| Polar
Bears of Churchill - On Hudson Bay
By
mid-November, ice covers much of Hudson Bay. Most of the bears,
young and old, have returned to the ice, but their work has just
begun. While seals are available, hunting is still difficult.
In
order to survive these extreme climates polar bears have developed
complex physical adaptations. By late October, the bears’
undercoat gets much thicker, so thick that it gets very hard to
find their skin through it. Researchers estimate that a bear’s
coat consists of almost ten thousand hairs per square inch by
mid-winter. Obviously, their cold resistance is considerable.
This
is not to say, however, that polar bears are completely resistant
to the arctic winter. Strong winds and cold ambient air temperatures
still affect them. The guard hairs keep a warm layer of air next
to the skin and strong winds penetrate these hairs, undermining
their insulative value. For this reason, they often wait out the
winter storms, taking shelter on the lee side of snow banks and
ice ridges. Sometimes, bears will stay motionless for days, only
to rise and shake away a layer of snow as the storm breaks.
As
well, water affects their ability to maintain heat. This affect
is very noticeable during Churchill’s bear season. Polar
bears go to some incredible efforts to avoid getting wet! They
will divert their path to avoid the many tundra ponds near Churchill.
In fact, the bulk of visiting polar bears do not arrive in the
Churchill area until many of the inland ponds have a fresh layer
of ice.
However,
the anticipation of winter is strong and testing ice is a common
pass time during bear season, sometimes ending with the groan
and crack of breaking ice and a very wet bear. On a warm day this
is welcome, on cold days it is less than comfortable. Absorbing
heat twenty five times faster than air, water can soak to the
bear’s skin and cools it quickly. To a large male with four
inches of fat, this may not matter but to a younger, thinner bear,
it could be fatal. To avoid this, their guard hairs are oily and
shed water quickly. Emerging from the ocean or a partially frozen
tundra pond, bears quickly shake excess water from their coat.
In
a further adaptation to life on the ice, polar bears are almost
completely furred, even much of their paws are covered. Their
foot pads are also covered with little bumps. These bumps, or
papillae, provide extra traction while traversing ice ridges on
the rugged sea ice. Finally, their claws, short and strong, are
also sharply curved; providing even greater ability to navigate
the frozen ocean.
As
with all arctic animals, their appendages, mainly their ears and
tail, are smaller than other bears. This follows the idea that
less surface area results in less heat loss. Polar bears emanate
almost no heat, only their black noses and a wisp of breath showing
up on infrared or heat sensitive cameras.
RETURN
TO POLAR BEARS OF CHURCHILL PAGE |
