Polar Bears Have Black Skin

The brilliant white coat of a polar bear is one of nature's great illusions. Its magnificent fur isn't actually white at all. Each hair is a pigment-free, transparent, and hollow tube. Much like snow, which is made of clear ice crystals, the fur appears white because the rough inner surfaces of the hollow hairs scatter and reflect all visible wavelengths of light. This structure also traps a layer of air, providing the bear (Review) with superb insulation against the frigid Arctic temperatures, keeping it warm even when the air is well below freezing.

The real thermal magic, however, happens underneath this insulating cloak. Polar bears have jet-black skin, which is highly effective at absorbing solar radiation that penetrates the translucent fur. Essentially, the bear's coat allows sunlight in to be absorbed by the skin, and the thick, air-filled fur then prevents that precious body heat from escaping. This clever combination of a heat-absorbing surface and a super-insulating cover is a key adaptation for survival in one of the world's harshest environments, allowing the animal to be both perfectly camouflaged and exceptionally warm.