How a polar bears white coat is an engineering marvel?


Picture of a mother and baby polar bear.


Polar bear coat


Canadian wildlife census takers have found that they could not simply take conventional aerial photos of these creatures, since they blend into the white landscape.

Infrared film, usually ideal for photographing warm-blooded animals, also failed.

The animals were simply too well insulated to give off enough heat for the film to detect.

However, when ultraviolet film was used, white seals and polar bears showed up as stark black objects on the white background.

“While the snow reflected ultraviolet rays, the animals absorbed them,” reports The Toronto Star.

Why?

According to physicist Grojean and Gregory Kowalski, an associate professor of mechanical engineering, the bear’s coat holds the answer.

At the invisible, ultraviolet end of the spectrum, the hairs of the coat trap 90 percent of the ultraviolet light and transmit it to the black skin beneath, thereby warming the bear.

In the Arctic, where the temperature often dips to -20 degrees Fahrenheit [-29° C.], the coat’s ability to keep its owner warm is remarkable.

Common rooftop solar collectors, in contrast, are far less efficient.

In fact, Kowalski estimates that man-made solar panels might be rendered 50 percent more efficient by applying the principles of the polar bear’s coat.

In the visible portion of the spectrum, the hairs on the coat behave in just the opposite way; they reflect 90 percent of the light.

This gives the bear its dazzling white appearance, even though the individual hairs themselves are not really white but transparent and pigmentless.

The coat’s whiteness enables the bear to hunt unseen on the Arctic snowscape.

Some observers have even seen polar bears covering their black noses as they stalk their prey, as if conscious of the need to blend into the snow.

The polar bear’s coat thus perfectly addresses two of the animal’s key needs: looking white and staying warm.

Little wonder, then, that physicist Grojean praised the coat as a “fantastic engineering feat.”