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A Long Winter's Nap
| Article
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16602 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
11 / 1989 |
1,538 Words |
| Author
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Larry S. Underwood
Larry S. Underwood is assistant professor of biology and
ecology at the Woodbridge Campus of Northern Virginia
Community College. He has worked extensively with cold-
tolerant mammals, including hibernators, in northern Alaska. |
Winter, for most animals and some people, is the most arduous of seasons. Cold temperatures and short days are hard to tolerate, and adequate food and shelter are often hard to find. Although a few hardy species are able to tough the season out, most do what they can to avoid winter. After laying eggs to ensure the species' survival, most insects simply die. Seeking environments where conditions are easier to tolerate, many birds, some mammals, and even a few insects migrate. But what about those species unable to leave and unwilling to die? For them, avoiding winter means hibernation. A long period of inactivity is the successful and necessary strategy allowing the hibernator to survive an otherwise inhospitable environment. For at least a few weeks in most cases, but up to 10 months in extreme ones, the worst rigors of winter can thus be avoided.
The advantages are obvious. Asleep in a cozy den, hibernators miss the worst of cold temperatures and bad weather. So what if temperatures plummet, snows deepen, winds howl, and rains freeze? These, the daily challenges facing the winter-active animal, are simply of no concern to the hibernator.
Other problems are likewise avoided by hibernation. For the winter-active animal, food is a near constant concern, and winter usually is the season when food is most limited. Potentially edible plants have either died or lost many of their more nutritious parts. Insects, a favorite food for many species, have either died or are themselves hibernating. Most birds, usually an important part of the winter diet of meat eaters, have migrated. What food is present often becomes hidden and inaccessible with the arrival of snow and ice.
For mammals that don't hibernate, exposure to winter cold itself demands a higher expenditure of energy just to keep warm. This energy, too, must come from food. Paradoxically, the season when energy is the least available is the season when energy is most needed. So, while the winter-active animal must constantly search for food, the hibernator's food needs are minimal.
Also, the winter-active animal is more likely to experience increased pressure from predators. During winter, predators, too, require more food and find supplies are limited. Thus, they spend more time hunting in winter than in any other season. Escape from predators is more difficult in winter. Cover plants are dead, leafless, or trampled, and movement is impeded by snow, wetness, and
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