exceeds 60% during the rotation [7,156], if concurrent management activities such as mechanical site preparation adversely impact grasses or other herbaceous species [156], or if harvesting equipment occludes gopher tortoise burrows (see Mechanical site preparation). In Florida, selective cutting of longleaf pine-oak habitat had varying effects on gopher tortoises. On average, selective cut longleaf pine-oak habitat at 5 sites in Florida showed an increase in density of 0.5 gopher tortoises/ha [9]:
Effect of management techniques on gopher tortoise density in 3 habitats in Florida [9] Habitat type and location Management technique Years between data collections* Change in gopher tortoises/ha Longleaf pine-oak Alachua County Clearcut 8 -3.63 Selective cut 5 0.79 Selective cut 5 2.57 Selective cut 5 -1.61 Columbia County Slash pine planting 3.5 -4.92 Selective cut 7 0.84 Levy County Selective cut 6 -0.27 Pasture 3.3 -1.75 Sand pine-scrub oak Lake County Clearcut 5 -0.77 Selective cut 5 -1.06 Xeric hammock Levy County Pasture 7.5 0.22 Pasture 6 -0.07 *Data from more than 8 years were excluded because of successional effects.A combination of even-aged management and prescribed fire is frequently recommended to maintain or improve gopher tortoise habitats (e.g., [6,43,73,107]). Farrar [57] suggested that since soil disturbance is "minimal compared to other methods", a group selection system including cyclical prescribed fire "as an integral component" may be compatible with gopher tortoise conservation. A study of the effect of stand thinning and summer burning in slash pine plantations on the Conecuh National Forest, Alabama, demonstrated that plant species richness (P=0.0041) and percent cover of groundlayer plants (<4 inches (10 cm) tall) available to gopher tortoises at active burrows increased on treated sites compared with untreated sites (P=0.02) [73]. In general, management for uneven-aged stands of longleaf pine regenerated naturally and maintained with fire is recommended over other management methods for maintaining gopher tortoise populations [105]. See Fire Management Considerations for additional information.
Silvicultural practices that appear less favorable to gopher tortoises in longleaf pine forest include clearcutting, particularly removal of longleaf pine and conversion to slash, sand, or loblolly pine plantations [9,83,85,93,94,158]. Pulliam (1987 cited in [73]) commented that the greatest threat to the gopher tortoise is Habitat management that favors a closed canopy of young pines, such as that produced in pine plantations. Clearcutting is likely most detrimental if it damages pine seedlings and herbaceous cover [149]. However, gopher tortoises may occupy pine plantations if the canopy is sufficiently open to allow growth of abundant herbs and provide nest sites in nearly full sunlight [59]. For a short time after clearcutting, a pine plantation may provide open and grassy areas suitable for gopher tortoises [9,72,156]. In a 2-year-old clearcut that was mechanically prepared and planted to slash pine at the Lochloosa Wildlife Management Area, gopher tortoises frequently excavated burrows in windrows created during clearcutting operations (see Windrows), and 1 female used the clearcut to nest [47]. Gopher tortoise populations may decline on pine plantations once the canopy closes and groundcover vegetation decreases. Unthinned pine plantations may develop a closed canopy 10 to 15 years after clearcutting [6,9]. Auffenberg (cited in Thomas 1978, cited in [94]) reported that gopher tortoise populations in longleaf pine areas in Florida declined 60% to 100% within 8 years of clearcutting and replanting to slash pine. Limited information from 2 sites in longleaf pine-oak and sand pine-scrub oak habitats in Florida suggested that clearcutting and planting slash pine reduced gopher tortoise densities by 0.8 to 4.9 gopher tortoises/ha [9]. Landers and Buckner [83] reported that gopher tortoises at the Southlands Experiment Forest were found at "moderately high" densities in seedling (3 years old) and pole stages (burned every 1-2 years) of slash pine plantations but at low densities in dense, unburned sapling-stage plantations. This pattern was attributed to the small amount of herbaceous ground cover in unburned sapling stage plantations. In slash pine-oak sandhills of Jasper County, South Carolina, "a few" gopher tortoises migrated from logged sites into adjacent unlogged sites. One year after logging, gopher tortoise populations were reduced, and 66% of juveniles and 32% of adults were not recaptured in the logged area. The author speculated that many of these individuals were probably killed within collapsed burrows or emigrated out of the study site [158]. In pine plantations, forest management recommendations to benefit gopher tortoises include using low-intensity site preparation [83,86] and selective tree harvesting so trees are widely spaced or there is a mosaic of treeless or sparsely treed openings [105]. Planting and retaining fire-tolerant species such as longleaf pine, maximizing edge where low-growing herbs may be more abundant [59], and conducting frequent (1- to 4-year intervals) prescribed fire are also recommended [45,83,86].
Although some pine plantations may support dense gopher tortoise populations [43,83,86], many researchers recommend that pine plantations be restored to longleaf pine forest to return historical fire, hydrologic, and nutrient dynamics to these communities [6,21,86]. Selective tree harvesting to retain longleaf pine and thin slash pine, loblolly pine, and other pines and hardwoods from the overstory has been suggested to help restore longleaf pine forest [6,43,156]. Clearcutting and planting longleaf pine has also been suggested as a means to convert loblolly or slash pine plantations to longleaf pine forest [43,149]. For more information on restoring longleaf pine forests, see Fire Management Considerations.
Mechanical site preparation: Mechanical site preparation techniques (e.g., roller chopping, anchor chaining, and web plowing) may reduce understory shrub cover and increase herbaceous ground cover in gopher tortoise habitats in the short term [2]. In slash pine/gallberry-wax-myrtle flatwoods in Florida, herbaceous diversity increased substantially after clearcutting, stump removal, burning, windrowing, discing, bedding, and slash pine planting. In posttreatment year 2, crown cover of previously dominant pines and shrubs was reduced from 151% to 12% of surface area; grasses (e.g., bluestem, threeawn, and panic grasses) decreased from 30% to 23% cover, rushes (e.g., Juncaceae) and sedges (Cyperaceae) increased from 3% to 6% cover, and forbs (e.g., aster (Aster spp.), buttonweed (Diodia spp.), dogfennel (Eupatorium spp.), deergrass (Rhexia spp.), and violet (Viola spp.)) increased from 3% to 21% cover [37]. At the Southlands Experiment Forest, herbaceous biomass and gopher tortoise densities on 16-year-old slash pine plantations that had been anchor chained and roller chopped were comparable to those on unaltered longleaf pine-oak habitat. In part, this was attributed to frequent prescribed fire and removal of pineland threeawn [86], which is sensitive to soil disturbance (review by [117]). For more information on this study, see Direct Fire Effects. Mechanical site preparation and removal of threeawn from gopher tortoise habitats may result in short-term increases in cover of some gopher tortoise forage species but also of "undesirable weedy colonizers" (review by [2]). In the long term, disturbance of the soil and removal of threeawn may adversely affect gopher tortoises by altering the fire regime. Fire-adapted groundcover vegetation such as threeawn in unaltered longleaf pine forests may help to carry surface fires, and removal of this native ground cover by mechanical means may impair fire spread [35,140]. Once threeawn and other fire-adapted groundcover plants are removed, restoring the ground cover and fire regime may be difficult, possibly requiring planting and seeding herbs in addition to prescribed fire [6,14,117,119].
Because mechanical site preparation involves soil disturbance, it may adversely affect gopher tortoise habitats by encouraging the establishment and spread of nonnative invasive species (see Invasive species) [2,35,149]. On Pebble Hill Plantation in southern Georgia and northern Florida, old fields that had succeeded to shortleaf pine (Pinus echinata) and loblolly pine had approximately 50% lower species richness and greater abundance of nonnative species than nearby, fire-maintained longleaf-shortleaf pine sandhills that had never been plowed [123]. Plant species composition was different between the habitats. Longleaf-shortleaf pine sandhills sites had high grass cover and relatively lower forb and woody species cover than old fields, which had minimal grass cover and high cover of large-statured forbs and woody plants. The longleaf-shortleaf pine sandhills habitat contained many herbaceous plants that were not typically present in old fields. Many of these plants are important in the gopher tortoise's diet [7], including Maryland golden aster (Chrysopsis mariana), Curtis's spurge (Euphorbia curtisii), summer spurge (E. discoidalis), hairawn muhley (Muhlenbergia capillaris), switchgrass (Panicum virgatum), and Virginia tephrosia (Tephrosia virginiana) (see Diet) [123].
Mechanical site preparation can be destructive to plants and soil and cause greater vegetation changes than prescribed fire. Prescribed fire in pine flatwoods reduces the cover of woody understory species and litter, and increases the frequency, biomass, and diversity of herbaceous species; however, the composition of woody species generally changes "only slightly", and woody species diversity is generally unaffected by prescribed fire. In contrast, mechanical site preparation tends to change woody understory species composition and relative abundance and may reduce woody species cover substantially. In addition, differential responses of herbs such as threeawn to mechanical site preparation change herb species composition and relative abundance (review by [2]). In sand pine scrub in Orange and Oceola counties, Florida, vegetation recovered more quickly on burned sites through sprouting and rapid release of nutrients into the soil (rather than slow release through decay) and stimulation of fire-adapted reproduction than vegetation on roller-chopped sites [128]. Conde and others [37] provided a review that compared the short-term (≤2 years after treatment) effects of prescribed fire and mechanical site preparation on plant community structure in slash pine flatwoods and found that mechanical site preparation had a "similar but more pronounced" effect:
A review of vegetation response to prescribed fire and mechanical site preparation in slash pine flatwoods [37] Plant community information Treatment February prescribed fire** February prescribed fire, clearcutting, double-chopping, and slash pine planting** Clearcutting, chopping, bedding, and slash pine planting*** Clearcutting, May prescribed fire, and very intensive site preparation* General description tree-dominated woody- to herb-dominated woody- to herb-dominated woody- to herb-dominated Woody plant response marginal reduction substantial (10 times) reduction substantial (10 times) reduction severe (100 times) reduction Herbaceous plant response marginal, uniform increase substantial, uniform increase substantial, variable increase highly variable increase Number of species marginal increase increase increase unchanged Species diversity marginal increase substantial increase substantial increase delayed increase *Very intensive site preparation included stump removal, windrowing, discing, bedding, and slash pine planting [37]. Prior to treatment, the site had not been burned in 40 years [38]. **Prior to treatment, the site had not been burned in "many" years [111]. ***Prior to treatment, the site had not been burned in 40 years [38].Breininger and others [16] recommended that, if mechanical site preparation is included in a Habitat management plan, it should retain enough groundcover vegetation to carry fire. Some researchers suggested that removal of some of the shrub component from a site by mechanical or other means is likely to enhance gopher tortoise habitats by reducing canopy cover and increasing light on the forest floor, but caution that because predation on juveniles may be greater in large open areas than in areas with shrub cover, retaining some shrub patches may be beneficial for juvenile gopher tortoises [16].
Gopher tortoises may be killed or maimed by heavy machinery associated with mechanical site preparation, and heavy machinery may occlude gopher tortoise burrows and kill gopher tortoises that are unable to dig themselves out [7,9,39,94,158]. Landers and Buckner [83] reported several occasions of direct mortality from heavy equipment. An adult gopher tortoise was decapitated by a disc pulled along a fireline, a hatchling gopher tortoise was killed by a disc in another area, 4 young (<4 years old) gopher tortoises were dug up and crushed by a road grader, and 6 nests laid in roads and along firelines were destroyed by heavy equipment. Heavy equipment frequently occludes gopher tortoise burrows, but its effect on resident gopher tortoises appears to vary by soil conditions and type of machinery used. The majority of studies indicate that gopher tortoises can dig out of collapsed burrows following site preparation on deep, sandy soils. The potential for gopher tortoises to be entrapped in clay soils is unknown but may potentially be greater [9,44,47,48,81,83]. In dry prairie habitat in Desota County, Florida, roller chopping reduced the canopy cover more than web plowing, but roller chopping occluded more burrows (72%) than web plowing (49%). None of these burrows were reopened following occlusion, and newly excavated burrows on nearby untreated sites indicated that at least some emigration occurred from treated sites to untreated sites [142]. After site preparation on the Southlands Experiment Forest, 7 of 11 gopher tortoises present before site preparation left the treated sites [83]. Occlusion of gopher tortoise burrows during mechanical site preparation may make fewer burrows available to gopher tortoises and cause individuals to relocate more frequently and create or use additional burrows ([48], Douglass 1990 cited in [46]). Although gopher tortoises may emigrate from mechanically treated sites, use of such sites soon after treatment has been documented. Diemer and Moler [48] found hatchling gopher tortoises on a site that had been recently roller chopped. Nests and burrows of young gopher tortoises, which are often shallow, may be particularly susceptible to damage by mechanical site preparation; however, such effects had not been well studied as of this writing (2009). Wilson and others [156] recommended that heavy machinery be excluded from a 25-foot (7.6 m) buffer around known burrows to avoid burrow occlusion and other disturbance to resident gopher tortoises.
Windrows: After harvesting pine stands, slash may be piled in windrows, which may be burned. Lohoefener and Lohmeier [94] suggested that unburned windrows may be barriers to gopher tortoise movements in young slash pine plantations on the Desoto National Forest. At this site, dense stands of deciduous woody plants (e.g., oaks, flowering dogwood (Cornus florida), persimmon, yaupon (Ilex vomitoria), grape, and greenbriar) growing out of unburned windrows inhibited gopher tortoise movements and divided areas occupied by gopher tortoises into "islands" [94]. However, unburned windrows were frequently burrow sites of juvenile gopher tortoises in a 2-year-old clearcut slash pine plantation at the Lochloosa Wildlife Management Area [47]. According to Landers and Buckner [83], windrow burning had no apparent adverse effect on gopher tortoises at the Southlands Experiment Station.
Grazing: As of this writing (2009), limited information was available on the effect of livestock grazing on gopher tortoises. Grazed pastures may support large gopher tortoise populations when adjacent to habitats with more herbaceous plant species diversity [9,47], suggesting that livestock grazing and gopher tortoises may be compatible. However, conversion of gopher tortoise habitat to pasture likely reduces diversity of gopher tortoise forage [7]. Anecdotal evidence suggests that cattle grazing in gopher tortoise habitats (e.g., xeric hammock, pine-oak sandhills, and sand pine-scrub oak) may maintain open canopies and encourage forage species for gopher tortoises, as long as these habitats are not overgrazed [7,9,84]. Historically, gopher tortoises were probably the primary grazers in upland xeric habitats [81]. Because it is a grazer, the gopher tortoise may potentially compete with other grazers for food. Livestock grazing may kill pine seedlings and prevent the natural regeneration of pine in longleaf pine-turkey oak sandhills habitat and indirectly affect gopher tortoises by altering the successional trajectory of the habitat [74,84]. Livestock trampling may occlude gopher tortoise burrows [47], consequently killing resident gopher tortoises if they become entombed.
Mowing: Limited information on the effect of mowing on gopher tortoises was available as of this writing (2009). Mowed areas are frequently used by gopher tortoises (see Plant Communities). Mowing in gopher tortoise habitats may reduce shrub cover and maintain herbaceous plants. It removes less digestible parts of plants and stimulates new, more digestible and accessible growth [7]. Means [105] suggested that mowing can be used as "a substitute for fire, or in combination with it, especially in the early stages of reclaiming overgrown gopher tortoise habitat". Ashton and Ashton [7] suggested that mowing at least once every 2 years, at a time when gopher tortoises are least active, may benefit the gopher tortoise. However, Means and Grow [106] suggested that mowing is not an adequate substitute for fire because unlike fire mowing "does not stimulate the flowering response of groundcover grasses and forbs" and "indiscriminately culls young trees and plants".
Herbicides: Herbicides are frequently used in gopher tortoise habitats to reduce hardwoods and thus increase growth of herbaceous forage for gopher tortoises [14,23], although the effects of herbicides on gopher tortoises themselves are not known.
Herbicides are often viewed as an attractive alternative to prescribed fire to reduce understory hardwoods, particularly due to concerns over smoke management, air quality, and litigation [131]. Some researchers suggest that herbicides may offer potential advantages over prescribed fire, including increased selectivity and decreased risk of off-site damage (Hunter 1990 cited in [131]). However, Brennan and others [19] argue that herbicides cannot duplicate the multiple ecosystem benefits provided by fire. Herbicides may reduce understory vegetation, but unlike herbicides, fire may release nutrients, scarify seeds for germination, reduce understory litter, increase sunlight on the ground by reducing understory, midstory, and occasionally overstory layers, and encourage fire-tolerant plants [19,21]. Several researchers recommend herbicides in conjunction with fire [19,23] or to facilitate the eventual use of prescribed fire [21,43] for managing gopher tortoise habitats. DeBerry and Pashley [43] suggest that herbicides may be particularly useful where hardwood and shrub encroachment is excessive or where a site has been degraded by invasive species, which may proliferate after fire. Where chemical treatments are used to selectively reduce undesirable plants, Wilson and others [156] recommended that soil disturbance, destruction of groundlayer vegetation, and nontarget effects of herbicides be minimized.
The short- and long-term effects of herbicide use on gopher tortoises were unknown as of this writing (2009), so herbicides should be used cautiously in gopher tortoise habitats [131]. In loblolly pine sandhills habitat with a diverse hardwood understory (e.g., oaks, black tupelo (Nyssa sylvatica), sweetgum, sassafras (Sassafras albidum), tree sparkleberry (Vaccinium arboreum), hackberry (Celtis occidentalis), wax-myrtle, and winged sumac (Rhus copallina)) in Marion County, Georgia, gopher tortoises continued to use an area after herbicide treatment [23]. However, herbicides were suspected of killing gopher tortoises in at least one instance (Dobie personal communication cited in [44]).
Other
Invasive species: Nonnative invasive plants may threaten gopher tortoise habitats by displacing native species, disrupting nutrient and fire cycles, and altering plant succession [24,92]. For example, cogon grass is considered a threat to gopher tortoises because it crowds out native plants and increases fire severity by increasing fuel loads [43,92] (see the FEIS review of cogon grass) . Nonnative invasive plants, such as kudzu (Pueraria montana var. lobata), air yam (Dioscorea bulbifera), and morning glory (Ipomoea spp.), may reduce the availability of native forage species and threaten long-term gopher tortoise population viability by reducing diversity of grasses and other herbaceous species. Brazilian pepper (Schinus terebinthifolius) and melaleuca (Melaleuca quinquenervia) appear particularly problematic in gopher tortoise habitats because they "often out-compete local forage species" or "shade out forage habitat". However, a review states that "managers should carefully weigh the goals for native species restoration with the need for sufficient quality forage for gopher tortoises". Some nonnative pasture grasses, such as bahia grass, centipede grass (Eremochloa ophiuroides), and St Augustine grass (Stenotaphrum secundatum), are "excellent" forage for gopher tortoises and may support high gopher tortoise densities. Kudzu, air yam, and morning glory may provide "a large supply of biomass" to gopher tortoises and are "fairly nutritious". Thus, removal of some nonnative plants may reduce the diversity and quantity of forage species, which may be detrimental to some gopher tortoise populations [7]. For more information on this topic, see Ashton and Ashton [7].
Relocation: When implemented appropriately, relocating gopher tortoises may augment populations and mitigate negative impacts of development, fragmentation, or other disturbances [7,54,95,156]. Consideration of the social structure of the resident population and the movements of relocated individuals may increase the likelihood of success [7]. Relocation of gopher tortoises to areas where they have been eradicated (i.e., rehabilitated forest and mine lands or areas where they have been eradicated due to fire exclusion) has had mixed results, and in many cases relocated gopher tortoises abandon sites to which they have been relocated [27]. Other considerations when relocating gopher tortoises include disease transmission and the genetic relationships of the relocated and resident gopher tortoises [7]. For more information on gopher tortoise relocation, see these reviews: [7,29,156].
Predator management: Because predation pressure on gopher tortoise populations may be substantial (see Survival), several researchers have suggested that "any management plan to sustain gopher tortoise populations must include serious predator control" [7]. Recommended management practices include nest protection and predator-proof enclosures for hatchlings [158], control of nest predators through hunting and trapping [81,135], and prescribed fire [76]. Establishment of preserves, protection of gopher tortoises from overharvest, and public education are suggested to reduce human predation of gopher tortoises [44,81].Gopher tortoise densities may range widely among habitats but are typically highest in ruderal habitats and fire-adapted plant associations such as longleaf pine-oak sandhills, pine flatwoods, and sand pine-scrub (see Plant Communities) [9,44]. In general, gopher tortoise densities are positively related to herbaceous ground cover [18,28,44,77,86]. Throughout Florida, gopher tortoise densities in longleaf pine-turkey oak sandhills, xeric live oak hammocks, and sand pine scrub habitats increased as the percent cover of herbs increased (r²=0.61, P=0.005; [10,16]). In a variety of habitats on the mainland and on islands in Florida, gopher tortoise densities increased with increasing herbaceous ground cover (r=0.461) [115]. At the Kennedy Space Center, gopher tortoise density was highest in disturbed habitat and similar among scrub and slash pine habitats; herbaceous ground cover (excluding threeawn) was greater and shrub cover was less in disturbed than in slash pine and scrub habitats [16]:
Mean (SD) gopher tortoise densities in spring and fall in 7 habitats at the Kennedy Space Center in Florida [16] Habitat Disturbed* Palmetto scrub Scrub Slash pine/Seasonal shifts in habitat may occur in gopher tortoise populations. At the Kennedy Space Center, shifts may have occurred between fall and spring in some habitats (e.g., disturbed, palmetto-scrub, and scrub) but not in others (e.g., oak scrub, slash pine-oak, and slash pine-palmetto) [16]. In longleaf pine-oak habitat at the Southlands Experiment Forest, gopher tortoises moved from burrows in xeric sites in spring to burrows in mesic sites beginning in late summer. Greater availability of preferred foods by late summer in the mesic sites or a preference for moist burrows may have explained shifts in habitat use in this study [103]. In coastal scrub and slash pine flatwoods at the Kennedy Space Center, Breininger and others [16] found that cover of all herbaceous species (r= -0.18, P=0.07) and herbaceous species excluding threeawn (r= -0.26, P<0.01) was greater on poorly drained soils than on well-drained soils. These authors suggested well-drained soils and sunlit areas may be particularly important for gopher tortoise reproduction in spring, and poorly drained areas may be particularly important in fall because poorly drained sites have comparatively more available forage [16].
Because herbaceous ground cover is often negatively correlated with canopy cover and shrub cover, gopher tortoise densities tend to increase as tree and shrub cover decrease [9,16,28]. Increased canopy closure and litter buildup associated with fire exclusion can reduce herbaceous forage production and gopher tortoise numbers. For more information on this topic, see Succession.
Some locations may exhibit elevated or reduced gopher tortoise densities due to factors not related to habitat. High population densities may signal a stressed population rather than a healthy population, particularly if high densities are the result of gopher tortoises being confined [115,156]. Some of the highest reported densities are associated with real or effective "habitat islands". An isolated gopher tortoise population on Cape Sable in Everglades National Park, Florida, had a density of 11.3 gopher tortoises/ha. This population was located in xeric coastal prairie grassland with button sage (Lantana involucrata), crimson bluestem (Schizachyrium semiberbe), broomsedge bluestem (Andropogon virginicus), alena (Boerhavia repens), coconut palm (Cocos nucifera), cabbage palm (Sabal palmetto), and agave (Agave sp.). Presence of small burrows suggested that population recruitment was occurring [80]. An island population on the Egmont Key National Wildlife Refuge had 12.4 gopher tortoises/ha [115]. Comparisons of gopher tortoise populations on true islands with populations on the mainland indicated that gopher tortoises on islands may be forced to live in suboptimal conditions. Both island and mainland gopher tortoise populations showed a positive relationship between the number of burrows and the area of the habitat. On the mainland, gopher tortoise burrow density decreased as area increased. 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. However, none of these relations could be demonstrated for gopher tortoises on islands. These findings suggested that gopher tortoises had a greater selection of habitats on the mainland than on islands [115]. A study of 51 gopher tortoise populations throughout Florida found that burrow abundance was negatively correlated with the area of available habitat (r= -0.46, P<0.01), possibly because gopher tortoises were concentrated in the only remaining suitable habitat [102]. The loss of preferred habitats may have increased gopher tortoise densities in habitats where gopher tortoises were previously less common [7]. In 1982, Auffenberg and Franz [9] indicated that gopher tortoises were not common in maintained pastures, but more recent studies (e.g., [159]) found that gopher tortoises are more commonly found in pastures and ruderal habitats as other available habitats are being lost or degraded [7]. Conversely, low population densities might not be indicative of less suitable habitat. Because of low recruitment, gopher tortoise densities may remain low for long time periods even if the cause of the initial decline (e.g., high rates of human predation) was removed. Measures of reproductive success and survival are important indicators of habitat suitability [146] and are frequently lacking in research addressing gopher tortoise habitat and density (e.g., [18]).
Differences in methodology make comparisons among population density studies difficult. Some studies have inferred gopher tortoise population densities from gopher tortoise burrow densities using a correction factor (e.g., [9,16,17,27,28,80,83,115,121]). Other studies have used mathematical relationships between the widths of burrow mouths and the sizes of gopher tortoises occupying them to construct age class distributions of gopher tortoise populations (e.g., [3,18,50,101,102,121,135,137,155]). Because of burrow use patterns—for example, use of several burrows by 1 individual and cooccupancy of a burrow by >1 individual—and the difficulty of detecting burrows of young gopher tortoises, some researchers contend that burrow densities or their dimensions are not likely to produce accurate estimates of gopher tortoise population density and structure [7,28,156]. In addition, the relationship between burrow density and actual gopher tortoise population density often varies with geographic location, predation pressure, habitat, season, and year [16,28,29,39,72]. For information on different methodologies used to capture gopher tortoises and determine burrow density and use, see the following reviews: [7,28].
Because gopher tortoise populations were reduced 80% between the late 1800s and late 1900s [9], an assessment of historical habitats, plant associations, and environmental conditions preferred by gopher tortoises is difficult. Current and historical human land-use practices have altered habitat throughout the gopher tortoise's range (see Status and threats), and "the habitats occupied by the gopher tortoise since human expansion within its range are not necessarily the 'preferred' ones but in many cases the only ones remaining that meet the gopher tortoise's needs" for survival [7].
Gopher tortoises are associated with a wide range of habitats within their range (see Plant Communities). Reviews state that within those habitats, gopher tortoises are consistently associated with well-drained, sandy soils that are suitable for burrowing and have deep (>2 feet (0.5 m)) groundwater tables (see Burrows), an open canopy (20-30% canopy closure) (see Cover Requirements), and an abundance of diverse herbaceous forage (see Diet). An open canopy provides sunlight necessary for high production of herbaceous forage and open, sunny sites required for nesting and basking [7,39]. Based on these associations, a review characterized "marginal", "moderately suitable", and "very suitable" gopher tortoise habitat throughout its range as follows [7]:
Characteristics of marginal, moderately suitable, and very suitable gopher tortoise habitat [7] Marginal Moderately suitable Very suitable Habitat examples Scrub, coastal strands, rocky habitats Ecotonal areas, drying marshlands, live oak savannahs, open mesic hardwoods Sandhills, nonflooded flatwoods, open treed savannahs, old pastures Soils very dry, sandy or rocky with thin soils seasonally dry to moderately wet moderately dry to very briefly seasonally wet Number of plant species in 1 season 30-100+ 130-170+ 75-200+ Number of plant species in 4 seasons 10-210+ 170-375+ 150-400+ Canopy cover (%) <60 <60 <60 Herbaceous ground cover (%) 20-70 50-80 50-100 Preferred forage species (%)* 0-65 45-90 60-95 Plant species diversity** low moderate high Forage species frequency of occurrence*** low moderate to high high Seed source security**** low moderate to high high Carrying capacityBody size and age at first reproduction appear to vary by geographic location and local conditions [156]. Sexual maturity may be reached at carapace lengths of 7.1 to 15.2 inches (18.0-38.7 cm) (about 10-21 years old) for female gopher tortoises and 7.0 to 11.8 inches (17.7-30.0 cm) (about 9-18 years old) for male gopher tortoises [7,54].
Gopher tortoise eggs take approximately 60 days to develop in the uterus. Female gopher tortoises produce 1 clutch annually, although a given female may not produce a clutch every year. The number of eggs/clutch varies geographically [7]. Heavy rainfall during late summer and early fall (when follicular development begins in the female gopher tortoise) partially explained a significant decline in reproduction and clutch size in the subsequent year in a gopher tortoise population at the Fort Stewart Army Reserve [110]. Gopher tortoise clutches typically contain 5 to 8 eggs (range: 1-25 eggs). Clutch size is correlated to female carapace length, with larger females having larger clutches (r=0.346, P<0.05, [135]; r=0.68, P<0.01, [85]). The typical hatching time is 80 to 100 days. Eggs may not hatch together, and neonates may not emerge together. The entire period from hatching to emergence may occur over 1 to 20 days. The number of neonates surviving upon hatching and emergence varies with location (see Survival). Gopher tortoises do not provide parental care [7].
Temperature-dependent sex determination occurs in the gopher tortoise. Neonates are 1.3 to 2.2 inches (3.2-5.5 cm) long at hatching. The yolk sac is absorbed in 1 to 3 days, and neonates typically do not forage for 48 hours after final absorption of the yolk sac. A neonate is referred to as a hatchling once the yolk sac is absorbed and it begins to forage, typically 2 days to 2 weeks after hatching. Neonates, hatchlings, and juveniles have soft shells, whereas subadults and adults have hard shells. Differentiation between age classes may also be determined by an individual gopher tortoise's behavior and its carapace size, shape, and coloration. Sexual differentiation, using external characteristics such as concave plastrons (i.e., lower shell) of males, begins to become apparent in subadults and is distinctive in adults; in addition, adults demonstrate sexual behaviors such as courtship, mating, and territorial defense. Nomenclature for age classes is frequently inconsistent among studies, making comparisons difficult [7]. This review uses the nomenclature presented in studies and makes no effort to reconcile any potential inconsistencies. See Ashton and Ashton [7] for more information on this topic.
Gopher tortoises are typically solitary [7] but live in loose aggregations of spatially clustered individuals with overlapping home ranges [103]. These groups are often referred to as "colonies". A colony may include >50 individuals [9]. Researchers further subdivided gopher tortoise colonies into subgroups, called pods, of highly aggregated gopher tortoises and their burrows. Interactions among individuals within a pod are presumably greater than those among pods, and interactions among pods within the same colony are presumably greater than those between colonies [7].
A dominance hierarchy may occur in gopher tortoise populations [54], and outcome of social interactions and distribution (i.e., home range, movement patterns, and burrow locations) of gopher tortoises may be based in part upon body size and gender ([10,42,103], Berry 1986 cited in [27], Douglass 1976 cited in [51]). Gopher tortoises may defend their burrows and feeding areas from other tortoises, particularly during the breeding season [7]. Territorial defense involves using aggressive and defensive postures, including combative charging and ramming [42,47]. Male movements and burrow preferences are mostly determined by reproductive and dominance behaviors. Adult males are often more aggressive, active, and wide ranging than females or younger age classes (e.g., juveniles and subadults) ([55], Berry 1986 cited in [27]). In coastal sand pine scrub at Savannas Preserve State Park in St Lucie County, Florida, male gopher tortoises spent significantly more time walking (P<0.001) and in social interactions (P<0.001) than females [42]. In longleaf pine-oak habitat at the Southlands Experiment Forest in Decatur County, Georgia, large (i.e., greater than the average carapace (i.e., upper shell) length) males defended burrow sites near adult females throughout the spring breeding season, apparently excluding small, subordinate males from breeding by preventing access to adult females [103]. At the Lochloosa Wildlife Management Area in Alachua County, Florida, a burrow occupied by a juvenile gopher tortoise was usurped by an adult male [47]. However, some studies found a relative lack of any social hierarchy influencing social interactions and distribution [13,27]. In slash pine-oak sandhills of Jasper County, South Carolina, burrow location was more heavily influenced by food supply and other habitat conditions than social interactions [158]. McRae and others [103] suggested that the formation of social hierarchies in the gopher tortoise population at the Southlands Experiment Forest may have been induced by increased density, pronounced social activities (e.g., courtship and aggressive interactions), and minimal dispersal during the spring breeding season.
Predators: According to reviews, predators of gopher tortoise eggs, neonates, hatchlings, and juveniles are northern raccoon (Procyon lotor), common gray fox (Urocyon cinereoargenteus), Virginia opossum (Didelphis virginiana), striped skunk (Mephitis mephitis), spotted skunk (Spilogale putorius), domestic dog (Canis familiaris), domestic cat (Felis catus), bobcat (Lynx rufus), coyote (Canis latrans), wild boar (Sus scrofa), nine-banded armadillo (Dasypus novemcinctus), snakes (e.g., eastern diamond-backed rattlesnake (Crotalus adamanteus), eastern indigo snake (Drymarchon couperi), coachwhip (Masticophis flagellum), racer (Coluber constrictor), common kingsnake (Lampropeltis getulus), and Florida cottonmouth (Agkistrodon piscivorus conanti)), native fire ants (Conomyrma spp.), and nonnative fire ants (Solenopsis spp.). Red-tailed hawks (Buteo jamaicensis), red-shouldered hawks (B. lineatus), bald eagles (Haliaeetus leucocephalus), American crows (Corvus brachyrhynchos), and blue jays (Cyanocitta cristata) also prey upon hatchling and juvenile gopher tortoises. Gopher tortoises have also been found in the scat of the Florida black bear (Ursus americanus floridanus) [99].
Larger gopher tortoises have few predators except humans, but subadults and adults may occasionally be killed by domestic dogs, domestic cats, coyotes, bobcats, wild boars, northern raccoons, hawks, and eagles. Nine-banded armadillos may cause indirect mortality of gopher tortoises by entombing them during excavation of burrows for their use as hibernation dens [10]. For additional information, see Survival.
Humans: Humans are the leading killer of adult gopher tortoises [7,54]. Gopher tortoises may be sold in the pet trade, killed on roads by vehicles, or slaughtered for food. Taylor [143] has made an extensive study of human predation on gopher tortoises in north-central Florida. For additional information, see Status and threats.
Parasites and diseases: Gopher tortoises of all ages may have ticks (e.g., Amblymma spp. and Ornithodorus turicata), botflies (Cistudinomya cistudinis), and other parasites, which may be debilitating or lead to the death of the individual. Stressors, such as extremes of temperature and lack of moisture, may make gopher tortoises susceptible to disease. A review of infectious diseases and pathogens of gopher tortoises, including upper respiratory tract disease, herpes virus, and iridovirus, is provided in Ashton and Ashton [7].
Gopher tortoise survival rates vary by age class. Survival from the egg through the juvenile stage is low, largely because these age classes are extremely vulnerable to predation [7]. Low mean survival (5.8%) between the time of egg laying and 1 year of age was attributed to high predation rates in ruderal and longleaf pine-turkey oak habitats in northern peninsular Florida [3]. Auffenberg and Iverson [10] reported that "several" colonies in Alachua County, Florida, produced no young for as long as 7 years due to high predation of eggs. In longleaf pine-oak habitat at the Southlands Experiment Forest, 89% of nests were depredated within a few weeks after laying [85]. Based on information from Alford [3], the authors estimated that a female gopher tortoise in that population would produce a successful clutch (about 6 individuals) once every 10 years [85]. In slash pine-oak sandhills in Jasper County, South Carolina, 74% of eggs were destroyed by predators; 92% of these were destroyed within 2 weeks of laying [158]. Predation rates appear high regardless of whether nests are close to or remote from burrows [10,30,81,83,100,135]. For more information on this topic, see Nests.
If nests are not destroyed by predators, hatching success may be high. In longleaf pine-oak habitat at the Southlands Experiment Forest, 86% of eggs hatched in nests protected from predation [85]. In Duval County, Florida, hatching success of protected eggs was 81% [30]. In pine-oak sandhills and old fields at the Katharine Ordway Preserve, 67% to 97% of eggs at protected nests hatched [135]. Thirteen eggs excavated from Alachua County, Florida, had a 92% hatch rate when incubated in the laboratory [5].
Neonate, hatchling, and juvenile gopher tortoises are vulnerable to predation because they are soft-shelled, small, and rely on protection of their burrows for safety [152]. Gopher tortoises are particularly vulnerable during their first few days and weeks of life after emergence from the nest [10]. At Camp Shelby Training Site in southern Mississippi, 65% of hatchlings were killed within 30 days of hatching [53]. In slash pine-oak sandhills in Jasper County, South Carolina, the predation rate on hatchlings during the first year of life was 70% [158]. Juvenile gopher tortoises may be particularly susceptible to predation when at their burrows to thermoregulate during cool months of the year. In pine-oak/saw-palmetto/pineland threeawn sandhills in Hillsborough County, Florida, predation of juvenile gopher tortoises was higher in October and November (survival rate: 69%) and April and May (survival rate: 74%) than any other 2-month interval of the year (range: 89-100%) [153]. In addition to predation, survival of neonate gopher tortoises may be affected by soil compaction and clay content at the nest. A study of 40 nests in Forrest County, Mississippi, found that while most of the eggs hatched, "only about half" of the hatchlings survived; the others were apparently unable to dig their way out of the nest due to the hard-packed overburden [22]. Impacts by human land use also affect survival of young gopher tortoises. Landers and Buckner [83] reported that 6 nests located in roads and along firelines were destroyed by heavy equipment (see Mechanical site preparation). Predation on young gopher tortoises may influence their activity patterns, movements, and burrow use. For example, juvenile gopher tortoises appear to have narrower foraging and activity ranges than adults (see Foraging activity and Home range and movement), perhaps in response to high predation [153]. See Wilson [152,153] and Wilson and others [154] for more information on this topic.
Subadult and adult gopher tortoises are typically protected from predators by their hard shells [152]. Survival of subadults and adults is typically high and is mostly affected by human actions (see Status and threats). Thus, high levels of predation may occur in areas with heavy human use [7]. Over 15 months, survivorship of subadult and adult (6.7-11.1 inches (16.9-28.2 cm) plastron length) gopher tortoises at Archbold Biological Station in Highlands County, Florida, was 93%, whereas that of younger age classes (1.8-6.2 inches (4.6-15.7 cm) plastron length) was 45% [90]. In Jasper County, South Carolina, all adult deaths in a slash pine-oak sandhill population were attributed to direct morality due to collecting or indirect morality due to habitat destruction by humans [158]. Populations might be dominated by large individuals due to low recruitment in young age classes and high survival and longevity of subadults and adults, although many researchers could not discount the possibility of underdetection of young individuals (e.g., [3,112,130,137,158]). A study of 51 gopher tortoise populations throughout Florida indicated that populations residing in habitats that experienced severe area reduction (>25% reduction over 20 years), had >50% tree canopy, or were <5 acres (2 ha) in size tended to have few small or few large burrows (an indicator that these populations had few small or few large individuals). The authors surmised that large individuals leave these sites, and recruitment of young individuals into these populations is reduced [102].
The gopher tortoise (Gopherus polyphemus) is a species of tortoise in the family Testudinidae. The species is native to the southeastern United States. The gopher tortoise is seen as a keystone species because it digs burrows that provide shelter for at least 360 other animal species. G. polyphemus is threatened by predation and habitat destruction. Habitat degradation is the primary reason that the gopher tortoise is listed as vulnerable on the IUCN Red List, but they are considered threatened in some states while they are endangered in others.[4]
The gopher tortoise is a representative of the genus Gopherus, which contains the only tortoises native to North America. The gopher tortoise is the state reptile of Georgia and the state tortoise of Florida.[5][6][7]
The specific name, polyphemus, refers to the cave-dwelling giant, Polyphemus, of Greek mythology.[8] Gopher tortoises are so named because of some species' habit of digging large, deep burrows like the gopher.
The gopher tortoise is a terrestrial reptile that possesses forefeet that are well adapted for burrowing, and elephantine hind feet. These features are common to most tortoises. The front legs have scales to protect the tortoise while burrowing. G. polyphemus is dark brown to gray-black in overall color, with a yellow plastron (bottom shell). A gular projection is evident on the anterior plastron where the head projects from the shell. Sexual dimorphism is evident, with the male gopher tortoise having a concave plastron, while that of the female is flat. In addition, the gular projection of a male plastron is generally longer than that of a female. Straight carapace length of adults usually ranges from 6 to 11 in (15 to 28 cm), with a maximum of 16 in (41 cm).[9] The carapace is at least twice as long as it is high.[9] Body mass averages 4 kg (8.8 lb), with a range of 2–6 kg (4.4–13.2 lb).[10][11]
Gopher tortoises are herbivore scavengers and opportunistic grazers.[12] Thus, their diets contains over 300 species of plants, with the dominant plants within their environment likely making up the bulk of their diet.[12] They consume a very wide range of plants, but mainly eat broad-leaved grass, regular grass, wiregrass, and terrestrial legumes.[13][14] However, other plant parts, including shoots, stems, leaves, and pine needles are also eaten.[15] They also eat mushrooms, and fruits such as gopher apple, pawpaw, blackberries, and saw palmetto berries.[13][14] In addition, gopher tortoises eat flowers from the genera Cnidoscolus (nettles), Tillandsia (Spanish and ball moss), Richardia, and Dyschoriste.[16] A very small portion of the tortoises’ diet is composed of fungi, lichens, carrion, bones, insects, and feces, eaten more commonly by females before and after nesting time.[15] Juvenile tortoises tend to eat more legumes, which are higher in protein, and fewer grasses and tough, fibrous plants than mature tortoises.[16] As gopher tortoises usually get water from the food they eat, they usually only drink standing water in times of extreme drought.[17]
Gopher tortoises, like other tortoises of the genus Gopherus, are known for their digging ability. Gopher tortoises spend most of their time in long burrows (up to 80% of their time).[18] On average, these burrows are 15 feet (4.6 m) long and 6.5 feet (2.0 m)[12] deep, but can extend up to 48 feet (15 m) in length and 9.8 feet (3.0 m) deep.[13] The length and depth of the burrow vary with the depth of sand and depth of the water table.[18] In these burrows, the tortoises are protected from summer heat, winter cold, fire, and predators.[13] The burrows are especially common in longleaf pine savannas, where the tortoises are the primary grazers, playing an essential role in their ecosystem.[13] Except during breeding season, gopher tortoises are solitary animals, inhabiting a small home range. Within their range they dig several burrows. On average, each gopher tortoise needs about 4 acres (16,000 m2) to live.[19]
Gopher tortoises can live more than 40 years.[20] One current specimen, Gus (age 100—the oldest known living gopher tortoise—as of 2022[21][22]), has been living continuously in captivity at the Nova Scotia Museum of Natural History in Halifax for 75 years as of 2018[23] and is believed to have hatched between 1920 and 1925. Additionally, there are journalistic reports of a specimen in North Texas with a verified age of 75–78 years old.
The gopher tortoise reaches maturity at approximately 10–15 years of age, when their shells are around 9 inches (23 cm) long.[24] Male tortoises reach adulthood at approximately 9–12 years of age, and females take up to 10–21 years to reach maturity.[12] Maturation time may vary based on local resource abundance and latitude. Gopher tortoises prefer to live solitary lifestyles, burrowing alone and only breaking this during mating season[25]
Sexual reproduction involves courtship rituals. During the mating season females only produce 1 clutch annually between April and November, females lay about 1–25 eggs and incubate them underground for 70-100 days. 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 degrees Celsius, it is a female and if below 30 degrees Celsius, the egg is a male. Incubation period can last from 80 to 90 days in Florida and 110 days in South Carolina. The eggs will stay in the uterus of the female for 60 days until oviposition occurs, they will use their uterine epithelium to supply "pumping water", and transport important nutrients to the eggs.[26]
Gopher tortoises may mate from February through September, with a peak throughout May and June.[27] Females may lay clutches of 3–14 eggs,[27] depending on body size, in a sandy mound very close to the entrance of their burrow.
Ninety percent of clutches may be destroyed by predators such as armadillos, raccoons, foxes, skunks, and alligators[24] before the eggs hatch, and less than 6% of eggs are expected to grow into tortoises that live one year or more after hatching.[28] As the tortoises age, they have fewer natural predators.[12] Egg predation rates are unchanged regardless of whether nests are close to or remain far from burrows.[18] Additionally, a denser soil composition may affect hatchlings' ability to emerge due to the hatchlings' apparent inability to dig themselves out of the nest.[18]
It has been suggested that gopher tortoises, more than other tortoise species, exhibit social behavior. While primarily solitary creatures, gopher tortoises live in well-defined colonies which are similar to those of highly social animals such as the prairie dog.[18] The distribution and proximity of burrows might be the consequence of social relationships between tortoises. Some females have been observed visiting the burrows of a particular female repeatedly, even if there are other tortoises nearby. This may be a sort of 'friendship', but such terms are not normally used to describe the relationships between animals.[29][30] Female gopher tortoises generally do not relocate once they have moved into a colony and larger males usually have their burrows adjacent to females in the spring.[31] It has been found that males can travel up to 500m to visit females and their burrows.[32]
Since July 7, 1987, the U.S. Fish and Wildlife Service (USFWS) has listed Gopherus polyphemus as "Threatened" wherever the tortoises are found west of the Mobile and Tombigbee Rivers in Alabama, Mississippi, and Louisiana. On November 9, 2009, the U.S. Fish and Wildlife Service proposed rulemaking to include the eastern population of Gopherus polyphemus in the List of Threatened Wildlife.[33] In October 2022, the USFWS announced that the species overall and its eastern distinct population segment (DPS) did not warrant listing at that time.[34] G. polyphemus appears on the IUCN Red List as a "Vulnerable" species; however, it has not been assessed for the purposes of this list since 1996.[1] In July 2011, the USFWS determined that listing the eastern population of the tortoise as Threatened under the Endangered Species Act is warranted, however, it is precluded from doing so at this time due to higher priority actions and a lack of sufficient funds to commence proposed rule development. In the interim period of time the USFWS will place the eastern population of the tortoise on its candidate species list until sufficient funding is available to initiate a proposed listing rule.[35] In 2018, the IUCN Tortoise and Freshwater Turtle Specialist Group recommended a re-assessment and re-classification of all six Gopherus species[36] This reclassification would move G. polyphemus from Vulnerable (VU) to Endangered (EN).[36] NatureServe considers the species to be Vulnerable.[37]
The Conservation Clinic at the University of Florida's Levin College of Law describes five main threats to the tortoise population, which are: (1) habitat loss through human development, (2) habitat loss through poor supervision, (3) human desire to use it as a pet or eat it as meat (see human predation), (4) relocation causing population disruption, and (5) disease caused by relocation.[41]
In Mississippi, along State Route 63, chain link fences were built to prevent gopher tortoise mortality from traffic. These fences, made from heavy gauge wire for durability, are three feet high and are buried one foot below the surface. The fences have "turnarounds" at either end, which are angled fences that redirect tortoises back into the area from which they come. As of 2003, no roadside gopher tortoise deaths had been reported along Route 63 since the construction of the fences.[42]
On July 27, 2016, the Florida Fish and Wildlife Conservation Commission issued a warning to residents and visitors to the state not to paint the shell of a gopher tortoise, as the paint can hinder their ability to absorb vitamins they need from the sun, cause respiratory problems, allow toxic chemicals into the bloodstream, and other harmful effects. The commission has also stated that it is illegal to do so otherwise.[43]
Head-start and release programs have been shown to be effective methods of combating gopher tortoise population decline. At the Yuchi Wildlife Management Area in Burke County, Georgia, during 2014 and 2015 145 tortoises were released and tracked. Survivorship was variable throughout the study but site fidelity remained high. Since tortoises were staying in the same area after release it could be a viable method of population recovery. Release strategy and predator mitigation are essential to its success.[44]
Gopher tortoises are known as a keystone species.[45] The Florida Fish and Wildlife Conservation Commission states the gopher tortoise provides temporary or permanent refuge for as many as 350 to 400 species, whether the gopher tortoise is present or not.[18][12] The burrows are used for feeding, resting, reproduction, and protection from temperature extremes, moisture loss, and predators.[45] These species include gopher frogs (Rana capito), several species of snake, such as the eastern indigo snake (Drymarchon couperi), small invertebrates, and burrowing owls (Athene cunicularia).[19] Several species associated with gopher tortoise burrows are listed as endangered, threatened, or species of special concern by the US Fish and Wildlife Service.[18] Therefore, conservation efforts focused on the gopher tortoise aid these species as well.[19] The largest threats to gopher tortoises are habitat destruction, habitat degradation, and human predation.[46]
Additionally, gopher tortoise burrows may benefit plant life by exposing mineral soil favorable for germination.[18]
Conversion of gopher tortoise habitat to urban areas, croplands, and pasture, along with adverse forest management practices, has drastically reduced the historic range of the gopher tortoise. The taking of gopher tortoises for sale or use as food or pets has also had a serious effect on some populations. The seriousness of the loss of adult tortoises is magnified by the length of time required for tortoises to reach maturity and their low reproductive rate. According to the website of the Brevard Zoo in Melbourne, Florida, current estimates of human predation and road mortality alone are at levels that could offset any annual addition to the population, and sightings of gopher tortoises have become rare in many areas, and the ones sighted are much smaller than in the past.[47] A number of other species also prey upon gopher tortoises, including the raccoon, which is the primary egg and hatchling predator, gray foxes, striped skunks, nine-banded armadillos, dogs, and snakes. Red imported fire ants also have been known to prey on hatchlings. A 1980 report indicated clutch and hatchling losses often approach 90 percent.[48]
In the past, approximately 83,955 gopher tortoises were incidentally taken (destroyed) and 137,759 acres of gopher tortoise habitat was permitted for development in Florida[49] as developers could acquire Florida Fish and Wildlife Conservation Commission Incidental Take Permits to build in the gopher tortoises' natural habitat. Additional gopher tortoise habitat was lost due to issuance of Special Tortoise Relocation Permits and Standard Tortoise Relocation Permits, but the total acreage of habitat lost and total number of gopher tortoises relocated cannot be estimated due to issuance of these two types of permits.[49] Both the tortoise and their burrows are now protected under state laws. On July 31, 2007, the Florida Fish and Wildlife Conservation Commission implemented new permitting rules requiring developers to relocate tortoises.[50] Starting on April 22, 2009, three types of permits were available in Florida for developers wishing to build on gopher tortoise habitat. Two of these permits allow for the relocation of gopher tortoises, either to some other place on the site being used for construction, or to a recipient site which has been certified by the Florida Fish and Wildlife Conservation Commission. The third type of permit allows for temporary relocation of tortoises while major utility lines are installed. In the third case, the tortoises are returned to their habitat after construction is complete.[50]
Gopher tortoises are sensitive to the stability or quality of the environment that they live in. There have many anthropogenic disturbances to gopher tortoise habitat, such as fire regimes to maintain healthy ecosystems, meaning this may disrupt potential vegetation that is essential to their diet. Though most research has been conducted on upland habitats for gopher tortoises, they also inhabit sand dune ecosystems. Far less is known about these tortoises' role and niche within these coastal environments. However, this also means that they are threatened by human activity causing these tortoises to be subject to sea level rise and irregular and intense hurricane patterns. An increase in storm intensity can lead to the ultimate destruction of these coastal habitats and therefore the species that occupy them, or at the very least misplacement into other unsuitable habitats. Many of these habitats are located on Florida beaches, which have decreased due to development and have left less than 86,000 acres of wild lands.[51] As a result of these storms, tortoises have been moving up in elevation and residing in abandoned burrows that are deeper in order be protected from the hurricanes.[52] This increase in storms may cause a range shift to higher elevation which may result in more human contact, which may reduce their populations over time. Since many beaches in Florida run parallel to trafficked roads and are therefore fragmented ecosystems, this may directly decrease the survival of these coastal gopher tortoises before there is adequate research done to understand the ecological importance that the coastal gopher tortoises contribute.
Tortoises are subjected to predation by other animals, including by humans. People have eaten gopher tortoises for thousands of years. During the Great Depression, the gopher tortoise was known as the "Hoover Chicken" because they were eaten by poor people out of work.[41] Some people see gopher tortoise meat as a delicacy, or as simply a free source of meat.[24] Although it is now illegal to hunt gopher tortoises or possess their meat or shells, illegal hunting was still taking place as of 2008[53] at an unsustainable rate, with some colonies being driven to extinction.[14][24] In 2006, police uncovered "five pounds of tortoise meat in [a] man's refrigerator" after they spotted empty tortoise shells along a highway in Florida. In nineteen counties in Alabama, as of 2007 tortoise was listed as "game species," though one with "no open season."[41]
Gopher tortoises have been kept as pets, preventing them from reproducing in their local populations. Captured gopher tortoises could be raced in tortoise races, but this practice was banned in Florida in 1989.[54] Moving a tortoise can lead to harmful consequences to the environment from which it came, because the tortoise is often not returned to the same place where it was found. Also, as tortoise racing involves several tortoises in close proximity to one another, diseases can easily spread from one tortoise to another. If an infected captive tortoise is then returned to the environment, other tortoises may be infected.[14]
Climate change poses another challenge for the gopher tortoise through alteration of habitat, but they are adapting by way of natural selection. According to the Florida Fish and Wildlife Conservation Commission, rising temperature and change in rainfall patterns may increase the numbers of invasive species which if more adapted to these environmental changes could drive out native plants essential for tortoise's diet. Invasive species can cause habitat fragmentation and increase stress to gopher tortoises and other native animals. Warmer temperatures cause sea level to rise and more extreme weather to occur. Extreme periods of rainfall and drought will cause fewer lands to become available. There will also be an increase or decrease in water availability. One meter rise in sea level leads to loss of 20% of existing conservation lands and 30% of the natural habitats. However, based on current sea level rise, a one-meter rise in ocean levels would occur only after the passage of several centuries. As the sea level rises, it will move storms closer to land and affect both coastal and marine environments. Species may move inland as less land is accessible. This can increase the spread of diseases or disrupt food cycles and reproduction.[55]
In 1987, human urbanization and various human activities in Mississippi, Louisiana, and Alabama caused dramatic declines in the tortoise population, and the U.S. Fish and Wildlife Service listed them as "endangered." Even though the population declined in Florida, Georgia, and South Carolina, they were not yet listed as threatened at the time. However, in recent years, habitat loss is increasing as southern states continue to experience human population growth, and expand on highway road construction. The southeast has had a 20% increase in human population between 1990 and 2000.[41]
One of the most suitable habitats for gopher tortoise is the longleaf pine ecosystem, which provides suitable well-drained and sandy soils for tortoises to inhabit.[41] Longleaf pine forests include abundant low herbaceous plant growth and open canopy/space for tortoise's eggs to incubate. Since European settlement, longleaf pine decreased in area by an estimated of 96%, which has contributed to an 80% decrease in population densities of gopher tortoise. This means that there is only 4% of longleaf pine remaining.[41]
Over its range in the southeast, there are still four large core areas that provide the opportunity to protect large areas of tortoise habitat, as well the biological diversity of the coastal plain.[56] They are (from west to east) De Soto National Forest, Eglin Air Force Base, Apalachicola National Forest, and Okefenokee Swamp in Florida. These areas offer an opportunity to restore forest stands and land areas containing populations of native vertebrate animals threatened by habitat fragmentation. Restoring the natural causal factors of fire, especially, and flooding would also assist in restoring the plant and animal communities.
If Florida's population doubles, 7,000,000 acres (11,000 sq mi; 28,000 km2) of land, which is the size of Vermont, could be developed. 3,000,000 acres (4,700 sq mi; 12,000 km2) of agricultural lands and 2,700,000 acres (4,200 sq mi; 11,000 km2) of unused land will be developed. This will cause more competition for water resources between animals and humans.[57] The low reproductive rate of the tortoise makes it more vulnerable to declines in longleaf ecosystem and extinction.
Anthropogenic activity appears to not only result in habitat loss but also habitat fragmentation. Turtles and tortoises are strongly impacted by railways, which can act as barriers to movement.[58] Radio telemetry data show that gopher tortoises cross railways significantly less frequently than expected.[59] Tortoises also have poor ability to escape from railways after entering the area between the rails. Railway habituated tortoises (those believed to live near railways and interact with them) and naïve tortoises (those unlikely to frequently interact with railways) do not differ substantially in their railway escape behavior, suggesting that prior experience may not improve tortoises’ ability to escape from railways that they have entered.[59] Trenches dug beneath railways can facilitate movement across and escape from railways. As railways are prevalent throughout the gopher tortoise’s geographic range, implementation of railway trenches may improve population connectivity and reduce habitat fragmentation.[59]
Gopher tortoises are known to contract upper respiratory tract diseases (URTDs) caused by various microorganisms, including the bacterium Mycoplasma agassizii and iridovirus and herpes viruses.[60] Symptoms of URTDs include serous, mucoid, or purulent discharge from the nares, excessive tearing to purulent ocular discharge, conjunctivitis, and edema of the eyelids and ocular glands.[61] M. agassizii is known to exist in tortoises without showing obvious symptoms.[62] Little is known about why some tortoises test positive and live for years, while others become seriously ill and die.[63] The antibiotic enrofloxacin has been used to treat bacterial URTDs in G. polyphemus.[64] However, there is no cure for URTD.[63]
Although long-term studies indicate URTDs can cause population declines in desert tortoise populations 10–15 years after initial infection, studies of such length have not been performed on G. polyphemus. One study, which observed G. polyphemus tortoises in Florida from 2003 to 2006, returned the unexpected observation that tortoises which were seropositive for URTD antibodies were less likely to die over that time than seronegative tortoises. However, the habitats of more seropositive populations had more remains of dead tortoises. The investigators offered the explanation that seropositive tortoises had survived an initial infection, then developed chronic disease. This evidence may imply a possible acute effect on mortality, followed by chronic disease in surviving individuals.[65] Further studies are needed to more fully understand the effects of URTD on this species.
There was a study that found that 14 out of 35 Florida gopher tortoises tested positive for a bacteria called, Candidatus Anaplasma testudinis. These tortoises came into the animal hospitals with anemia and Cytoplasmic vacuolization.[1] With this bacteria present, it can cause anaplasmosis, that is thought to damage red blood cells. It can spread by ticks or other biological vectors and this disease is transmittable, but not contagious. Since this disease was so prevalent within the tortoises studied, it is believed that this disease occurs frequently and is common occurrence in wild populations. This then becomes a pressing issue in terms of the conservation efforts put forward to decrease the likelihood of this disease affecting the population counts. This study will allow us to develop more diagnostic tests to ensure the effective diagnosis and treatment of wild gopher tortoises, and will also ensure a method is cemented for the identification and removal of the potential biological vectors.[66] Ticks are the predicted biological vector, but more research needs to be done to identify other potential carriers and which tick species are more likely to spread diseases to gopher tortoises.
Since the preservation of the longleaf pine ecosystem in particular is required for the maintenance of the gopher tortoise, conservation efforts are needed to maintain this endangered ecosystem.[18] The longleaf pine ecosystem provides extreme conditions such as "nutrient" deprived soil and "sandy sites" for gopher's habitation. The longleaf pine is a relatively long-lived tree for this region of the world, with individual trees often persisting for several centuries.[67] Conserving these forests would provide the natural habitats gopher tortoises need.
Successful reforestation efforts have been made. According to the Environmental Defense Fund's website, environmentalists and private land owners are working together to maintain the wildlife habitat while maintaining crops productivity. Groups provide assistance to private landowners to ensure funding for conservation incentives to landowners who are willing to preserve wildlife on their soil.[68] Most lands in the East are privately owned. Landowners used "prescribed burns' to restore favorable habitat conditions. Prescribed burns managed by the Safe Harbor Agreement benefits U.S. Fish & Wildlife, serve under Federal Endangered Species Act help reduces and prevents the amount of invasive species that are threatening to the tortoise; Invasive species such as the (1) cogongrass aka Imperata cylindrica and (2) Fire ants disrupt gopher tortoise's habitat and kill tortoise eggs can be controlled. Prescribed fire is one method to provide sufficient ground for the tortoise and its eggs to survive and maintain biodiversity.[69]
The gopher tortoise (Gopherus polyphemus) is a species of tortoise in the family Testudinidae. The species is native to the southeastern United States. The gopher tortoise is seen as a keystone species because it digs burrows that provide shelter for at least 360 other animal species. G. polyphemus is threatened by predation and habitat destruction. Habitat degradation is the primary reason that the gopher tortoise is listed as vulnerable on the IUCN Red List, but they are considered threatened in some states while they are endangered in others.
The gopher tortoise is a representative of the genus Gopherus, which contains the only tortoises native to North America. The gopher tortoise is the state reptile of Georgia and the state tortoise of Florida.
