Montana Field Guide

Idaho Giant Salamander - Dicamptodon aterrimus

Adults have light or tan bronze marbling on a dark brown or black background. They are heavy-bodied, with a large head and muscular legs; body length varies from 3.5 to 8 inches. Eggs and Larvae: Larvae are identified by their short, bushy, external gills; their large size; a dorsal fin starting at or behind the rear limbs; and their stream habitat. Other larval salamanders in Montana live in ponds have long, feather gills, and a dorsal fin originating far forward of the rear legs.

Montana Range

Nonmigratory.

Known to occur up to 2160 m in elev. (Nussbaum et al. 1983). Transformed adults, although seldom seen, inhabit moist coniferous forests where they may be found under logs, bark, or rocks. They are most active on warm, rainy nights. Larvae are usually found in swift, cold mountain streams, but may occasionally be found in lakes or ponds (Reichel and Flath 1995).

Larvae: diet influenced by size, consisting of 52% Trichoptera larvae, 46% Plecoptera nymphs, 30% Coleoptera larvae, 28% Ephemeroptera nymphs/Coleoptera adults. ASCAPHUS larvae (14%) may be important food for larger larvae (Metter 1963). Females do not feed during 7 months spent in nest with eggs (Nussbaum et al. 1983).

Neoteny uncommon in small streams, but neotenes may constitute major breeding force in populations in large streams and ponds/lakes (Nussbaum and Clothier 1973).

Ovipost in spring (May in coastal regions) and fall (noted in ID); incubation 275 days (Nussbaum 1969). Larvae hatch at SVL 18.25 mm, but do not feed for 3-4 more months until 24.43 SVL. Metamorphose during second year (Nussbaum and Clothier 1973). Females do not feed during the 7 months spent in nest with eggs; therefore, they likely only breed during alternate years (Nussbaum et al. 1983).