Historically, this species occurred on the coastal plain of the southern USA from eastern Louisiana and southern Mississippi to the Mobile River delta in Alabama, USA. By 2003 it was only known from Glen's Pond in Desoto National Forest in Harrison County, Mississippi (USFWS 2000h; Young and Crother 2001). However, very recently individuals have been seen at two other sites: one calling male was seen at McCoy's Pond 50 miles east of Glen's Pond, and 50 tadpoles were collected from Mike's Pond, 20 miles west of Glen's Pond (Zippel 2005). It is not known whether or not these are stable breeding populations. It occurs from near sea level to 65m asl.
Habitat and Ecology
Breeding and non-breeding habitat includes both upland sandy habitats historically forested with longleaf pine and isolated temporary wetland breeding sites imbedded within this forested landscape. This frog spends the majority of its life in or near underground refugia and historically used gopher tortoise burrows for this purpose (Allen 1932; Richter et al. 2001). The Glen's Pond population occurs in an area presently lacking gopher tortoises, although tortoises probably occurred historically in the area and do occur nearby. Refugia include abandoned mammal burrows and holes in and under old stumps (L.V. LaClaire pers. obs., 1996; Richter et al. 2001). This species does not adapt to human disturbance of its habitat.
Only one extant population was known as of 2000 (Richter et al. 2003). Historical records exist for three parishes in Louisiana, eight counties in Mississippi, and one county in Alabama. Recent surveys have been unable to document the continued existence of the species in Louisiana (Seigel and Doody 1992; Thomas 1996; J. Pechmann pers. comm. 2003) or Alabama (Bailey 1992b, 1994). The last observation of this gopher frog in Louisiana was made in 1967 (G. Lester, Louisiana Natural Heritage pers. comm., 1991) and in Alabama in 1922 (Löding 1922). In 1987 and 1988, surveys of ponds in six Mississippi counties verified the presence of the species at only four sites in Harrison County (Crawford 1988). At three of the four sites, only one individual was observed. Subsequent to this work, surveys have documented the continued existence of only one population, represented by Crawford's fourth site in Harrison County. Based on census data collected 1996-2001, the population was estimated at 60-100 individuals (Richter and Seigel 2002; Richter et al. 2003). The population appears to be declining because of two fungal diseases, one of them chytridiomycosis.
Major threats include population isolation (inbreeding and susceptibility to catastrophic events), urbanization, two diseases, and apparent lack of a nearby suitable habitat. The range has been significantly reduced as a result of habitat destruction, fragmentation, and modification. Pre-settlement longleaf pine forests were the dominant forest type of the south-eastern coastal plain. Today, less than two percent of the original longleaf pine forests remain (Ware, Frost and Doerr 1993). These areas are usually second-growth forests often degraded by turpentine, grazing, and disruption of the natural fire regime (Boyce and Martin 1993; Ware, Frost and Doerr 1993). Many areas have been converted from open longleaf pine sand hill communities to dense monocultures of sand, loblolly, or slash pine (Boyce and Martin 1993; Ware, Frost and Doerr 1993). Land management practices have altered the soil horizon, forest litter, herbaceous community, and the occurrence of fallen trees and stumps used as refugia. Isolated temporary wetlands are required for breeding. Factors affecting quality of breeding ponds include timber site preparation methods that alter existing hydrology, domestic animal grazing, clearing and draining for agricultural or urban uses, ditching, soil disturbance, and fire exclusion. The breeding habitat at Glen's Pond, and most of the surrounding adult habitat, are located in the DeSoto National Forest. Silviculture, including timber sales with associated clear-cutting, is the primary activity in this area. Less than 50 percent of the Forest is maintained as longleaf pine, with the remainder converted to slash pine or loblolly pine. The Mississippi Gulf Coast has experienced a recent upsurge in residential development, largely as a consequence of gambling casinos located in the Biloxi-Gulfport area. The land immediately north and west of the only known breeding site was owned by International Paper and managed for paper production until it was sold in 1999 to a land developer who intends to build a retirement community and golf course. This development will make conducting prescribed burns difficult and increase the chances of further modification to the breeding site and the associated upland habitat. The US Forest Service is negotiating the purchase of a small (30 ha) buffer to facilitate burning. Habitat alteration is likely the primary factor in the loss of gopher frog populations in Alabama, Louisiana, and Mississippi. At least 13 (72 percent) of the 18 historic gopher frog sites have been degraded due to intensive forestry practices. Forests around breeding ponds were clear-cut extensively in the mid-1950s and then again in the 1980s and 1990s. In most cases, these forests were replaced with dense pine plantations. Within these plantations and in the longleaf pine habitats, fire suppression has further has reduced the quality of the terrestrial and aquatic habitat for the Dusky Gopher Frog. Both the forests and the ponds have lost the open, grassy character that is necessary habitat for the species. Canopy closure from fire suppression also alters the forest floor vegetation. Without fire, encroachment of woody vegetation threatens the open, herbaceous character typical of most gopher frog breeding ponds. In addition, fire causes the release of nutrients bound in plant material. This release of nutrients results in a flush of primary productivity that is important to the herbivorous gopher frog tadpoles. Fire suppression has negatively impacted at least 13 (72 percent) of the 18 historical sites, but controlled burns conducted 1987-2003 have improved conditions at Glen's Pond. Expanding urbanization has been a factor in the degradation of at least three (17 percent) other sites. One of these historic breeding ponds is in a residential backyard and has been altered to hold water permanently (Thomas 1996). Forestry practices and expanding urbanization are also threats to the single remaining population. For example, a four-lane highway is being constructed that will further subdivide available habitat. Direct take for commercial, recreational, scientific, or educational purposes is not currently considered to be a threat. An unidentified fungal disease has caused >90% mortality of tadpoles. Chytridiomycosis has also been detected in other species of frog at the breeding site, but its effects on Dusky Gopher Frogs are currently unknown. Temporary ponds altered to form more permanent bodies of water and stocked with fishes are no longer suitable breeding sites. The Dusky Gopher Frog is adapted to temporary wetlands and its larvae cannot survive the heavy predation of bass and sunfish commonly used to stock ponds. Introduction of predatory fishes into ponds for recreational use has caused declines in Gopher Frog (Rana capito) populations in Alabama (M. Bailey pers. comm., 1995). Construction of drainage ditches and firebreaks into ponds might also provide avenues for introduction of fish into breeding sites. High annual variation (5-37%) in intensity of egg mass mortality occurred during a three-year study (Richter et al. 2003). An additional undetermined amount of the egg mortality was due to predation by caddisfly larvae (Order Trichoptera, Family Phryganeidae) on the egg masses (Richter 2000). Gopher frog breeding sites have been degraded by roads that pass through or are adjacent to ponds. Erosion of unpaved roads adjacent to breeding sites may result in an influx of sedimentation from surrounding uplands during rainstorms. Off-road recreational vehicle (ORV) use can cause direct mortality of tadpoles and adults (J. Jensen, Georgia Department of Natural Resources pers. comm., 1996) and alter the quality of a breeding site. Vehicular traffic disrupts the contours of the pond floor, eliminates herbaceous vegetation, and can alter the hydrology of the site (L.V. LaClaire pers. obs., 1995). Loss of herbaceous vegetation from ORV usage could also discourage gopher frog reproduction, since egg masses are attached to stems of herbaceous vegetation (Bailey 1990; Palis 1995). ORV tracks have been documented within the Glen's Pond breeding site (G. Johnson, U.S. Forest Service pers. comm., 1994). Low reproductive potential might also represent a threat to this species' continued existence. Studies at the Mississippi breeding site suggest that females do not breed until two to three years of age and might breed only in alternate years and/or have only a single lifetime breeding event (Richter and Seigel 2002). Both larval and metamorph survival appears to be low (Richter et al. 2003). Variability in weather events can further reduce reproductive potential. Annual variability in rainfall, which influences how frequently and how long a pond is appropriate breeding habitat, can result in a number of years with complete reproductive failure (Richter et al. 2003). Studies of other species of ranid frogs (e.g., Berven and Grudzien 1990) suggest that many anuran populations show a strong meta-population structure. In meta-populations, adults are typically faithful to breeding sites but juveniles may disperse to new breeding areas before reaching maturity. As a result, reproductive failure at a single pond can be compensated for by recruitment at another site. Such a strategy also leads to a lower probability of genetic isolation and inbreeding (Stacey, Taper and Johnson 1997). Because there is only one known breeding site (until very recently), this population is highly susceptible to genetic isolation, inbreeding, and catastrophic events. Thus, the probability of extinction is higher than would otherwise be the case. Insecticides and herbicides might pose a threat. The aquatic larvae are likely most vulnerable to chemical changes in their environment. Adult gopher frogs are predaceous and could be affected by pesticides accumulated in their invertebrate prey. If a golf course is built in the drainage area of the breeding pond, as proposed, the chemicals used to maintain the golf course could pose a significant threat to the population.
The last known population in the Desoto National Forest, Mississippi, is not entirely protected. In Mississippi, the gopher frog is classified as Endangered by the Mississippi Department of Wildlife, Fisheries, and Parks (R. L. Jones, MDWFP pers. comm., 1995). In December 2001, the species was listed as Endangered under the US Endangered Species Act, but no critical habitat was designated (USFWS 2001). A Gopher Frog Recovery Team has since overseen conservation strategies that include pond water supplementation in dry years, habitat management, assisting larval survivorship, captive rearing, construction of an alternative-breeding pond, and treating infected larvae. This programme needs to be continued and expanded. Surveys are needed to check the status of the recently discovered populations, and to determine whether or not the species survives elsewhere.
Red List Status
Critically Endangered (CR)
Listed as Critically Endangered because its Extent of Occurrence is less than 100 km2 and its Area Of Occupancy is less than 10km2, all individuals are in a single location, and there is continuing decline in the extent and quality of its habitat, and in the number of mature individuals, in Harrison County, Mississippi; and because its population size is estimated to number fewer than 250 mature individuals, with all individuals in a single sub-population, and it is experiencing a continuing decline.
Genetic studies showed that this form is distinct from populations of Lithobates capito and L. areolata, and has therefore been established as a separate species (Young and Crother 1991).
Geoffrey Hammerson, Stephen Richter, Richard Siegel, Linda LaClaire, Tom Mann 2004. Lithobates sevosus. The IUCN Red List of Threatened Species 2004: e.T58714A11828596. http://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T58714A11828596.en .Downloaded on 20 February 2019