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Posted by on Jul 18, 2015 in Tell Me Why |

Why Are Polar Bears White?

Why Are Polar Bears White?

The bear’s color helps it to find food. Polar bears live in a part of the world that is usually covered with snow and ice. Often they hunt animals that have trouble seeing the bear against the white snow.

The white hair also helps to trap heat from the sun. Believe it or not, their hair isn’t actually white! Their long outer hairs, which protect their soft, thick undercoat, are hollow and transparent. The thinner hairs of their undercoat are also colorless.

Polar bear hair looks white because the air spaces in the hairs scatter light of all colors. When something reflects all of the visible wavelengths of light, we see the color white. Some scientists believe the polar bear was once a close relative to the brown bear.

They think that, over time, polar bears moved to the Arctic, where they adapted to their surroundings by developing fur that would help them blend in with the harsh, white Arctic ice.

Not all polar bears look white, though. If you’ve ever seen a polar bear in a zoo, you may have noticed that its fur can appear almost green.

Scientists discovered that algae from the pond waters in the bears’ enclosures made the bears turn green. They learned these algae were found not on the surface of the hairs but inside the hollow hairs!

So What Color Are Polar Bears?

Polar bears are white, but their hair is mostly clear! When the sunlight shines on the Polar bear’s mostly clear guard hair, some light gets trapped in the hair and bounces around, creating luminescence.

When it hits a light scattering particle on the inside or salt on the outside, the light breaks up even more and gets sent in all different directions. This light scattering gives off more white-colored light due to luminescence.

When sun shines on a Polar bear, the UV in the sunlight shoots down to the base of the guard hair, where it makes contact with the bear’s dark skin. When the UV light hits the skin it produces a whitish color due to fluorescence.

Just like you, Polar bears have keratin protein in their hair too. These protein molecules have a slight off-white color, which further contributes to Polar bear fur appearing white. Each of these elements brings you the white Polar bear you know and love.

Content for this question contributed by Sandra Lopez, resident of Ontario, Canada