Polar bear (Ursus maritimus) COSEWIC assessment and status report: chapter 10

10. Technical Summary

Ursus maritimus

Polar bear – Ours blanc

Inuktitut name: Nanuq, Nanuk

Cree name: Wapusk

Range of Occurrence in Canada:

Yukon, Northwest Territories, Nunavut, Manitoba, Ontario, Quebec, Newfoundland and Labrador

Extent and Area Information

Extent of occurrence (EO) (km²)

9.1 × 106 km²
See Sections 3.1 and 3.2

Specify trend in EO

Stable

Are there extreme fluctuations in EO?

No

Area of occupancy (AO) (km²)

5.6 × 106 km²
See Sections 3.1 and 3.2

Specify trend in AO

Stable

Are there extreme fluctuations in AO?

No

Number of known or inferred current locations

One

Specify trend in #

Stable

Are there extreme fluctuations in number of locations?

No

Specify trend in area, extent or quality of habitat

Decline in quality where climate change is increasing the duration of the ice-free season.

Population Information

Generation time (average age of parents in the population)

12 years

Number of mature individuals

  • Total population 15,500;
  • mature individuals >10,000

Total population trend:

Decline

% decline over the last/next 10 years or 3 generations.

Variable among subpopulations, overall likely less than 30%

Are there extreme fluctuations in number of mature individuals?

No

Is the total population severely fragmented?

No

Specify trend in number of populations

n/a

Are there extreme fluctuations in number of populations?

n/a

List populations with number of mature individuals in each:

n/a

Threats (actual or imminent threats to populations or habitats)

Climate warming, over-harvest, pollution, increased offshore oil and gas development

Rescue Effect (immigration from an outside source)

Status of outside population(s)?

  • USA: Alaska, South Beaufort Sea (likely decline)
  • Greenland: West Greenland (severe decline)
  • Arctic Basin: Nomadic bears (unknown status)

Is immigration known or possible?

Yes

Would immigrants be adapted to survive in Canada?

Yes

Is there sufficient habitat for immigrants in Canada?

Yes

Is rescue from outside populations likely?

No

Quantitative Analysis

Current Status

  • COSEWIC: Special concern, April, 2008
  • IUCN: Vulnerable
  • CITES: Appendix II
  • US ESA: Threatened

Status and Reasons for Designation

Status: Special Concern

Alpha-numeric code: n/a

Reasons for Designation: The species is an apex predator adapted to hunting seals on the sea ice and is highly sensitive to over harvest. Although there are some genetic differences among bears from different parts of the Arctic, movement and genetic data support a single designatable unit in Canada. It is useful, however, to report trends by subpopulation because harvest rates, threats, and, hence, predicted population viability, vary substantially over the species’ range. Some subpopulations are over harvested and current management mostly seeks the maximum sustainable harvest, which may cause declines if population monitoring is inadequate. Until 2006, some shared subpopulations were subject to harvest in Greenland that was not based on quotas. Population models project that 4 of 13 subpopulations (including approximately 28% of 15,500 polar bears in Canada) have a high risk of declining by 30% or more over the next 3 bear generations (36 years). Declines are partly attributed to climate change for Western Hudson Bay and Southern Beaufort Sea, but are mostly due to unsustainable harvest in Kane Basin and Baffin Bay. Seven subpopulations (about 43% of the total population) are projected to be stable or increasing. Trends currently cannot be projected for 2 subpopulations (29% of the total population). Bears in some subpopulations show declining body condition and changes in denning location linked to decreased availability of sea ice. For most subpopulations with repeated censuses, data suggest a slight increase in the last 10-25 years. All estimates of current population growth rates are based on currently available data and do not account for the possible effects of climate change. The species cannot persist without seasonal sea ice. Continuing decline in seasonal availability of sea ice makes it likely that a range contraction will occur in parts of the species range. Decreasing ice thickness in parts of the High Arctic may provide better habitat for the bears. Although there is uncertainty over the overall impact of climate change on the species’ distribution and numbers, considerable concern exists over the future of this species in Canada.

Applicability of Criteria

Criterion A (Declining Total Population): The Canadian population is now declining, but has increased over the past few decades. Four subpopulations (approximately 28% of 15,500 polar bears in Canada) have a high risk of declining by 30% or more over the next 3 bear generations. Seven subpopulations (about 43% of the total population) appear stable or increasing. Trends currently cannot be projected for 2 subpopulations (29% of the total population).
Criterion B (Small Distribution, and Decline or Fluctuation): The Area of Occupancy is over 5 million square kilometres.
Criterion C (Small Total Population Size and Decline): There are over 10,000 mature polar bears in Canada.
Criterion D (Very Small Population or Restricted Distribution): There are over 10,000 mature polar bears in Canada.
Criterion E (Quantitative Analysis): Trends assessed by management unit show that some subpopulations are declining whereas others are increasing. Overall trends are impossible to assess because trends differ by management unit, and not all units have adequate data. In addition, the expected negative effects of continuing global warming cannot be reliably assessed. Some declines are due to over harvest, and steps are being taken to reduce harvest in some management units. The best available data suggest that it is unlikely that the Canadian population of polar bears will decline by 30% over the next 36 years.

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