Wapiti Winter Coats
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Microscopic view of an elk's guard hair. Photo courtesy of Ronald Davis |
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Over the course of a year, elk may experience temperatures ranging from 100° F (38° C) to minus 40° F (minus 40° C). Somehow they have to keep their body temperature steady no matter how extreme the weather. How do they do it? After all, they don't have the luxury of peeling off a shirt or zipping up a parka. Elk have only two coats--one for summer and one for winter. Their coats help them regulate their body temperatures.
Twice a year, they shed every hair on their body. Their spring shedding is noticeable because ragged tatters of old winter hair dangle like long scraggly beards from their necks and sides. By July their winter coat is completely replaced by their summer coat. This summer coat is a thin, sleek layer of short hair that is the color of copper.
Their summer coat lasts only two short months. The elk don't look like they're shedding in September, but they are. Summer hair is falling out as the long, thick winter coat begins growing in. The longer, darker hair begins appearing on their heads and necks -- they have manes again. And their summer coats give way to winter tones of light brown and tan.
An elk's winter coat is five times warmer than its summer coat. The summer coat has just one short, thin layer of hair. The winter coat consists of two layers -- thick, long guard hairs and a dense, woolly undercoat.
If you split open a guard hair and look at it through a microscope, the inside looks like the honeycomb in a bee's nest (see photo above). Thousands of tiny air pockets fill each guard hair. That makes them waterproof and warm. This warm winter coat is so thick that it can keep snow from melting on an elk's back.
The catalyst that causes coat-switching takes its cue not from increasing or decreasing temperatures, but from the increasing or decreasing light available each day -- the photoperiod. This is the same cue that causes leaves to fall in autumn.
Elk have other tricks for staying warm in winter. For example, elk can make their hair stand on end, trapping more air and creating a thicker coat. They can also tuck their legs beneath them when they lie down so they lose less heat through their legs, chest and belly.
What's the best way for elk to stay warm? They seek thermal cover -- on cold, sunless days or at night, they head for the north and east slopes. There they bed beneath thick trees. The trees hold warmer air near the earth, catch snow before it hits the ground, and break the wind. On sunny days, elk move to open south and west slopes.
From the Yukon Territory to Arizona, elk usually have the right coat for winter. But even with a warm winter coat, elk still need appropriate habitat -- no matter what the season.