Lions and Twinks and Bears, Oh My!

It is MAL weekend in DC (look it up if you don’t know what it is, but not at work) and I started thinking about bears and then I remembered learning about polar bears and so here is another post for today. Do you know why polar bears are white?

No one does. Polar bears live in very cold places (right? I bet you didn’t know that one). Since they swim to catch food, they obviously need to be very well insulated. To help, evolution gave polar bears a solid 10cm (almost 4 inches) layer of blubber and two layers of fur. Each bear has a dark thick underfur and then 5-15cm long guard hairs (this is the fur you see). They are actually so well insulted that polar bears are invisible on thermal imaging cameras.

The guard hairs are what appear to be white. The most basic hypothesis for why they are white would be camouflage – to stay protected or to stay unseen while hunting. This guess doesn’t hold up because, 1. they don’t have any real predators to hide from and 2. their hunting technique is not one that requires camouflage. Another issue with this idea is that polar bear hair is not really white. The hairs are transparent and only appear white/pale yellow when looking straight down the hair fiber. This caused some scientists to think the hairs acted like fiber-optic tubes. They could direct the sunlight right down to the polar bear’s black skin and help with staying warm. A bunch of physicists proved that wrong recently.

Science is back to the drawing board on this one. I doubt any of you will lose sleep over it, but hey, it’s a fun random fact to pull out someday. Happy MAL to all you bears out there!