Polar bear (female) near Kaktovik, Barter Island, Alaska (Alan Wilsonwww.naturespicsonline.com)

Polar bear (Ursus maritimus)

OVERVIEW

Polar bears are found throughout the Arctic and are the only bear species classified as a marine mammal.  There are polar bear populations in the territories of Canada, Denmark (Greenland), Norway, Russia and the USA (Alaska).

Although polar bears are omnivores, their diet consists almost exclusively of meat, primarily ringed and bearded seals hunted on the sea ice.  They also eat other mammals and will utilise carrion such as whales.  When meat is unobtainable they will forage for eggs, seaweed, grasses, moss and lichens.

Polar bears spend much of their time at sea, mainly on the ice but also in the water.  Following the spring break-up of the ice the they come ashore until the ice reforms in the fall.  They are extremely strong swimmers and have been recorded swimming long distances, the longest being 354 kilometres.

Mating takes place on the sea ice in April and May.  When the ice begins to break up in the fall pregnant females excavate a den, usually on land in the snow, sometimes underground in the permafrost and, less commonly, out on the sea ice.  Once in the den, the female enters a dormant state similar to hibernation.  Cubs are born between November and February and litters usually comprise two cubs, but single and triplet births also occur.  Cubs stay with their mothers for up to thirty months during which time the mother will not become pregnant again.

Life expectancy in the wild is around 25 years, in captivity up to around 40 years (the maximum recorded is 43 years).

SUMMARY

Status:  The polar bear is classified as “vulnerable” on the IUCN Red List. It is listed in Appendix 2 of CITES.  Polar bears are listed in the USA as a threatened species under the Endangered Species Act. In Canada they are listed as a species of special concern and Russia also considers them a species of concern.  The current worldwide population is estimated at around 26,000 bears with around 16,000 of these in Canada.

Kingdom: Animalia  Phylum: Chordata  Class: Mammalia  Order: Carnivora Family: Ursidae

Genus and species: Ursus maritimus (Phipps, 1774)

General Description: The largest of the extant species of bear with relatively short and muscular limbs and an elongated body.  Whilst polar bear fur appears white when clean, it actually lacks any pigment and can appear yellow in setting or rising sunlight or bluish on cloudy or misty days.  In late winter and spring bears often take on a yellowish or “dirty white” appearance from the oils of their prey.  Beneath their fur the skin of polar bears is uniformly black.  The nose is also black.

Size: Length 240 to 300 cm.  Height at shoulder 100 to 160 cm.

Weight: Males 350 to 650 kg.  Females 150 to 350 kg.

Life Expectancy: In the wild usually around 15 to 18 years (bears in their early 30’s have been recorded), in captivity up to 43 years.

Also known as: Inuit: Nanuk (“animal worthy of great respect”).  Russian: beliy medved (“white bear”).  Norway & Denmark: isbjorn (“ice bear”).

Range:  Found only in the northern hemisphere, the range of polar bears is limited to areas which are covered in sea ice for much of the year.  Many bears remain on the ice throughout the year, others visit land for only short periods when the ice coverage is reduced.  The bears are common in the Chukchi and Beaufort Seas to the north of Alaska, USA; in the East Siberian, Laptev, and Kara Seas of Russia; the Barent’s Sea of northern Europe; the northern part of the Greenland; in Baffin Bay between Canada and Greenland; and in most of the Canadian Arctic Archipelago.


This map shows the status of the 19 polar bear subpopulations, according to the 2014 IUCN Polar Bear Specialist Group report.  Populations are declining in three areas; Southern Beaufort Sea (SB), Kane Basin (KB) and Baffin Bay (BB).  Just one subpopulation is increasing; McClintock Channel (MC).

There are six stable subpopulations; Northern Beaufort Sea (NB), Western Hudson Bay (WH), Gulf of Boothia (GB), Foxe Basin (FB), Southern Hudson Bay (SH) and Davis Strait (DS).

For the remaining nine subpopulations there is insufficient data to make a determination; Chukchi Sea (CS), Laptev Sea (LP), Arctic Basin (AB), Kara Sea (KS), Barents Sea (BS), East Greenland (EG), Viscount Melville Sound (VM), Lancaster Sound (LS) and Norwegian Bay (NW).

See the Map courtesy of the Norweigan Polar Institute


Subspecies: There are no recognised subspecies of the polar bear.

THREATS

Changes in the Arctic habitat of polar bears are currently of more concern than the effects of hunting, and are likely to remain so into the foreseeable future.  The extent, thickness and duration of Arctic sea ice in particular is leading to increasing challenges to the health and long-term viability of the nineteen subpopulations.  Coupled with a worrying lack of knowledge regarding many of those subpopulations, this makes the future of the polar bear a matter of significant concern.

As the Arctic polar region becomes more accessible there are consequent increases in human activities in the area, most notably in resource exploration and development (for example, oil and gas) and accompanying shipping and ice-breaking.  Oil and gas development pose a range of threats including oil spills, increased human-bear interactions, and exposure to pollutants.

Whilst the Arctic so far remains a largely pristine environment, persistent organic pollutants are transported to the Arctic region by air and ocean currents, and via river run-off.  The bears are particularly susceptible to ingesting these human-created pollutants with sometimes fatal consequences.

According to a statement by the U.S. Fish and Wildlife Service in 2013 bear hides sell for between around $2,000 and $12,500.  In June 2012 two pelts were sold at auction in Ontario, Canada, and fetched $16,500 each (source LA Times).

MORE INFORMATION

There are a large number of books and articles about polar bears and an internet search will reveal a wide range of titles and approaches to the subject.  We list a couple of the best below and will be adding information on further books and some articles soon.

 Polar Bears: A Complete Guide to Their Biology and Behavior.  Written by Andrew E Derocher and published in 2012 in association with Polar Bears International.  This superb book is already regarded by many as the definitive work on polar bears.  Comprehensive, informative and very readable it is further enhanced by Wayne Lynch’s superb photographs.  Click here for the book on Amazon.co.uk.

 Polar Bears: The Natural History of a Threatened Species.  Written by Ian Stirling and first published in 1998, the 2012 edition is fully revised and updated.  Provides an in depth insight into the natural history and ecology of the bears, aided by maps, tables, graphs and a diverse collection of photographs.  Click here for the book on Amazon.co.uk.

For much more detailed information on the threats being faced by polar bears we recommend the IUCN page on Ursus maritimus.

Polar bears in zoos.

Page created 18 September 2017

 

 

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