Ellen Terry
Curious Nature
Vail, CO Colorado

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January 12, 2013
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Vail Daily column: True hibernators hunker down for winter season

The Eagle Valley's animals are now deeply enveloped in winter. As the temperature drops, it is quite tempting for us humans to do the same. I'd love to eat as much as possible then get cozy with my family and friends. If we really followed the animals' lead though, we would end up missing ski season. Unacceptable. Because we can't sleep off our body fat in the winter, let's live vicariously through the animals that do.

First of all, bears. They don't really hibernate! Take a moment and forgive your fourth grade teachers for perpetuating this semi-lie. True hibernation is characterized as a dormant state where an animal experiences a sharp reduction in body temperature and metabolism. Bears don't actually have a sharp reduction in body temperature. What they go through is called torpor. A bear in torpor will have a body temperature around 88 degrees, not too much of a difference compared to their regular 101 degrees.

Animals that go dormant for the winter, from garter snakes to bats, need to eat a seemingly absurd amount of food in late summer and fall. The fat stores they put on during this time are what get them through up to six months without eating. This brings up the reason for hibernation: lack of food. When your food source disappears for a season, the best thing to do is to dramatically lower your heart rate and body temperature and then settle in for a nap.

We've eliminated bears from our "true hibernator list," but who are the true hibernators? In our lovely valley there are a number of them. Bats, garter snakes and marmots all hibernate. This is by no means a comprehensive list; but each of these animals give us a glimpse of the unique way each of these animals make it through to spring.

Marmots and garter snakes both venture deep underground, below the frost line. Marmots are very social animals, much like humans. For much of the year, they live in colonies of yard-deep burrows. In preparation for winter, marmots move into burrows that are much deeper, 15-20 feet, and spend up to eight months underground. These goofy little guys will hunker down with just their families, which consist of a male, his harem of a few ladies and their young.

Garter snakes also head underground, but they're less particular about who they spend the winter with. Each snake goes to the same hibernaculum (deep hole) every winter, along with hundreds of other members of its species. They flock together to keep each other warm and to be readily accessible for breeding in the spring. Usually treated as harmless to humans, garter snakes become a problem if you build a home on a hibernaculum, as one Idaho family did. No one wants a yard or home crawling with snakes for a couple of weeks each year.

Bats are unlike any other mammal and therefore their hibernation strategy is unique, too. Rather than venturing underground, bats seek out abandoned wells, mine shafts and caves for winter roosting. A bat's heart typically beats 300-400 times per minute in the summertime. During hibernation, it can drop to as low as 10 beats per minute.

Animals have developed some amazing adaptations to get through difficult situations; hibernation is just one of them. So this winter, while you're relaxing in a warm home, outside wearing a down jacket or shopping at a fully stocked grocery store, take a moment to appreciate that human adaptations are really not too bad at all.

Ellen Terry was a summer naturalist at the Walking Mountains Science Center in Avon. For her, the onset of winter means skiing, snowball throwing and making hearty soups!


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The VailDaily Updated Jan 12, 2013 09:06PM Published Jan 12, 2013 09:04PM Copyright 2013 The VailDaily. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.