Polar Bear

Ursus maritimus

Polar Bear (Ursus maritimus) is a species in the genus Ursus, family Ursidae, order Carnivora.

Scientific classification

Description

The polar bear is the largest living bear and the most carnivorous. Adult males typically weigh 350–700 kilograms. The fur appears white but each hair is unpigmented and hollow; the skin beneath is black. Insulation comes mainly from a fat layer up to about 10 centimetres thick, which also provides buoyancy for the long swims the species undertakes.

The feet are very large, spreading weight on thin ice, and the soles carry papillae and small depressions that improve grip.

Distribution and habitat

Circumpolar Arctic. The polar bear is best understood as a marine mammal that hunts from a platform of sea ice rather than as a terrestrial bear that visits the coast, and its distribution follows the ice rather than the land.

Behaviour

The principal prey is ringed seal, usually taken by waiting at a breathing hole or by stalking animals hauled out on the ice. Hunting success depends on the presence of that ice; on land, bears subsist largely on stored fat.

Only pregnant females den through winter. Cubs, usually two, are born tiny — under a kilogram — and emerge from the den in spring.

Conservation

Vulnerable. The clearest threat is the loss of sea ice: shorter ice seasons lengthen the fasting period, reduce body condition, and lower cub survival. Because the mechanism runs through the physical habitat rather than through direct exploitation, it is difficult to address locally.

References

• Wiig, Ø. et al. (2015). Ursus maritimus. IUCN Red List assessment 22823.
• Stirling, I. (2011). Polar Bears: The Natural History of a Threatened Species.