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For metamorphic adults, the snout-to-vent length is 36-66 mm and total length ranges from 68-116 mm (Hayslett 2003; Semlitsch 1987). Female metamorphic adults are generally larger than male metamorphic adults, with females ranging from 39-72 mm in snout-vent length and males from 41-62 mm in snout-vent length (Raymond and Hardy 1990). Paedomorphic sexually mature adults range in size from about 30-50 mm in snout-to-vent length (Semlitch 1985). The body size of individuals varies across time; it appears that individuals tend to reach a maximum size and then decline with age (Verrell and Krenz 1998). This growth pattern is likely an indication of reproductive senility and asymptotic growth, in contrast to other salamander species that have continuous growth over the lifespan (Raymond and Hardy 1990).
This species is facultatively paedomorphic and both morphs can be found within one population. Adults have disproportionately large and broad heads, small chunky bodies and relatively short tails (Rothermal and Luhring 2005). The body has 10-11 costal grooves (Powell et al. 1998). Four toes are present on each forefoot and five toes on each hindfoot, with hindfeet being disproportionately large (Conant and Collins 1998). Teeth are hooked in shape and are arranged in a single row along both the maxillary and the dentary (Tihen 1958). Paedomorphic adults retain external gills and have a vertically compressed tail. The tail is slightly vertically flattened in metamorphic adults (Conant and Collins 1998).
Metamorphic adults have variable ground body color ranging from black to gray. Some individuals have small blue, white or gray flecks concentrated along the dorsum, sides and tail. The top of the tail often has a white edge, which can be a distinguishing feature if present. Paedomorphic individuals have a gray or brown ground color, often with light flecks that concentrate along the dorsum, tail and sides and distinct yellow ventral stripes. Newly metamorphic individuals will display remnant yellow ventral stripes for a time after metamorphosis. In preservative, the flecked pattern often fades and the coloration is gray to black (Conant and Collins 1998).
Newly hatched larval body sizes can vary from 4.5-8.0 mm in snout-to-vent length. Larvae that did not metamorphose after the breeding season range in snout-to-vent length from about 25-48 mm. External gills are present. Larval coloration is similar to that of paedomorphic adults with a gray or brown ground color, light-colored flecks and yellow ventral stripes. Tail is dorsoventrally flattened with tail fins (Semlitch 1985).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: United States
U.S. state distribution from AmphibiaWeb's database: Alabama, Arkansas, Florida, Georgia, Illinois, Kentucky, Louisiana, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Virginia
This species is endemic to the southeastern and central United States, from South Carolina to northern Florida and east to eastern Texas and southeastern Oklahoma. The range extends north in the Mississippi valley to southern Illinois. There are a number of disjunct populations in Virginia, North and South Carolina, Georgia, Alabama, Tennessee and Kentucky (Conant and Collins 1998).
Terrestrial morphs of this species are usually found near breeding ponds (ephemeral or persistent in wooded areas (Hammerson 2004; Mosely et al. 2004). The woodlands and forested habitats include upland conifer-hardwood forests, pine flatwoods and bottomland hardwood forests (Shoop 1960; Semlitsch 1981). They are often found in expansive floodplains in areas near gum and cypress ponds (Shoop 1960; Semlitsch 1981). They usually avoid clear cuts and open field (Mosely et al. 2004). The elimination of ground cover reduces availability of suitable temperature and moisture conditions which are required by salamanders (Moseley et al. 2004). Terrestrial adult habitats are often in close proximity with a wetland or an ephemeral pond. Paedomorphic adults inhabit permanent wetlands free of predatory fish (Semlitch 1985).
Life History, Abundance, Activity, and Special Behaviors
Activity: The terrestrial morphs are largely fossorial and occupy small mammal burrows or other underground refugia (Rothermel and Luhring 2005). These salamanders move above ground only during the night or when it is raining, so although it is fossorial, Ambystoma talpoideum is also considered to be nocturnal (Rothermel and Luhring 2005).
Individuals inhabit burrows or tunnels under the leaf litter. They can burrow in loose soil but often rely on crevices or burrows made by roots or burrowing animals. These refuges provide protection from predators, desiccation and freezing (Rothermel and Luhring 2005). The salamanders are found at an average of 4.7 cm below the surface of the leaf litter and they do not inhabit burrows more than 9 cm below the surface. These salamanders have only been found in the A soil horizon; burrow systems tend to run parallel to the surface (Semlitsch 1980). In cases where burrows are limited, these salamanders are capable of exploiting other microhabitats. Mole salamanders can adapt to change and utilize different resources. In habitats where the organic soil layer has been disturbed, leaf litter can become important. In addition to providing an alternative microhabitat that salamanders can utilize, plant litter can facilitate the recovery of soil structure.
Terrestrial morphs are usually never more than 200 m from either a permanent or semi-permanent body of water. This body of water is often the breeding site (Semlitsch 1980). Aquatic paedomorphic salamanders are more common in permanent wetlands and thrive in fishless water bodies while terrestrial adults are more common in ephemeral wetlands (Williams and MacGowan 2004).
Home range: These salamanders inhabit a non-breeding home range and a breeding home range. The non-breeding home range for males averages to about 3.6 m2 and 5.3 m2 for females. These animals spend most of their time in an activity center, which ranges in area from 0.02-0.21 m2. Each salamander’s home range has 1-6 activity centers. The breeding home range is an associated wetland, either persistent or temporary (Semlitsch 1981).
Breeding season: Breeding is aquatic and occurs primarily between December and March (Semlitsch 1980). The breeding season lasts anywhere from a few days to a few weeks (Verrell and Krenz 1998). Although the breeding season is generally longer than that of other species of Ambystoma, breeding biology of A. talpoideum is similar to that of other Ambystoma (Verrell and Krenz 1998). Large numbers of individuals gather in small ponds which results in high densities and frenzied sexual activity (Verrell and Krenz 1998). These salamanders are terrestrial during the non-breeding seasons and migrate to water bodies to breed (Verrell and Krenz 1998).
Breeding migration: Breeding migration is heavily dependent on temperature and rainfall (Ryan and Semlitsch 1998) and most adults are philopatric. Terrestrial morphs tend to migrate to and emigrate from breeding grounds on rainy nights, moving through corridors of continuous hardwood vegetation rather than moving through open grasslands (Patterson 1978; Semlitsch 1980). Terrestrial adults will remain at the breeding site anywhere from 8 to 108 days (Hardy and Raymond 1980). Males tend to arrive at the breeding site before terrestrial females, so the operational sex ratio is likely male-biased (Verrell and Krenz 1998). Both males and females emigrate from the breeding site at the same time. Typical rates of movement through the home range for terrestrial salamander morphs average about 3.9 m/hr in an undisturbed habitat (Rothermel and Luhring 2005), while emigration rates from the breeding site average 13.7 m/hr (Semlitsch 1980). In contrast, paedomorphic morphs do not migrate (Ryan and Semlitsch 1998).
Courtship behavior: Intermorph courtship does occur and is potentially common, according to some field data (Whiteman et al. 2006). Metamorphic male with paedomorphic female is the most common intermorph relationship. There is no reproductive isolation between morphs, although intramorph mating is more likely than intermorph mating (Whiteman and Semlitsch 2005). Most male-female encounters appear to be accidental. The initial steps of courtship include the male nudging the female with his snout and the male and female rubbing heads. Next, the male moves ahead of the female and produces lateral undulations of his tail, beginning in the pelvic region. As the male moves forward the female follows, nudging his undulating tail and cloacal region with her snout. These behaviors continue for a variable period of time and then the male arches his back and presses his cloaca to the substrate to deposit a spermatophore. He moves forward, she follows and picks up the spermatophore with her cloaca. A single encounter may result in multiple episodes of spermatophore deposition (Verrell and Krenz 1998).
Mating system: Population densities can be high in some breeding sites. Breeding aggregations have been reported to be very large with as many as 8,000 individuals migrating to one Carolina bay in a single day. Because terrestrial males tend to migrate earlier to the breeding pond than terrestrial females, in the early breeding season there is a male biased sex ratio and competition for mates is likely intense. The mating system has been classified as scramble competition with potential for polygyny (Verrell and Krenz 1980).
Timing of breeding: Paedomorphic individuals remain in the breeding site year round and tend to breed earlier in the season than metamorphs in the same population because they do not depend on ecological cues as heavily as metamorphic individuals. Paedomorphic individuals can begin breeding as early as September (Ryan and Semlitsch 1998). Metamorphic females tend to migrate to the breeding ground more than one week after paedomorphic females have laid eggs. Earlier oviposition tends to result in earlier larval hatching; Larvae of paedomorphic females hatch up to 6 weeks earlier than metamorphic females (Scott 1993).
Reproductive cycle: These salamanders show high individual variation in their reproductive cycle. In multiyear studies individuals can breed annually, biennially or have a multiyear reproductive cycle. In one population 68% bred annually, 18% bred biennially and 14% bred in a multi-year cycle (Raymond and Hardy 1990).
Age at sexual maturity: It takes one to two years for juveniles to sexually mature. At the end of a breeding season, newly metamorphic individuals are not sexually mature but can reach sexual maturity before the next breeding season. Larval individuals can overwinter and metamorphose the following spring or remain a paedomorphic individual. Individuals who become sexually mature paedomorphs have the opportunity to metamorphose in later seasons, sometimes even several years after sexual maturity (Doyle and Whiteman 2008; Semlitsch 1985; Ryan and Semlitsch 1998).
Egg deposition and description: Eggs are either laid singly or in clusters on the bottom of the pond on small twigs or leaves. Egg masses are surrounded by a matrix of jelly which distinguishes them from anuran egg masses (Raymond and Hardy 1990). Females often require several days to complete oviposition (Shoop 1960). Females will deposit 10-1,000 eggs at each oviposition event and typical clutch size tends to vary greatly among populations and among individuals. On average females will lay 200-700 eggs per year, and eggs range from 1-3 mm in diameter. Egg clusters are often stained brown. Clutch size is positively correlated with female age. Paedomorphic females are typically smaller than metamorphic females and typically lay smaller clusters with smaller egg sizes (Raymond and Hardy 1990; Semlitsch 1985).
Larval development: Eggs typically hatch within 20-60 days of deposition. The larval period ranges from 3-4 months but larvae can overwinter and metamorphose the following spring. Most larvae will metamorphose between 12 and 15 months after hatching, if the pond is permanent. Larval growth is related to egg size in that smaller eggs lead to smaller larvae at hatching (Ryan and Semlitsch 1998).
Adult mortality: Most individuals have a life span in the wild of seven years, with some rare individuals living at least eight years. Nine years is the oldest verified A. talpoideum in nature. In captivity the oldest recorded individual was reported to live up to 25 years. Breeding season mortality has been reported to range from 10-30%. Terrestrial adult mortality varies from 16-37% yearly and 45% of adults die before leaving the breeding wetland area. The aquatic life stage has a higher mortality than the terrestrial life stage (Raymond and Hardy 1990).
Predation and defense: These salamanders tend to breed in fishless ponds, and paedomorphic forms are found only in ponds without fish, which indicates that fish are potential predators or competitors. Larvae metamorphose more quickly when exposed to predatory fish such as bluegills (Lepomis macrochirus). Bluegills have been reported to feed on mole salamander eggs (Jackson and Semlitsch 1993; Semlitsch 1988). Metamorphic salamanders have parotoid glands (which secrete noxious chemicals) and when attacked will exhibit a head down posture to expose the glands (Brodie 1977).
Interspecific associations: Mole salamanders can be found breeding in ponds with marbled salamanders (A. opacum), spotted salamanders (A. maculatum), tiger salamanders (A. tigrinum), dwarf salamanders (Eurycea quadridigitata), eastern newts (Notophthalmus viridescens), southern toads (Bufo terrestris), spring peepers (Pseudacris crucifer), southern chorus frogs (P. nigrita), little grass frogs (P. ocularis), bronze frogs (Rana clamitans), southern leopard frogs (R. sphenocephala), and eastern spadefoot toads (Scaphiopus holbrookii) (Semlitsch et al. 1996).
Diet and foraging behavior: Adult A. talpoideum are carnivorous night feeders and eat primarily invertebrates, although their diet also includes amphibian eggs and larvae (Gibbons and Semlitsch 1991). Adults can consume a considerable number of mosquito larvae; one study found that adult A. talpoideum could consume an average of 439 mosquito larvae per day, with the largest individual in the study consuming 902 mosquito larvae in a single day (DuRant and Hopkins 2008). Paedomorphic adults have been reported to consume aquatic insects, zooplankton and tadpoles (Gibbons and Semlitsch 1991). Larvae feed primarily on zooplankton when young and feed on larger prey as they grow. Larvae remain in the leaf litter at the bottom of the pond during the day and feed at night (Taylor et al 1988).
Phenotypic variation: Mole salamander species have two different adult morphs: paedomorphic (aquatic) and metamorphic (terrestrial). Paedomorphic forms only occur in permanent water bodies. Rates of paedomorphic and metamorphic adults vary depending on the population and breeding habitat. Although the environmental and genetic reasons for varying proportions of paedomorphic and metamorphic individuals are largely unknown, it is typically true that paedomorphic adults have a smaller snout to vent length than metamorphic adults of the same age and paedomorphic adults tend to have a larger body mass than metamorphic adults of the same snout to vent length (Doyle and Whiteman 2008; Ryan and Plague 2004; Ryan and Semlitsch 2003; Semlitsch 1987; Winne and Ryan 2001).
Trends and Threats
In North Carolina this species is listed as a species of special concern and in Tennessee it is listed as a species in Need of Management. Special permits are required to conduct any activity involving this species in those areas. This species is affected by clear-cutting of forests surrounding breeding ponds and introduction of predatory fish into breeding ponds. Although mole salamanders are considered to have stable populations throughout most of their range (Rothermel and Luhring 2005), local populations have been extirpated as forest are converted to agricultural or urban use (Hammerson 2004).
Habitat fragmentation is an issue and should be minimized wherever possible. Seasonal ponds should be protected from draining, filling, or fish introduction. Adjacent wooded areas should be protected to at least 200-250 m away from the ponds (Hammerson 2004).
Possible reasons for amphibian decline
General habitat alteration and loss
Brodie, E. D., Jr. (1977). "Salamander antipredator postures." Copeia, 1977, 523-535.
Conant, R. and Collins, J.T. (1998). A Field Guide to Reptiles and Amphibians of Eastern and Central North America. 3rd Edition. Houghton Mifflin Company, Boston, Massachusetts.
Doyle, J.M. and Whiteman, H.H. (2008). ''Paedomorphosis in Ambystoma talpoideum: effects of initial body size variation and density.'' Oecologia, 156, 87-94.
DuRant, S. E. and Hopkins, W. A. (2008). ''Amphibian predation on larval mosquitoes.'' Canadian Journal of Zoology, 86, 1159-1164.
Gibbons, J.W. and Semlitsch, R.D. (1991). Guide to Reptiles and Amphibians of the Savannah River Site. University of Georgia Press, Athens GA, US.
Hammerson, G. (2004). Ambystoma talpoideum. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. www.iucnredlist.org. Downloaded on 23 May 2011.
Hayslett, M.S. (2003). Natural History of the Mole Salamander Ambystoma talpoideum in Virginia. Thesis, Longwood University, Virginia, US.
Holbrooke, J.E. (1836). North American Herpetology; or a Description of the Reptiles Inhabiting the United States. Volume II. J. Dobson, Philadelphia, US.
Jackson, M. E., and Semlitsch, R. D. (1993). ''Paedomorphosis in the salamander Ambystoma talpoideum: Effects of a fish predator.'' Ecology, 74(2), 342-350.
Moseley K.R., Castleberry, S.B. and Ford, W.M. (2004). ''Coarse woody debris and pine litter manipulation effects on movement and microhabitat use of Ambystoma talpoideum in a Pinus taeda stand.'' Forest Ecology and Management, 191, 387-396.
Written by Laura Brannelly (lbrannel AT tulane.edu), Tulane Uniiversity
First submitted 2011-05-16
Edited by Kellie Whittaker (2011-07-10)
Species Account Citation: AmphibiaWeb 2011 Ambystoma talpoideum: Mole Salamander <http://amphibiaweb.org/species/3847> University of California, Berkeley, CA, USA. Accessed Oct 22, 2019.
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Citation: AmphibiaWeb. 2019. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Oct 2019.
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