Scientific Classification

Common Name

polar bear

Kingdom

Animalia

Phylum

Chordata

Class

Mammalia

Order

Carnivora

Family

Ursidae

Genus Species

Ursus (bear) maritimus (sea)

Fast Facts

Description

Polar bears are the largest land carnivore. Adapted for the cold, polar bears have a thick fur coat that appears white in coloration, but is really translucent. Their black skin color is readily apparent on the nose, eyes, lips and footpads. In addition to their size and color, polar bears may also be distinguished from other bear species by their smaller ears, longer necks and the lack of a dorsal hump in adults.
Male:  Adult male polar bears, called boars, are substantially larger than adult females.

Size

At birth, cubs are about 30 cm (12 in.) long
Male:  2.5 to 3 m (8.2 to 9.8 ft) long
Female:  2 to 2.5 m (6.6 to 8.2 ft) long

Weight

Newborn calves weigh about 454 to 680 g (16 to 24 oz.)
Male: 350 to 650 kg (772 to 1,433 lbs.)
Female: 150 to 250 kg (331 to 551 lbs.)

Diet

Adult polar bears need an average of 2 kg (4.4 lbs.) of fat per day to maintain their weight. Their diet includes mostly ringed and bearded seals and also includes other seal species, walruses, narwhals, beluga whales, whale carcasses, fish, reindeer, birds, eggs, berries and kelp.

Incubation

About 8 months; includes about a 4 month period of delayed implantation

Estral Period

Females are induced ovulators; mating triggers the release of an egg for fertilization

Nursing Duration

18 to 30 months (wean)

Sexual Maturity

Male:  About 6 years
Female: About 4 years

Life Span

Typically 15 to 18 years; some have lived over 30 years

Range

Circumpolar arctic

Habitat

Inhabit Arctic sea ice, water, islands, and continental coastlines

Population

Global: Estimated at 21,500 to 25,000

Status 

IUCN: Lower Risk/Conservation Dependent
CITES: Appendix II
USFWS: Not listed

Fun Facts

1. Adapted for the cold, polar bears have a thick fur coat. The coat of a polar bear can appear in a number of color variations from pure white to creamy yellow to light brown, depending on season and angle of light. A polar bear's black skin absorbs heat from the sun, helping it stay warm. In addition, the long guard hairs of a polar bears coat can trap a still layer of water in the under-fur and help insulate the bear's body while submerged; acting in a similar manner to a wetsuit. Polar bears also possess a fat layer that can reach a thickness of up to 11 cm (4.3 in.) This fat layer acts as an energy reserve in times of low food availability and possibly also aids in thermoregulation.
2. Polar bears are strong swimmers, paddling dog-style with their partially webbed front paws while holding their hind feet and legs flat like rudders. Scientists have tracked polar bears swimming continuously for 100 km (62 mi.). On land they are capable of reaching speeds of 40 kph (25 mph) while running in short bursts.
3. Only female polar bears, especially pregnant females, enter into a state of carnivore lethargy or "hibernation." They do so from October or November through March or April. During hibernation, the female's heart rate slows from a normal resting rate of about 46 beats per minute to about 27 beats per minute. Females also fast throughout hibernation, losing all or most of their fat stores. Though hibernating females sleep soundly, they are easily aroused.
4. Unlike most other hibernators, female polar bears give birth while hibernating. Sows give birth in their dens from November through January. Typically, 2 cubs are born. Cubs are born helpless with their eyes closed, and appear hairless because of their very fine fur. Cubs open their eyes within the first month and begin walking at 2 months. At 4 to 6 months of age, cubs emerge from the den. By 8 months, they weigh more than 45 kg (99 lbs.).
5. For more information about polar bears, explore the Polar Bear Info Book.

Ecology and Conservation

Polar bears at zoological parks provide opportunities for the public to learn about these animals and how human activities may impact their survival. Scientists and specialists study polar bear biology, including polar bear reproduction, birth and care of young, and communication. 

As with other marine mammals found in the United States, the U.S. Marine Mammal Protection Act of 1972 protects polar bears.

Bibliography

Jefferson, T.J. Leatherwood, S. and M.A. Webber. FAO Species Identification Guide. Marine Mammals of the World. Rome. FAO, 1993.

Nowak, Ronald M. (ed.). Walker's Mammals of the World. Vol. II. Baltimore: Johns Hopkins University Press, 1991.

Parker, S. (ed.). Grizmek's Encyclopedia of Mammals. Vol. IV. New York: McGraw-Hill Publishing Co., 1990.

Reeves, R. R., Stewart, B.S., Clapman, P.J., and J.A. Powell (Peter Folkens illustrator). National Audubon Society: Guide to Marine Mammals of the World. New York: Random House, 2002.

Reeves, R.R., Stewart, B.S. and S. Stephen. The Sierra Club Handbook of Seals and Sirenians. San Francisco: Sierra Club Books, 1992.

Reynolds III, J.E and S.A. Rommel (ed). Biology of Marine Mammals. Washington and London. Smithsonian Institution Press, 1999.

IUCN Polar Bear Specialist Group
http://pbsg.npolar.no/

University of Michigan - Animal Diversity Web
http://animaldiversity.ummz.umich.edu