Ambystoma tigrinumEastern Tiger Salamander(Also: Tiger Salamander)

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Geographic Range

This mole salamander is the largest land dwelling salamander in North America. It also has the greatest range of any other North American salamander, spreading in range from southeastern Alaska east to the southern part of Labrador, and south throughout all of the United States down to the southern edge of the Mexican Plateau (Indiviglio 1997).

Habitat

Fully metamorphosed adults lead a terrestrial existance and, depending upon where in the country they are found, some may inhabit forests, grasslands, or marshy areas (Petranka 1998). Tiger salamanders are less dependent on the forest than most other Ambystomids. One general requirement seems to be soil in which they are able to burrow or in which the burrow of other species of other animals might be utilized (Petranka1998). While they are well suited for terrestrial existence in terms of their skin consistency and thickness, they do need to be able to burrow underground in order to seek the proper humidity levels. Another requirement is that they live close enough for permanent access to ponds and othe small waters for their breeding. During dry periods, large numbers of tiger salamanders have been found lying in piles beneath suitable cover or underground (Indiviglio 1997).

Physical Description

Adult Length 17-33 cm.

The adult tiger salamander is a thick-bodied creature generally with yellow blotches or spots against a black background. Once in a while there will be one with blotches that are tan or olive green in color. The spots or blotches are never in any set shape, size or position. Actually you may even be able to tell its origin by the color and pattern of the background and/or spots (Indiviglio 1997). A. tigrinum has a rather large head and a broad rounded snout. Their eyes are round. The belly is usually yellowish or olive with invading dark pigment. It has about 12-13 coastal grooves (Harding 1997). Males tend to be proportionally longer, with a more compressed tail and longer stalkier hind legs than the females. During the breeding season the males have a swollen vent area. The larvae have a yellowish green or olive body with the dark blotches and a stripe along each side. They also have a whitish belly. As they grow, specimens tend to be grayish or greenish in color, and within a few weeks they start to show yellow or tan spots and gradually merge into the patterns of the adult bodies (Harding 1997).

  • Average mass
    9.402 g
    0.33 oz
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  • Average basal metabolic rate
    0.00196 W
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Development

Eggs are laid in small pools and hatch within a time period of 19 to 50 days. The larvae remain in the pond until they turn into adults at 2.5 to 5 months of age. Sometimes, adult tiger salamanders remain in the aquatic larval form for their entire lives.

Reproduction

Ambystoma tigrinum migrates to the breeding ponds in late winter or early spring, usually after a warm rain that thaws out the ground's surface. Males tend to arrive earlier than the females, probably due to the fact that they live closer to the ponds during the winter months. Courtship happens during the night where the males nudge and bump other salamanders. Upon coming across a female, the male will nudge her with his snout to get her away from the other males (Harding 1997). Once away from the other males, the male walks under the females chin, leading her forward and then she nudges his tail and vent area. This behavior stimulates the male to deposit a spermatophore. The female moves her body so that the spermatophore contacts her vent, thus allowing her to take sperm into her cloaca. This behavioral movement continues and produces more spermatophores. The competition for breeding is great in this species and sometimes other males may interupt the courting pairs and replaces the spermatophores with its own. The laying of eggs occurs a night, usually 24-48 hours after the courtship and insemination. They lay the eggs and attach them with twigs, grass stems and leaves that have decayed on the bottom floor of the pond. Each mass can obtain up to 100 eggs (Harding 1997). When large enough, the masses can resemble that of a spotted salamander but the mass of a tiger salamander is less firm and is very fragile if handled. Each female produces anything from 100 to 1000 eggs per season (Harding 1997).

  • Average number of offspring
    37
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  • Average time to hatching
    28 days
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  • Average age at sexual or reproductive maturity (female)
    Sex: female
    1460 days
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  • Average age at sexual or reproductive maturity (male)
    Sex: male
    1460 days
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Lifespan/Longevity

Aquatic adult tiger salamanders live up to 25 years in captivity. Normal adults have reached ages of 16 years.

Behavior

Adult Tiger Salamanders live underground for most of the year and usually dig their own burrows, unlike other species that use burrows of other animals. They have been found over 60 cm below the surface (Harding 1997). This allows them to escape the temperature extremes on the surface and may explain why they have such a wide array of habitat types.

Food Habits

The tiger salamander's food source consists of worms, snails, insects, and slugs in the wild; while captive specimens rely on smaller salamanders, frogs, newborn mice, and baby snakes. Tiger salamanders in the wild also tend to eat the same thing as captives, if opportunity presents itself (Indviviglio 1997). The larvae begin feeding on small crustaceans and insect larvae and once grown, they will feast on tadpoles and smaller salamander larvae and even small fish (Harding 1997).

Predation

Tiger salamanders are eaten by badgers, snakes, bobcats, and owls. Larvae are eaten by aquatic insects, the larvae of other salamanders, and snakes.

Ecosystem Roles

They are efficient predators in their aqautic and subterranean environment, and their prey includes some insect pests.

Economic Importance for Humans: Positive

In some places Ambystoma tigrinum are captured and sold for fish bait (Harding 1997).

Economic Importance for Humans: Negative

The larvae are sometimes considered a nuisance in fish hatcheries. Large larvae will feed on very small fish, but their main effect might be to act as competitors with the fish. As the fish grow larger they can turn the tables and feed on the salamander larvae.

Conservation Status

Populations in the southeastern U.S. have been affected by deforestation and loss of wetland habitats and appear to be declining in many areas. According to studies in the Colorado Rockies done by Harte and Hoffman, acid rain may be responsible for this. Other studies indicate that it might not have anything to do with it (Petranka 1998). Other threats for these salamanders are being hit by cars and polluting of their ponds and habitats.

Contributors

Alissa Wentz (author), Michigan State University, James Harding (editor), Michigan State University.

Glossary

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.

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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.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

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.

internal fertilization

fertilization takes place within the female's body

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.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

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

solitary

lives alone

References

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, Mi: The University of Michigan Press.

Indiviglio, F. 1997. Newts and Salamanders. New York: Barron's Educational Series.

Petranka, J. 1998. Salamanders of the United States and Canada. Washington and London: Smithsonian Institution Press.