Polar Bear Facts (Ursus maritimus)

The polar bear (Ursus maritimus) is the largest terrestrial carnivore in the world, rivaled in size only by the Kodiak bear. Polar bears play an important role in the life and culture of the Arctic Circle. Most people are familiar with polar bears from visiting zoos or seeing the bear depicted in the media, but there are many misconceptions about this fascinating animal.

Description

Polar bears are easily recognizable by their white fur, which yellows with age. Each hair on a polar bear is hollow, and the skin beneath its fur is black. Compared to brown bears, polar bears have an elongated body and face.

With their small ears and tails and short legs, polar bears are adapted to life in the Arctic cold. Their large feet help to help distribute weight on ice and snow. Small dermal bumps cover the pads of their paws to improve traction.

Polar bears are extremely large animals. While both sexes look alike, males are about twice the size of females. An adult male ranges from 7.9 to 9.8 feet in length and weighs 770 to 1500 pounds. The largest male polar bear on record weighed 2209 pounds. Females measure 5.9 to 7.9 feet in length and weigh between 330 to 550 pounds. However, females can double their weight when pregnant.

Habitat and Distribution

The polar bear's scientific name means "maritime bear." Polar bears are born on land, but they spend most of their lives on ice or open water in the Arctic. In fact, they can live as far south as Newfoundland Island.

Polar bears are found in five countries: Canada, the United States (Alaska), Denmark (Greenland), Norway (Svalbard), and Russia. Although penguins and polar bears are shown together at zoos or in the media, these two creatures don't typically meet: penguins live only in the Southern Hemisphere and polar bears live only in the Northern Hemisphere.

Diet and Behavior

While many bears are omnivorous, polar bears are almost exclusively carnivorous. Seals are their primary prey. The bears can smell seals from up to a mile (1.6 kilometers) away and buried beneath 3 feet (0.9 meters) of snow. The most common hunting technique is called still-hunting. A bear locates a seal's breathing hole by smell, waits for the seal to surface, and drags it onto the ice with a forepaw to crush its skull with powerful jaws.

Polar bears also eat eggs, juvenile walruses, young beluga whales, carrion, crabs, shellfish, reindeer, rodents, and sometimes other polar bears. Occasionally, they will eat berries, kelp, or roots. The polar bears will eat garbage, including hazardous materials, such as motor oil, antifreeze, and plastic if they encounter such materials.

Bears are stealth hunters on land. They rarely attack humans, but starving or provoked bears have killed and eaten people.

As an apex predator, adult bears are not hunted except by humans. Cubs may be taken by wolves. Polar bears are susceptible to a variety of parasites and diseases, including mites, Trichinella, Leptospirosis, and Morbillivirus.

Reproduction and Offspring

Female polar bears reach sexual maturity and begin breeding at four or five years of age. Males become mature around six years of age, but rarely breed before age eight due to fierce competition from other males.

Male polar bears fight for mating rights and court females in April and May. Once mating takes place, the fertilized egg is suspended until August or September, when the sea floes break up and the female digs a den either on sea ice or land. The pregnant female enters a state similar to hibernation, giving birth to two cubs between November and February.

The mother polar bear remains inside the den with the cubs until mid-February to mid-April. For the first couple of weeks after she breaks out of the den, she feeds on vegetation while the cubs learn to walk. Finally, the mother and her cubs walk to the sea ice. In some cases, the female may have fasted for eight months before she returns to hunting seals once again.

Polar bears can live about 25 years in the wild. Some bears die from illness or injuries, while others starve after becoming too weak to hunt.

Conservation Status

The IUCN Red List classifies the polar bear as a vulnerable species. The bear has been listed as a threatened species under the Endangered Species Act since 2008. At present, the estimated polar bear population ranges from 20,000 to 25,000.

Polar bears face multiple threats, including pollution, various impacts from oil and gas development, hunting, habitat loss, conflicts from ships, stress from tourism, and climate change. Hunting is regulated in all five of the countries where polar bears are found. However, global warming is the greatest threat to the species. Climate change shrinks the bear's habitat, shortens their hunting season, makes hunting more difficult, increases disease, and reduces the availability of suitable dens. In 2006, the IUCN predicted the polar bear population would diminish more than 30% over the next 45 years due to climate change. Other agencies predict that the species might go extinct.

Sources

• DeMaster, Douglas P. and Ian Stirling. "Ursus Maritimus". Mammalian Species. 145 (145): 1–7, 1981. doi:10.2307/3503828
• Derocher, Andrew E.; Lunn, Nicholas J.; Stirling, Ian. "Polar Bears in a Warming Climate". Integrative and Comparative Biology. 44 (2): 163–176, 2004. doi:10.1093/icb/44.2.163
• Paetkau, S.; Amstrup, C.; Born, E. W.; Calvert, W.; Derocher, A.E.; Garner, G.W.; Messier, F; Stirling, I; Taylor, M.K. "Genetic structure of the world's polar bear populations". Molecular Ecology. 8 (10): 1571–1584, 1999. doi:10.1046/j.1365-294x.1999.00733.x
• Stirling, Ian. Polar Bears. Ann Arbor: University of Michigan Press, 1988. ISBN 0-472-10100-5.
• Wiig, Ø., Amstrup, S., Atwood, T., Laidre, K., Lunn, N., Obbard, M., Regehr, E. & Thiemann, G.. Ursus maritimus. The IUCN Red List of Threatened Species 2015: e.T22823A14871490. doi:10.2305/IUCN.UK.2015-4.RLTS.T22823A14871490.en