Tiger Salamander. Ambystoma tigrinum

Description: Adult: Total length 140-180 mm, rarely to 200 mm (snout-vent length 70-90 mm). A large, robust salamander with a short, round head and relatively small eyes. Normally thirteen costal grooves on each side of the body. Limbs robust, toes relatively short, stout and unwebbed. A pair of tubercles on the underside of the feet. General colour blotched, barred or reticulate pattern of yellow (or white) and black (or grey, dark brown or olive green). Boundaries of blotches not always sharp. Belly sooty grey.

Larvae: Hatch at about 15 mm total length and may reach 75-80 mm, but neotenic individuals exist that may be as large as fully grown, metamorphosed tiger salamanders. General colour dull yellow to olive green or dark brown, with pale undersides. There are prominent external gills, with fifteen or more gill rakers on the anterior surface of the third gill arch, and a conspicuous tail fin. The larvae lack balancers.

Variation: Juvenile metamorphosed individuals with smaller and brighter markings than adults. Old individuals may become uniform olive, brown or black in colour. Males with proportionately longer tails and hind legs than those of females. In the breeding season, the cloacal region is swollen in males.

Natural history: In Alberta, active from early spring to early fall; particularly active in spring rains. Although tolerant of very dry conditions, usually found near small lakes, ponds or dugouts, often in subterranean burrows which may be excavated by the salamanders themselves. Feeds on insects, mites, earthworms, molluscs and small vertebrates. Hatchlings feed mainly on zoo-plankton and crustaceans; older larvae and neotenic adults may eat fish, insect egg masses and larvae, worms, frogs and other salamanders. Larvae maybe cannibalistic. Metamorphosed adults are rarely seen in the open except during the breeding season. Primarily nocturnal in activity patterns.

Reproduction: Mating occurs after early spring migration to breeding sites in permanent or semi-permanent standing water. No amplexus occurs, but males push and nuzzle females in courtship, then lead them to deposited spermatophores. Males may be aggressive towards each other during courtship bouts and may even cover previously deposited spermatophores with their own. Breeding may take place in water of less than 10°C. Eggs (2-5 mm in diameter) are laid singly or in small groups shortly after mating, and are attached to stones, plants or debris. Eggs hatch after approximately three weeks and metamorphosis occurs (if at all) after three to four months, usually in August. Larval development may often take two years.

Distribution: In Alberta, occurs at elevations of up to 2,800 m. Found in short-grass prairie, aspen parkland, boreal forest and subal- pine habitats. Widely distributed south from Edmonton, with an isolated population near Grande Prairie. Probably introduced in many areas throughout the province. Extralimitally, broadly distributed east of the Rockies, south to the Mexican plateau (absent from parts of the Gulf Coast, Florida, the Appalachians, the northern United States and Eastern Canada). Scattered isolated populations throughout the west, south from the Okanagan Valley, B.C.

The inset map showing the total range of Ambystoma tigrinum indicates some of the uncertainty surrounding the taxonomic status of this taxon and its component parts. The light grey area to the east represents the distribution of Ambystoma tigrinum tigrinum. The remainder of the distribution, indicated in black, represents the other subspecies. Those portions occupying Canada and the U.S.A. have recently been advocated to belong to a separate species, Ambystoma mavortium, but this opinion has not yet won widespread acceptance. The taxonomic status of the Mexican populations is uncertain - hence the question mark.

Conservation status: The former range of this species has probably become fragmented as a result of human activities, but the species remains common in suitable habitats and shows no signs of broad scale population decline.

Remarks: Five to seven subspecies are recognized, although the validity of some of these, including Ambystoma tigrinum melanostictum (the Alberta form) is questionable. A. tigrinum melanostictum occurs south to Idaho and Wyoming and east to eastern South Dakota. Disjunct populations occur in eastern Washington and adjacent parts of British Columbia, the Idaho panhandle and the Columbia River Valley. Neoteny is particularly common in

A. t. melanostictum. This species has been widely used as live bait and this has influenced its distribution. Individuals may live for up to 16 years. Stebbins (1985) shows in his distribution map Ambystoma tigrinum diaboli present marginally in east central Alberta. As yet we have no confirmation of this.

Significant references: Anderson 1968b, 1970; Anderson et al. 1971; Arnold 1976; Bizer 1978; Brophy 1980; Burger 1950; Clark and Chandler, 1991; Delson and Whitford 1973; Dodson and Dodson 1971; Dunn 1940; Else and Bennett 1987; Fowler 1935; Franz 1971; Gehlbach 1967; Gruberg and Sterling 1972; Hassinger et al. 1970; Heath 1975, 1976; Hetherington and Lombard 1983; Holomuzki 1986,1989; Holomuzki and Collins 1987; Kristensen 1981; Kumpf 1934; Lannoo and Bachman 1984; Lannoo et al. 1989; Larsen, J.H. and Guthrie 1975; Lauder and Shaffer 1985, 1986; Lewin 1963a; Malvin and Heisler 1988; Moore and Strickland 1955; Nussbaum 1985; Patch and Stewart 1924; Pedersen 1991; Petranka 1998; Pierce et al. 1983; Rohrbach and Stiffler 1987; Salt 1979; Semlitsch 1983a, b; Shaffer and Lauder 1985; Shaffer and McKnight 1996; Sprules 1974; Stark 1986a; Stebbins 1985; Whitford and Massey 1970.