Wednesday, 12 December 2012

Living In Extreme Weather

Do you know the name of animals that live in very cold weather?
How do they survive?

Polar bears
Polar bears have thick furs to enable them to live in very cold weather.  Polar bears' fur consists of a dense, insulating undercoat topped by guard hairs of various lengths.  It is not actually white.  It just looks that way.

Each hair shaft pigment-free and transparent with a hollow core that scatters and reflects visible light, much like what happens with ice and snow.

Polar bears look whitest when they are clean and in sunlight, especially just after the molt period, which usually begins in spring and is complete by late summer.  Before molting, oils from the seals they eat can make them look yellow.

In zoos, polar bears have been known to turn green due to colonies of algae growing in their hallow hair shafts.  This happened at San Diego Zoo in 1979.  No harm came to the bears, and zoo veterinarian Phillip Robinson restored the bears to white by killing the algae with a salt solution.

Polar bears have black skin under which there is a layer of fat that can measure 4.5 inches (11.5 centimeters) thick.  But it is their fur, not their fat, that prevents bears from suffering nearly any heat loss.  In fact, adult males quickly overheat when they run.


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