If you have always admired the snowy white fur of polar bears, you will be surprised to know that their fur isn’t white at all!
A polar bear has two coats of hair to keep it warm in the snowy arctic regions that are its home. The long outer hair that protects the soft, thick undercoat is hollow and transparent, and the thinner hairs of the undercoat are also colourless.
Each hair shaft is pigments-free and transparent, with a hollow core that scatters and reflects visible light- much like what happens with ice and snow. When visible light is scattered, it appears white.
Polar bears look whitest when they are clean, and in sunlight. Did you know that in zoos, polar bears have been known to turn green due to colonies of algae growing in their hollow hair shafts?