Northern Red-legged Frog
Scientific Name: Rana aurora
Other/Previous Names: Red-legged Frog
Taxonomy Group: Amphibians
COSEWIC Range: British Columbia
COSEWIC Assessment Date and Status Change: May 2015
COSEWIC Status: Special Concern
COSEWIC Status Criteria:
COSEWIC Reason for Designation:
The Canadian distribution of this species is restricted to southwestern British Columbia, where it overlaps areas of dense human population in the Lower Fraser Valley and southeastern Vancouver Island and actively managed forest lands within the remainder of its range. Over the past ten years, local declines and disappearances have been documented, but the species has persisted across its known historical range. The frog continues to face many threats from introduced species such as American Bullfrog and illegally stocked sport fish, road mortality, urban development, logging, dams and water management, and the pollution of breeding sites. If those threats are not effectively mitigated, the species is likely to decline further and become Threatened.
COSEWIC History of Status Designation: Designated Special Concern in April 1999. Status re-examined and confirmed in May 2002, November 2004, and May 2015.
SARA Status: Schedule 1, Special Concern
Date of Listing (yyyy-mm-dd): 2005-01-12
Please note that this information is provided for general information purposes only. For the most up to date and accurate list of species listed under the Species at Risk Act, please see the Justice Laws Website.
Image of Northern Red-legged Frog
The only subspecies of the Red-legged Frog that occurs in Canada is the Northern Red-legged Frog, Rana aurora aurora.
The Northern Red-legged Frog, Rana aurora, is a member of the family Ranidae, true frogs. The name Rana aurora was applied to R. aurora and R. draytonii (California Red-legged Frog) until 2004 when genetic evidence showed that they are distinct species. Only R. aurora occurs in Canada. The Northern Red-legged Frog is a medium-sized frog with adult snout-vent length usually from 50 to 70 mm. The brown back is flecked with black spots and the legs have black bands. The common name refers to the red colour seen through translucent skin on the underside of the hind legs of adults. The Northern Red-legged Frog plays important ecological roles both as a consumer of invertebrates, including insect pests, and as prey for fish, reptiles, birds, and mammals. Regular movements between aquatic and terrestrial habitats give it a role in transferring nutrients and energy between ecosystems. The species is sensitive to pollutants including pesticides and nitrogenous by-products. (Updated 2017/05/30)
Distribution and Population
The range of the Northern Red-legged Frog extends from southwestern British Columbia, south along the Pacific coast, west of the Cascade Mountains, to northwestern California. An introduced population occurs in Chichagof Island, Alaska, and a population of unknown origin occurs on Graham Island, British Columbia. Recent distribution records for the Northern Red-legged Frog confirm that the species remains widespread on Vancouver Island and the adjacent mainland of British Columbia. New records extend the species' range throughout the Sunshine Coast (southern mainland coast northwest of Greater Vancouver) and the Sea-to-Sky Corridor (Highway 99 from Vancouver north to Whistler) and farther up valleys surrounding the Fraser Lowlands. Populations remain in some urbanized areas within the Lower Mainland and Fraser Valley, but failed searches over the past 5 years suggest they may be extirpated from parts of the cities of Vancouver, Richmond, and Delta, where they occurred historically. Intensive search effort and no detections at Stanley Park since the 1970s indicate that the species is extirpated there. (Updated 2017/05/30)
The Northern Red-legged Frog requires both aquatic breeding and terrestrial foraging habitats at low elevations (usually below 500 m, although the species can occur as high as 1040 m). Eggs are laid on submerged parts of plants within permanent and temporary seasonal wetlands that have sun exposure, water at least 30 cm deep, and low flow. Tadpole survival is higher in temporary wetlands with complex structure and relatively few predators compared to permanent wetlands. Adults and juvenile frogs disperse up to 5 km away from wetlands into moist forest habitats, where they find refuge in moist burrows, under large pieces of downed wood, and within understory vegetation. Overwintering habitat includes below-ground refuges in forests and wetlands. Habitat degradation and loss have been extensive on southern and eastern Vancouver Island and the Lower Fraser Valley because of agriculture, urbanization, roads, the introduction of American Bullfrogs, and logging. (Updated 2017/05/30)
Adults breed in the late winter or early spring, often returning to the same breeding sites year after year. Males produce an advertisement call under water. Females lay 200 to 1100 eggs in a single egg mass. Early mortality is relatively high but decreases when maturity is reached; annual adult survival is estimated at 69%. Males usually reach sexual maturity at 2 years of age, while females may take up to 4 years. The maximum reported lifespan of the Northern Red-legged Frog in captivity is 15 years. The generation time is estimated at 4 to 6 years. (Updated 2017/05/30)
Threats known to impact the Northern Red-legged Frog are urban development, road mortality, logging, dams and water management, invasive species, introduced fish, disease, and pollution. Within the Lower Fraser Valley, human population growth is predicted to double every 20 - 30 years. Growth is also expected along the southeastern side of Vancouver Island, parts of the Sea-to-Sky Corridor, and the Sunshine Coast. Some of the existing habitat in urban and rural agricultural areas will be converted to housing and thereby undergo further fragmentation and exposure to pollution. American Bullfrog populations are predicted to grow and spread, increasing competition and predation pressure and augmenting damage to breeding habitats caused by dams and water management, introduced fish, and disease. Logging has the potential to alter habitat throughout the vast remote parts of the species' range. Temperature extremes, storms, and flooding events associated with climate change will likely exacerbate habitat loss and degradation caused by other factors. (Updated 2017/05/30)
More information about SARA, including how it protects individual species, is available in the Species at Risk Act: A Guide.
Provincial and Territorial Protection
PLEASE NOTE: Not all COSEWIC reports are currently available on the SARA Public Registry. Most of the reports not yet available are status reports for species assessed by COSEWIC prior to May 2002. Other COSEWIC reports not yet available may include those species assessed as Extinct, Data Deficient or Not at Risk. In the meantime, they are available on request from the COSEWIC Secretariat.
20 record(s) found.
- COSEWIC Status Reports (3 record(s) found.)
- Response Statements (3 record(s) found.)
- Action Plans (2 record(s) found.)
- Management Plans (1 record(s) found.)
- Orders (2 record(s) found.)
- COSEWIC Annual Reports (2 record(s) found.)
- Permits and Related Agreements (5 record(s) found.)
- Consultation Documents (1 record(s) found.)
- Recovery Document Posting Plans (1 record(s) found.)
COSEWIC Status Reports
Response Statement - Northern Red-legged Frog (2015-12-23)The Canadian distribution of this species is restricted to southwestern British Columbia, where it overlaps areas of dense human population in the Lower Fraser Valley and southeastern Vancouver Island and actively managed forest lands within the remainder of its range. Over the past ten years, local declines and disappearances have been documented, but the species has persisted across its known historical range. The frog continues to face many threats from introduced species such as American Bullfrog and illegally stocked sport fish, road mortality, urban development, logging, dams and water management, and the pollution of breeding sites. If those threats are not effectively mitigated, the species is likely to decline further and become Threatened.
Response Statements - Red-legged Frog (2004-04-21)A response statement is a communications document that identifies how the Minister of the Environment intends to respond to the assessment of a wildlife species by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). The document provides a start to the listing and recovery process for those species identified as being at risk, and provides timelines for action to the extent possible.
Response Statements - Red-legged Frog (2005-11-15)A large proportion of the known Canadian distribution of this species occurs in the densely populated southwestern part of British Columbia. Habitats are becoming increasingly lost and fragmented due to land conversions and other human activities. Introduced Bullfrog and Green Frog, which are spreading rapidly, have replaced this species at many sites and appear to adversely affect the use of wetland breeding sites and reproductive success. Populations of this species, and other amphibian species that require extensive habitat, are inherently vulnerable to habitat fragmentation which can be expected to exacerbate isolation effects and local extinctions.
COSEWIC Annual Reports
COSEWIC Annual Report - 2005 (2005-08-12)2005 Annual Report to the Canadian Endangered Species Conservation Council (CESCC) from the Committee on the Status of Endangered Wildlife in Canada.
COSEWIC Annual Report - 2014-2015 (2015-11-20)Under Canada’s Species at Risk Act (SARA), the foremost function of COSEWIC is to "assess the status of each wildlife species considered by COSEWIC to be at risk and, as part of the assessment, identify existing and potential threats to the species". COSEWIC held two Wildlife Species Assessment Meetings in this reporting year (October, 2014 to September, 2015) from November 23 to November 28, 2014 and from April 27 to May 1, 2015. During the current reporting period, COSEWIC assessed the status or reviewed the classification of 56 wildlife species. The wildlife species assessment results for the 2014-2015 reporting period include the following: Extinct: 0 Extirpated: 1 Endangered: 21 Threatened: 11 Special Concern: 21 Data Deficient: 1 Not at Risk: 1 Total: 56 Of the 56 wildlife species examined, COSEWIC reviewed the classification of 40 that had been previously assessed. The review of classification for 24 of those wildlife species resulted in a confirmation of the same risk status as the previous assessment.