Amphibians of North Carolina
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NC Records

Eurycea quadridigitata - Southern Dwarf Salamander


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Taxonomy
Class: Amphibia Order: Caudata Family: Plethodontidae Subfamily: Spelerpinae Other Common Name(s): Dwarf Salamander
Taxonomic Comments: Eurycea chamberlaini and E. quadridigitata are members of a species complex that was traditionally treated as a single species known as the Dwarf Salamander (E. quadridigitata sensu lato). Members of this group are small salamanders that deviate from all other Eurycea species by having only four toes on each rear limb. Members of the complex occur throughout the southeastern US, from eastern Texas eastward across the Gulf Coast states, then northward to North Carolina. Recent molecular and morphological studies show that several ancient genetic lineages exist within E. quadridigitata sensu lato (Bonett et al. 2014, Harrison and Guttman 2003, Kozak et al. 2009, Lamb and Beamer 2012, Wray and Steppan 2016, Wray et al. 2017), with one western group being more related to the neotenic Eurycea species from the Edwards Plateau than to more eastern members of the species complex. These lineages have subsequently been recognized as five species. These include E. paludicola in eastern Texas, Louisiana, and southern Mississippi, Eurycea hillisi in Alabama, Georgia, and the panhandle of Florida, E. sphagnicola in southern Mississippi, southern Alabama, and the Florida Panhandle, E. chamberlaini in the Carolinas, and E. quadridigitata (sensu stricto) from Florida northward to North Carolina.
Species Comments:
Identification
Description: The Southern Dwarf Salamander is a small, slender Eurycea that somewhat resembles a miniature two-lined salamander. This is the only Eurycea in North Carolina other than E. chamberlaini that has four toes on each hind foot. The dorsum has a broad dark brown to bronze ground color that is bordered by a wide, blackish dorsolateral stripe on either side. Whitish speckling or streaking is usually evident along the lower sides of the body. The dorsolateral stripes extend from the head to the tip of the tail, and the sides of the tail are darkly pigmented and do not contrast sharply with the stripes. The venter is silvery-gray. The tail is keeled and comprises about 50-60% of the total length of adults. Sexually active males have cirri and elongated, monocuspid teeth, and the average SVL of the adults is approximately the same for males and females (Petranka 1998). The SVL of adults measured by Harrison and Guttman (2003) varied from 21-34 mm, while Beane et al. (2010) reported the TL to vary from 54-90 mm.

This species is most easily confused with E. chamberlaini, which differs in having a bright yellow venter, relatively narrow dorsolateral stripes, a slightly smaller average size, relatively longer limbs, fewer paravomerine teeth, and a greater average number of ovarian eggs (Harrison and Guttman 2003). In the field, this species is best distinguished from E. chamberlaini by its overall darker color, its relatively wide dorsolateral stripes, and its silvery-gray venter. In addition, the sides of the tail are darkly pigmented and do not contrast sharply with the dorsolateral stripes. Eurycea chamberlaini is generally lighter overall, has narrower dorsolateral stripes, and a bright yellow venter that is unmarked. The sides of the tail are lightly pigmented and contrast sharply with the dorsolateral stripes (Beane et al. 2010, Harrison and Guttman 2003). In North Carolina, specimens of E. chamberlaini typically have only 16 costal grooves versus 18 for E. quadridigitata. These two species tend to segregate geographically in North Carolina, with E. quadridigitata occurring in the southernmost tier of counties, and E. chamberlaini occurring farther north.

The hatchlings are uniformly grayish-brown with light venters and lack dorsal spots. They have a well-develop dorsal fin that extends from the tail forward before terminating near the mid-body region. The older larvae tend to develop pigment-free regions along the sides that resemble longitudinal streaks or dashes (Harrison and Guttman, 2003).
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Observation Methods: Breeding takes place during the late fall and winter when the ponds are full. The migrating adults have been collected using drift fences around pond margins. Adults can be found during the non-breeding season in leaf litter or under logs and other woody debris either within the dried-out breeding depressions or along their margins.
AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: The Southern Dwarf Salamander is found in Coastal Plain habitats, with the main range extending from Florida northward to extreme southern North Carolina. In North Carolina it occurs in the Sandhills region eastward to Brunswick (Harrison and Guttman 2003) and Pender counties. Isolated populations have also been found in extreme southwestern Alabama and extreme eastern Louisiana (Wray et al. 2017).
Distribution Reference: Harrison and Guttman (2003); Wray et al. (2017)
County Map: Clicking on a county returns the records for the species in that county.
GBIF Global Distribution
Key Habitat Requirements
Habitat: In North Carolina, this species is associated primarily with clay-based Carolina bays (Beane et al. 2010). Farther south, it makes use of a wider variety of wetland habitats, including cypress swamps, and tupelo-cypress bottomland hardwoods. Unlike E. chamberlaini, E. quadridigitata appears to breed only in standing-water habitats. It generally requires breeding sites with long hydroperiods due to a larval period that last 6 months or more. The adults can be found during the non-breeding season under logs and other woody debris either within the dried-out breeding depressions or along their margins. In some areas the adults migrate away from the ponds following breeding and have been found far from the breeding sites (Petranka 1988, Wray et al. 2017). In North Carolina, the extent to which they use the fire-maintained savanna and flatwoods habitats that surround Carolina bays is unclear.
Biotic Relationships: Although poorly documented, Southern Dwarf Salamanders are probably eaten by numerous predators including birds, small snakes, and large invertebrates such as crayfishes and spiders. Lamb (1984) found four dwarf salamanders in the stomachs of Pig Frogs (Lithobates grylio) that were collected from southwest Georgia.
See also Habitat Account for Longleaf Pine Woodlands with Isolated Pools
Life History and Autecology
Breeding and Courtship: Much of our knowledge about the breeding biology of this species is based on studies in coastal South Carolina. The following accounts of the life history are mostly from the Savannah River Site where both E. quadridigitata and E. chamberlaini occur sympatrically at some sites, such as the Rainbow Bay complex. Because both species have been collected in the same pitfall traps (Harrison and Guttman 2003), the following information is likely based on specimens of both species.

Semlitsch and Pechmann (1985) found that the adults that are living away from pond margins migrate in late summer and the fall to the breeding ponds. They are generally more likely to move during the day than other species such as mole salamanders. In South Carolina, migrations to breeding ponds occur from around mid-July through October, particularly following the onset of cooler autumn weather (McMillan and Semlitsch 1980, Semlitsch and McMillan 1980). Mating occurs from late August or early September through February. Harrison (1973) collected females with spermatophores in their vents or observed courtship in the laboratory from September to early November in South Carolina populations. Courtship behavior has not been described, but presumably involves a tail-straddle walk as in other plethodontids. Sex ratios in South Carolina populations are about 1:1 (Harrison 1973, Semlitsch 1980a, Semlitsch and McMillan 1980).
Reproductive Mode: Females oviposit in mid-autumn through mid-winter in woodland pools, roadside ditches, Carolina bays, cypress ponds, and other standing bodies of water. Within a given population, oviposition appears to be restricted to a 1-2 month period. Females in a South Carolina population oviposit in October and November (Harrison 1973), while clutches have been found in Florida from 22 November-15 January (Petranka 1998). The females normally lay their eggs in water, but in some instances may oviposit in unflooded pond depressions. Females at a South Carolina site laid eggs in the autumn when the breeding site was dry (Taylor et al. 1988). The eggs apparently develop normally to advanced stages, then hatch shortly after the site floods. Terrestrial nests have also been found in Florida in shallow depressions beneath wet logs along pond margins (Petranka 1998).

The freshly laid eggs are slightly less than 2 mm in diameter, are creamy white, and are surrounded by two envelopes. Females attach them either single or in small, loose strings to vegetation or other support structures. Clutch size is positively correlated with female SVL (Harrison 1973, Semlitsch and McMillan 1980) and often varies substantially between local populations. Number of ovarian eggs in 31 females from one population studied by Semlitsch and McMillan (1980) varied from 18-48 and averaged 33, while that in 24 females in a second population varied from 7-42 and averaged 21. The clutch sizes of other specimens from South Carolina varied from 13-36 and averaged 22 eggs (Harrison 1973). Eggs that were maintained in the laboratory required 30-40 days to develop to the hatching stages (Harrison 1973). Hatchlings have been found in late January and early February in South Carolina (Harrison 1973, Semlitsch 1980a).
Aquatic Life History: The larvae are primarily benthic feeders and consume small invertebrates. Larvae in a South Carolina population fed mostly on ostracods, cladocerans, and chironomid larvae, and appeared to selectively take the larger individuals of cladocerans (Taylor et al. 1988). The larval period is shorter than that of many Eurycea. Hatchlings in two South Carolina populations transformed after 5-6.5 months of growth when 21-26 mm SVL (Semlitsch 1980a), while those in other populations transformed after 3-6 months of growth when 17-20 mm SVL (Harrison 1973). In the studies above, larvae metamorphosed primarily between April and June (Harrison 1973), and from mid-June through early July (Semlitsch 1980a). Larvae in another South Carolina study averaged about 22 mm SVL in mid-May, and most transformed before June (Taylor et al. 1988).
Terrestrial Life History: After metamorphosing, the juveniles either remain in the vicinity of wetlands or disperse into the surrounding forest. They reach sexual maturity more rapidly then most Eurycea species. In South Carolina, individuals become sexually mature during the autumn of their first year of life. Harrison (1973) found that juveniles become sexually mature when about 24 mm SVL. The smallest mature females collected by Semlitsch and McMillan (1980) were 23 mm SVL. In a South Carolina population, males matured sexually in September and October, 8-9 months after hatching (Semlitsch 1980a). Females also mature during their first year of life, but probably require an additional year before eggs are sufficiently large to oviposit. The adults appear to be generalist feeders. McMillan and Semlitsch (1980a) found a variety of small invertebrates in the stomachs of 124 adults from South Carolina that include flies, beetles, hemipterans, homopterans, ants, wasps, collembolans, spiders, pseudoscorpions, mites, ticks, and millipedes. Ants, mites, and collembolans are the most common prey of individuals in this population.
General Ecology
Population Ecology: Local populations are organized around local breeding sites such as Carolina bays and seasonal, depressional ponds. The only study of population dynamics is that of Semlitsch et al. (1996) who conducted a 16-year study at Rainbow Bay at the Savannah River Site in South Carolina. The size of the breeding adult population was low at the initiation of the study, increased dramatically during year 7, then dropped sharply and remained consistently low during the last 6 years of monitoring (1989-1994). The size of the annual breeding population was not correlated with the amount of rainfall that occurred during the breeding season, but was positively correlated with the number of metamorphs produced in subsequent years. The number of juveniles produced per female was independent of the initial number of larvae in the pond and there was little evidence that larval production was negatively affected by the densities of other salamander larvae in the pond. Gibbons and Semlitsch (1991) estimated that local breeding populations can vary from around 10-10,000 animals.

McKee et al. (2017) examined fine-scale genetic variation using microsatellite loci on a preserve in southwestern Georgia. Local pond populations exhibited genetic isolation by distance, indicating that populations closer in proximity to each other were more similar. Their evidence suggests that pond populations that are only a few hundred meters apart have high connectivity due to frequent dispersal among neighboring wetlands.
Community Ecology: Taylor et al. (1988) compared the diet of E. quadridigitata larvae with that of larval Ambystoma talpoideum and Notophthalmus viridescens that share a Carolina bay in South Carolina. Dietary overlap between A. talpoideum and E. quadridigitata is much lower than between A. talpoideum and Notophthalmus. These differences are likely due to size differences between larvae and the fact that A. talpoideum feeds in the water column at night while E. quadridigitata does not. All three species feed rather heavily on small zooplankton when small, but incorporate larger prey such as chironomid larvae into the diet as they grow.

Adverse Environmental Impacts
Habitat Fragmentation: McKee et al. (2017) found a negative association between local allelic richness and roads within 0.5 km of breeding sites. This suggests that roads can act as potential barriers to dispersal and have a negative effect on amphibian genetic diversity.
Status in North Carolina
NHP State Rank: S1
Global Rank: G5
Status in North Carolina: SC

Photo Gallery for Eurycea quadridigitata - Southern Dwarf Salamander

2 photos are shown.

Recorded by: Steve Hall and Chuck Smith
Robeson Co.		Recorded by: Steve Hall and Chuck Smith
Robeson Co.
Comment: Note the presence of only four toes on the hind foot.