The polar bear, Ursus maritimus, is uniquely adapted to life in the extreme environment of the Arctic. Despite being the world’s largest land carnivore, it is officially classified as a marine mammal due to its profound dependence on the ocean ecosystem. The species’ native range spans the circumpolar Arctic across five nations: Canada, the United States, Russia, Norway, and Greenland. Polar bears inhabit 19 recognized subpopulations across the seasonally and permanently ice-covered waters, but their distribution is highly specialized.
The Necessity of Sea Ice Habitat
The southern limit of the polar bear’s range is strictly defined by the seasonal availability of stable sea ice, which serves as its primary hunting platform. Polar bears are highly specialized predators, relying almost entirely on seals, particularly ringed seals, for the high-fat diet necessary to maintain their massive body size. They employ hunting techniques such as waiting by breathing holes, known as aglus, or stalking seals resting on the ice surface.
A seal’s blubber provides the bear with the caloric density needed to sustain itself for long periods and build up fat reserves. Without the sea ice, bears are forced onto land, where alternative food sources like bird eggs or vegetation are nutritionally inadequate. The energetic cost of terrestrial movement and hunting on land is significantly higher than hunting on the ice, making survival less likely. The annual formation and melt of sea ice therefore acts as an environmental barrier, ecologically limiting how far south a viable population can exist.
Geographic Limits: The Established Southern Range
The established southernmost boundary for a self-sustaining polar bear population is found in Canada, centered on the Hudson Bay ecosystem. The most southerly continuously occupied area for the species is the Southern Hudson Bay subpopulation, which extends into James Bay. James Bay, an arm of Hudson Bay, dips down to approximately 51° North latitude.
Bears in this area are adapted to a seasonal sea ice environment. They spend the winter and spring hunting seals on the ice, but when the ice melts completely in summer, they are forced onto the mainland coast to fast until the bay refreezes in late fall. The Labrador Coast of Canada also represents an extreme southern limit for the Davis Strait bears, whose range seasonally extends south to Newfoundland. The seasonal ice cover in these regions is sufficiently reliable and present for long enough to allow the bears to build the necessary fat reserves.
Rare Sightings and Southern Vagrants
While James Bay marks the consistent southern limit, individual polar bears occasionally travel far beyond their established range as “vagrants.” These sightings are usually the result of a bear drifting on ice floes, following prey, or becoming disoriented. Vagrant sightings are most common in eastern Canada, particularly in areas like Newfoundland and the Gulf of St. Lawrence, especially in years with heavy pack ice extending further south than normal.
One bear was spotted in 2022 at Madeleine-Centre, Quebec, hundreds of kilometers south of the typical range. Historically, records exist of bears reaching as far as the southern tip of Norway, or even the Canadian province of Nova Scotia. These individual bears are rarely able to establish a presence, often resulting in human-wildlife conflict or the bear’s death, and they do not represent an extension of the species’ breeding range.