Habitat & Distribution

Polar Bears

Habitat & Distribution

Distribution

  1. Polar bears are found throughout the circumpolar Arctic.
  2. Polar bears are found throughout the circumpolar Arctic.

  3. Polar bears, or their tracks, have been reported almost as far north as the pole; however, scientists believe few bears frequent areas north of 88° north latitude on the ice over the continental shelf. The northern Arctic Ocean has little food for them.
  4. The polar bears' southern range is limited by the amount of sea ice that forms in the winter. Polar bears prefer to travel on sea ice and must have ice from which to hunt seals.
    • In the south, polar bears are annual visitors to southern Labrador, Newfoundland, and Norway. They can reach the Gulf of St. Lawrence and Bering Sea during years with heavy pack ice.
    • The most southerly dwelling polar bears live year-round in James Bay, Canada.
  5. The majority of polar bears are found near land masses around the edge of the polar basin, where the continental shelf makes conditions ideal for hunting.
  6. Scientists believe there are 15 relatively discrete polar bear subpopulations (four others are recognized for management purposes). A subpopulation is a group of polar bears that interbreed with a range independent of but overlapping that of other polar bears. For example, two subpopulations live in the James/Hudson Bay area, one in western Hudson Bay, and the other in northwestern Ontario and James Bay.

Habitat

  1. Polar bears inhabit arctic sea ice, water, islands, and continental coastlines.
  2. Polar bears make extensive migrations over land and
    through water as the ice recedes and advances.

  3. Polar bears prefer sea ice habitat with leads and polynyas, next to continental coastlines or islands.
    • Leads are water channels or cracks through ice which may remain open (ice free) for only a few minutes to several months, depending upon weather conditions and water currents. Polar bears hunt seals in the leads, using sea ice as a platform.
    • Polynyas are areas of water, surrounded by ice, that remain open throughout the year due to winds, upwellings, and tidal currents. Polynyas are important breathing and feeding areas for wintering or migrating marine mammals and birds.
  4. Some polar bears follow the southern edge of the ice pack year-round, making extensive migrations as the ice recedes and advances.
  5. Some polar bears spend part of the year on land. They have been found as far inland as 402 km (250 mi.).
    • Polar bears in warmer climates may become stranded on land. In summer, sea ice melts along the coastlines, and pack ice (floating sea ice, or floes, not connected to land) moves so far north, that polar bears can't reach it, even though they are excellent swimmers.
    • Most pregnant females spend the autumn and winter on land in maternity dens.
  6. Air temperatures in the Arctic average -34°C (-29°F) in winter and 0°C (32°F) in summer. The coldest area in winter is northeastern Siberia, where the temperature has been recorded as low as -69°C (-92°F). The warmest areas in summer are inland regions of Siberia, Alaska, and Canada where temperatures can reach as high as 32°C (90°F).
  7. The ocean temperatures in the Arctic are about -1.5°C (29°F) in summer. In winter the ocean temperatures can drop to -2°C (28°F), at which point seawater begins to freeze.

Migration

  1. Polar bears travel throughout the year within loose, individual home ranges.
    • Home range size varies among individuals depending upon access to food, mates, and dens.
    • Home ranges tend to be larger than for other mammal species because sea ice habitat changes from season to season and year to year.
      • A small home range may be 50,000 to 60,000 sq. km (19,305-23,166 sq. mi.). Small home ranges can be found near Canadian Arctic islands.
      • A large home range may be in excess of 350,000 sq. km (135,135 sq. mi.). Large home ranges can be found in the Bering or Chukchi seas.
    • Polar bears don't mark their home ranges.
  2. Polar bears undergo seasonal migrations, following the movements of the ice pack. Some bears prefer to remain at the edge of the ice pack year-round, making extensive migrations as the ice advances and recedes. On the southern shores of Hudson Bay, some bears move onto land for summer and disperse over ice for the winter.
  3. Polar bears are capable of traveling 30 km (19 mi.) or more per day for several days. One polar bear was tracked traveling 80 km (50 mi.) in 24 hours. Another polar bear traveled 1,119 km (695 mi.) in one year.

Population

  1. The world polar bear population is estimated at 20,000 to 25,000 individuals.
  2. The ratio of males to females is approximately one to one.
  3. 1972 estimates of polar bears ranged from 5,000 to 20,000 bears. The current, worldwide population of polar bears may or may not have increased from this estimate.
  4. More recently, some polar bear populations are declining due to loss of vital sea ice habitat.