Largest
Carnivore on Land...
POLAR BEAR Ursus maritimus
Polar Bears
are Cool
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.)
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.
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.
