Amphibians of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

Ambystomatidae Members:
Ambystoma talpoideum - Mole Salamander

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Taxonomy

Class: Amphibia

Order: Caudata

Family: Ambystomatidae


Taxonomic Comments: The genus Ambystoma consists of 32 currently recognized species that are found in North America and Mexico. The terrestrial adults have stout bodies and legs, widely spaced eyes, and well-developed costal grooves.
Species Comments:

Identification

Description: The adults of the Mole Salamander are unusual in that they occur as both terrestrial forms and gilled adults that never leave the water. Most local populations have only terrestrial adults, but some populations have a mixture of gilled adults (paedomorphic larvae) and terrestrial adults. The terrestrial adults are short, stocky salamanders with short tails, large limbs, and prominent, rounded heads. The dorsum varies from light brown or bluish gray to dark gray or blackish. The dorsum and sides have light gray specks which are inconspicuous in many specimens. Both the juvenile and adults have parotoid glands that produce noxious secretions that repel predators. Sexually active males have swollen vents and rough, granular regions on the dorsolateral regions of the tail. The adults vary from 8-12 cm TL (Petranka 1998).

The hatchlings have bold, alternating black and yellow blotches along the midline of the back, and conspicuous patches of yellow and black on the tail fin. Larvae in late developmental stages have two conspicuous cream or dull yellow stripes on each side that break into blotches near the tail. A characteristic dark band extends along the midline of the belly in older larvae, gilled adults, and recently transformed juveniles. The gilled adults have a less prominent lateral stripe, and are generally darker than sexually-immature larvae. Sexually-active males of both adult types can be distinguished from females by their swollen cloacal glands.

Technical Reference: Petranka (1998), Trauth (2021)

Online Photos: Google iNaturalist

Observation Methods: The adults are most commonly found when they undergo seasonal migrations to the breeding ponds during late autumn through late winter. They can be found beneath logs or other cover objects around the pond perimeters during the breeding season. The larvae are distinctively marked and most easily obtained by dip-netting during the spring and summer months. The larvae hide in leaf litter during the day but feed in the water column at night, where they can be observed with a flashlight.

AmphibiaWeb Account

Distribution in North Carolina

Distribution Comments: Ambystoma talpoideum occurs throughout much of the southern Atlantic and Gulf Coastal Plains from South Carolina to eastern Texas, then northward along the Mississippi River Valley to southern Illinois. Disjunct populations that are mostly outside of the Coastal Plain occur at scattered localities in Kentucky, Virginia, Tennessee, North Carolina, northern South Carolina, northern Georgia, and northern Alabama (Petranka 1998, Trauth 2021). In North Carolina, populations have only been found in the Piedmont and lower elevations in the Blue Ridge Mountains, even though they are common in Coastal Plain habitats in South Carolina.
Distribution Reference: Beane et al. (2010), Petranka (1998), Trauth (2021)
County Map: Clicking on a county returns the records for the species in that county.


GBIF Global Distribution

Key Habitat Requirements

Habitat: Mole Salamanders require forested habits and are generally restricted to using fish-free breeding sites. Adults breed in a wide variety of both temporary, semi-permanent, and permanent habitats, including flooded roadside ditches, gravel pits, woodland pools, abandoned farm ponds that lack fish, and Carolina bays. On rare occasions they may use breeding sites in the Coastal Plain that have low densities of fish. They occur in a variety of forest types, including upland hardwood forests, mixed pine-hardwood forests, Longleaf Pine-dominated habitats, and bottomland forests and swamplands. In the Coastal Plain of South Carolina and elsewhere, the terrestrial juveniles and adults are most abundant in extensive floodplain forests and in areas near gum and cypress ponds (Semlitsch 1981, Shoop 1960). A local population may consists entirely of terrestrial adults or have a mixture of gilled and terrestrial adults. Populations with only terrestrial adults predominate in areas where the breeding sites dry annually, while gilled adults predominate where there are permanent or semipermanent ponds that lack fish (Scott 1993, Semlitsch and Gibbons 1985, Semlitsch et al. 1990).

In North Carolina, most populations appear to be comprised entirely of terrestrial adults, although larvae that overwinter in ponds may reach sizes that approximate the size of sexually mature, gilled adults. Local populations have been found in or near hardwood or mixed hardwood-pine forests with seasonal or permanent ponds that lack fish. The breeding sites include marshes, vernal ponds, seasonal ponds in floodplains, bogs, and artificial habitats such as constructed ponds and farm ponds.

Biotic Relationships: The larvae, gilled adults, and terrestrial adults are all generalized predators on small invertebrates, and occasionally on other amphibian larvae. Small seasonal and semipermanent ponds tend to be driven by the seasonal decay of leaf litter and aquatic vegetation, which in turn supports thriving communities of zooplankton and aquatic insects. The larvae and gilled adults typically inhabit fish-free breeding sites and in many ways fulfill the functional role of small fishes in permanent ponds where they are top predators on pond invertebrates. The larvae are palatable and lack chemical defenses against predatory fish, which is presumably why local populations are largely restricted to areas where fish-free breeding sites are present. The larvae and gilled adults are undoubtedly preyed upon by numerous aquatic predators such as odonates, diving beetles, wading birds, and aquatic snakes (Durso et al. 2013).

See also Habitat Account for General Forests with Isolated Pools

Life History and Autecology

Breeding and Courtship: The terrestrial adults begin migrating to the breeding sites on rainy nights in the late fall or early winter as cool rains arrive, and continue until courtship and breeding is underway. Heavy rains often trigger relatively large numbers of adults to migrate, while autumnal droughts can reduce the number of migrants. In South Carolina, a peak in arrival occurs from November through January depending on annual rainfall patterns. Where a local population consists of both gilled and terrestrial adults, gilled adults normally breed 6 weeks or more before the terrestrial adults and the larvae gain a size advantage (Petranka 1998). Breeding of the terrestrial adults occurs from December through March depending of the locale, with southern populations often beginning in December.

Courtship involves the male and female prodding each others cloacal region and engaging in a circular waltz for one or two revolutions (Shoop 1960). The male then begins wagging his pelvic region and tail, and leads the female forward while she keeps her head in close proximity to his tail. The male eventually deposits a spermatophore on the substrate, and the female moves over the spermatophore and picks up the entire spermatophore or the sperm cap with her cloacal lips. Females are often courted by several males, and one male may break up courting pairs to lead the female away from a rival.

Reproductive Mode: The mode of egg deposition differs among Gulf Coastal Plain and Atlantic Seaboard populations. Females in Gulf Coast populations lay their eggs in small masses that are often placed on the same twig, while females along the Atlantic Seaboard lay their eggs singly and attach them to twigs, vegetation, leaf litter or other substrates. All populations in South Carolina and North Carolina appear to lay their eggs singly in ponds (Petranka 1998), and a single female may lay four hundred or more eggs over the course of several days. After breeding, the adults leave the ponds and migrate into the surrounding forest.

Aquatic Life History: The hatchlings begin feeding almost immediately on cladocerans, copepods and other zooplankton. As the larvae grow they incorporate larger prey into the diet such as midge larvae and other aquatic insects, but continue to feed rather heavily on zooplankton. Larvae grow rapidly following the spring warm-up and in some populations metamorphose into terrestrial juveniles after 3-6 months of growth. In coastal South Carolina where populations have been intensively studied, some of the larvae begin to mature sexually as gilled adults by September when > 30 mm SVL. They first breed in December or January when about 1-year old. Gilled females at this time are typically > 34-36 mm SVL. Others leave the ponds as terrestrial juveniles and require a longer period to reach adulthood. Populations in North Carolina appear to consist of only terrestrial adults, although a small proportion of larvae in populations in the mountains often overwinter in the ponds and transform the following spring or early summer when they are nearing the reported minimum size of gilled adults. Seasonal pond drying and low food levels can trigger the larvae to metamorphose (Semlitsch et al. 1990), but only if they are > 32-38 mm SVL. In drought years, larval survival is often 0% due to early pond drying.

Terrestrial Life History: The recently transformed juveniles move from the pond margins to the surrounding forest during periods of rainy weather. Semlitsch (1981) estimated that juveniles move a median distance of only 47 m from ponds in coastal South Carolina, compared to 156 m for females and 213 m for males. The adults establish small home ranges and live in underground borrows and tunnels during the summer that on average are about 5 cm beneath the soil surface. They feed on earthworms, insects, and other invertebrates. Juveniles studied by Shoop (1960) became sexually mature when about 44-48 mm SVL. Raymond and Hardy (1990) found that most post-metamorphic growth occurs during the first year after transformation in Louisiana populations. Individuals first breed when about 2-years old and 52-55 mm SVL. Recaptures indicate that some individuals live for at least 8 years. Semlitsch et al. (1993) also noted that some individuals live for 6-8 years in Coastal Plain populations in South Carolina. Neither the juveniles or adults are aggressive towards one another, which suggests that there is little competition for burrows or food resources on land.

General Ecology

Population Ecology: Regional populations of the Mole Salamander show evidence of metapopulation structure where clusters of local pond populations are connected by the occasional movement of individuals between populations. Connectivity between local populations allows for the recolonization of ponds following local extinctions, and reduces the chance of a local population going extinct when a population is in decline. Local pond populations typically are comprised of a few hundred or fewer terrestrial adults, although one very large breeding site in South Carolina had at least 6,000 individuals (Trauth 2021). At sites where the surrounding forest buffer is intact and there is adequate habitat for the adults, the upper limit on adult population size in presumably set by density-dependent regulation during the larval stage. Larvae grow fastest when their densities in ponds are low, food levels are high, and the pond does not dry prematurely due to low seasonal rainfall. The larvae are aggressive towards their own and other Ambystoma species that share breeding sites and have similar diets. Competition for food can result in high mortality, stunted growth, and small size at metamorphosis (Petranka, 1998). Early pond drying associated with seasonal rainfall patterns will trigger the larvae to metamorphosis at a relatively small size, and can interact with density-dependent competition to further reduce the number and quality of juveniles that leave the ponds. In years when larval growth is severely compromised by crowding, none may be able to reach a sufficient size to metamorphosis before a pond dries prematurely.

Community Ecology: The Mole Salamander is an important member of seasonal and semipermanent pond communities where the larvae function as top predators on zooplankton and aquatic insects. The large larvae also feed on anuran larvae, and may compete with other salamanders for food. Ambystoma talpoideum tends to out compete A. maculatum larvae, presumably because A. talpoideum grows to a large size and is more aggressive (Semlitsch and Walls 1993). The gilled adults are undoubtedly important in fish-free permanent and semipermanent systems since they can be present year-round.

Adverse Environmental Impacts

Habitat Loss: Since European colonization, populations of this and other Ambystoma species have experienced significant long-term declines associated with deforestation, urbanization, agricultural and silvicultural activities, and the filling and draining of wetlands. Local populations require both fish-free breeding sites and large forested, hardwood buffers to support the juveniles and adults. Small wetlands like those used by the Mole Salamander are largely unprotected. From the 1950s–1970s the loss of wetlands in the Southeast was greater than in any other region of the country, with a net annual loss of 386,000 ac/yr (Hefner and Brown 1985). In North Carolina approximately 51% of all wetland acreage on the Coastal Plain has been lost. As local pond populations are lost from factors such as deforestation or wetland filling, metapopulation structure can be compromised as the distance between the nearest populations exceeds the dispersal distance of juveniles and adults.

Habitat Fragmentation: Much of the original Eastern Deciduous Forest has suffered from habitat fragmentation as the extensive tracts of hardwoods that blanketed North Carolina have been converted into a patchwork of agricultural fields, residential homes, urban development, pine plantations, roadways, and isolated hardwood parcels. In some cases small woodlots may have seasonal ponds that are adequate for the larval stage, but the surrounding hardwood forest is too small to support a viable adult population, especially a metapopulation. Even when hardwood parcels are sufficient to support a population, they may be isolated from nearest neighbors due to barriers to dispersal such as roadways or large agricultural fields.

The Mole Salamander has southern affinities, with populations being most common in the Coastal Plain. The northern portion of the range is fragmented and has several geographically isolated groups in Virginia, North Carolina, Tennessee and elsewhere. These may reflect the fact that this species expanded its range northward during interglacial warm periods, and has since retreated, leaving isolated local and regional populations outside of the Coastal Plain. In North Carolina, many populations appear to conform to this pattern, with most being single populations or a few regional groups that tend to be geographically isolated from nearest neighbors.

Small, isolated populations are vulnerable to local extinction and many may ultimately be lost with time. Human-altered landscapes have accentuated the problem by creating barriers to movement such as large agricultural fields and urban development. Absolute barriers include multiple-lane roads, especially those with concrete median barriers. Large bodies of water may also serve as barriers but rivers and streams may or may not be passible, depending on width, current, and presence of predatory fish. NatureServe additionally estimates that populations separated by > 1 km of unsuitable habitat are effectively isolated from one another. Unsuitable habitat for this species includes open fields, pine plantations, and developed areas.

Status in North Carolina

NHP State Rank: S2S3

Global Rank: G5

Status in North Carolina: SC

Environmental Threats: Clearcutting and other forest management practices that remove the forest canopy and disturb the ground cover can adversely affect amphibians that live in forested landscapes. Rothermel and Luhring (2005) found that A. talpoideum that were experimentally enclosed in clearcuts rapidly dehydrated relative to those in more intact forests. Only 40% of the salamanders in clearcuts survived versus 90% in a thinned stand and 100% in an intact forest. When provided artificial burrows, survival improved on the clearcuts. Raymond and Hardy (1991) also found a decline in adult A. talpoideum that returned to a breeding pond following clearcutting, while Cromer et al. (2002) found that the abundance of A. talpoideum was negatively associated with areas with less canopy cover and pronounced rutting (i.e., gaps and skidder trails). The more permanent loss of forested habitat around breeding ponds due to the conversion of land to agricultural fields or urban development presents even greater risks. Deaths from increasing vehicular traffic, and the continued loss and degradation of small, seasonal and semipermanent wetlands from pond filling, excessive sedimentation, and environmental pollutants present significant future risks to the remaining North Carolina populations.

Status Comments: The Mole Salamander largely consists of scattered, isolated populations in North Carolina that may reflect relicts from a previous range expansion and subsequent contraction. Small, isolated populations are vulnerable to local extinctions, and there is concern that many of the known populations may suffer losses in the future.

Stewardship: Populations of these and most other Ambystoma species are best maintained by having a cluster of seasonal ponds in close proximity, along with protective forest buffers that extend for 200 m or more from the pond margins.

Photo Gallery for Ambystoma talpoideum - Mole Salamander		14 photos are shown.
	Recorded by: Emily Stanley Buncombe Co.	Recorded by: Emily Stanley Buncombe Co.
	Recorded by: Emily Stanley Buncombe Co.	Recorded by: Emily Stanley Buncombe Co.
	Recorded by: Emily Stanley Buncombe Co.	Recorded by: R. Spainhour, M. Mabe Surry Co.
	Recorded by: R. Spainhour, M. Mabe Surry Co.	Recorded by: R. Spainhour Surry Co.
	Recorded by: Max Ramey Buncombe Co.	Recorded by: Max Ramey Buncombe Co.
	Recorded by: K. Long Rockingham Co.	Recorded by: K. Long Rockingham Co.
	Recorded by: Jim Petranka Buncombe Co. Comment: An overwintering larva from Buncombe Co.	Recorded by: Jim Petranka Buncombe Co.

Ambystoma talpoideum - Mole Salamander

Photo Gallery for Ambystoma talpoideum - Mole Salamander

14 photos are shown.