| Adult males measure 240-260 cm in
total length
and weigh 500-600 kg.
Polar
bears are well adapted to their arctic surroundings. Their thick winter
coats, with glossy guard hairs and dense, furry undercoat, and the thick layers of fat beneath
their skin protect them against the cold. The guard hairs shed water easily, and after a
swim bears usually shake themselves like dogs to decrease chilling. Polar bear hair is
translucent (you can look through it) and reflects solar heat down to the base, where it
is absorbed by the black skin. So actually they just look white!!!
The soles of the bears’ feet have
small bumps and cavities that act like suction cups and help to keep them from slipping on
the ice.
Polar bears have a keen sense of smell.
They can locate seal breathing holes covered by layers of ice and snow 90 cm
thick, or more, up to a kilometer away. Their eyesight and hearing are similar to those of a human.
Their normal gait is a slow,
distance-devouring gait of about 5-6 km/h. They may gallop when chased. Although immature
bears can run as far as 2 km, older bears seem to tire quickly because they are fat and
well insulated, which causes them to overheat. When polar bears swim, they use only their
front paws, whereas their rear paws trail behind, acting like rudders. Under water they keep their eyes open but
close their nostrils. A polar bear may remain underwater for over a minute.
Polar bears are distributed
throughout the coastal areas of the circumpolar Arctic. Although polar bears of both sexes
and various ages may occupy dens during periods of cold or stormy weather, only pregnant
females remain in dens throughout the winter. The young are born from late November to
early January - usually twins, sometimes a single cub, rarely triplets, and extremely
rarely, quadruplets. At birth, the cubs are only about 25 cm long and weigh less
than a
kilogram. Their eyes are closed at birth and they are covered with hair so fine that in
some early descriptions the cubs were reported as being hairless.
Seal pups and their mothers constitute
the main part of spring diet of polar bears, except for the nursing cubs. Besides hunting
seals at breathing holes and birth lairs, bears stalk seals basking on land-fast ice or
ice pans. During spring and early summer when seals are most accessible, a bear may catch
one every four to five days. Polar bears feed most on ringed seals but also kill walruses,
white whales, and narwhales.
Polar bears in areas like
the Beaufort Sea may remain on the ice throughout the year, even building their dens in snow
drifts on the ice. However, in much of the Arctic, and in Hudson Bay, most of the pack ice
melts by mid- to late summer, and the bears are forced to spend from two to four months on
shore waiting for the ice to freeze again. During this period, they live mainly on their
fat stores and remain inactive over 80 % of the time to conserve energy. They will eat
carcasses if they find them and, occasionally grasses and berries. Bears have even been
seen diving for seaweed.
The family group breaks up when the
cubs are almost 2.5 years of age. Occasionally, cubs remain with their mothers until they
are 3.5 years old.
Male polar bears that die of natural
causes commonly live to 20 years of age and females to their mid-twenties. In captivity
one lived to be over 40, but in the wild 30 is rare.
The human hunter is
the primary predator of the polar bear. In recent years hunters have
killed less than 1000 yearly, of which between 600 and 700 are taken by Inuk and American
hunters in Canada. (The current world polar bear population is probably 20.000-40.000, and
the Canadian population likely exceeds 15.000)
Untanned polar bear pelts sell for
$500-$3000 depending on their size and quality. This can be a significant portion of an
Inuk hunter’s cash income. The annual economic value of the hunt and the hides is
about $ 1 million in Canada. Polar bears are also highly valued as display animals in zoos
and are one of the central attractions of the famous Moscow circus.
Bear meat may be eaten by humans and is
used as dog food. However, polar bear meat is sometimes infected with trichinosis, so it
should be cooked thoroughly before being eaten. Polar bear liver can also be dangerous to
humans and dogs because of its high vitamin A concentrations.
Although polar bears
do not stand in immediate danger of extinction they face threats common to large predators: human
encroachment on their habitat, illegal hunting, and toxic contaminants in their prey
species. |