Dwarf Salamander, Coastal Plain Dwarf Salamander
© 2017 Dr. Joachim Nerz (1 of 21)
Country distribution from AmphibiaWeb's database: United States
Eurycea quadridigitata, Holbrook, 1842
Ronald M. Bonett1
1. Historical versus Current Distribution. Dwarf salamanders (Eurycea quadridigitata) were described (as Salamandra quadridigitata) by Holbrook (1842); the type locality was restricted by Schmidt (1953) to the vicinity of Charleston, South Carolina. Cope (1869) transferred this taxon to the genus Manculus (as M. quadridigitatus). Dunn (1923) considered Manculus a junior synonym of Eurycea, and Wake (1966) concurred. However, Mittleman (1947, 1967) supported recognition of the genus Manculus, and recognized three subspecies: M. q. quadridigitatus throughout the southeast and much of the Gulf Coastal Plain; M. q. paludicolus from Louisiana and eastern Texas; and M. q. uvidus from northeastern Texas, western Arkansas, and southwestern Missouri. Nearly all recent authors consider this taxon a single species, Eurycea quadridigitata. Molecular work supports inclusion of this taxon in Eurycea under the Linnean system of nomenclature (Chippindale et al., 2000; C. Hass and R. Highton, unpublished data; P.T.C., unpublished data). In the broad sense, dwarf salamanders have a wide range from North Carolina south into much of peninsular Florida, and west into eastern Texas and southern Arkansas; they occur primarily in the Atlantic and Gulf Coastal Plain regions (see map in Petranka, 1998). However, recent molecular work has revealed deep divergences within this "species," and also suggests that the taxon may not be monophyletic (Chippindale et al., 2000; C. Hass and R. Highton, unpublished data; P.T.C., unpublished data). Eurycea quadridigitata probably consists of at least four distinct species, some of which occur sympatrically but apparently do not interbreed (R. Highton, personal communication). In fact, Harrison and Guttman (2003) have recently described Chamberlain’s dwarf salamanders (Eurycea chamberlaini) from an isolated area in the western Piedmont of South Carolina, the lower Piedmont of North Carolina, the upper Coastal Plain of South Carolina, and the central portion of the Coastal Plain in North Carolina (see account, this volume). Even in the area of the type locality, at least two species are present and sometimes sympatric (R. Highton, personal communication). A formal taxonomic treatment of this complex is expected in the near future. Given this situation, the information for "E. quadridigitata" summarized here almost certainly represents a composite of data for several, perhaps distantly related, species.
2. Historical versus Current Abundance. Generally unknown, but numbers are undoubtedly lower in areas impacted by human activities (Petranka, 1998). Local abundance of adult members of the E. quadridigitata complex was monitored during a 16-yr study (1979–'94) of a Carolina bay in South Carolina (Semlitsch et al., 1996). Breeding adult numbers were not influenced by seasonal rainfall amounts, and recruitment of juveniles was not influenced by larval densities. Juvenile recruitment was, however, influenced by the number of breeding adults. Members of this complex appear to be common in suitable habitat (Petranka, 1998), but given the current confusion regarding species boundaries and the probable occurrence of multiple, sometimes sympatric species, estimates of distribution and abundance should be considered questionable.
3. Life History Features.
A. Breeding. Reproduction is aquatic.
i. Breeding migrations. In South Carolina, E. quadridigitata migrate to breeding ponds from August–October (Gibbons and Semlitsch, 1991) and have been collected during migration until late November (McMillan and Semlitsch, 1980). South Carolina breeding populations can include ≤ 10,000 adults, with approximately equal representation of males and females (Gibbons and Semlitsch, 1991). In South Carolina, breeding migrations occur primarily at night, but individuals will also migrate crepuscularly and diurnally (Semlitsch and Pechmann, 1985; Gibbons and Semlitsch, 1991). It has been suggested that dwarf salamanders avoid predation and desiccation during diurnal migrations by traveling beneath the leaf litter (Semlitsch and Pechmann, 1985). Individuals were collected during apparent breeding migrations from late autumn to early winter in east-central Alabama (Trauth, 1983).
ii. Breeding habitat. In the Atlantic Coastal Plain of South Carolina, Eurycea quadridigitata use lentic habitats such as Carolina bays and ephemeral ponds (Gibbons and Semlitsch, 1991). Similarly, in Florida, dwarf salamanders were found only to be associated with ponds (Goin, 1951). In east-central North Carolina, however, adult dwarf salamanders and their eggs have been found along small streams (Brimley, 1923), suggesting that members of this complex will also breed in lotic habitats (Goin, 1951).
i. Egg deposition sites. Females attach their eggs singly to vegetation and other substrates such as twigs, rootlets, and debris. Eggs usually are laid so that they are associated with flowing water (Brimley, 1923; Carr, 1940a; Harrison, 1973; Trauth, 1983). Eggs may also be laid in shallow depressions beneath cover objects along wetland margins (Goin, 1951) or in dry depressions that will fill with spring rains (Taylor et al., 1988).
ii. Clutch size. Developmental data have been collected on members of the E. quadridigitata complex from several localities throughout the range. Clutches containing from 7–48 eggs are oviposited by South Carolina females from November–December when breeding ponds fill (Gibbons and Semlitsch, 1991). Females from east-central Alabama populations had previtellogenic follicles within their ovaries from March–September and enlarged ovarian follicles (14–59) from October–February; oviposition probably occurs over a broad time period in this region (Trauth, 1983). Numerous eggs have been discovered in the field in east-central North Carolina during early February (Brimley, 1923). In Florida, single clutches containing 20 eggs and 62 eggs were recovered from the field in November and February, respectively (Goin, 1951). This lack of synchrony in oviposition by populations in different locations may actually reflect interspecific differences among members of this complex. In the lab, eggs from Florida populations took approximately 3–4 wk to hatch, with hatchlings measuring from 7.5–8.3 mm in total length (Goin, 1951).
C. Larvae/Metamorphosis. As with all hemidactyliines, members of the E. quadridigitata complex have an aquatic larval stage (Petranka, 1998). Goin (1951) described larvae from Florida populations to be morphologically intermediate between typical pond-type and stream-type salamander larvae, with a dorsal caudal fin that extends anteriorly to the mid dorsum (pond characteristic) and relatively few gill filaments (stream characteristic). A photograph of a larval dwarf salamander from southeastern North Carolina (R.W. VanDevender, in Petranka, 1998) matches the description of dwarf salamander larvae from Florida by Goin (1951). Larvae of members of the Eurycea quadridigitata complex have been found to inhabit temporary ponds and Carolina bays in South Carolina (Semlitsch, 1980a; Taylor et al., 1988; Gibbons and Semlitsch, 1991). Additionally, it is likely that larvae develop in the aquatic habitats immediately adjacent to oviposition sites. This suggests that hammock ponds (Goin, 1951) and streams (Brimley, 1923) should also be included as larval habitats for members of this complex. It is unclear whether these reported differences in larval habitat reflect interspecific differences among members of this complex or the ability of larvae of these species to use a variety of aquatic habitats.
i. Length of larval stage. Most larvae metamorphose 2–6 mo after hatching (Brimley, 1923; Harrison, 1973; Semlitsch, 1980a; Petranka, 1998). Harrison (1973) and Semlitsch (1980a) found small larvae in January and February in South Carolina. Mount (1975; see also Petranka, 1998) noted small larvae in pools and ditches in March in Alabama.
ii. Larval requirements.
a. Food. According to Petranka (1998), larvae are benthic feeders. Prey include small invertebrates such as zooplankton, ostracods, and insect larvae (Taylor et al., 1988; see also Petranka, 1998).
b. Cover. Larvae are likely benthic.
iii. Larval polymorphisms. Unknown and unlikely.
iv. Features of metamorphosis. Newly metamorphosed dwarf salamanders have been found from April (Harrison, 1973) to early July (Semlitsch, 1980a; Taylor et al., 1988; see also Petranka, 1998).
v. Post-metamorphic migrations. Unknown and unlikely.
vi. Neoteny. Unknown.
D. Juvenile Habitat. Similar to adult habitat.
E. Adult Habitat. Most studies of adult members of the E. quadridigitata complex have involved individuals intercepted during migrations to and from breeding ponds. Therefore, aside from general notes on habitats where adult dwarf salamanders have been uncovered in the field, little is known about their terrestrial habitat characteristics outside of the breeding season. In general, members of the E. quadridigitata complex have been found beneath cover objects at the edges of ponds and swamps as well as in seeps and amongst leaf litter in springs (Mount, 1975; Petranka, 1998).
F. Home Range Size. Unknown. However, Carr (1940a) notes that dwarf salamanders from Florida can be found at considerable distances from aquatic habitats outside of the breeding season.
G. Territories. Unknown.
H. Aestivation/Avoiding Dessication. Aestivation is unknown.
I. Seasonal Migrations. The only known migrations for the species of the E. quadridigitata complex are apparently for breeding purposes.
J. Torpor (Hibernation). Unknown.
K. Interspecific Associations/Exclusions. Studies in South Carolina have examined diel patterns of adult migratory activity (Semlitsch and Pechmann, 1985), and larval trophic relations of dwarf salamanders and other sympatric salamanders such as eastern newts (Notophthalmus viridescens) and various ambystomatids (Taylor et al., 1988). These studies have revealed a host of interspecific differences, but none that can be directly attributed to interactions between the species examined. Some members of the E. quadridigitata complex are known to occur sympatrically and are distinguishable based on both external morphology and molecular markers (R. Highton, personal communication). Other plethodontids that have been found syntopic with members of the E. quadridigitata complex in southern Mississippi and southeastern Louisiana include three-lined salamanders (Eurycea guttolineata), southern red salamanders (Pseudotriton ruber vioscai), and spotted dusky salamanders (Desmognathus conanti; R.M.B., personal observation).
L. Age/Size at Reproductive Maturity. In east-central North Carolina, dwarf salamanders are reported to hatch in March and transform 2–3 mo later (Brimley, 1923). Larval periods of approximately 5–6.5 mo are reported for South Carolina populations (Harrison, 1973; Semlitsch, 1980a), and both males and females reach sexual maturity about 8–9 mo after hatching (Semlitsch, 1980a). Semlitsch (1980a) proposes that males are likely to reproduce during their first year, while females likely take an additional year for ova to develop. There has been considerable variation in size at maturity reported among populations of this complex, and the different species that currently are considered E. quadridigitata may mature at different sizes. Monitoring natural populations in South Carolina, Semlitsch (1980a) found larval periods to last from 5–6 mo when individuals attain lengths of 20.7–25.6 mm SVL. Other measurements of newly metamorphosed individuals from South Carolina showed a smaller size at metamorphosis (17–20 mm SVL; Harrison, 1973).
M. Longevity. Unknown.
N. Feeding Behavior. In South Carolina, dwarf salamander larvae feed diurnally, with small individuals taking primarily zooplankton and large larvae consuming small invertebrates (Taylor et al., 1988). Metamorphosed individuals in South Carolina were found to feed upon acarinans, arachnids, coleopterans, collembolans, diplopods, dipterans, hemipterans, homopterans, hymenopterans, and pseudoscorpionids (McMillan and Semlitsch, 1980). Acarinans, arachnids, coleopterans, collembolans, hymenopterans, and larval insects were recovered from the stomachs of terrestrial individuals from southern Georgia (Powders and Cate, 1980). The individuals examined by Powders and Cate (1980) were from two distinct size classes, but showed no differences in preferred prey items. Individuals from Florida populations were found to feed upon coleopterans (larval and adult), annelids, and amphipods (Carr, 1940a).
O. Predators. Examination of stomach contents of 122 pig frogs (Rana grylio) from southwest Georgia revealed four dwarf salamanders (Lamb, 1984). This is the only evidence of predation on dwarf salamanders, although it has been speculated that birds, snakes, and large invertebrates are likely predators (Petranka, 1998).
P. Anti-Predator Mechanisms. Unknown.
Q. Diseases. Unknown.
R. Parasites. Unknown.
4. Conservation. Members of the Eurycea quadridigitata complex currently are given no special protective status. Given the existence of several putative, currently undescribed species in the group, their conservation status should be re-examined after species boundaries and geographic ranges have been accurately delineated.
1Ronald M. Bonett
2Paul T. Chippindale
Literature references for Amphibian Declines: The Conservation Status of United States Species, edited by Michael Lannoo, are here.
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Citation: AmphibiaWeb. 2019. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 15 Dec 2019.
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