Marine Mammals
Polar Bear
Ursus maritimus
ALSO KNOWN AS
Sea bear, ice bear, white bear, Nanuq
DISTRIBUTION
Circumpolar Arctic
ECOSYSTEM/HABITAT
Ice edge and coastal regions
FEEDING HABITS
Aggressive predator
TAXONOMY
Order Carnivora (carnivorans); Family Ursidae (bears)
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Polar bears are a true Canadian icon. They have great cultural significance, particularly for Inuit and other northern communities. Almost two thirds of the world’s polar bears are found in Canada. Although polar bears appear white, their skin is actually black and their two dense layers of fur are transparent, reflecting light and directing heat from the sun’s rays down the hair shaft where it is absorbed by their black skin.
Polar bears are a true Canadian icon. They have great cultural significance, particularly for Inuit and other northern communities. Almost two thirds of the world’s polar bears are found in Canada. Although polar bears appear white, their skin is actually black and their two dense layers of fur are transparent, reflecting light and directing heat from the sun’s rays down the hair shaft where it is absorbed by their black skin.
Polar bears are perfectly adapted for life in the Arctic. Their large, wide paws, strong claws, and the small bumps and fur on the underside of their paws all help them to easily traverse the sea ice. They are considered marine mammals, just like whales, because of their dependence on the ocean. Polar bears are strong swimmers, using their long streamlined body and wide paws to move between ice floes with ease. Their fur looks creamy to yellowish-white in colour and they have a small head in comparison to their body. On average, polar bears are the largest member of the bear family, with males able to reach 2.8 metres in length and weighing up to 800 kilograms. More commonly, however, adult males range from 2.4 to 2.6 metres in length and weigh between 400 and 600 kilograms, with smaller adult females typically 1.9 to 2.1 metres in length and weighing 200 to 300 kilograms.
Male and female polar bears become sexually mature at around four or five years of age, however, most males won’t breed until they are between eight and 10 years old. Mating takes place in the spring, but the embryo does not begin to grow until between September and October. At this time, the female will excavate a birthing den, ideally in a few metres into a snowdrift. The den will maintain a temperature close to zero degrees Celsius regardless of the outside temperature, thanks to the insulation provided by the snow. After around two months of gestation, one or two cubs are born, with twins being most common. At birth, cubs are almost bald and weigh less than one kilogram, but they grow rapidly because of their mother’s rich milk, which is 31 per cent fat. Mother polar bears fast while in the den – all her energy and fat stores are used to feed and raise her cubs.
The family will emerge from the den between the end of February and early April, but will stay near it for a few weeks to exercise and get used to the cold. They will then begin their trek toward the sea and ice edge, where the mother can finally feed and teach her cubs how to hunt. Cubs will continue to nurse for about two years, while also eating meat provided by their mother. Polar bears feed primarily on ringed seals, but they also eat bearded seals, harp seals, hooded seals and harbour seals, and will occasionally hunt smaller walruses, beluga whales and narwhals. Polar bears are dependent on sea ice to catch seals as they are most efficient as ambush hunters. They catch seals by waiting for them to surface at their breathing holes, stalking them sunbathing on the sea ice and by breaking into the birthing chambers of ringed seals.
Due to their largely terrestrial lifestyle, polar bears are not directly affected by fishing operations. However, they may be indirectly impacted by expanding fisheries in the Arctic, if fish populations that seals rely on are overexploited. By limiting food availability, seal populations would decline, affecting top predators in the ecosystem, such as polar bears. A subsistence hunt targeting polar bears is carried out by Inuit communities, which is regulated by the Canadian government. This subsistence hunt has been around for centuries and has very high social, cultural and economic importance for Inuit communities.
Polar bears in Canada were classified by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2008 as of Special Concern. They are also listed under Schedule 1 of the Species at Risk Act (SARA) as of Special Concern. Currently, the 13 subpopulations of polar bears found in Canada show varying population trends, with some showing decreases, some stable and some showing increases. However, they were given the designation of Special Concern because of the inherent threat of decreased availability of sea ice caused by climate change. This warrants concern and the need for further research on how the Arctic ecosystem is changing and how best to protect polar bears.
