Geographic Range
Ambystoma talpoideum
is endemic to the southeastern and central United States. It is found along the southern
Atlantic and Gulf Coastal plains, north along the Mississippi River to southern Illinois,
and from central South Carolina to eastern Texas. There are isolated populations in
Virginia, Tennessee, Kentucky, North Carolina, and northern South Carolina, Georgia,
and Alabama. Mole salamanders are not present in southern Florida or southern Louisiana.
Habitat
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.
- Habitat Regions
- temperate
- terrestrial
- freshwater
- Terrestrial Biomes
- forest
- Aquatic Biomes
- lakes and ponds
- temporary pools
- Wetlands
- swamp
- Other Habitat Features
- riparian
Physical Description
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.
- Other Physical Features
- ectothermic
- heterothermic
- bilateral symmetry
- polymorphic
- Sexual Dimorphism
- male larger
Development
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.
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.
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.
- Development - Life Cycle
- neotenic/paedomorphic
- metamorphosis
Reproduction
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.
- 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.
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.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
- oviparous
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.
- Parental Investment
- no parental involvement
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- female
-
provisioning
Lifespan/Longevity
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.
Behavior
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.
Home Range
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.
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.
Food Habits
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.
- Primary Diet
-
carnivore
- insectivore
- eats non-insect arthropods
- Animal Foods
- amphibians
- eggs
- insects
- terrestrial non-insect arthropods
- terrestrial worms
- zooplankton
- Other Foods
- microbes
Predation
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.
Ecosystem Roles
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.
- nematodes ( Brachycoelium salatnandrae )
Economic Importance for Humans: Positive
Healthy mole salamander populations are indicators of aquatic system health.
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.
- Positive Impacts
- research and education
- controls pest population
Economic Importance for Humans: Negative
There are no known negative effects of Ambystoma talpoideum on humans.
Conservation Status
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.
Additional Links
Contributors
Tanya Dewey (editor), Animal Diversity Web.
Ashlee Behr (author), Radford University, Karen Powers (editor, instructor), Radford University.
- Nearctic
-
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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- temperate
-
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).
- terrestrial
-
Living on the ground.
- freshwater
-
mainly lives in water that is not salty.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- swamp
-
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- heterothermic
-
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.
- 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.
- polymorphic
-
"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.
- metamorphosis
-
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.
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- iteroparous
-
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).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- internal fertilization
-
fertilization takes place within the female's body
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- fossorial
-
Referring to a burrowing life-style or behavior, specialized for digging or burrowing.
- natatorial
-
specialized for swimming
- nocturnal
-
active during the night
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- solitary
-
lives alone
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- zooplankton
-
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
- carnivore
-
an animal that mainly eats meat
- insectivore
-
An animal that eats mainly insects or spiders.
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