Cœur d’Alene salamander COSEWIC assessment and status report: chapter 2

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Executive Summary

Species information

Plethodon idahoensis is the only member of the family Plethodontidae (lungless salamanders) in southeastern British Columbia. It is dark brown to black with a scalloped, usually orange, dorsal stripe. Snout-vent length (SVL) averages 54 mm and total length (including the tail) averages109 mm. The largest individual ever recorded was a female with a SVL of 69 mm, north of Creston, BC.

Distribution

The species range is limited to northwestern Montana, northern Idaho and southeastern British Columbia. Found in seven general areas of the Purcell and Selkirk mountain ranges, its range is discontinuous and follows roughly the Columbia and Kootenay Rivers and their tributaries. In BC its northern limit is 95 km north of Revelstoke, and its eastern limit is near the town of Kimberley.

Habitat

Plethodon idahoensis occupies moist microhabitats in steep terrain where fractured, incised bedrock or talus occurs in association with water. Habitats include rock walls with seepages or streams flowing over them, waterfall splash zones, caves, step-like streams with exposed bedrock, avalanche paths, and wet talus. Overstory vegetation includes deciduous shrubs (at avalanche paths or seepages) and coniferous forest (young to mature structural stages).

Biology

Plethodon idahoensis spends much of its life in subterranean retreats. Reproduction is delayed until 3 – 4 years of age, and females lay eggs in alternate years. There is no larval stage. The diet consists primarily of aquatic and semi-aquatic insects. As with other plethodontids, this species has physiological constraints – it requires moist micro-environments to facilitate oxygen transfer across the skin and is prone to dehydration through evaporation. Plethodon idahoensis is most active on the surface during rainy nights when substrate temperatures are above 4° C. Home range size is not known, but movements >100 m were recorded for one individual. Another moved 48 m in a seven week period.

Population sizes and trends

Nocturnal surveys between 1995 and 2003 detected 919 P. idahoensis at 56 sites in British Columbia. Reproduction was noted at 52% of occurrence sites. It is probable that there are more than 10,000 individuals considering the uncertainties involved in estimating total population size and our knowledge of the number of localities. Broad size class distributions and the presence of juveniles indirectly suggest that the population may be stable. Due to steep topography and difficulties of access at night, much of the suitable habitat between known occurrence sites remains unsurveyed.

Limiting factors and threats

The most imminent threat to >20 occurrence sites is highway widening and maintenance. Other threats include water diversion, sedimentation of interstitial spaces, removal of overstory vegetation and alterations to hydrology arising from logging. Silvicultural activities such as burning and herbicide application can be carried out right to the edge of non-fish bearing streams that support P. idahoensis. Further threats may include increased isolation of habitat patches, the effects on habitats of small scale hydro developments and the effects of climate change on metabolism and habitat availability.

Special significance of the species

Plethodon idahoensis may be a relic of a previously widespread plethodontid salamander fauna. It is the only lungless salamander in eastern British Columbia.

Existing protection or other status designations

Plethodon idahoensis was assessed by COSEWICin 1998 as Vulnerable (= Special Concern) and re-confirmed, as Special Concern, in 2001. The species is listed under Schedule 1 (Part 4) of the Species at Risk Act. Its Global Rank is G4 and its British Columbia rank is S3 (Blue-listed). It is S2 in both Idaho and Montana. Individuals are protected under the Wildlife Act. Habitat at 27 of the 56 known localities for this species in British Columbia have been designated Wildlife Habitat Areas, two are in national parks, one is in a provincial park, and one is on property managed by the Columbia Basin Fish and Wildlife Compensation Program.

COSEWIC History

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2007)

Wildlife Species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC) ^Footnotea

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR) ^Footnoteb

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD) ^Footnotec

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.