Question:
I've read that there are people who insist that a polar bear's fur is not white, yet it seems pretty clear that it is! It also makes sense because the white offers good camouflage. What's the deal -- how could polar bear fur be anything but white?

From: P. Lenhart, CT.

Answer:
While it makes sense that the king of the great white north would have an  outfit to match his kingdom, the truth behind polar bears' magnificent coat may surprise you. Polar bear fur is actually clear! The keratin fibers in their fur have the unique ability to absorb ultra-violet light from the sun and help keep the bear a robust 98 degrees Fahrenheit, even in sub-zero conditions. Scientists from the Library of Congress have this to say:

The hair of a polar bear looks white because the air spaces in each hair scatter light of all colors. The color white becomes visible to our eyes when an object reflects back all of the visible wavelengths of light, rather than absorbing some of the wavelengths.

The white appearance is also notable because the bear's skin is actually black, an adaptation that helps absorb as much heat as possible from the sun. The hollow-fibered hairs are tough, water-repellant and resist matting. When polar bears are subject to warmer climates, algae may grow inside the hollow tubes of the hair resulting in bear of different colors, such as this poor fellow who turned partially green. If you'd like to read more about polar bear fur, click here for a report from the Alaska Science Forum or click here for a page on polar bear facts.