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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.
Adult male polar bears, called boars, are substantially larger than adult females.
At birth, cubs are about 30 cm (12 in.) long
2.5-3 m (8.2-9.8 ft.) long
2-2.5 m (6.6-8.2 ft.) long
Newborn calves weigh about 454-680 g (16-24 oz.)
350-650 kg (772-1,433 lb.)
150-250 kg (331-551 lb.)
Adult polar bears need an average of 2 kg (4.4 lb.) 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.
About 8 months; includes about a 4 month period of delayed implantation
Females are induced ovulators; mating triggers the release of an egg for fertilization
18-30 months (wean)
About 6 years
About 4 years
Typically 15-18 years; some have lived over 30 years
Inhabit Arctic sea ice, water, islands, and continental coastlines
Estimated at 21,500-25,000
Lower Risk/Conservation Dependent
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.
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.
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.
Unlike most other hibernators, female polar bears give birth while hibernating. Sows give birth in their dens from November through January. Typically, two 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 two months. At four to six months of age, cubs emerge from the den. By eight months, they weigh more than 45 kg (99 lb.).
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.
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FAO Species Identification Guide. Marine Mammals of the World
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Nowak, Ronald M. (ed.).
Walker's Mammals of the World. Vol. II
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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
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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
University of Michigan - Animal Diversity Web