Montana Field Guide

Tiger Salamander - Ambystoma tigrinum

Adults vary in color pattern, but background color is usually dark, with lighter blotches of yellow, tan, or green. Adults are large and heavy-bodied with a body length of 3 to 6 inches. Eggs and Larvae: Eggs are typically laid in small clusters of 5 to 120, but may be laid singly. Larvae are typically pale green or brown. They have external gills and are relatively large and heavy-bodied (0.75 to 4 inches) (FWP). Coloration geographically variable to an extreme, often mottled, blotched, or spotted; adults are stocky, with 11-14 (usually 12-13) costal grooves, a broad head, small eyes, and tubercles on the soles of the feet; pond-type larva (but lacks balancers), with three large pairs of gills, vomerine teeth in U-shaped pattern, and dorsal fin extending to region of axilla; adults usually are about 15-22 cm in total length (to about 34 cm) (Stebbins 1951, 1985; Behler and King 1979; Conant and Collins 1991).

The following pertains to metamorphosed adults. differs from a. macrodactylum in lacking a distinct dorsal stripe or stripelike row of spots. differs from a. gracile in having distinct dorsal markings and tubercles on the underside of the feet and by lacking parotoid glands and a glandular ridge on the tail. differs from a. annulatum in lacking a light grayish stripe along the lower side of the body and generally lacking narrow light bands across the body. differs from a. maculatum and a. opacum in having large light blotches on the sides. differs from a. talpoideum in having sharply defined spots and usually more than 11 costal grooves (vs. 10-11). differs from all other north american ambystoma in having tubercles on the soles of the feet. differs from plethodontid salamanders in lacking a nasolabial groove.

Montana Range

Has breeding migrations.

Tiger salamanders in Montana are primarily associated with prairie or agricultural habitats. They breed in ponds, lakes, springs, intermittent streams, and stock ponds, usually those without fish present. Adults go to the breeding ponds soon after snowmelt; after breeding, adults may remain in the ponds or move to upland areas and live in burrows. Eggs hatch in 2 to 5 weeks and metamorphosis takes 2 to 24 months. In some locations larval salamanders never transform, but rather become sexually mature and breed while retaining external gills (referred to as neotony). These salamanders are often called "axolotls" or "water dogs" (FWP). Are benthic in ponds but may enter upper water column at night . At high elevation, tend to select warmest water in ponds (rarely >25 C) - shallows during day, deep water at night.

Larva: (W CO): mostly arthropods, taken proportional to abun. Ad. (S Manitoba): (% by wt.) Cammarus 87, coleop 7, hirud 8.

Late metamorph. probably caused by temp rather than food a- bundance. Paedomorphic pops tend to occur at higher elevations. High elevation populations use behavioral thermoregulation (Heath 1975).

Breeds in May on prairie; Jun-mid Aug at 7780 ft. in SW MT. Eggs hatch in ca. 15 days, Jun-Aug. Metamorph. in Aug of 1st yr on prairie; not un- til yr 2-3 at high elevevation.