There are two mole salamander morphs, each occupying different habitats. Terrestrial mole salamanders are most abundant in expansive floodplain forests near ponds or similiar bodies of water. They can be found in areas surrounding gum and cypress ponds. Those salamanders living outside the Atlantic and Gulf coasts can be found in forested uplands. Terrestrial salamanders often live in burrows in moist soil and leaf litter. Seasonal and/or semipermanent ponds are associated with producing terrestrial adults. Neotenic, or aquatic, mole salamanders thrive in fishless, permanent ponds. Eggs are laid by both terrestrial and neotenic adults on twigs or other debris under the water. (Garland, 2002; Lannoo, 2005; Rothermel and Luhring, 2005; Williams and MacGowan, 2004)
- Terrestrial Biomes
- Aquatic Biomes
- lakes and ponds
- temporary pools
- Other Habitat Features
- Range elevation
- 0 to 700 m
- 0.00 to 2296.59 ft
Mole salamanders are facultatively paedomorphic; they can either become terrestrial adults (metamorphic adults) or retain their aquatic larval form even as they become sexually mature (paedomorphic, branchiate, or neotenic adults). Paedomorphic adults can eventually undergo metamorphosis or they may remain in the aquatic form throughout life. Terrestrial adults live in areas surrounding breeding ponds while paedomorphic adults remain in permanent ponds. Environmental conditions present during larval development can determine which life form an individual salamander will become. Both mole salamander morphs have short, stout bodies with broad, disproportionally large heads. Body size of terrestrial and aquatic males varies across populations and time. In some years and ponds, aquatic males will be larger, on average, than terrestrial males. In other years, the opposite can be true. Body size also varies within the same year, because smaller terrestrial adults have been known to arrive at a pond before larger adults. Neotenic adults have distinctive yellow ventral stripes that makes identification of this species more accurate. They also have light and dark stripes on their their bellies, that is present even in the larval form. Terrestrial adults can have variable body color, ranging from gray to black sometimes with clusters of small bluish-white flecks that are concentrated on the tail and back. Another distinguishing feature of the mole salamander is that there is often a white edge running along the top of the tail. For a period of time after the metamorphosis to a terrestrial creature, these salamanders will still display the remnants of the yellow ventral stripes that are so prominent in the neotonic life cycle. (Garland, 2002; Lannoo, 2005; Rothermel and Luhring, 2005; Ryan and Swenson, 2001; Verrell and Krenz, 1998)
- Sexual Dimorphism
- male larger
- Range length
- 8 to 12 cm
- 3.15 to 4.72 in
Mole salamander life cycles are characterized by facultative paedomorphosis. There are two different life cycles that these salamanders can follow. One life cycle occurs when aquatic larvae undergo metamorphosis and become terrestrial juveniles that will mature in terrain surrounding the breeding area. These individuals are referred to as terrestrial or metamorphic adults. The alternate life cycle is when aquatic larvae retain their aquatic morphology as they mature and remain in their natal ponds. These are referred to as branchiate, neotenic, or paedomorphic adults. (Ryan and Swenson, 2001; Whiteman, et al., 2006; Winne and Ryan, 2001)
Factors that influence the metamorphosis of mole salamanders at different stages in their lives include sex, altitude, temperature, nutrition, and pond drying. Size and metabolic rates differ between the sexes, which can lead to differences in metamorphosis. As a general standard, metamorphosis can occur once a salamander has reached a minimum of 25mm snout-vent length. Males typically reach this size sooner after hatching and can undergo metamorphosis earlier. Regardless of sex, most salamanders will undergo metamorphosis between 12 and 15 months after hatching. Metamorphosis after 15 months is typically associated with high altitudes and cooler temperatures. After metamorphosis, terrestrial juveniles remain immature and require several months to mature. Nutritional resources also play into timing of metamorphosis. Salamanders are more likely to metamorphosize when food levels and growth rates are higher later in development. The availability of food during the larval period is also directly related to metamorphosis. Environmental influences play a huge role in life cycles. When salamanders are hatched in a permanent pond, they typically remain there for at least a year or could even remain permanently aquatic. Sexually immature salamanders can metamorphosize early if they are exposed to certain conditions, such as pond drying. If a salamander remains aquatic, they remain immature and go through a period known as overwintering, then they can either metamophosize or become a branchiate adult. Aquatic forms of mole salamanders tend to mature at age a younger age and can also breed earlier. It is still possible for branchiate adults to undergo metamorphosis even after reaching sexual maturity. (Patterson, 1978; Ryan and Plague, 2004; Ryan and Semlitsch, 2003; Ryan and Swenson, 2001; Whiteman, et al., 2006; Winne and Ryan, 2001)
Larval growth is related to egg and hatchling size. The smaller the egg, the smaller the larva will be at hatching. Time to hatching also influences length of the larval period, survival to metamorphosis, and size at metamorphosis. Eggs can hatch anywhere between 20 to 60 days after being laid and larval transformation occurs 60 to 90 days after hatching. (Kinkead and Otis, 2007; Lannoo, 2005; Ryan and Plague, 2004; Whiteman, et al., 2006)
- Development - Life Cycle
Mole salamanders exhibit complex courtship behavior and use visual, chemosensory, and tactile cues during courtship. Aquatic adults attract females through tail-waving. Aquatic individuals peak breeding occurs earlier than terrestrial individuals, in early November as compared to mid-January. This difference in breeding times can lead to partial reproductive isolation. Courtship in heteromorphic pairing tends to occur less frequently, proceeds more slowly, and is more likely to end before sperm transfer. Also, female mate choice may influence mating success among morphs. Females, regardless of morph, have a strong aversion to aquatic males. (Calfee, et al., 2006; Duellman and Trueb, 1994; Lannoo, 2005; Ryan and Plague, 2004)
- Mating System
- polygynandrous (promiscuous)
Breeding in mole salamanders occurs mainly from December to March. There is some variation in the time of breeding due to climatic conditions that can restrict the movement of some individuals. Mole salamanders may skip breeding in a year if conditions are not appropriate. On average, only about 35% of mole salamanders will breed in any given year. Ponds used for breeding tend to be ponds with no fish in forested areas. Ponds can be permanent, semi-permanent, or seasonal. Mole salamanders can also breed in areas such as gravel pits or roadside ditches that have been filled with water during heavy rains. Terrestrial and aquatic morphs successfully interbreed, with intermorph breeding influenced by temporal, spatial, and behavioral separation. Breeding cycles vary between aquatic and terrestrial adults, resulting in temporal separation of breeding. Terrestrial adults tend to breed after pond filling and are more susceptible to competitive and predatory pressures. Terrestrial adults migrate to breeding ponds mainly at night and during periods of heavy, sustained rains and cold temperatures. If these conditions aren't met, then fewer terrestrial adults will come to breeding ponds. Aquatic adults remain in their original breeding ponds to reproduce and tend to breed earlier than terrestrial adults. In some cases, the offspring of aquatic adults may hatch before terrestrial adults even begin to breed. Spatial separation of the morphs within breeding ponds depends on the depth at which concentrations of aquatic individuals is greatest. (Kinkead and Otis, 2007; Lannoo, 2005; Ryan and Plague, 2004; Whiteman, et al., 2006)
Mole salamanders reproduce sexually. Male salamanders produce balls of sperm and other substances, called spermatophores. Males can produce multiple spermatophores and can compete with other males by covering competing spermatophores with their own. Females will collect a spermatophore in their cloacae to fertilize the eggs. When the female's eggs become fertilized, she will lay them in a group, called a clutch, loosely attached to submerged vegetation, such as a twig or other object, in the pond. Clutch size is positively correlated with body size in the female salamander. Larger terrestrial females produce larger clutches than same-age aquatic females. On average, a female will lay between 200 to 700 eggs per year. Eggs are 1 to 3 mm in diameter. Females lay their eggs at night and can take several days to lay all of her eggs. Populations that reside in the Atlantic coastal plain tend to have larger clutch sizes. Both male and female mole salamanders reach sexual maturity around 2 years of age or when they are larger than 44 mm. (Kinkead and Otis, 2007; Lannoo, 2005; Ryan and Plague, 2004; Whiteman, et al., 2006)
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- Breeding interval
- Mole salamanders breed once a year.
- Breeding season
- Breeding season typically occurs between December and March and lasts between 7 and 15 days.
- Range number of offspring
- 200 to 700
- Range time to hatching
- 20 to 60 days
- Range time to independence
- 12 to 14 months
- Average time to independence
- 15 months
- Average age at sexual or reproductive maturity (female)
- 2 years
- Average age at sexual or reproductive maturity (male)
- 2 years
Male salamanders have no parental investment in their young. Female mole salamanders provision their eggs with yolk for development and place them in a protected area in a breeding pond. After egg deposition, there is no further parental involvement. (Semlitsch, 1985)
- Parental Investment
- no parental involvement
The life cycle of a mole salamander has a great impact on the individual's longevity. Once a salamander becomes mature in an aquatic environment, 45% of adults will die before ever leaving the breeding pond. This high rate of mortality is due to pond drying and aquatic predators. When a salamander becomes terrestrial, however, chances of survival improve greatly. Mole salamanders in the wild can live up to 20 years. (Lannoo, 2005)
- Typical lifespan
- 10 to 20 years
- Typical lifespan
Mole salamanders can be active at any time of the day, although most activity is at night. Their activity patterns and seasonal migrations are influenced by environmental conditions, such as rainfall and temperature. Terrestrial salamanders are active and migrate on moist, cool nights. These salamanders are relatively sedentary, occurring either in their natal pond (as aquatic morphs) or in the forests around breeding ponds (as terrestrial morphs). Adults are found farther from breeding ponds than juveniles. On average, adult salamanders travel 170 m to breeding ponds while juveniles travel approximately 50 m. The peak period of emigration of terrestrial juveniles from breeding ponds occurs between June and November, when temperatures are higher and pond drying becomes more of a factor. (Lannoo, 2005; Patterson, 1978; Whiteman, et al., 2006)
- Range territory size
- 3.61 to 5.29 m^2
Terrestrial mole salamanders spend the majority of their lives under ground or under leaf litter and other debris. Mole salamanders are found in home ranges of 3.61 to 5.29 square meters. (Lannoo, 2005)
Communication and Perception
Mole salamanders use their sense of sight and smell the most to communicate with conspecifics and to perceive their environment. Tactile cues may also be important. (Kinkead and Otis, 2007; Lannoo, 2005)
Mole salamanders are carnivorous. Recently hatched larvae feed on zooplankton and other small, aquatic organisms. As larvae develop, they add larger prey items as they are able to ingest them. Mole salamanders pick their prey based on size relative to their own body size, and tend to choose larger prey as they grow. Larvae have been known to eat mole salamander eggs as well as eggs of other Ambystoma salamanders. They also eat copepods, ostracods, water fleas, and midge larvae. Adult mole salamanders have been described as opportunistic feeders and eat a variety of items, including aquatic insects, tadpoles, earthworms, athropods, and an assortment of other invertebrates. (Lannoo, 2005; Whiteman, et al., 2006)
- Animal Foods
- terrestrial non-insect arthropods
- terrestrial worms
- Other Foods
Mole salamanders are subject to predation from other salamanders as well as other aquatic predators. Larval salamander communities are highly structured by predation. Mole salamanders tend to breed later than other species of Ambystoma and are subject to more competition and predation as a result. Marbled salamanders (Ambystoma opacuum) breed earlier and their larvae feed on mole salamander eggs and larvae. Bluegill sunfish, if present, also feed heavily on mole salamander eggs. When a terrestrial adult mole salamander is attacked, is will stand in a posture with its head lowered in order to expose the well developed paratoid glands to the predator. These glands secrete a noxious chemical. They also lash their tails, head-butt, bite, writhe, flee, or feign death to deter predators. (Boone, et al., 2002; Lannoo, 2005; Whiteman, et al., 2006)
The health of salamander populations is used as an indicator of ecosystem health because of their sensitivity to toxins and increased ultraviolet radiation. Declining mole salamander populations are used as an indicator of water quality. Juvenile mole salamanders serve as prey to larger terrestrial and aquatic predators. Mole salamanders also act as predators, consuming both aquatic and terrestrial invertebrates. (Calfee, et al., 2006; Lannoo, 2005)
- nematodes (Brachycoelium salatnandrae)
Economic Importance for Humans: Positive
Larval mole salamanders successfully reduce mosquito larvae abundance. Mosquito consumption is directly related to salamander body size. In one study, researchers found that the largest salamanders (4.4 g) consumed 902 mosquitoes in one day. (DuRant and Hopkins, 2008)
- Positive Impacts
- research and education
- controls pest population
Economic Importance for Humans: Negative
There are no known negative effects ofon humans.
In North Carolina, mole salamanders are listed as a species of special concern and a permit is required to conduct any activity involving this species. A similar permit is also required in Tennessee, where the species is considered in need of management. Mole salamander populations have been affected by clear cutting of forests surrounding breeding ponds, draining or filling of breeding ponds, and the introduction of predatory fishes due to the deepening of breeding ponds. However, mole salamander populations are currently considered stable throughout most of their range. (Chazal and Niewiarowski, 1998; Lannoo, 2005; Moseley, et al., 2004; Rothermel and Luhring, 2005)
Tanya Dewey (editor), Animal Diversity Web.
Ashlee Behr (author), Radford University, Karen Powers (editor, instructor), Radford University.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
uses sound to communicate
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
union of egg and spermatozoan
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
Referring to a burrowing life-style or behavior, specialized for digging or burrowing.
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
An animal that eats mainly insects or spiders.
- internal fertilization
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
having the capacity to move from one place to another.
specialized for swimming
- native range
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- seasonal breeding
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
uses sight to communicate
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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