Amphibians of North Carolina
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Sole representative of Amphiumidae in NC
NC Records

Amphiuma means - Two-toed Amphiuma

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Taxonomy
Class: Amphibia Order: Caudata Family: Amphiumidae
Taxonomic Comments:
Species Comments:
Identification
Description: The Two-toed Amphiuma is an impressively large, elongated, eel-like salamander with four tiny limbs and two toes on each foot. Adults have lungs and there is a single pair of gill slits, but no external gills (Beane et al. 2010, Petranka 1998). The tail is laterally compressed and comprises 20-25% of the body length. The number of costal grooves varies from 57-60 and averages about 58. The dorsum is nondescript and varies from black to dark brown or gray. The venter is similar, but lighter, and does not sharply contrast with the darker dorsum. This species is one of the largest salamanders in the world, with adults reaching 46-116 cm TL. Males that Mitchell (2016) collected from Virginia were about 15% larger than females on average. The hatchlings average around 55 mm TL, are black above, and have tan bellies, grayish throats, and white gills. All four limbs are functional at hatching and the juveniles are similar in color to the adults (Petranka 1998). The Two-toed Amphiuma superficially resembles our two Siren species, but sirens have a single pair of legs and conspicuous, bushy gills.
Vocalizations: The Two-toed Amphiuma produces sounds that consist of low-, mid-, and high-frequency clicks. These appear to only be produced when they are near other individuals, and individuals are capable of detecting the low- and mid-frequency clicks (Crovo et al. 2016). The exact function of the clicking behavior is uncertain, but it is presumed to have a social function such as being a defensive or warning response.
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Observation Methods: Specimens are most easily collected by dipnetting, seining, or trapping with turtle, minnow, and commercial crayfish traps. Johnson and Barichivich (2004) found that commercially available crayfish funnel traps were very effective in trapping both A. means and Siren lacertina.
AmphibiaWeb Account
Distribution in North Carolina
Distribution Comments: The Two-toed Amphiuma occurs primarily in Coastal Plain habitats from southeastern Virginia to extreme southeastern Louisiana. A few populations have been found in the eastern Piedmont in areas adjoining the Coastal Plain.
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GBIF Global Distribution
Key Habitat Requirements
Habitat: This species is strongly affiliated with permanent or semipermanent aquatic habitats. It can be found in swamps, ponds, sloughs, abandoned rice fields, slow-moving streams, flooded ditches, semipermanent seasonal wetlands and other still and sluggish waters (Beane et al. 2010, Petranka 1998). Individuals have been found in crayfish burrows, but also create their own burrows. Sites that have dense aquatic vegetation and soft substrates that allow burrowing often harbor robust populations. Schalk et al. (2010) found that summer-active animals at a South Carolina site were most commonly trapped in relatively shallow water where fish and crayfish were most abundance, while Sorensen (2003) only collected animals in vegetation mats. Snodgrass et al. (1999) surveyed sites in South Carolina for A. means, Siren intermedia, and S. lacertina and found that the likelihood of finding these large aquatic species increased with seasonal duration of the sites and whether other sites were in close proximity. Sites that held water for less than six months were not occupied, and those that were relatively close to adjoining wetlands were more likely to have populations of A. means and sirens.

In North Carolina, Two-toed Amphiumas occur in a variety of permanent and semipermanent habitats. Commonly used habitats include the sluggish portions of bottomland streams and rivers, cypress swamps, ponds and small lakes, canals, flooded ditches, beaver ponds, and semipermanent marshes.
Biotic Relationships: Amphiumas are preyed upon by water snakes (Nerodia), mud and rainbow snakes (Farancia spp.), cottonmouths (Agkistrodon piscivorus), and large wading birds (Petranka 1998). Defensive behavior primarily involves biting, and large specimens can deliver a painful bite.
See also Habitat Account for Coastal Plain Still and Sluggish Waters
Life History and Autecology
Breeding and Courtship: Although A. means is common in many regions of its range, many aspects of the breeding biology of this species are poorly documented. Mating apparently occurs during the winter months. Populations in Louisiana appear to court and mate from December through February based on seasonal changes in reproductive structures (Rose 1967), while brooding females with eggs at early developmental stages have been found in February in Florida (Petranka, 1998). Courtship behavior has not been described, but fertilization is internal (Rose 1967).
Reproductive Mode: Females deposit their eggs in oblong cavities that they construct, then remain coiled about their eggs through hatching. The eggs are laid in rosary-like fashion and have 1 mm diameter constrictions of the outer sheaths that separate adjoining ova by a distance of 5-10 cm. The eggs and outer sheaths are about 10 mm in diameter (Petranka 1998). The estimated clutch size of 22 females from southern Louisiana population averaged 201 (range = 106-354 eggs) and was positively correlated with female SVL (Rose 1966).

Most nesting females have been found on land close to standing water, but in some cases this may reflect instances where females laid in water and their nests were exposed as water levels receded seasonally. Gunzburger (2003) discovered three clutches with attending females in a dried bed of a lake in Florida that were buried about 50 cm below the surface. Other examples include a female that was guarding 33 late-term eggs in September in a hollow log in the dried bed of a tupelo-cypress swamp in Georgia, a female that was coiled around a cluster of 49 eggs in southern Florida in early February, and four groups of eggs that were found in July beneath logs in the partially dried beds of ponds (Petranka 1998). In Florida the nests are occasionally found in the nest mounds of the American Alligator. The alligator nests are usually constructed in June and Amphiuma eggs can be found in July. The relatively large eggs may take as long as 5-6 months to develop, with hatching occurring during the summer. Gunzburger (2003) found that the developing embryos exhibit delayed hatching and were capable of surviving an average of 110 days on moist substrate without hatching. Eggs that were inundated later in development produced larger hatchlings.
Aquatic Life History: Larvae reabsorb their gills within a few days to a week or two after hatching. The hatchlings have large yolk reserves and can survive for several months without feeding (Gunzburger 2003). Very small juveniles presumably feed on small invertebrates, but little is known about their diet. The older juveniles and adults construct burrows in or near aquatic habitats and have been excavated by farmers and construction crews > 1 m below the ground surface (Petranka 1998). Individuals are primarily active at night and tend to be less active during the winter months (Sorensen 2003). Their feeding modes include actively prowling about in shallow water in search of prey, as well as ambushing passing prey that approach their burrow entrances (Carr 1940, Dundee and Rossman 1989, Funderburg 1955).

The adults appear to maintain small home ranges or possibly territories that may reflect fidelity to their burrows. Sorensen (2003) repeatedly trapped animals in a Florida lake and found that 83% of recaptures occurred at the same trapping station as the original capture. The maximum distance between captures for the exceptions to this general pattern was only 5 m over two months. The estimated population density was 0.28 individuals/m2.

Individuals are occasionally taken in terrestrial pitfall traps and have been seen on rare occasion crossing roads on rainy nights. This suggests that this species is capable of dispersing short distances over land (Gibbons and Semlitsch 1991, Petranka 1998). During seasonal droughts individuals aestivate in burrows deep underground and survive on stored fat. Remarkably, captive adults can live 1-3 years without food (Gunter 1968, Rose 1966). Four live A. means were plowed up after a wetland had been dry for two years (Knepton 1954), which implies that they can endure multiyear droughts that occur infrequently. Snodgrass et al. (1999) did not find any animals in ponds that held water for < 6 months per year. They surmised that animals that are forced to aestivate annually in ponds with short hydroperiods may not be able to store sufficient fats on an annual basis to survive over many years. Almost no data are available on survival and longevity in nature, but captive specimens may live as long as 27 years (Nigrelli 1954).

The adults are large, powerful predators and can handle both vertebrate and invertebrate prey. Crayfishes appear to be particularly important in the diet, but numerous other prey items are consumed depending on the size of the individuals (Petranka 1998). Mitchell (2013) found tadpoles, small frogs, a crayfish, small fishes, and several taxa of insects in Virginia specimens. Carr (1940) noted that crayfishes, salamanders, and small frogs are important food items in Florida populations, while Duellman and Schwartz (1958) found maggots, odonates, aquatic beetles, crayfishes, and a fish in southern Florida specimens. Specimens from southern Florida and South Carolina that were examined by Hamilton (1950) consumed insects, snails, spiders, crayfishes, tadpoles, frogs, snakes, turtles, lizards, and fishes, including mosquitofish, sunfishes and bass.
General Ecology
Population Ecology: Factors that regulate local populations are poorly understood. Individuals can deliver a powerful bite, but it is uncertain if they are territorial or aggressively defend their burrows from conspecifics.
Community Ecology: The Two-toed Amphiuma and the Greater Siren (Siren lacertina) commonly co-occur in coastal wetlands throughout the southeast and could potentially compete or function as mutual predators on each other's young (Snodgrass et al. 1999). Schalk et al. (2010) examined summer habitat use in a South Carolina pond and found evidence of partial spatial segregation. Siren lacertina was mostly found in relatively deep areas of the pond where aquatic insects were most abundant and floating and emergent vegetation prevailed. In contrast, A. means occurred more frequently in relatively shallow areas where fishes and crayfishes were most abundant and floating and submerged vegetation prevailed. Siren lacertina appeared to use the entire water column, while A. means were only caught in the lower water column.
Adverse Environmental Impacts
Habitat Loss: Snodgrass et al. (1999) surveyed intermittent ponds in South Carolina and provided data which suggest that prolonged droughts may cause local populations to be extirpated. Amphiuma means has a difficult time dispersing over land or in very shallow water (Schalk and Luhring 2010). To disperse to and recolonized isolated wetlands, this species likely relies on the formation of aquatic connections during flooding events. Road construction or other human activities that alter flooding events and watershed connectivity may compromise the metapopulation viability of populations that use semipermanent wetlands. The outright destruction of wetlands across a landscape would also increase the distance to nearest neighbors and reduce the probability that local ponds could be recolonized following local extirpations.
Status in North Carolina
NHP State Rank: S4
Global Rank: G5
Status Comments: The status of this species in North Carolina is uncertain because of the difficulty of monitoring this secretive, aquatic species. Many of our records are based on the occasional capture of single individuals in minnow traps, or when seining or dip-netting.