Amphibians of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

Ambystomatidae Members:
Ambystoma opacum - Marbled 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: The Marbled Salamander is one of five species of mole salamanders that are found in North Carolina. This strikingly marked species is one of numerous amphibians in the state that rely on small, seasonal ponds for successful reproduction. This species is unique in being the only Ambystoma that breeds on land, and the only Ambystoma that exhibits parental care of the eggs.

Identification

Description: The Marbled Salamander is a stout, medium-sized Ambystoma that has a black ground color that is overlain by conspicuous white or light gray crossbands across the head, back and tail. The crossbands often run together or are interrupted, and are broader on the sides of the body. Males have silvery white crossbands while those of females are silvery gray. The venter is black and lacks crossbands. Sexually active males can be readily distinguished from females by their white crossbands (light gray in females) and swollen cloacal glands. The adults vary from 77-127 mm TL.

The larvae have bushy gills and dorsal fins that extend almost to the front limbs. The body varies from drab brown or blackish above and has a ventrolateral series of light spots that form a line just below the level of the limb insertions. The throat is uniformly stippled with dark pigment, which is helpful in distinguishing this species from other Ambystoma larvae that share breeding ponds. The older larvae often develop mottling on the body and have varying degrees of light yellowish green coloration. Because of fall breeding, larvae collected in the early spring are normally much larger than other Ambystoma larvae that share breeding ponds. Recently transformed juveniles are brown or black with light flecks. The flecks become more pronounced and form lichenlike patterns within 1-3 weeks after metamorphosis. The juveniles begin developing the adult pattern within 1-2 months after transformation (Petranka 1998).

Technical Reference: Petranka (1998); Scott (2021)

Field Guide Descriptions: Beane et al. (2010)

Online Photos: iNaturalist Google iNaturalist

Observation Methods: The adults can be found beneath cover objects in and around breeding pools during the fall breeding season. The larvae can often be seen resting on leaf litter around the margins of ponds in late winter and spring and can be easily captured using dip-nets. During the summer both adults and juveniles are often active on the ground surface during wet weather.

AmphibiaWeb Account

Distribution in North Carolina

Distribution Comments: Ambystoma opacum occurs throughout much of the eastern United States in association with the Eastern Deciduous Forest. The range extends from southern New Hampshire and central Massachusetts southward to northern Florida, and westward to eastern Texas, southeastern Oklahoma, southern Missouri, southern Illinois and southwestern Indiana. Disjunct populations occur along the southern edge of Lake Michigan (Scott 2021). In North Carolina the Marbled Salamander is common in the Coastal Plain and eastern and central Piedmont, but uncommon to rare in the western Piedmont and Blue Ridge.
Distribution Reference: Beane et al. (2010); Petranka (1998); Scott (2021)
County Map: Clicking on a county returns the records for the species in that county.


GBIF Global Distribution

Key Habitat Requirements

Habitat: Marbled Salamanders are associated with hardwood forests, where the presence of hardwood leaf litter appears to be a critical factor for both adults and larvae. It provides both shelter for the salamanders themselves and support for the rich community of forest-floor invertebrates upon which they feed. The adults are commonly found in floodplain forests, but also occur in upland stands of hardwoods, including fairly dry ridge-tops. In all cases, suitable breeding habitat must be present. In North Carolina, this and other members of this genus breed in fish-free pools. These include vernal pools in the uplands, and depression ponds, isolated terrace pools, oxbows, and cut-off stream channels in floodplains. Females typically lay their eggs under hardwood leaf litter in the dried pool beds. Leaf litter in the flooded pools provides shelter for the larvae and supports a rich diversity of pool invertebrates that serve as prey.

Environmental and Physiological Tolerances: The juveniles and adults are vulnerable to desiccation and likely undergo prolonged periods of summer inactivity during periods with little or no rainfall. Despite reports that this species can occur in relatively dry habitats, there is no evidence that it differs from more aquatic species in terms of rates of water loss when placed on a dry substrate (Scott 2021). Although poorly documented, the juveniles and adults likely retreat to deep subsurface burrows during periods of hot, dry weather in the summer and fall. This species appears to be less cold-tolerant than the Spotted Salamander, ranging only as far north as southern New England rather than well up into Canada. It also occurs at lower elevations and is essentially absent from the mountains excepts for a few of the lower river basins and foothills of the Blue Ridge. Conversely, it may be more heat-tolerant, ranging well into the Coastal Plain where the Spotted Salamander is largely absent. No strong preferences for soil types have been observed, with populations occurring on mafic flats and ridges as well as blackwater floodplains.

Adaptations to Natural Disturbances: This species makes some use of dry ridges, where natural fires were once frequent and helped keep the habitat in open woodlands rather than closed canopy forest. However, Marbled Salamanders do not show any specializations for living in habitats where fires were once naturally frequent. Instead, they appear to be more adapted to habitats with long intervals between burns, where the leaf litter has a chance to build up and woody debris is common on the forest floor. At the other extreme, this species uses floodplain habitats, but typically where extensive flooding that scours the leaf litter from the pond beds occurs infrequently. Flooding from nearby streams can also introduce predatory fish. Regions in the upper terraces of floodplains are often ideal since infrequent flooding allows the accumulation of leaf litter and keeps the pools fish-free.

Biotic Relationships: Both adults and larvae are generalized predators on small invertebrates and occasionally other amphibian larvae. While they depend upon the presence of a well-developed detritivore food web in both their aquatic and terrestrial phases, they do not appear to be specialized on any one prey species. A key biotic relationship is their own existence as prey species, particularly in the larval stage. The larvae are palatable and lack chemical defenses against predatory fish. They can also suffer high mortality from invertebrate predators such as crayfishes and the larvae of dragonflies and dytiscid beetles. Seasonal pond drying helps to eliminate fish and other predators from the breeding ponds and enhances juvenile recruitment.

See also Habitat Account for Hardwood Forests with Isolated Pools

Life History and Autecology

Breeding and Courtship: Females nest in the dried beds of temporary ponds or along the margins of reduced ponds. The adults begin migrating from the surrounding woods to the breeding sites in late summer or autumn and move at night during rainy weather. The adults court and mate on land either while migrating to the ponds (Krenz and Scott 1994) or after reaching the dried pond beds. Populations in North Carolina typically breed in late-September through October, and in some instances into November (Brimley 1920, Petranka 1990). The males arrive at the breeding ponds from a few days to a week or more before the females. When courting, the male actively moves about and butts and lifts the female. The female often responds by nudging the cloacal region of the male. The male eventually moves forward along the body of the female and deposits a spermatophore on the substrate. If responsive, the female positions her cloaca over the sperm cap and picks up seminal fluid from the top of the spermatophore.

Reproductive Mode: After mating, each female selects a site in the dried or partially dried bed of a temporary pond and constructs a shallow nest. In most populations females appear to actively select nesting sites along elevational gradients in ponds. They typically avoid the deepest areas of the pond bed, and usually prefer intermediate elevations (Petranka 1990). The breeding ponds tend to fill incrementally as sequential rain events increase the pond's depth until it is at full capacity. Laying in a pond bottom can result in catastrophic mortality if the pond fills partially and triggers the embryos to hatch, then dries before the next rain event. Laying at the margins of ponds can also be disadvantageous since the embryos hatch later than those at intermediate elevations and may be at a competitive disadvantage.

The nest is made by burrowing an ovoid to oblong cavity in the soil surface immediately below the leaf litter or below a cover object. The female then lays her eggs singly within the depression, coils around her clutch, and occasionally moves about and turns the eggs while brooding. Females typically brood their eggs until their nests are flooded as a pond fills. However, nests without females are frequently found and often suffer higher egg mortality than guarded nests. Stenhouse (1987) found an average of 79 eggs per nest in two North Carolina populations. Petranka (1990) surveyed 11 populations in North Carolina and found an average of 92 eggs per nest when a female was attending the eggs, versus only 76.5 eggs per nest when the eggs were unattended.

Aquatic Life History: The embryos develop to the hatching stages within 9-15 days after oviposition, but do not hatch until the eggs are flooded by rising water. Flooding reduces the oxygen supply to the embryos and triggers the release of enzymes that dissolve the egg capsule and allow the embryos to escape (Petranka et al. 1982). This typically occurs during the fall or early winter as the ponds fill, but during dry years the embryos may remain enclosed in the egg capsules for prolonged periods before hatching.

The hatchlings feed mostly on cladocerans, copepods, and ostracods. As they grow, they incorporate larger prey into their diets, including insects, isopods, mites, snails, and oligochaetes (Petranka 1998). The large larvae will also eat small tadpoles and the hatchlings of other ambystomatid salamanders, including those of the Spotted Salamander in North Carolina (Stenhouse 1985). Larvae grow rapidly as water temperatures increase seasonally in late winter and spring. They may begin metamorphosing as early as March and April in the South. Stewart (1956) collected metamorphosing larvae from central North Carolina ponds between 31 March and 9 June that averaged 45-58 mm TL. Survival from hatching to the initiation of metamorphosis in 11 ponds that Petranka (1989) studied in the Piedmont of North Carolina varied from 1-44% and averaged 15% for larvae at natural densities.

Terrestrial Life History: Recently transformed individuals can be found beneath litter and debris around the margins of breeding ponds, but the juveniles disperse from ponds during rainy weather soon after transforming (Stenhouse 1987). Gamble et al. (2007) encircled 14 breeding ponds in Massachusetts with drift fences and found that juveniles occasionally moved between ponds, which helps to maintain metapopulation structure. Seventy-six individuals moved from 142-1297 m from their natal ponds. The juveniles and adults are fossorial throughout much of the year, but are sometimes active on the ground surface following rains in the summer and autumn. They establish small home ranges and feed on earthworms, insects, and other invertebrates. The males reach sexually maturity in about 2.5-3.3 years, while the female take slightly longer (2.8-4.9 years; Scott 2021). The mean size at first reproduction is approximately 53–60 mm SVL for both sexes. Adults that migrate to ponds tend to return to their home ranges after breeding, but a small percentage may move to adjoining ponds (Gamble et al. 2007). Using partial drift fences, Scott et al. (2013) found that 28% of adults moved > 172 m from a breeding pond in South Carolina., while adults migrated an average of 194 m (range = 0–450 m) in an Indiana study (Williams 1973).

General Ecology

Population Ecology: Local populations of the Marbled Salamander tend to be organized as metapopulations. A metapopulation is a regional group of local populations that 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. Density-dependent regulation of local populations appears to occur primarily during the larval stage. Data from several studies, including those in North Carolina (Stenhouse 1985, Petranka 1989), indicate that larval growth, size at metamorphosis, and survival are often inversely related to larval densities in ponds. The larvae compete with conspecifics for food and will aggressively attack conspecifics, particularly when the ponds contract seasonally and larvae are crowded in drying pond beds. In natural populations larval survival is usually low and most individuals in a cohort die before metamorphosing. Competition with other Ambystoma can also function in a density-dependent matter to limit the size of local adult populations. In North Carolina and elsewhere, small, fish-free wetlands are patchily distributed across the landscape and tend to support relatively small populations of Marbled Salamanders. Each breeding site typically has a few dozen to < 1000 adults (Scott 2021).

Community Ecology: Because this species is usually the first amphibian to hatch after seasonal ponds fill with water, the larvae are often much larger than other amphibian larvae that share breeding sites. Large A. opacum larvae are often major predators on other amphibian larvae and may outcompete other Ambystoma species for food due to their size advantage. The large larvae are aggressive and will eat both conspecific and heterospecific salamander larvae in ponds. In addition, individuals may bite off and eat the limbs, tails, or gills of live conspecifics. In North Carolina ponds, premetamorphic survivorship of A. maculatum is < 1% in ponds with A. opacum, and in some cases appears to be zero because of intense predation of the large larvae on hatchling A. maculatum (Stenhouse 1985). In addition, densities of A. maculatum are negatively correlated with densities of A. opacum across study ponds.

Adverse Environmental Impacts

Habitat Loss: Since European colonization, populations of the Marbled Salamander have experienced significant long-term declines associated with deforestation, urbanization, agricultural 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 this species 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 extensive tracts of hardwoods 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. Small, isolated populations are vulnerable to local extinction and may ultimately be lost with time. Absolute barriers to the movements of this species include multiple-lane roads, especially those with concrete median barriers. Bartoszek and Greenwald (2009) found that even a railroad track can function as a significant barrier to movement between neighboring pond populations. Large bodies of water such as reservoirs may also serve as barriers. Rivers and streams may or may not be passible, depending on width, current, and the presence of predatory fish. NatureServe 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.

Effects of Pollution: Like other small aquatic species, Marbled Salamander larvae are vulnerable to the impacts of chemical pollution and sedimentation. Although this species typically uses pools that are separated from streams, increased storm water runoff due to construction, timber harvest, and other human activities is making pool habitats more vulnerable to increased sedimentation and pond filling, particularly in floodplains. Even completely isolated pools in the uplands can suffer some degree of impacts due to encroachment of human development, where runoff from agricultural fields, residential yards, and impervious surfaces can drain into these pools. No pools, upland or lowland, are isolated from the effects of aerial application of insecticides to control mosquitos.

Interactions with Humans: This species is subject to fairly low levels of collecting, which does not currently appear to be threatening any populations. Most impacts due to humans are indirect or inadvertent. Many juveniles and adults are killed on roads when migrating to and from their breeding ponds. There is also some potential for trampling to harm the eggs and nesting females when they are concentrated around the edges of breeding pools. A much greater threat comes from attempts to drain or fill these ponds. Many ponds, especially those in upland areas, show evidence of old drainage channels. Some of these efforts may have been due to attempts to control mosquito populations. A more modern threat is that the pools will be sprayed with insecticides intended for that purpose. Even if the control agents are essentially harmless to the salamanders themselves, the use of mosquito-specific controls such as BTK can affect salamander populations by reducing some of their most important prey species.

Status in North Carolina

NHP State Rank: S5

Global Rank: G5

Populations: Within the Piedmont and Coastal Plain – the main regions occupied by this species in North Carolina – urban development, road construction, and agricultural activites are particularly concentrated along the upland divides that separate the major river basins. Whereas Marbled Salamanders were once able to traverse these divides when they were covered with native deciduous forests, their populations may now be largely isolated from populations in adjoining drainage basins. Within the individual drainage basins, populations are more isolated due to habitat fragmentation. The number of viable populations in the state with intact metapopulation structure is not known.

Protected Lands: Populations are protected within 13 state parks, including four in the Coastal Plain and nine in the Piedmont.

Status Comments: Despite extensive habitat loss and degradation, numerous local populations of this species still exist in North Carolina that can be found in a wide range of hardwood forests and woodlands. Although highly dependent on isolated pools for breeding, Marbled Salamanders utilize such a wide range of bottomland and upland wetlands that their populations are likely to persist for the foreseeable future. Populations in the mountains are at greatest risk since most of the seasonal wetlands have been destroyed and the few remaining populations are geographically isolated from one another.

Stewardship: Management practices should be aimed both at protecting local breeding sites and at maintaining the integrity of the metapopulation structure that is critical to their survival. Within an individual sub-population, preservation of both the breeding pool and a hardwood or mixed pine-hardwood buffer of around 250-300 m is necessary to maintain local pond populations. At sites where vernal ponds have been lost or degraded due to wetland filling, siltation, or other causes, construction or restoration of ponds should be considered to restore connectivity between neighboring ponds. Spraying for mosquito control should be avoided whenever possible. Where public health does require it, the use of species-specific control agents should be used in place of broad-spectrum insecticides. In addition to protection efforts aimed at local sub-populations, forest corridors that allow animals to disperse between local ponds or sub-populations also need to be protected. Ideally, conservation should be targeted at protecting a large number of sub-populations, all interconnected by way of intact movement corridors.

Photo Gallery for Ambystoma opacum - Marbled Salamander		50 photos are available. Only the most recent 30 are shown.
	Recorded by: Paul C. Hart Harnett Co.	Recorded by: B. Bockhahn Chatham Co.
	Recorded by: Caleb Garner Wake Co.	Recorded by: Caleb Garner Wake Co.
	Recorded by: Rob Van Epps Mecklenburg Co.	Recorded by: L. Osteen Orange Co. Comment: Guarding eggs.
	Recorded by: David George Orange Co.	Recorded by: K. Bischof Beaufort Co.
	Recorded by: Steve Hall Orange Co.	Recorded by: Jennifer Smith & Michael P. Morales Cumberland Co.
	Recorded by: Jennifer Smith & Michael P. Morales Cumberland Co.	Recorded by: J. Hawley Beaufort Co.
	Recorded by: L. Osteen Orange Co.	Recorded by: J. Mickey Surry Co.
	Recorded by: A. Early Stanly Co.	Recorded by: L. Purvis, L. Farr Chatham Co.
	Recorded by: L. Purvis Chatham Co.	Recorded by: R. Swikle, To. Johnson, A. Early Stanly Co.
	Recorded by: N. Bowman Yadkin Co.	Recorded by: Morgan Freese Durham Co.
	Recorded by: K. Bischof Beaufort Co.	Recorded by: k nealson Orange Co.
	Recorded by: K. Sanford Camden Co.	Recorded by: K. Bischof Burke Co.
	Recorded by: N. Crider Beaufort Co.	Recorded by: Owen McConnell Durham Co.
	Recorded by: K.Trotter Stanly Co.	Recorded by: J. Davidson Harnett Co.
	Recorded by: Steve Hall and Harry LeGrand Northampton Co. Comment: A young juvenile that was under a log next to a large pool.	Recorded by: Owen McConnell Durham Co.

Ambystoma opacum - Marbled Salamander

Photo Gallery for Ambystoma opacum - Marbled Salamander

50 photos are available. Only the most recent 30 are shown.