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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Eastern Tiger Salamander
Ambystoma tigrinum
Family: Ambystomatidae
COSEWIC status:- Extirpated (Carolinian population)
- Endangered (Prairie population)
- Extirpated (Carolinian population)
- Endangered (Prairie population)
- Least Concern
Description
The Eastern Tiger Salamander is one of the largest terrestrial salamanders in North America and can grow to over 30 cm in total length, although most individuals are smaller than this. Eastern Tiger Salamanders are very heavy-bodied with broad heads, small eyes, 12–13 costal grooves and a laterally compressed tail. Individuals have light yellow or cream-coloured spots or small blotches on a dark background the belly is dark grey. Neotenic individuals (see biology) tend to attain larger sizes than terrestrial adults. Aquatic larvae have a tail fin, legs (both front and back) and feathery gills behind the head. The larvae are generally yellow to brown with dark dorsal blotches, light stripes on the sides and light-coloured bellies.
Similar Species
Eastern Tiger Salamanders are most easily confused with the Gray Tiger Salamander, but the ranges of these two subspecies do not overlap. The Gray Tiger Salamander has bars and large blotches rather than spots or small blotches.
Distribution
Until recently, the only record of the Eastern Tiger Salamander in Canada was from Point Pelee in 1915 and the species was considered extirpated. Recently, however, this species was also discovered in southeastern Manitoba. The Eastern Tiger Salamanders has a large distribution in the US and occurs throughout the Midwest, the eastern seaboard south of Long Island and in the southern US west to Texas.
Habitat
Eastern Tiger Salamanders breed in permanent or semi-permanent lakes, ponds or wetlands that are fish-free. They inhabit a variety of terrestrial habitats within close proximity to these breeding sites, including forest edge, parkland, savannah and grassland. Loose or sandy soil that the salamanders can burrow into, cover objects (rocks, woody debris) and small mammal burrows are important microhabitat features that provide shelter. Individuals overwinter underground below the frost line in burrows they excavate or in mammal burrows.
Biology
Eastern Tiger Salamanders migrate to breeding wetlands on rainy nights in the early spring just after the ice cover recedes from the breeding habitats. After breeding, females attach eggs singly or in small clusters of up to 100 eggs to submerged sticks or other vegetation at least 30 cm below the surface of the water. The number of eggs that each female lays depends on geographic location and female body size, but can range from 100 to 5000. The eggs hatch into aquatic larvae after two to three weeks. The larvae transform into terrestrial juveniles in late summer or they overwinter as larvae and transform the following spring. Some individuals retain larval features as adults and remain aquatic their entire life (neoteny). Males generally reach sexual maturity in two years, while females may not reach maturity until they are three to five years old. Females may only breed every two years. Tiger Salamanders are long-lived, and individuals may live over 25 years. After the breeding season, adults spend most of their time in underground burrows and cavities, making them difficult to find during the summer and fall. Tiger Salamanders are opportunistic predators and eat a wide variety of insects, spiders, worms and other terrestrial invertebrates, as well as small vertebrates such as mice. Larvae prey on aquatic invertebrates, larval frogs and salamander larvae, including other Tiger Salamander larvae.
Threats
Habitat loss and fragmentation, particularly the destruction of wetlands, is a threat to this species within its very limited Canadian range. Road mortality can be a significant threat to Ambystoma salamanders when roads bisect spring migration routes. Pollution, such as herbicides, agricultural effluent and road salt can be detrimental to salamanders since toxins are easily absorbed though their skin. The introduction of predatory sport fish into breeding habitats can quickly decimate local populations. Climate change and introduced pathogens pose potentially serious threats to Canadian salamanders.