ZOO-ology column: Winter Whites
Dec. 25, 2011 at 6:25 a.m.
By Judie Farnsworth
In far northern areas like the Arctic, some animals with darker coats in the spring and summer begin changing color as winter approaches. White or nearly white fur replaces the darker fur and they're right in style as their landscape becomes snow covered. Arctic hares, Arctic foxes and three species of chicken-like birds called ptarmigans (tar'migen) are great examples.
Winter whites - fur, feathers and specialized footwear are more than a desire to be chic. Warmth, safety and staying dry are vital to survival. In addition, animals must be dressed for success as "shoppers" (hunters). Interestingly, Arctic foxes that live in areas without much snow, tend to stay browner all year and those that live year round in snow, stay white.
A thick white coat provides camouflage or cryptic coloration in a snowy environment. Blending into surroundings helps keep an animal safe, but also helps in its foraging activities. But how does a white coat offer more warmth? After all, doesn't dark pigment (color) absorb heat and light pigment reflect it away? In this case there's a lack of any pigment in the hair cells. This leaves space for air warmed by the body - thermal insulation.
Ptarmigans (sometimes referred to as a snow chickens) avoid predators or severe cold by diving or flying into a bank of snow. Very clever - no footprints to give them away. These birds are even apt to roost beneath the snow. Like other grouse or quail these birds tend to explode from cover if surprised. Imagine the shock of birds blasting from a snow bank.
Winter can mean frosty feet, but the Arctic fox and hare have feet almost completely wrapped in fur. With anti-skid qualities, they can speed along over the snow. The fox's tail serves as a wonderful muffler, covering its face. Its fur is thought to be the warmest of any mammal. Thick long feathers cover the tops and bottoms of a ptarmigan's feet. Its claws grow longer in winter which helps navigate and dig. It's like growing its own snowshoes. The huge feet of the Arctic hare also have snowshoe-like qualities.
Many mammals that live in cold climates have a compact body shape. For example, the Arctic fox is rounder and shorter than the red fox we know. Its legs, muzzle, ears and tail are shorter. The Arctic hare has shorter ears. A compact shape with less outward area helps with warmth. An Arctic fox has exceptional hearing and listens for creatures under the snow. When prey is heard it pounces, breaking through the snow to see what's there.
The Texas Zoo hopes you are enjoying the cooler weather. Our animals are more active and waiting for you to visit often in 2012. I will continue to contribute the ZOO-ology feature in the coming year with one change - because of time constraints it will be every other week. Your many nice comments are appreciated and show a real interest in our natural world. Education is a primary goal that we try to fulfill.
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Judie Farnsworth is a longtime volunteer at the Texas Zoo specializing in educational programs.