If asked what colour a polar bear is, most people would say “white”, but there’s actually no white on a polar bear at all!

If you look beneath their thick fur, a polar bear’s skin is black. This is useful because dark colours absorb heat very well, so the polar bear’s black skin can absorb the heat of the sun to help keep it warm.

The polar bear’s fur is also unusual. It looks white, but if you look closely, each of the polar bear’s thick guard hairs are hollow and clear – they only appear white because the hollow hair shafts scatter light the way ice and snow do.

This leads to many unusual observations when polar bears are photographed under different lights. Under ultraviolet light, a polar bear looks black. And because they are so well insulated and give off so little heat, polar bears are practically invisible to infrared cameras. One scientist managed to take a picture in which the polar bear disappeared entirely – the only spot in the picture was from the polar bear’s breath!

In addition to their unusual photographs, polar bears may appear to be other colours as well. Arctic animals, including the polar bear, have a very thick layer of yellow fat called blubber that keeps them warm. Often, when a polar bear catches and eats one of these animals, their fur becomes coated in oil and fat and appears yellow.

And most bizzarely, some polar bears in zoos have been observed to turn green! This happens because tiny plants called algae grow within the hollow shafts of the polar bear’s fur!