Marine Science Chapters

4.4.3

Polar Bears


Polar bears, Ursus maritimus, are the mightiest hunters of the Arctic, living their entire life associated with the pack ice. A large population of over 2,000 animals lives in and around Svalbard – making the population of polar bears larger than the human population in this area. World-wide there is estimated to be over 22,000 polar bears.


The Polar Bear
The polar bear on an iceberg above Svalbard.

One of the largest of all the bears, the males can be over nine feet long and weigh over 1,000 pounds. Females are generally smaller and weigh just over 500 pounds.


Camouflaged polar bears on an iceberg
Camouflaged polar bears on an iceberg.
Polar bear fur
Polar bear fur.

The white fur of the polar bear is camouflage against the ice allowing them to blend into their environment and sneak up on their prey. This fur provides excellent insulation from the cold, even when they are swimming in the Arctic Ocean. The outer guard hairs form a layer that protects the inner fur from getting wet when the polar bear is in the ocean. These guard hairs are hollow and filled with air. Thus, they always have a layer of trapped air surrounding their bodies. After a swim they need only give a quick shake and they are nearly dry. There is also a thick layer of blubber that helps insulate the polar bear from the cold.


Black skin of polar bear nose Black skin of polar bear under its white fur
Black skin of polar bear nose (left). Black skin of polar bear under its white fur (right).

The skin of the polar bear is black, something that is not easy to see. Its white fur actually allows light to reach this skin and the dark skin absorbs the heat from the sun, another adaptation of the polar bear to living in the extreme cold of the Arctic.


The polar bear in smelling posture
The polar bear in smelling posture.

Polar bears have an excellent sense of smell. Females are able to smell through three feet of snow and over a half mile away. When viewing polar bears it is a good idea to approach from the downwind side and be cautious. They are predators on mammals and occasionally kill humans.


Arctic guide with a gun Polar bear warning sign
Our Arctic guide with a gun for protection against polar bears (left). Polar bear warning sign posted in Norwegian Arctic areas where polar bears are found (right).

A firearm is needed at all times in polar bear country. Polar bears do not generally attack humans but if someone is alone they are easy prey for a hungry polar bear. Polar bears are stealthy creatures and sometimes seem to appear out of nowhere so it is required that visitors to polar bear territory stay in groups and have a firearm present in the group. Encounters with polar bears and humans are often quick as the bear can be scared away easily. But, if there is a problem in Norway and a bear must be shot, for human protection, then the shooter must go to court and explain the circumstances because polar bears are protected.


Polar bear with a fresh seal kill
A polar bear with a fresh seal kill, probably a bearded seal. Note the gull nearby, it is an ivory gull - one of the few true Arctic birds. It never gets below about 70 degrees north latitude in its entire life.

The preferred prey of the polar bear is seals. They are mostly carnivorous but if food is scarce they will eat plants and berries. The polar bear is an excellent swimmer and has been known to spend many days at sea swimming long distances presumably in search of food. It is quite buoyant and floats with its head easily held above the water, looking for seals. They consume most of their food during the Arctic summer – hunting all day and most of the night using the 24 hours of polar summer daylight. This allows them to build up a thick layer of blubber before winter (when food will be scarce).


Hairy feet of the polar bear Sharp claws of the polar bear
Hairy feet of the polar bear (left). Sharp claws of the polar bear (right).

Polar bears have sharp claws on their hairy feet. The fur even covers the soles of their feet, providing insulation. These sharp claws allow polar bears to easily kill their prey and then to rip it apart into small chunks to eat.


Polar bear skull
Polar bear skull.

Polar bears have large, sharp teeth although they appear to have a rather small head in comparison to their massive body. Using their sharp claws and teeth the polar bear is a formidable predator on whatever it can catch. They are surprisingly agile in the water and on land and definitely pose a threat to humans who are alone and unaware. In general the polar bear does not seek out humans as prey however.


Polar bears
Polar bears.

It is rare to see gatherings of polar bears as it is only in the event of a large source of food that this occurs. For example, if a dead whale washes in there may be 10-50 polar bears taking turns feeding. The greater part of the year finds the polar bear as a solitary creature except during mating.


Polar bears eating
Polar bears eating, the mother teaches her cubs to hunt, kill, and eat mammals.

Mating occurs in the late spring and early summer. The males abandon their mates after copulation. The fertilized egg has delayed implantation (a condition common in many marine mammals) which puts the fertilized egg in a state of ‘waiting’ for a time. The fertilized egg (zygote) then implants and begins development at exactly the right time so that the cubs will be born in late December (no matter when mating occurred). The female digs a den in the snow in late fall and stays there all winter.


Polar bear baculum
Polar bear baculum.

Male polar bears have a baculum (penis bone) which aids in successful copulation. A baculum is not found in humans or whales but is found in several marine mammals including polar bears, walruses, seals, and sea lions.


Polar bear mother and her twin cubs
Polar bear mother and her twin cubs.

Polar bear cubs are born in the winter den at about a pound and half as helpless babies. They are nursed in the den with rich milk from their mother (30 percent fat) until April when they are about 25 pounds and ready to run about. One or two cubs are normal for polar bear mothers.


Polar bear mother eating while her cubs relax
Polar bear mother eating while her twin cubs relax. Notice the yawning cub and the ivory gull that is trying to steal some food.

The polar bear cubs stay with their mother for two years while she teaches them to hunt. After this the mother abandons her cubs and they are left to the solitary existence of the polar bear. The next few years of a young polar bear’s life are often tough and many starve to death. Only the strongest survive.


Polar bear cub
Polar bear cub.

Polar bears have had circumpolar protection since 1973. This is why a court appearance is necessary if one has to shoot a polar bear in self defense. They are a unique and wonderful creature found only in the Arctic.

 Copyright and Credits
(Revised 23 August 2006)
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