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Canadian Herpetological Society Société d'Herpétologie du Canada |
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Gray Tiger Salamander
Ambystoma mavortium diaboli
Family: Ambystomatidae
The Gray Tiger Salamander is a subspecies of the Western Tiger Salamander (Ambystoma mavortium).
COSEWIC status:- Special Concern
- Special Concern
- Least Concern
Description
The Gray 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. Gray Tiger Salamanders are very heavy-bodied with broad heads, small eyes, 11–14 costal grooves and a laterally compressed tail (especially in males). Adults have black blotches or bars on a light yellow or cream-coloured background and the belly is dark grey. Neotenic individuals (see biology) tend to attain larger sizes than terrestrial adults. Aquatic larvae are generally olive to greenish yellow with a tail fin, legs (both front and back) and feathery gills that are longer than the head.
Similar Species
Gray Tiger Salamanders are most easily confused with the Eastern Tiger Salamander and the Blotched Tiger Salamander. The Gray and Blotched Tiger Salamanders are both sub-species of the Western Tiger Salamander and are very difficult to differentiate based on appearance. For the most part, the ranges of these two subspecies do not overlap and they are best identified based on their location. The Eastern Tiger Salamander has smaller light spots (rather than bars and blotches) on a dark background.
Distribution
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In Canada, the Gray Tiger Salamander occurs in southwestern Manitoba and south-central Saskatchewan, but is absent from southwestern Saskatchewan. This subspecies also occurs south of the border in North Dakota, northeastern South Dakota and a small part of Wisconsin.
Habitat
Gray 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, parkland, grassland, sub-alpine meadows and semi-desert. 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
Gray 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 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, and the larvae transform into terrestrial juveniles in late summer. 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 throughout its 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.