Polar Bears - Data, Pictures and Videos

[sanjay]

Question from Kika: Is it true that polar bears have black skin underneath all the fur? And if so, why?

Answer from Dr. Thea Bechshoft: 
Yes, that is absolutely true!

Actually, it is mostly true: polar bears are born with pink skin. See this video

Image of polar bear cub with pink skin

*This image is copyright of its original author

But it turns black around the age of 4 months. The color of the skin is easily seen on the bear’s nose, lips, and under its feet. You can see the black skin in this picture of a polar bear in Buffalo Zoo:

*This image is copyright of its original author

This bear had to go through surgery because of an ankle injury. In connection with this procedure, the veterinarian had to shave a bit of her fur off, and as you can see, the black skin is visible through the hair that was growing back while she was in recovery.

So why do polar bears have black skin?

Interestingly, no albino polar bears have ever been reported in the wild or in zoos, which indicates to me that having black skin (and dark eyes) is apparently very important in this species.

Our two best explanations as to why having black skin is essential to polar bears are both related to the sun:
Firstly, darker colors are better at absorbing heat from the sun, which is an advantage to a polar bear trying to stay warm in the cold Arctic. Secondly, the dark color is likely protecting the bear against harmful UV radiation from the sun. Generally speaking, darker skin (or rather, higher concentration of the dark pigment called melanin in the skin) has been found to provide better protection against the sun’s UV rays. This goes for a wide range of organisms, from humans to blue whales. In the case of the polar bear, the sunlight it is exposed to is intensified when it is reflected off of the snow, sea ice, and water that make up the bear’s environment most of the year. Reply