Southeastern Amphibians

Taxonomic Review

Of the estimated 4300 to 4500 amphibian species worldwide (Vial and Saylor, 1993; Zug, 1993; McDiarmid, 1994), 135 species are described from the southeastern United States, Puerto Rico, and the US Virgin Islands (Appendix I). Within North America, the Southeast has the greatest regional amphibian species richness (Duellman and Sweet, 1999). In addition, a number of species await formal taxonomic description, particularly in the salamander families Plethodontidae, Proteidae and Sirenidae and possibly in the frog family Ranidae. Most of the native amphibians in the Southeast are salamanders, with 77 described species. Amphibian species richness by southeastern state and territory is shown in Appendix I.

Order Caudata.- Of the seven salamander families in the southeastern United States, two (Amphiumidae and Sirenidae) are endemic to the region and two others (Ambystomatidae and Proteidae) have their greatest species richness in the Southeast. One of the three extant cryptobranchids occurs primarily in southern streams and rivers, whereas the other species are found in Asia. The lungless salamanders, family Plethodontidae, are very diverse in the Southeast (55+ species), although their greatest diversity occurs in the mountainous Neotropics of southern Mexico and Central America. The family Salamandridae is primarily Palearctic and Oriental in distribution, although two species of Notophthalmus are found in the Southeast. There are no salamanders in Puerto Rico or the U.S. Virgin Islands.

The following salamander genera have their centers of distribution within the Southeastern United States: Cryptobranchus, Necturus, Amphiuma, Siren, Pseudobranchus, Phaeognathus, Haideotriton, and Stereochilus. Most or all species of Desmognathus, Eurycea, Gyrinophilus, Notophthalmus, Plethodon, and Pseudotriton also occur in the Southeast, although the ranges of individual species may extend substantially northward.

Order Anura.-There are no endemic families of frogs in the southeastern United States, and only two genera (Acris and Pseudacris) have centers of species richness within the region. The highest diversity (17 native species) of southeastern frogs occurs within the family Hylidae (treefrogs), followed by the Ranidae (true frogs: 11+ species) and the Bufonidae (toads: 4 native species). Gastrophryne and Scaphiopus are represented by a total of two species. In addition to the native species of frogs, four non-indigenous species (Bufo marinus, Eleutherodactylus coqui, E. planirostris, Osteopilus septentrionalis) have established breeding populations (all in Florida).

In the Caribbean, there are 17 species of frogs in the family Leptodactylidae in Puerto Rico (Joglar, 1998; Rivero, 1998), 16 of which are in the direct-developing terrestrial and arboreal species-rich genus Eleutherodactylus. Several species are endemic to the island, including Eleutherodactylus jasperi, the only frog in the Western Hemisphere that gives birth to living young; development occurs entirely within the mother's body. Two species of hylids (Osteopilus septentrionalis, Scinax rubra), the toad Bufo marinus, the pig frog (Rana grylio) (Rios-López and Joglar, 2000), and the American bullfrog (Rana catesbeiana) have been introduced and have established breeding populations. The green treefrog Hyla cinerea was introduced in the past but there are no established breeding colonies.

There are eight species of frogs in the U.S. Virgin Islands, of which three are introduced (Bufo marinus, Osteopilus septentrionalis, Eleutherodactylus coqui) (Maclean, 1982). Only the species E. lentus is endemic to the U.S. Virgin Islands (on St. Croix, but introduced elsewhere).

Distribution and Habitats

Physiographic Regions and Centers of Speciation.-Amphibians are found in all physiographic regions of the southeastern United States. They are found from sea level to the tops of the highest Appalachian Mountains. Centers of species richness and endemism include the Appalachian Mountains, particularly at higher elevations (salamanders, especially the family Plethodontidae and the genus (Plethodon), and the Atlantic and Gulf Coastal Plain (many salamanders and frogs, especially Amphiuma, Siren, Pseudobranchus, Necturus, Haideotriton and Pseudacris). Several of the frogs in Puerto Rico and the US Virgin Islands are endemic to the islands or have their primary centers of distribution within these islands.

In the following section, the types of habitats inhabited by southeastern and Caribbean amphibians are briefly discussed. A more comprehensive discussion with references to the published scientific literature is in Dodd (1997).

Aquatic Habitats.-Amphibians are found in all aquatic wetland types except those associated with the saline waters of the coast. Even there, however, some species occasionally are found in brackish habitats. Southeastern aquatic environments include temporary ponds, man made ponds (e.g. ponds at former mine sites), wetlands in pine flatwoods, saturated forested wetlands, cypress domes, bayheads, large swamps, wet prairies, lakes, and streams. Much information on amphibian use of aquatic habitats is contained in state or regional books (e.g. Wright and Wright, 1932) and in numerous accounts of species in need of conservation.

Large fully-aquatic salamanders (Cryptobranchus, Necturus) typically are found in the larger rivers and streams, whereas small aquatic salamanders (Desmognathus, Eurycea) frequent small streams and seeps. In these salamanders, larval development occurs within the stream and, after metamorphosis, adults live along the wet stream sides or among the gravely substrate. The salamanders Siren, Pseudobranchus, and Amphiuma inhabit various types of vegetated ponds and mucky swamps. Newts and most Ambystoma species require temporary ponds to complete metamorphosis, and premature pond drying is an ever present threat to their development. Of course, even salamanders that do not require water to breed need moist environments to prevent desiccation.

As with salamanders, frogs use a variety of wetlands for reproduction. Most frog species have tadpoles which develop within ponds, lakes, wet prairies or other lentic waters. Fewer species use streams, rivers, or swift flowing waters (e.g., Rana heckscheri in rivers, streams, and oxbows in addition to lentic waters). Some frogs are very habitat specific, such as Rana capito and Hyla gratiosa, which require fishless temporary ponds for reproduction. Some species, such as Bufo terrestris, breed in a wide variety of wetland habitats.

Terrestrial Habitats.-Although amphibians are usually associated with water, most species spend a substantial amount of time in terrestrial habitats. Individuals of some species often can be found at great distances from the nearest breeding ponds (Dodd, 1996). Franz et al. (1988) recorded a gopher frog (Rana capito) at a tortoise burrow 2 km from where the frog was marked. Such long distance movements probably are not unusual. Greenberg (1993) captured southern toads (Bufo terrestris), eastern narrow-mouthed toads (Gastrophryne carolinensis), and eastern spadefoot toads (Scaphiopus holbrooki) in Florida sand pine scrub between 5 and 6 km from the nearest known water source.

Terrestrial refugia include caves, burrows of tortoises, pocket gophers, crayfish (especially by Rana capito) and other invertebrates, tree roots, rock crevices, surface debris, and probably many other subterranean habitats. Treefrogs often use arboreal retreats. Selected references on the use of terrestrial habitats by amphibians that require water to breed are found in Dodd (1997).

Tropical Habitats. - In the Caribbean, much of the lowlands have been modified for agriculture and urbanization, although certain frogs have adapted well to human presence. Amphibian species richness is greatest in the high-elevation forests of the interior mountains of Puerto Rico, where frogs are found in habitats from the forest floor litter to the forest canopy. Certain species require bromeliads (e.g., the recently extinct E. jasperi), whereas others live in boulder caves (E. cooki) or in torrential streams (e.g., the recently extinct E. karlschmidti). All Eleutherodactylus require moist places to deposit their eggs.

Aquatic Amphibian Life History

In North America, many amphibians have a biphasic life cycle consisting of an egg and larval stage in water, metamorphosis into a terrestrial adult, and remigration back to water as adults to breed and lay eggs. The time between metamorphosis and first breeding varies among species, although it is usually from 1-4 years (Duellman and Trueb, 1986). The life span of wild individuals also varies. For example, Gastrophryne carolinensis may live 4 or more years whereas the entirely aquatic hellbender may live >25 years. Generally, salamanders live longer than frogs, and larger species live longer than smaller species (Duellman and Trueb, 1986). Duellman and Trueb (1986) discussed life history variations and the factors that affect reproduction, life cycles, and other facets of amphibian biology.

There are exceptions to the "typical" amphibian life cycle. All non-hemidactyline salamanders of the family Plethodontidae (i.e., Aneides, Plethodon), two species of Desmognathus (D. aeneus and D. wrighti), and Phaeognathus hubrichti skip the aquatic larval stage. Instead, eggs are laid on land in moist environments, the larval stage is passed within the egg, and the hatchling resembles a miniature adult.

Several salamanders, including all Siren spp., Pseudobranchus spp. and  Necturus spp. some Eurycea spp., and Haideotriton wallacei and Cryptobranchus alleganiensis, are entirely aquatic and never leave the water or boggy wetlands. Eggs are deposited in vegetation, debris, or under rocks, young usually pass through a larval stage, and adults often retain larval features, such as exposed gills. Amphiuma spp. generally are aquatic, although eggs are deposited on land near water. Other species (Ambystoma talpoideum, Notophthalmus spp.) have individuals or populations that are facultative paedomorphs (that is, they do not transform as long as permanent water remains, and they become reproductively active while otherwise retaining larval phenotypes).

All native southeastern frogs, as well as most of the nonindigenous species in Puerto Rico,  have a "typical" amphibian life cycle. All of the Eleutherodactylus spp. are direct developers with no aquatic life stage, except for the now presumably extinct ovoviviparous E. jasperi.

Terrestrial Amphibian Life History

All members of the Tribe Plethodontinii in the salamander family Plethodontidae, several salamanders of the subfamily Desmognathinae, and most members of the tropical frog family Leptodactylidae are entirely terrestrial and do not use standing water for reproduction. All deposit their eggs in moist situations, however, and the young develop within the eggs and hatch as miniature adults. For most salamanders, this is thought to occur in underground retreats or deep within large rotting logs; the eggs of some of these species have never been found under natural conditions. For the small Desmognathus aeneus and D. wrighti, nests may be placed in seeps or crevices near wet areas. For the native Puerto Rican and Virgin Island Eleutherodactylus, eggs are deposited in moist leaf litter on the forest floor, in tree cavities, in boulder caves, in rotten logs, or arboreally in bromeliads, depending on species.

Terrestrial amphibians have a three or four-dimensional spatial life history pattern which may vary seasonally. During favorable environmental conditions, they are active under surface debris and on the surface of the ground. Some of the tropical Puerto Rican frogs and some of the Appalachian salamanders are or become arboreal, taking to vegetation to feed. However, during unfavorable conditions, animals may retreat underground to inaccessible locations. Likewise, some of the species retreat underground or to specialized places to deposit eggs. A terrestrial life history activity pattern does not imply continuous surface activity.

Federal status

The following species are protected by the Endangered Species Act of 1973, as amended:

Ambystoma cingulatum                   Flatwoods salamander              AL, GA, FL, SC

Phaeognathus hubrichti                   Red Hills salamander                AL

Eleutherodactylus cooki                 Guajón                                           PR

Eleutherodactylus jasperi               Golden coqui                               PR

Peltophryne lemur                           Puerto Rican crested toad          PR

In addition to these species, the dusky gopher frog (Rana sevosa) will be listed in the near future. The listing of the Junaluska salamander (Eurycea junaluska) has been found "warranted but precluded" by more pressing agency priorities. The striped newt (Notophthalmus perstriatus) also is a likely candidate for federal protection. Unfortunately, among these species only the Junaluska salamander and possibly the Puerto Rican crested toad occur on DOI lands (in the Great Smokies and Virgin Islands N.P., respectively).

Although not federally protected, substantial declines of a number of amphibians have occurred in the southeastern states, including the Blue Ridge Escarpment populations of Aneides aeneus (green salamander; Corser, 2000), Desmognathus auriculatus (southern dusky salamander; Dodd, 1998), Pseudacris brachyphona (Mountain chorus frog), and Rana c. capito (Carolina gopher frog; Braswell, 1993). Whereas some of these declines are the result of habitat destruction or alteration, the cause of the declines of others (green salamander, southern dusky salamander) remain unknown and speculative. The status of southeastern amphibians was reviewed by Dodd (1997); the status of Puerto Rican frogs was reviewed by Joglar and Burrowes (1996).

Field Sampling

Although the distribution of amphibians is reasonably well understood on certain DOI lands, such as in the Great Smoky Mountains National Park, this is not the case for most units of the National Park Service and National Wildlife Refuges. There is a need to survey amphibian species richness and distribution patterns on many DOI lands prior to selecting species to be monitored and sampling protocols. Some of the inventory techniques available to sample amphibians are the same as those used to monitor populations. Sampling will occur over a large area to include all habitat types; multiple sampling techniques may be employed; and sampling may be restricted by time (that is, it may be extensive rather than site intensive).

All sampling techniques employ some variation of a time constraint approach whereby search or trap effort is quantified and results are expressed in catch per unit effort of sampling. In all cases, characteristics of the environment/habitat, sampling conditions, and the number of animals observed or captured by species are recorded. Examples of such techniques include: visual searches while walking predetermined paths or transects; searching cave walls; searches of terrestrial leaf litter and under surface debris (logs, rocks, coarse woody debris); searches of aquatic habitats by moving stream debris or by using dipnets to look for adults and larvae; snorkeling for large salamanders; road surveys during favorable activity periods (e.g., during rain near breeding ponds).

Frogs may be inventoried by listening for calls during the breeding season, although not all frogs are easily sampled this way. Some frogs call very softly and may not be heard except in their immediate vicinity. When conducting inventories using calls, it may be necessary to categorize the numbers of animals calling categorically, for example: 1 (1 calling), 2 (2-5 calling), 3 (6-10 calling), 4 (>10 calling), 5 (large chorus). This is because it is often very difficult to determine how many frogs are calling when a chorus is in progress. In southern wet prairies, literally hundreds or thousands of males may call simultaneously.

In certain instances, it may be desirable to inventory amphibians using specialized techniques, such as by employing traps (e.g., soft or hard minnow traps), coverboards, PVC pipe, debris bags (Pauley and Little, 1998) or drift fences with pitfalls. Each of these techniques has sampling biases, although they are useful to determine the presence of some species in certain habitats (techniques discussed in Heyer et al., 1994).

Terrestrial Surveys. - Many species of lungless salamanders inhabit terrestrial situations, often far from the nearest water. Members of the genus Plethodon, in particular, require moist habitats but not standing water. Eggs are deposited in moist locations, sometimes deep underground, and development is direct. Individuals are seasonally active (at cooler times of the year), but surface activity patterns vary with moisture conditions and elevation. High elevation species are active throughout the summer as long as moisture conditions are favorable. The presence of terrestrial plethodontids is often detected using some form of time constrained sampling within a defined area either at night or diurnally during or immediately following (preferably) rainfall. Salamanders may be observed on the ground surface or arboreally on vegetation and tree trunks, by searching leaf litter in plots of predetermined size (e.g., 10 x 10 meters), or by turning surface objects such as logs, rocks, and coarse woody debris. Terrestrial plethodontids also have been sampled using artificial coverboards made of various types of material (seasoned untreated wood, shingles, metal sheets, bricks, plastic, etc); coverboards may be placed in grid patterns or evenly spaced singly or in groups along transect lines of varying lengths.

Monitoring terrestrial salamanders has proved far more difficult than determining presence, and every technique tested thus far has serious biases and limitations (in this case, permanent large study plots censussed by annual litter and debris searches; removal sampling; coverboards, night searches, and visual transect searches). Results from studies on terrestrial salamanders in the Great Smoky Mountains and nearby Nantahala Mountains suggest that no one technique will be sufficient to monitor all species (Smith and Petranka, 2000; Petranka and Starnes, 2000; Hyde and Simons, 2000). Indeed, some authors have suggested that "community surveys are simply not a viable option for rigorous monitoring under current technology" (Thompson et al., 1998), and this caution seems apropos to species-rich terrestrial salamander communities in the southern mountains. Nothing is known about how to monitor terrestrial salamanders in the Piedmont and Coastal Plain where fewer species are present during more restricted times of year, and where individual densities are not as great as in the mountains. Amphibian monitoring programs in the southeast will likely, of necessity, concentrate efforts on certain species or groups of species while developing protocols for others.

Stream Surveys. - Many amphibians use small streams for all of a portion of their life cycle. Within the southeast, small streams vary considerably in physical characteristics, from high mountain trickles and torrents in the Southern Appalachians to the slow-moving coastal plain streams of Florida. The techniques used to sample and monitor amphibians will vary accordingly. Smaller streams may be sampled by using time constrained visual searches, by removal sampling (i.e., by blocking a section of stream and removing all animals within the section), by quadrat sampling (such as by measuring a series of 5 m quadrats spaced evenly or randomly along a stream section and counting all amphibians within the series of quadrats), or by trapping (using soft or hard mesh traps, which come in many designs, or by using porous bags containing debris; Pauley and Little, 1998). The efficacy of these techniques has largely been untested in the southeast (but see Bruce, 1995, concerning temporary removal sampling of aquatic salamanders in a Southern Appalachian stream). The type of aquatic funnel trap (metal vs. plastic) has been shown to influence capture efficiencies of certain larval salamanders (Fronzuto and Verrell, 2000).

Large Stream/River Surveys.- Few large streams or rivers within the southeast contain resident amphibians. However, several frogs breed in or along larger rivers, and certain permanently aquatic salamanders (hellbenders [Cryptobranchus] and mud puppies [Necturus]) reside in them; larval salamanders use pools along large streams, depending on the physical characteristics of the banks of the stream or river. The presence of frogs can be determined by visual or acoustic surveys, and larvae can be sampled using dipnets. Larger salamanders are observed by systematically turning large river rocks, by snorkeling randomly or along transects (Peterson, 1987), by trapping using soft or hard mesh nets or minnow traps, and by intensively dredging or dipnetting large leaf beds, especially in the autumn or winter. Smaller salamanders are observed visually or by searching bottom rocks and debris using small nets.

Pond Surveys. - In the southeastern United States, significant amphibian breeding occurs in isolated ponds. Ponds range in size from large and permanent to very small and temporary. Different amphibian assemblages use ponds of various sizes and hydroperiods. Small temporary ponds are particularly difficult to monitor since hydroperiods may vary considerably both annually and seasonally. Ponds may be used throughout the year, as different species breed at different times, from winter through late autumn. The sampling and monitoring protocols chosen must recognize the variation in timing in which ponds are used and the different species assemblages that use them.

Ponds may be surveyed and monitored using visual shoreline and shallow water searches, by dipnetting randomly or at predetermined intervals along the shoreline, by trapping using a variety of trap designs and configurations, and by call surveys. Eggs, larvae, and adults may be sampled or monitored, depending on season. However, monitoring only one life history stage may mask certain population trends. For example, counting egg masses says nothing about recruitment, although it provides an index of the numbers of breeding females. In addition, many southeastern ponds are difficult to survey because of tannin stained water, thick floating mats of vegetation, and dangerous bottom conditions (e.g., deep gooey layers of mud and muck). In or near water, sampling may be supplemented by searching nearby surface debris or by placing coverboards on or near the shoreline.

Freshwater Marshes and Swamps. - Significant questions remain about sampling large wetlands (e.g., extensive swamps at Okefenokee National Wildlife Refuge or Everglades National Park). These habitats are difficult to sample and describe, and it may be extremely difficult to delineate exactly what constitutes an amphibian population. Standard methods developed for discrete ponds or small wetlands may not be especially useful, and additional research may be necessary to determine effective ways to sample these habitats. In certain large wetland systems, a combination of call surveys, systematic visual searches (either randomly selected or along predetermined transects of specified lengths), intensive manual sampling (using nets or Goin dredges), and passive trapping (using minnow traps or PVC pipes; Boughton, 1997) will be necessary.

Specialized Habitats. - Specialized habitats in the southeast and the Caribbean may contain unusual or unique amphibian species. Examples of such habitats include caves and cave entrances, the granitic boulder caves of Puerto Rico, the axils of bromeliads, gopher tortoise or crayfish burrows (inhabited by gopher frogs, Rana capito and R. areolata), crevices (Aneides aeneus), and deep muck (inhabited by Amphiuma pholeter). Sampling methodology either has not been developed or has not been tested for species in these habitats. In Parks and Refuges where such habitats and species are found, sampling/monitoring protocols will have to be developed and tested on a case by case basis.

Literature Cited

Alford, R. A., and S. J. Richards. 1999.  Global amphibian declines: a problem in applied ecology. Ann. Rev. Ecol. Syst. 30:133-165.

Boughton, R.G. 1997. The use of PVC pipe refugia as a trapping technique for hylid treefrogs. M.S. thesis, Univ. of Florida, Gainesville. 95 pp.

Braswell, A.L. 1993. Status report on Rana capito capito Le Conte, the Carolina gopher frog, in North Carolina. Unpubl. report to North Carolina Wildl. Comm., Raleigh.

Bruce, R.C. 1995. The use of temporary removal sampling in a study of the population dynamics of the salamander Desmognathus monticola. Aust. J. Ecol. 20:403-412.

Bury, R.B. and P.S. Corn. 1991. Sampling methods for amphibians in streams in the Pacific Northwest. USDA For. Serv. Gen. Tech. Rep. PNW-GTR-275, 29 pp.

Carey, C. and C.J. Bryant. 1995. Possible interrelations among environmental toxicants, amphibian development, and decline of amphibian populations. Environ. Health Perspec. 103(Suppl. 4):13-17.

Corn, P. S. and R. B. Bury. 1990. Sampling methods for terrestrial amphibians and reptiles. USDA For. Serv. Gen. Tech. Rep. PNW-GTR-256, 34 pp.

Corser, J.D. 2000.  Decline of disjunct green salamander populations in the southern Appalachians.  Biological Conservation. Submitted.

Daszak, P., L. Berger, A.A. Cunningham, A.D. Hyatt, D.E. Green, and R. Speare. 1999. Emerging infectious diseases and amphibian population declines. Emerging Infectious Diseases 5(6):735-748.

Dodd, C.K., Jr. 1996. Use of terrestrial habitats by amphibians in the sandhill uplands of north-central Florida. Alytes 14:42-52.

Dodd, C.K., Jr. 1997. Imperiled amphibians: a historical perspective. Pp. 165-200 In G.W. Benz and D.E. Collins (eds.), Aquatic Fauna in Peril: The Southeastern Perspective. Spec. Publ. 1, Lenz Design & Communications, Decatur, GA.

Dodd, C.K., Jr. 1998. Desmognathus auriculatus at Devil's Millhopper State Geological Site, Alachua County, Florida. Florida Sci. 61:38-45.

Droege, S., L. Monti, and D. Lantz. 1997. The terrestrial salamander monitoring program. http://www.im.nbs.gov/sally/

Duellman, W.E., and L. Trueb. 1986. Biology of Amphibians. McGraw Hill Book Co., New York.

Duellman, W.E. and S.S. Sweet. 1999. Distributional patterns of amphibians in the Nearctic Region of North America. Pp. 31-109 In W.E. Duellman (ed.), Patterns of Distribution of Amphibians. A Global Perspective. Johns Hopkins Press, Baltimore.

Fellers, G.M. and K.L. Freel. 1995. A standardized protocol for surveying aquatic amphibians. Nat. Park Serv. Tech. Rep. NPS/WRUC/NRTR-95-01, 117 pp.

Franz, R., C.K. Dodd, Jr., and C. Jones. 1988. Rana areolata aesopus (Florida gopher frog). Movement. Herp. Rev. 19:33.

Fronzuto, J. and P.A. Verrell. 2000. Sampling aquatic salamanders: tests of the efficiency of two funnel traps. J. Herpetol. 34:146-147.

Greenberg, C.H. 1993. Effect of high-intensity wildfire and silvicultural treatments on biotic communities of sand pine scrub. Ph.D. diss., Univ. Florida, Gainesville.

Heyer, W. R., M. A. Donnelly, R.W. McDiarmid, L.C. Hayek, and M.S. Foster (eds.). 1994. Measuring and Monitoring Biological Diversity: Standard Methods for Amphibians. Smithsonian Institution Press, Washington, D.C.

Hyde, E.J. and T. R. Simons. 2000. Sampling plethodontid salamanders: sources of variability. J. Wildl. Manage. Submitted.

Joglar, R.L. 1998. Los Coquíes de Puerto Rico. Su Historia Natural y Conservación. Editorial de la Universidad de Puerto Rico, San Juan.

Joglar, R.L. and P.A. Burrowes. 1996. Declining amphibian populations in Puerto Rico. Pp.371-380 In R. Powell and R.W. Henderson (eds.), Contributions to West Indian Herpetology: A Tribute to Albert Schwartz. SSAR, Ithaca, NY.

Maclean, W.P. 1982. Reptiles and Amphibians of the Virgin Islands. MacMillan Caribbean, London.

McDiarmid, R.W. 1994. Amphibian diversity and natural history: an overview. Pp. 5-15 In W.R. Heyer, M.A. Donnelly, R.W. McDiarmid, L.A.C. Hayek, and M.S. Foster (eds.), Measuring and Monitoring Biological Diversity. Standard Methods for Amphibians. Smithsonian Inst. Press, Washington, D.C.

Olson, D.H., W.P. Leonard, and R.B. Bury (eds.). 1997. Sampling Amphibians in Lentic Habitats. Northwest Fauna 4:1-134.

Pauley, T.K. and M. Little. 1998. A new technique to monitor larval and juvenile salamanders in stream habitats. Banisteria 12:32-36.

Peterson, C.L. 1987. Movement and catchability of the hellbender, Cryptobranchus alleganiensis. J. Herp. 21:197-204.

Petranka, J.W. and S.M. Starnes. 2000. Effectiveness of removal sampling for determining salamander density and biomass: a case study in an Appalachian streamside community. J. Herpetol., in press.

Rios-López, N. and R.L. Joglar. 2000. Geographic Distribution: Rana grylio (Pig Frog). Puerto Rico: Toa Baja: Sabana Seca. Herp. Rev. 31:50-51.

Rivero, J.A. 1998. Los anfibios y reptiles de Puerto Rico. 2^nd Ed. Editorial de la Universidad de Puerto Rico, San Juan.

Smith, C.K. and J.W. Petranka. 2000. Monitoring terrestrial salamander populations: repeatability and validity of area-constrained cover object searches. J. Herpetol., in press.

Thompson, W.L., G.C. White, and C. Gowan. 1998. Monitoring Vertebrate Populations. Academic Press, San Diego.

Vial, J.L., and L. Saylor. 1993. The status of amphibian populations. A compilation and analysis. IUCN/SSC Declining Amphibian Populations Task Force, Working Doc. No. 1, Corvallis, Oregon.

Wright, A.H. 1932. Life-histories of frogs of Okefinokee Swamp, Georgia. MacMillan Co., New York.

Zug, G.R. 1993. Herpetology. An Introductory Biology of Amphibians and Reptiles. Academic Press, San Diego, California.