Animal Field Guide

Coeur d'Alene Salamander

Plethodon idahoensis
(Plethodontidae)

Montana Species of Concern
Global Rank: G4
State Rank: S2

Agency Status
USFWS:
USFS: SENSITIVE
BLM: SENSITIVE

The Coeur d'Alene salamander is a small, dark gray to black, lungless salamander with a yellowish throat patch, and a yellow, orange, green, or red dorsal stripe. The stripe usually has scalloped edges, though they may be even. The legs are relatively long with short, slightly webbed toes. The adult body length is about 5 to 6 centimeters (2 to 2.4 inches).

The maximum snout-vent length (SVL) (body length without tail) of the Coeur d'Alene salamander is 62 millimeters with only 0.5 to 3.0 intercostal folds between adpressed limbs. It has the fewest costal grooves of all western Plethodon. It also has more vomerine and premaxillary-maxillary teeth and a relatively shorter tail than other western Plethodon.

The species is a non-migrant.

The occupied habitat for Coeur d'Alene salamanders in Montana is like that for the entire global range, and includes the three major habitat categories: springs and seeps, waterfall spray zones, and stream edges (Wilson and Larsen 1988, Werner and Reichel 1994, Boundy 2001, Maxell 2002).

More specifically, primary habitats are seepages and streamside talus; they also inhabit talus far from free water (deep talus mixed with moist soil on well-shaded north-facing slopes). In wet weather, it occurs also in leaf litter and under bark and logs in coniferous forests. The species is a terrestrial breeder, with eggs presumably laid in underground rock crevices, although no nest sites have been found in the wild.

All plethodontid salamanders respire through their skin; terrestrial species lose water to the environment through evaporation and are therefore restricted to cool, damp environments. Because Coeur d'Alene salamanders may live in the harshest climate of any northwestern plethodontid (Nussbaum et al. 1983), they are highly dependent on the thermal and hydrologic stability provided by wet habitats in otherwise inhospitable surroundings. For this reason, Coeur d'Alene salamanders are closely tied to water and are considered among the most aquatic plethodontids (Brodie and Storm 1970).

Coeur d'Alene salamanders have been found in three major types of habitat: springs or seeps, waterfall spray zones, and edges of streams. Seventy-six percent of known locations are classified as seeps, 6% as waterfalls, and 17% as streams. Two sites occur in abandoned mines. However, the relative number of locations in each type is biased by differences in survey efficiency and probably does not reflect the importance of the different habitats. The abundance of seep locations is at least partly due to the relative ease of surveying roadside seeps. Streams and waterfalls are often less accessible, particularly at night. Salamanders are most difficult to find in streamside habitat, where they are usually observed underneath moist rocks on the banks adjacent to the water. Searches of 30 minutes to find a salamander at a stream site during daylight are not uncommon (Groves 1988).

Coeur d'Alene salamander occurrences are generally located in coniferous forests, but are not restricted to a particular overstory species or aspect. Populations have been found in areas with ponderosa pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii), western larch (Larix occidentalis), western red cedar (Thuja plicata) and western hemlock (Tsuga heterophylla) overstories (Groves 1988, Groves et al. 1996) at all aspects.

Ninety percent of 99 Idaho occurrences where habitat data have been collected were in areas of greater than 25% canopy cover and only two (both seeps) were in an area with 10% cover or less. Forest cover may be more important near stream sites than seep sites. Average cover at seven streamside sites (83% + or - 15%) was significantly greater than at seep locations (57% + or - 5%), (Cassirer et al. 1994). Minimum canopy cover measured at stream sites was 42%. Terrain at sites was typically steep, with average slopes of 62% (range 10-90%) (Groves 1988, Wilson 1991).

Known populations occur in association with sharply fractured rock formations (used for underground refugia) from 488 meters to 1,524 meters in elevation. This fractured rock is often found in the Belt Rock formation but can also occur in talus and in other geologic types (Wilson and Simon 1987, Groves and Cassirer 1989). The species is found in conjunction with both persistent and intermittent surface water. Thus, it is possible to locate salamanders at a wet site in the spring, yet be unable to find any animals at the same site later in the summer when the site is dry on the surface.

This species is an invertivore. When above ground, Coeur d'Alene salamanders feed primarily on insects (11 orders documented) and other invertebrates, including millipeds, mites, spiders, harvestmen, snails, and segmented worms (Wilson and Larsen 1988). They appear to be opportunistic feeders and generally restrict foraging activities to moist spray zones, seeps, or streamside rocks and vegetation, although they may venture beyond these areas during rainy periods. The diet is most similar to other salamanders that occupy semi-aquatic habitats.

The Coeur d'Alene salamander is most often nocturnal when surface-active, although it has been seen in daytime during rain, heavy overcast, and clear sky conditions (Wilson and Larsen 1988). Surface activity is weakly and positively correlated to nighttime substrate temperature, and negatively correlated to daytime substrate temperature and number of days since the last rain. Surface activity is most prevalent during spring and fall. The wet microclimate it occupies buffers this species from climatic extremes and may explain its persistence in a region lacking other species of plethodontid salamanders. Altogether, this species may spend up to seven months underground (Nussbaum et al. 1983, Cassirer et al. 1994, Groves et al. 1996).

Population sizes are difficult to measure, and no estimates are available. Predators include birds, garter snakes, and possibly small mammals or ground beetles (Wilson and Simon 1985, Staub 1995, Wilson and Wilson 1996). Other sources of mortality include trampling (Werner and Reichel 1994).
Males are sexually mature in about 39 months (44 millimeters SVL); females at 42 months (48 to 49 millimeters SVL). They typically lay their first clutch during their 5th spring (Lynch 1984). Activity positively correlated with nighttime substrate temperature (Wilson and Larsen 1988). Summer activity was negatively correlated with daytime substrate temperatures and number of days since the last rain (Wilson and Larsen 1988). Evidence exists for snake predation upon the species: on July 24, 1986 in the Kootenai River Gorge, Lincoln County, Wilson and Wilson (1996) retrieved a 2.5 centimeter P. idahoensis tail tip from a fresh road-killed snake, Thamnophis sirtalis parietalis (39.5 centimeters SVL), and on June 8, 1987, they palped a neonate P. idahoensis (1.8 centimeters SVL) from an immature T.s. parietalis (18.9 centimeters SVL) above the west shore of Lake Koocanusa, Lincoln County, Montana.

Little information exists regarding Coeur d'Alene salamander reproduction in Montana. An egg mass was laid by a captive female in early June. The egg mass was 21 millimeters maximum dimension and contained a clutch of seven eggs (Larson et al. 1998).

Generally, Coeur d'Alene salamanders mate above ground in late summer and fall (August to October) and, to a lesser extent, in spring (April and May) (Lynch 1984). After a courtship ritual of an hour or more, the male deposits a spermatophore, which is picked up by the female with her cloaca (Lynch and Wallace 1987). Females store sperm up to nine months before fertilizing eggs. An average of six eggs is deposited in April or May. The young emerge in mid-September (Lynch 1984).

Neonates apparently grow more slowly than other Plethodon species. Growth probably occurs in spurts associated with wet weather in the spring and fall. Male Coeur d'Alene salamanders reach sexual maturity at 3.5 years of age and females at 4.5 years, but some individuals may delay breeding. Males mate every year, whereas females mate in alternate years (Lynch 1984).

Potential threats for the species across its global range apply also to Montana populations, but population declines or extinctions have not yet been documented. Some populations continue to be vulnerable to highway construction activity, and most occur at elevations and in forest types where timber harvest is a common activity. Routine monitoring (Groves et al. 1996) of known populations should be conducted to identify threats to each, as well as to determine their continued viability.