Polar bear (Ursus maritimus) COSEWIC assessment and status report: executive summary

Executive Summary

Polar Bear
Ursus Maritimus

Species information

The polar bear (Ursus maritimus Phipps) evolved within less than 400,000 years to occupy the niche of hunting seals from a sea-ice platform. Many of the physical traits of polar bears can be viewed as adaptations to hunting arctic seals.

Distribution

Polar bears are a circumpolar species that occur in Canada from Yukon to Newfoundland and Labrador, and from northern Ellesmere Island south to James Bay. The population is distributed among 13 subpopulations with some evidence for genetic separation between them. The length and frequency of seasonal movements undertaken by bears within subpopulations varies with the size of the geographic area occupied, the annual pattern of freezing and break-up of sea ice, and availability of features such as land masses, multi-year ice, and polynyas. Distinctions between subpopulations or larger-scale divisions based on ecoregions are insufficient for status to be assigned to designatable units below the species level.

Habitat

The productivity of polar bear habitat is closely linked to the physical attributes of sea ice (type and distribution) and the density and distribution of ice-dependent seals, especially ringed seals (Pusa hispida). From early winter until break-up of annual sea ice in spring, polar bears are dispersed predominantly over sea ice along the coast. They may range >200 km offshore. Maternal denning sites are generally located on land near the coast, being excavated in snowdrifts and in some places frozen ground. Offshore maternal dens on multi-year ice floes are also known to occur, particularly in the western Canadian Arctic.

Biology

Reproductive rates vary among subpopulations of polar bears but all are relatively low. Females reach sexual maturity at 4–6 years and have litters of typically 1–2 cubs approximately every 3 years. Most males generally breed at 8–10 years. Few polar bears live longer than 25 years.

Population sizes and trends

Data on survival and reproduction suggest that 4 of 13 subpopulations (Western Hudson Bay, Southern Beaufort Sea, Baffin Bay, and Kane Basin), representing approximately 27.8% of the total population of 15,500 polar bears shared by Canada and its immediate neighbours (Greenland and the United States), are likely declining at the present time. Four subpopulations are most likely to be stable (including 1 slightly increasing and 1 possibly slowly declining) at the present time (comprising 29.3% of the total population), and 3 subpopulations are most likely to be increasing (13.5% of the total population). Trend cannot be reported due to pending analysis or lack of data for the 2 remaining subpopulations (29.4% of the total population). Estimates of possible declines over longer periods (e.g., 3 generations) are complicated by potential changes in survival and reproduction due to climate change and/or alterations in harvest management. Current declines are due to over harvest (Baffin Bay, Kane Basin) and climate change (Western Hudson Bay, Southern Beaufort Sea). Long-term population trends will ultimately be determined by changes in extent and types of sea ice associated with a warming climate in the Arctic.

Limiting factors and threats

The main, proximate limiting factors affecting polar bear distribution and numbers today are availability of food (access to and abundance of ice-dependent seals) and human-caused mortality (almost exclusively from hunting). Other potential limiting factors include intraspecific predation, pollution, especially that associated with offshore development of hydrocarbon reserves and increased ship traffic, and the accumulation of environmental contaminants (mainly organochlorines) in tissues of polar bears. Climate change is likely to influence all of the factors above and should thus be treated as the ultimate limiting factor to polar bears.If the climate continues to warm as projected by the Intergovernmental Panel on Climate Change (IPCC), all populations of polar bears will eventually be affected.

Special significance of the species

The polar bear is the only terrestrial carnivore to occupy the highest trophic level of a marine ecosystem. The polar bear is an icon of Canada’s wildlife heritage, and is of great cultural significance to the Canadian people. Polar bears are also of cultural, spiritual, and economic significance to some northern native peoples. As a symbol of the pristine Arctic environment, polar bears are seen throughout the world as a barometer of important environmental issues, especially climate change and pollution. Canada has national and international responsibilities with respect to the study, management, and protection of polar bears, as outlined in the international Agreement on the Conservation of Polar Bears. This obligation is particularly important to our nation because we collectively manage 55–65% of the world’s polar bears.

Existing protection or other status designations

In 2006, largely in response to the threat posed by global warming, the polar bear was moved from Least Concern-Conservation Dependent to the category of Vulnerable in the Red List of the Species Survival Commission (SSC) of the IUCN-The World Conservation Union, corresponding to the Threatened category of COSEWIC. This uplisting was based on an assessment of available data and the unanimous opinion of the IUCN/SSC Polar Bear Specialist Group. Polar bears are on Appendix II of CITES (Convention on International Trade in Endangered Species). Under CITES, any international shipment of polar bears or parts thereof requires a permit. The US Secretary of the Interior announced on May 14, 2008, that the polar bear will be listed as Threatened under the U.S. Endangered Species Act. Management authority for this species rests with the provinces, territories, and wildlife management boards established under land claims. Hunting is largely managed through quota systems and according to Aboriginal treaty rights. Internationally, the management of polar bears is coordinated under the Agreement on the Conservation of Polar Bears, signed by the federal government on behalf of all Canadian jurisdictions in November 1973. At the time of writing, habitat of polar bears is formally protected only through Canada’s terrestrial system of national parks and Ontario’s provincial park system; these protected areas encompass approximately 2.9% of the area of occupancy of the species in Canada. The majority of polar bear habitat is marine, for which there are no federal, provincial, or territorial protected areas.

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, theSpecies 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 (2008)

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.

Canadian Wildlife Service

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

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