Polar bear Ursus maritimus conservation in Canada: an ecological basis for identifying designatable units

Gregory W. Thiemanna1 c1, Andrew E. Derochera1 and Ian Stirlinga1 p1

a1 Department of Biological Sciences, CW405 Biological Sciences Building, University of Alberta, Edmonton, AB T6G 2E9, Canada.


Polar bears Ursus maritimus have a circumpolar distribution that is directly tied to the Arctic sea ice. Although they are wide-ranging, polar bears do not belong to a single population but rather are comprised of 19 largely discrete subpopulations, 13 of which are fully or partly under Canadian jurisdiction. These subpopulations are used to manage the sustainable harvest of polar bears in Canada but for conservation purposes the species is currently considered a single biological unit. Long-term climate warming has reduced the availability of sea ice that polar bears require for feeding, movement and reproduction, and continued declines in ice extent and duration are forecast to have significant negative effects on polar bears in some areas. Under the Canadian Species at Risk Act separate legal protection may be given to intraspecific groups (so called designatable units, DUs) that are genetically, geographically and/or biogeographically distinct. We examined the conservation status of polar bears across their Canadian range and compared large-scale ecosystem properties across subpopulations. We found that threats to the conservation of polar bears are not spatially uniform and we identified five DUs that captured broad patterns of polar bear biodiversity. We conclude that the use of DUs provides a biologically-sound framework for the conservation of polar bears.

(Received October 16 2007)

(Reviewed January 11 2008)

(Accepted February 16 2008)