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Red-legged Frog (Rana Aurora)

Distribution

Global Range

The distribution of the Northern Red-legged Frog extends from southwestern British Columbia south to northwestern California (Figure 2). This species occurs throughout western Washington and Oregon west of the Cascade Mountains to the Pacific coast. In northwestern California, the Northern Red-legged Frog is replaced by the California Red-legged Frog (R. aurora draytonii), the range of which extends south to Baja California, Mexico. An isolated population in southeastern Alaska is the result of a recent introduction (K. MacAllister, pers. comm.). A population in the Queen Charlotte Islands is probably also introduced (see below). Most of the global distribution of the Red-legged Frog is in the United States with about one quarter being in Canada.

 

Canadian Range

In Canada, the Red-legged Frog occurs in southwestern British Columbia, where it is found throughout Vancouver Island, on several of the islands in the Strait of Georgia, and on the adjacent mainland (Figure 3). Populations in these areas are geographically isolated from each other by stretches of ocean; the extent of the open ocean between Vancouver Island and the mainland is the shortest (less than 1 km) through offshore islands in the Johnstone Strait. The mainland portion is contiguous with the species’ range in Washington State.

Figure 2: North American Distribution of the Northern Red-legged Frog

Figure 2.  North American distribution of the Northern Red-legged Frog.

Distribution in the United States based on a maps provided by R. Nauman and K. MacAllister; BC distribution based on Figure 3.

Vancouver Island comprises the bulk (over 50%) of the species’ known Canadian range. On the mainland, the species’ distribution extends through the lower Fraser Valley east to near Hope and north along the coast to Bramham Island in the vicinity of Cape Caution. In the north, an isolated record exists from near Kitimat on the central coast (RBCM #1199, 12000). Specimens associated with the Kitimat record could not be located but were probably misidentified and represent the Columbia Spotted Frog, which is known from the area. In the southwest, a record from the Manning Park (RBCM #816, 817) probably also represents the Columbia Spotted Frog; unfortunately, these specimens could also not be located.

Figure 3: Locality Records for the Red-legged Frog in British Columbia, 1887 – 2003

Figure 3.  Locality records for the Red-legged Frog in British Columbia, 1887 – 2003.

Open symbols represent approximate locations.

There are only a few records north of Vancouver along the mainland coast. The northernmost record (excluding the Kitimat record) is from Bramham Island, where students of the Coastal Ecosystem Foundation studied the ecology of the Red-legged Frog in the late 1990s (W. Meggill, pers. comm.). There are no museum specimens associated with this record. Three museum records exist from north of Powell River (from the Kingcome area and Loughborough Inlet near Powell River; CMC #1879, 1886A, B). The identification of these specimens has been confirmed (in September 2003, by Dr. Francis Cook, Researcher Emeritus, Canadian Museum of Nature). The rugged coastal forests north of Powell River and along the central coast have not been surveyed systematically for amphibians, and the limits of this species on the mainland remain unknown.

In 2001, the Red-legged Frog was documented from the Queen Charlotte Islands (Haida Gwaii) (Ovaska et al. 2002). The species was found at 10 localities in the vicinity of Port Clements, Graham Island, including both settled and remote areas. It is possible that this population is a result of human introduction, similar to the deliberate release of individuals of the Pacific Treefrog (Pseudacris regilla), which is now widespread on the islands (Reimchen 1991). However, the possibility that the Red-legged Frog is an overlooked native species cannot be ruled out conclusively without further investigation.

Other distribution records for the Red-legged Frog obtained since 1998, after the preparation of the COSEWIC status report by Waye (1999), are from within the known portions of the species’ Canadian distribution on Vancouver Island and the Lower Mainland (Figure 3).