Location: in the Arctic
circle, northern Canada, Alaska, Norway and northern Russia.
Facts: The average adult
male weighs between 850-900 lbs/380-400 kgs, but one killed in
1960 weighed 2,210 lbs/995 kgs! He was 12 ft. long. That's the
size of a family car!
The Scientists Who Study this Cool
Stuff?
Biologists, Zoologists.
These
guys seriously know how to pose for the camera! Not only are they cool
in front of the camera, but they live in the coolest places on the planet
- literally. Arctic sea ice, water, islands, and continental coastlines
around the arctic circle are home to these massive carnivores. The temperatures
where these bears live ranges from an average -29°F/-34°C in
winter and 32°F/0°C in summer. The coldest area in winter is
northeastern Siberia, where the temperature has been recorded as low
as -92°F/-69°C. Not so great for people, but fine if you're
a polar bear with an extremely dense fur coat.
Polar bears
spend a lot of time moving great distances in search of their favorite
food - seals. The range of these bears can
vary from 20,000 to as many as 135,000 square miles. They hunt for seals
through the winter ice that forms over the ocean, where the seals spend
most of their time (to get away from the bears). When the ice over the
sea melts in summer the polar bears can't hunt for the seals as easily,
so they fast all summer long. In order to survive an entire summer without
food they eat a LOT of seals in winter building up fat stores untilhalf of their body mass is pure fat. That
enormously thick layer of fat also helps to keep them comfortably warm
while living in an inhospitably cold environment.
During the summer
months when the sea ice melts they will roam as far south as Hudson
Bay, where they hang out and "chill" until the sea ice forms again in
the fall. The warmest areas in summer are inland regions of Siberia,
Alaska, and Canada where temperatures can reach as high as 90°F/32°C,
which is pretty comfortable for folks without fur coats (you
and me).
The coat
of fur on an average polar bear is about 1-2 in./2.5 to 5 cm thick.
A dense, wooly, insulating layer of underhair is covered by a relatively
thin layer of stiff, shiny, guard hairs. Believe it or not, their fur
isn't actually white. If you got up real close to a polar bear and plucked
one of his hairs you would see that the polar bear's coat is made of
clear, colorless hairs (and you would probably find out how powerful
the bear is). The hairs scatter light, making it appear white
(or sometimes yellow, depending upon the angle of the sun). If you were
to pull out all of the polar bear's hairs (which would really be stupid)
you would see black skin underneath all that white fur. In the photo
(below, at left) where the bear's fur is thinnest on the snout you can
see the black skin beneath.
The bears' black
skin absorbs the heat from the sun and the six-inch layer of fat under
their skin insulates them from the extreme cold of the Arctic circle.
You and I would be miserably cold living outside all the time above
the Arctic circle, but polar bears are quite comfortable. In fact, polar
bears are so well insulated against the brutal cold of their environment
that they have a tendency to get overheated. How do they cool
off? Usually by going for a swim.
Polar bears
are excellent swimmers. Researchers have tracked polar bears swimming
for several hours straight, as much as 100 kilometers in a single stretch.
They can only hold their breath for about two minutes, but they can
close their nostrils (without having to pinch their noses, or wear nose
plugs) when they dive underwater.
Another physical
adaptation of the polar bear to its icy habitat is its enormous paws.
Polar bears' paws are massive compared to their body size if you compare
them with other bears. These large, rounded paws give the bears increased
surface area for walking over snow and ice - kind of like built-in snowshoes.
A male polar bear can weigh two to
three times as much as a female bear. Male polar bears are called boars
and female bears are called sows, while their babies are called cubs.
Males and females only get together during mating season. When female
polar bears are pregnant they go into a modified hibernation state -
it's not a deep hibernation because their body temperatures remain high.
They have to in order to facilitate the growth and nourishment of their
developing cubs.
When pregnant a female polar bear
will dig a den in a southward-facing snowbank and crawl inside to rest
for up to eight months or more. She will give birth to one or two, two-pound
cubs while she is hibernating. Polar bear cubs are too tiny at first
to tolerate the extreme cold of their native habitat. She and her babies
will stay holed up inside the den alternating between sleeping and nursing.
Mama bear will not eat while caring for her tiny babies. She will devote
herself exclusively to nursing her cubs, her body providing nourishment
for them by drawing from her fat stores. It takes a tremendous amount
of energy for a female polar bear to bear, give birth to, and nourish
cubs for the better part of a year. In the spring
she will emerge from her den and begin to hunt for seals to provide
meat for her growing cubs. Polar bear cubs will stay with their mother
for as long as 30 months before she, or a prospective mate, will drive
them away to fend for themselves.
More World
Record Bears
Though
a polar bear holds the world record for largest land carnivore, the
Kodiak bear holds a close second place. Kodiak bears are believed to
be a sub-species of Brown bear (Ursus arctos) found living
exclusively on Kodiak Island, Alaska. The average size of a Kodiak bear
is usually not as big as the average polar bear, but because of the
abundant food supply they can get pretty big. The largest Kodiak bear
on record was a male taken in 1894 that weighed 1,656lbs/745kgs!
(see
the Alaska Dept. of Fish & Game for more information on Brown Bears.)
NEWS
FLASH!!! Back in May of 2006 scientists confirmed the
parentage of a bear, taken by an American hunter, as being half
polar bear and half grizzly. Territorial officials seized the
animal after noticing its white fur was scattered with brown patches
and that it had the long claws and humped back of a grizzly. Now a DNA
test has confirmed that it is indeed a hybrid. A polar bear for a mother
and a grizzly bear for a father.
Pairings between polar bears and grizzlies have
happened in zoos before and their offspring were
The awesome power of a polar bear is demonstrated
in this video of a large bear taking a full-grown bull walrus
weighing close to 2 tons!
fertile, so it was known to be possible.
There had also been vary rare sightings of 'strange-looking polar' bears
reported by locals, but dismissed as an impossibility. This incident
of a polar-grizzly bear cross shows that although these pairing are
extremely rare in the wild, they are very possible.
How did a Grizzly and Polar bear "get
together"? The two bear species have overlapping territories in
the western arctic around the Beaufort Sea. Grizzly bears have been
known to wander far north from Alaska and Canada's Northwestern Territories
across the sea ice into Banks and Victoria islands where they will scavenge
dead seals that polar bears have hunted.