Wednesday, January 22, 2014

The White Stuff

Yesterday here in Philadelphia we got some snow. We got a lot of snow. We got enough snow to merit nonstop hyped up snow coverage on the news, two days of school cancellations, and a post apocalyptic scene in the local grocery stores. 
"It's beginning to snow and we're out of Pop Tarts?

Granted, it only takes about 2" of snow to cause this kind of mass hysteria in Philadelphia, but this time we received over a foot of the fluffy white utterly terrifying stuff.

I don't understand why snow causes such a panic around here, but that's probably because I grew up in North Dakota where they only cancel school for -65 degree wind chills and enough snow that you risk losing your toddler in. There are lots of animals that also laugh in the face of so-called "snow events" and today I thought I'd highlight some monochromatic critters and their ways of keeping their cool when faced with heaps of snow.

Polar Bears
Ah the pure white fur of the polar bear, as beautiful as the freshly fallen Arctic snow.

Except that a polar bear's fur is not actually white. Geek alert! A polar bear's fur is actually transparent in order to let the sun's heat go right through the dense fur and be absorbed by the bear's black skin, an incredible adaptation for keeping warm in a land of snow and ice.
A close up of polar bear skin and fur.

So why does it appear white? For the same reason that the snow outside my window forms a giant white drift instead of a clear one; the structure scatters visible light which causes it to appear white. Think of it as a kind of optical illusion. It works out pretty well...snow forts wouldn't be nearly as cool if everyone could see you inside of them. And let's face it, if a polar bear's fur was completely transparent and all you saw was the skin, Coca-Cola wouldn't have a very successful marketing campaign.
"Hey kids, wanna share a Coke and a nightmare?"
(This is not a polar bear, but rather a spectacled bear 
with a rather unfortunate skin infection)

White-tailed Ptarmigans
These small members of the grouse family are ready to strut their stuff no matter what season nature throws at them. For winter strutting, these birds have fluffy, feather duster feet to keep them warm. They even have feathers around their nostrils (nares) to pre-warm the air before it is breathed in. And of course, the bird's pure white plumage helps it to blend right in to its winter surroundings.
Sleeping in your own personal snow cave helps with camouflage too.
*pops head up* "Is that the pizza guy?"

But living in the alpine regions of Canada and down through the United States, it is not like the arctic home of the polar bear which stays white year 'round. So, like a little feathered fashionista, it changes its feathers to match the occasion.
Winter or spring, the white-tailed ptarmigan has just the thing!

Short-tailed Weasel (aka Stoat or Ermine)
This little weasel also goes through a wardrobe change in the winter and summer in the northern parts of its range. However the short-tailed weasel always keeps just a hint of black on the end of its tail to use as a decoy for predators. A hawk swooping in for the kill focuses on the easy to spot black tip of the weasel's tail, which is much harder to grasp in one's talons. Studies have found that this color strategy makes the short-tailed weasel harder for a hawk to catch than an animal that is entirely white, in which the bird's focus remains on the prey's entire body.  
"Can't catch meeeeee!"

Philadelphians may not be capable of dealing with a lot of snow, but the polar bear, white-tailed ptarmigan, and short-tailed weasel are built for life in the white stuff. Now if you'll excuse me, I have to start working on eating that stockpile of Pop Tarts.

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