Amphibians of North Carolina

Scientific Name:	Common Name:		Family (Alpha):

NC Records
Ambystomatidae Members:
Ambystoma maculatum - Spotted Salamander

caption

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 Spotted Salamander is one of five species of mole salamanders that are found in North Carolina. This beautiful species is one of many amphibians in the state that depend on small, seasonal wetlands for successful reproduction.

Identification

Description: The Spotted Salamander is a relatively large Ambystoma that has two irregular rows of large, yellow or yellowish orange spots on a steel gray or black dorsum. The spots extend from the head to the tip of the tail and individuals in some populations have bright orange spots on the head that contrast with yellow spots on the body and tail. Adults that lack spotting, as well as albinos and leucistic individuals, occur in very low frequencies in certain populations. The adults are 15-25 cm long, and the females typically average slightly larger than the males. The males develop conspicuously swollen vents during the breeding season. Outside of the breeding season males are best identified by the presence of a series of parallel ridges on the inside of the cloaca that run perpendicular to the cloacal slit.

The hatchlings are dull olive green, lack conspicuous markings, and are 12-17 mm long. The older larvae have bushy gills and dorsal fins that extend almost to the front limbs, and are dull greenish. Larvae at all stages have white or light bellies that are generally free of dark pigmentation, and the tail fin is finely stippled or lightly mottled with dark pigmentation. The absence of dark pigmentation on the throat provides a way to distinguish the larvae from those of the Marbled Salamander. Juveniles begin to develop the yellow spots within a few weeks after metamorphosing. They are similar to adults, but have lighter venters and less prominent spotting on the dorsum (Petranka 1998).

Technical Reference: Petranka (1998); Savage and Zamudio (2021)

Field Guide Descriptions: Beane et al. (2010)

Online Photos: iNaturalist Google iNaturalist

Observation Methods: The adults migrate to breeding ponds during the late winter and early spring and can be found crossing roads on rainy nights or gathering around the margins of ponds. Groups of courting adults can be seen in the breeding ponds, and the presence of fields of spermatophores provide evidence that a local population is present at a site. The larvae are best obtained by dip-netting, and care needs to be taken to not confuse these with the larvae of other Ambystoma that sometimes share breeding pools.

AmphibiaWeb Account

Distribution in North Carolina

Distribution Comments: Ambystoma maculatum occurs throughout much of the eastern United States and in portions of southern Canada. Populations occur in Canada from northwestern Ontario to Nova Scotia and Prince Edward Island. In the US, the range extends from Maine southward to southern Georgia, and westward to eastern Texas, eastern Oklahoma, Missouri, Illinois, and Wisconsin. This species is rare throughout much of the Atlantic Coastal Plain from New Jersey to Georgia. In North Carolina, this species is rare in the Coastal Plain and most common in the eastern Piedmont, where it often shares breeding sites with the Marbled Salamander. Scattered populations can be found farther west in the western Piedmont and at lower elevations in the Blue Ridge Mountains.
Distribution Reference: Petranka (1998); Savage and Zamudio (2021)
County Map: Clicking on a county returns the records for the species in that county.


GBIF Global Distribution

Key Habitat Requirements

Habitat: Adults are most common in bottomland forests in or adjoining floodplains, but occur sporadically in upland forests and in mountainous regions where suitable breeding sites are available. Felix et al. (2010) experimentally manipulated canopy cover and found that the adults prefer closed canopy sites relative to open canopy sites such as seen in clearcuts.

In North Carolina, individuals typically use fish-free pools for breeding. Vernal pools that fill with water during the winter and hold water for 6-9 months are prime breeding sites, as are bogs, marshes, and other seasonal sites that lack fishes. The adults will occasionally breed in beaver ponds, flooded pits that are created from wind-thrown tree fall, flooded roadside ditches, and shallow puddles. Many of these very small, shallow habitats may dry prematurely and function as ecological traps with no juvenile recruitment. Some populations may be associated with mixed or conifer-dominated stands (Petranka 1998), but this species is most commonly encountered in hardwood forests and is largely absent from the peatlands and Longleaf Pine-dominated habitats in the Coastal Plain. In the Blue Ridge, they are generally found below 915 m (3000') in elevation.

Environmental and Physiological Tolerances: The juveniles and adults acquire a substantial amount of their oxygen needs through their skin (cutaneous respiration) and need moist microhabitats such as those found in mesic hardwood forests with well-developed leaf litter layers. Studies of temperature tolerances suggest that in some areas of the range the adults experience surface temperatures above their critical thermal maximum and must retreat to underground burrows where conditions are cooler and moister. Hatching success, larval development, and survival can be compromised if the aquatic sites are too acidic. In general, adverse effects develop when water pH drops below 4.5–5.5. Values in this range are not uncommon in the eastern US. Over an 8-yr period in eastern Virginia, reproductive activity of spotted salamanders declined severely in breeding ponds with low pH levels and high aluminum, copper, silicon, and zinc concentrations. Elevated hydrogen ion and aluminum concentrations in breeding ponds may also negatively affect hatching success. In Pennsylvania, the number of eggs present is positively correlated with pH and pond size, but negatively correlated with cations and silica levels. Petranka (1998) and Savage and Zamudio (2021) have details of these and related studies.

Biotic Relationships: The larvae of this and other Ambystoma species function as top predators in seasonal pond communities where they feed on a diverse array of invertebrates. The larvae are palatable and lack chemical defenses against predatory fish and invertebrate predators. Seasonal pond drying helps to eliminate fish and often reduces the number of invertebrate predators in the ponds. Wood Frog tadpoles can be important predators on the developing eggs (Petranka et al. 1998), and Eastern Newts and Marbled Salamander larvae frequently feed on the hatchlings. This species has a symbiotic relationship with a green alga (Oophila amblystomatis) that lives in the egg membrane that surrounds the developing embryo. The alga supplies oxygen to the developing embryo via photosynthesis, and the alga receives carbon dioxide from the embryo that is used for photosynthesis. The egg masses often have a greenish cast due to the larger number of algal cells in the egg membranes.

See also Habitat Account for Hardwood Forests with Isolated Pools

Life History and Autecology

Breeding and Courtship: The adults migrate from the surrounding forest to breeding ponds during the winter and early spring. They typically move on rainy or foggy nights when temperatures are moderate, but in some instances may migrate in the absence of rain if the humidity is very high and temperatures are warm. Individuals begin breeding as early as December in the southern portion of the range, but may not begin until March or April farther north (Petranka 1998). Breeding normally occurs from late January through late March in North Carolina (Brimley 1921, Gray 1941, Harris 1980), and there are typically two or three major breeding bouts locally as periodic rains trigger new migrations to the breeding pond. Stenhouse (1985a) found that the adults remained for 56-73 days at a breeding site in North Carolina.

The adults normally court in groups that are scattered about shallow regions of the pond. A group may contain from 3-50 or more adults, and males typically outnumber females in local breeding aggregates (Petranka 1998). The males actively swim about and prod and nudge the bodies of both females and other males, and the females may respond by nudging the males with their snouts. Each male eventually deposits numerous spermatophores on the pond bottom, and each female responds by positioning her cloaca over a spermatophore and picking off the sperm cap on top. A single male may deposit 40 or more spermatophores, and a single female may mount 15 or more spermatophores. Aggregates of spermatophores can usually be seen in the shallow regions of ponds following a night of breeding.

Reproductive Mode: Within 2-3 days after mating, females begin depositing eggs on twigs, fallen tree branches, and aquatic plants. The eggs are occasionally laid directly on the pond bottom and not placed on support structures. They are deposited in firm, ovoid to cylindrical masses that are typically 5-15 cm wide and 5-25 cm long. The egg masses are either scattered individually about the pond or deposited in dense, communal aggregates that may contain 50 or more egg masses. The jelly layer surrounding the eggs is frequently colonized by a unicellular green alga (Oophila amblystomatis) that may increase oxygen supply to the developing embryos. A female normally deposits 2-4 egg masses. Harris (1980) found that the mean number of eggs per mass in a central North Carolina pond decreased as the breeding season progressed and varied from 65-104 eggs per mass.

The egg masses normally come in two color forms. Some have clear jelly coats that allow the eggs to be easily seen, while others are white with opaque, milky-colored jelly coats that mask the underlying eggs. Local pond populations often lay only the clear egg masses; however, masses that are milky white in appearance can comprise a high percentage of egg masses in some populations. In North Carolina, populations in the mountains tend to have a high percentage of white egg masses, while those farther east mostly produce clear masses.

The mechanisms that maintain egg mass polymorphisms in local populations of this species are poorly understood. The white masses tend to be firmer and provide better protection from predators such as Wood Frog tadpoles and Eastern Newts (D'Errico et al. 2020, Jacobson 2015, Petranka et al. 1998). However, the advantages of having clear egg masses are poorly resolved. D'Errico et al. (2020) have a comprehensive summary of studies that have been conducted in North Carolina and elsewhere that address the maintenance of egg mass polymorphisms in this species.

Aquatic Life History: The Spotted Salamander has a relatively long incubation period, with the eggs taking a month or more to develop to the hatching stages. The larvae are gape-limited predators and show a general tendency to incorporate a broader array of prey into their diets as they grow. Zooplankton constitute the bulk of the diet, but older larvae will occasionally consume other prey such as isopods, odonates, chironomids, beetles, caddisflies, and even hatchlings of the Eastern Newt (Petranka 1998). The larvae grow rapidly and most transform within 2-4 months after hatching. In extremely cold ponds, larvae may rarely overwinter and transform the following spring. Competition for food is often intense, and predators and disease take their toll on the larvae. Survival to metamorphosis is usually < 10% and often much lower. Stenhouse (1985, 1987) found that premetamorphic survival in populations in North Carolina was typically < 1%, with the high mortality due in part to intense predation from Marbled Salamander larvae.

Terrestrial Life History: Within a few weeks after metamorphosing, the juveniles leave the ponds and disperse into the surrounding forest during rainy weather. Juveniles that successfully disperse away from ponds presumably spend most of their time burrowed in the soil and do not return to the breeding ponds until sexually mature. They feed on insects, snails, earthworms, and other invertebrates. Although detailed data are lacking, individuals in more southern localities may require only 2-3 years to reach sexual maturity. In Michigan, males and females reach maturity after 2-3 and 3-5 years, respectively (Petranka 1998). The adults are long-lived, with many living a decade or more in the wild. One wild-caught specimen in Canada was estimated to be 32 years old!

After breeding, the adults may move 200 m or more from the pond margin before establishing a home range. Regosin et al. (2005) found that 60% of spotted salamanders in a Massachusetts pond moved >100 m from the breeding pond. Sexton et al. (1986) collected two adults 172 m from a breeding pond, but most were within 100 m of the pond. Eight radioactively-tagged adults tracked by Douglas and Monroe (1981) moved 6-220 m (mean = 150 m) compared to 157-249 m (mean = 192 m) for six animals monitored by Kleeberger and Werner (1983).

The adults have small home ranges and mostly live in rodent burrows, rotted tree root channels, or other openings beneath the ground. On rainy nights individuals are occasionally found on the forest floor and may feed while protruding their heads from burrow entrances. The diet of the adults includes earthworms, mollusks, spiders, millipedes, centipedes, and a wide variety of larval and adult insects (Petranka 1998).

General Ecology

Population Ecology: At sites where forest buffers that surround the breeding ponds are intact, local populations are thought to be limited by density-dependent interactions that occur during the larval stage. Crowding generally decreases the growth rates, survival, and size at metamorphosis of larvae and ultimately affects the number and vigor of juveniles that leave the pond. Crowding effects are likely due to direct competition for food and aggressive interactions between conspecifics. Density-dependent competition and predation by other Ambystoma species that share ponds may also limit the size of adult populations (Petranka 1998, Savage and Zamudio 2021).

In North Carolina and elsewhere, small, fish-free wetlands are patchily distributed across the landscape and tend to support relatively small populations of adults. Based on egg mass counts, most local pond populations in North Carolina appear to rarely exceed more than 500-600 adults, and often consists of far fewer individuals. Local populations of the Spotted Salamander tend to be organized as metapopulations, with each metapopulation consisting of a cluster of local pond populations that are connected by the occasional movement of individuals between sites (Zamudio and Wieczorek 2007). 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. Because small, isolated populations are vulnerable to extinction, connectivity between populations is essential for maintaining the long-term viability of regional populations.

Community Ecology: Spotted Salamander larvae often share breeding ponds with other Ambystoma species and have strong dietary overlap with congenerics. Ambystoma larvae in general rely heavily on zooplankton as a food resource, and competition for food is often intense. Several researchers have examined size-specific interactions among these species, particularly between A. maculatum and A. opacum. In many ponds A. opacum larvae are nearing metamorphosis when A. maculatum larvae hatch. At this stage A. opacum is sufficiently large to eat A. maculatum (Stenhouse et al. 1985, Stewart 1956). Stenhouse (1985) found that premetamorphic survivorship of A. maculatum in North Carolina ponds in the Piedmont is < 1% in ponds when A. opacum is present, and in some cases appears to be zero because of intense predation. In addition, densities of A. maculatum are negatively correlated with densities of A. opacum across study ponds.

At other sites in the eastern US, predation of A. opacum larvae on A. maculatum larvae does not appear to be as severe (Petranka 1998). Despite the low premetamorphic survivorship of A. maculatum, large populations of A. maculatum often coexist locally with A. opacum. Dispersal from surrounding populations, high adult survivorship, and selection for long life spans may be important features that allow A. maculatum to maintain healthy populations in areas where A. opacum is a major predator (Husting 1965, Stenhouse 1985).

Adverse Environmental Impacts

Habitat Fragmentation: The broad swaths of deciduous forest that covered much of North Carolina and the eastern US at the time of European colonization have been severely fragmented as extensive tracts of hardwoods have been converted into a patchwork of agricultural fields, residential homes, urban development, pine plantations, and roadways. In many cases a small deciduous woodlot may have one or more seasonal ponds that are adequate for the larval stage, but the surrounding hardwood forest is too small to support a viable adult population. Even when hardwood parcels are sufficient to support an adult population, the population may be isolated from nearest neighbors due to barriers to dispersal such as roadways or large agricultural fields (e.g., Rittenhouse and Semlitsch 2006). Small, isolated populations are vulnerable to local extinction from outbreaks of disease, severe droughts, logging, or other factors, and may ultimately be lost with time.

Effects of Introduced Species/Induced Increases of Native Species: Emerging infectious diseases are considered to be one of the most important factors contributing to global amphibian declines and have been implicated in the local extinction of several species. Ranavirus is a highly virulent pathogen that affects many amphibian species, including the larvae of the Spotted Salamander. Infected larvae develop characteristic bloody, hemorrhagic patches on the body and die shortly thereafter. Ranavirus is highly infectious and lethal. Populations in western North Carolina frequently have complete die-offs of larvae during outbreaks, with no larvae surviving to metamorphosis (Petranka et al. 2003, 2007). This pathogen also infects Wood Frog larvae, which likely spread the disease to Spotted Salamander larvae that share breeding ponds.

Interactions with Humans: Overcollecting does not appear to be a significant threat to populations in North Carolina. The juveniles and adults that are migrating to or from ponds often suffer heavy road mortality. In some areas heavily trafficked roads may entirely block migrating salamanders from reaching a breeding pond (Trombulak and Frissell 2000). A much greater threat, however, comes from attempts to drain or fill breeding ponds. Many ponds, especially 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. Healthy seasonal ponds that abound with salamander and frog larvae have surprisingly few mosquito larvae, in part because the female mosquitoes avoid ovipositing in pools where their offspring are likely to suffer high mortality from competitors and predators (Petranka and Fakoury 1991).

Status in North Carolina

NHP State Rank: S5

Global Rank: G5

Environmental Threats: Local populations of Spotted Salamanders have become increasingly isolated from each other as urbanization, deforestation, habitat fragmentation, and the filling of seasonal wetlands have eliminated local populations across the landscape. Population losses and anthropogenic barriers to movement have resulted in many local populations being completely isolated from their nearest neighbors. Inbreeding depression could eventually become a significant problem in some of the smaller, isolated populations. In addition, colonists may not be able to reach ponds where populations have suffered local extinctions. Conservationists are increasingly concerned that acid deposition in the eastern US is resulting in the long-term acidification of seasonally-ephemeral breeding sites used by this and many other amphibians. In some populations pH in the 4.5-5.5 range can reduce hatching success and larval growth and development (Petranka 1998). Values within this range are not uncommon in many areas of the eastern US and southern Canada. Adults that undergo migrations to and from ponds are often killed by vehicular traffic, and the problem is getting worse due to the historical increase in traffic volume on our roads.

Stewardship: Management practices should focus on protecting local breeding sites and forest buffers, as well as maintaining metapopulation structure that is critical for the long-term survival of local and regional populations. Within an individual sub-population (local pond population), preservation of both the breeding pool and a hardwood or mixed pine-hardwood buffer of around 250-300 m is necessary to ensure successful reproduction. 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 or created. Ideally, conservation should be targeted at protecting a large number of sub-populations, all interconnected by way of intact movement corridors.

Petranka et al. (2007) examined the long-term population persistence of the Spotted Salamander at a wetland restoration site in Graham County where the design strategy was to create a large number of wetlands on site that varied in size, depth, and hydroperiod, and that provided multiple breeding sites for all resident species. The Spotted Salamander population on site persisted over a 13-year monitoring period and remained robust despite the fact that the output of metamorphs in many ponds was near zero due to outbreaks of Ranavirus, fish invasions, and drought. They provide specific recommendations for wetland design that are relevant for restoring wetlands for seasonal pond breeders in North Carolina.

Photo Gallery for Ambystoma maculatum - Spotted Salamander		18 photos are shown.
	Recorded by: B. Bockhahn Macon Co.	Recorded by: J. Thomson and B. Bockhahn Macon Co.
	Recorded by: Mary Stevens, Paul Hart Harnett Co.	Recorded by: Rachelle Roake Chatham Co.
	Recorded by: Simpson Eason and Owen McConnell Durham Co.	Recorded by: Simpson Eason and Owen McConnell Durham Co.
	Recorded by: A. Lasley Burke Co.	Recorded by: W. Morris Stokes Co.
	Recorded by: A. Lasley, S. Cojocaru, R. McDonough Burke Co.	Recorded by: Jim Petranka and Becky Elkin Madison Co. Comment: white and clear egg masses.
	Recorded by: M. Griffin Burke Co.	Recorded by: L. Osteen Orange Co.
	Recorded by: L. Osteen Orange Co.	Recorded by: B. Bockhahn Wake Co.
	Recorded by: Steve Hall Orange Co.	Recorded by: Owen McConnell Durham Co.
	Recorded by: Jim Petranka Buncombe Co.	Recorded by: Jim Petranka Graham Co.

Ambystoma maculatum - Spotted Salamander

Photo Gallery for Ambystoma maculatum - Spotted Salamander

18 photos are shown.