These guard hairs are mostly transparent or clear, but thanks to some special characteristics that work to create cool optical tricks, these hairs appear white. Here are the special characteristics of guard hairs: they are coarse, tapered (gradually come to a point) and have a hollow core filled with air; they are made of a protein called keratin; they have light scattering particles inside them; and have tiny salt particles that sit between each hair.
All of these special characteristics of a Polar bear’s guard hair work with the power of light to make Polar bears appear white. Here’s how:
When the sun’s rays hit off of the Polar bear’s transparent guard hair, some of this light energy travels into the hair and gets trapped. This energy bounces around inside the hollow part of the hair causing a reaction called , which is an emission of light. This happens every time the beam of light makes contact with the side of the hair.