Polar bears have a problem with overheating, even in the north.
http://www.nationalgeographic.com/ngkids/0112/ws_main.html
"Imagine running around outside in a heavy down jacket. Even if it?s
cold out, you might start to feel too warm. And much like you in that
jacket, a polar bear is so well insulated that it can easily become
overheated by moving too fast. ?It will often grab a mouthful of snow
to cool off,? says polar bear biologist François Messier. ?Or it may
lie flat with its legs extended to expose its belly directly to the
snow, since belly fur is much less dense.? To keep from overheating, a
polar bear usually moves slowly and doesn?t run very often"
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http://www.seaworld.org/infobooks/PolarBears/pbadaptations.html
"1. Body temperature, which is normally 37C (98.6F), is maintained
through a thick layer of fur, a tough hide, and an insulating layer of
blubber. This excellent insulation keeps a polar bear warm even when
air temperatures drop to -37C (-34F) (Stirling, 1988).
2. Overheating.
a. Polar bears are so well insulated they tend to overheat.
b. Polar bears move slowly and rest often to avoid overheating.
c. Excess heat is released from the body through areas where fur is
absent or blood vessels are close to the skin. These areas include the
muzzle, nose, ears, footpads, inner thighs, and shoulders.
d. Polar bears will also swim to cool down on warm days or after
physical activity."
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http://www.polarbearsinternational.org/faq/
"Two layers of fur provide the bears with such good insulation that
they experience almost no heat loss. In addition, they are protected
with a layer of blubber that can measure 11.5 cm (4.5 inches) thick.
Compact ears and a small tail also prevent heat loss.
Polar bears are so well protected from the cold that they have more
problems with overheating than they do from the cold. Even in very
cold weather, they quickly overheat when they try to run."
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Soooo, what must "they" / "the others" being doing to keep their polar bear alive?
Well, the San Diego uses a cooled pool to keep their bears from overheating:
http://www.sandiegozoo.org/zoo/ex_polar_bear_plunge.html
"the Plunge holds 130,000 gallons (494,000 liters) of water cooled to
58 degrees Fahrenheit (14 degrees Celsius)"
Even closer to the equator, the Singapore Zoo also uses cooling:
http://www.zoo.com.sg/spotlight/polarbear.htm
"They have a thick coat of hollow hairs and a thick layer of body fat
to insulate themselves against the cold. So, how does a tropical zoo
like ours keep our polar bears and bred a male cub in 1990, the first
such birth in the tropics?
The answers lie in having a large, 3.5-metre deep pool to allow the
polar bears to cool off, an air-conditioned den and a separate cubbing
den for rearing cubs.
Our success with the polar bears can also be attributed to the
provision of behavioural enrichment. Live fish are released so that
the polar bears can go `fishing' as they would in the wild. Pieces of
fruit and meat frozen in ice blocks are thrown in for the bears to
toss and discover the goodies as the ice melts away, not forgetting
toys such as traffic cones for the bears' amusement as well.
As a physiological reaction to the warm climate, our polar bears have
a thinner coat and they moult more often than their counterparts in
cold countries. "
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My question is: "How did they get a polar bear to run in the tropics?"
(Animation?, a brown bear painted white? (don't try this at home!),
fast forwarding a movie of a polar bear? or putting a block of ice in
front of it?) |
