Life Continues Under the Ice

by Kevin Struass

With at least four inches of ice on most of our lakes, one might imagine that all lake life is either dead or hibernating until spring. But for beavers, winter is the season in which they get to eat all of that food they stored in the mud in the bottom of their ponds. Much of what beavers do throughout the warm weather months is geared to preparing for the winter. Even dam building is winter preparation.

Biologists tell us that beavers seem to prefer a lake or pond that is five feet deep. If they don’t find a lake that deep, beavers will build a beaver dam out of sticks, mud and rocks to hold back the water and create their pond. This isn’t by accident, although scientists tell us that it is probably by instinct rather than by planning. It appears that instinct serves beavers well in this regard. In a cold winter, we can get 2-3 feet of ice on area lakes. If a beaver pond were only three feet deep, it would freeze to the bottom and beavers would be trapped in their lodges for the winter. Under those conditions, they would likely starve.

Lodge construction is also a winter adaptation. Once they have constructed their dam, a family of beavers will build a lodge out of mud and sticks either on the shore or in a “beaver-made” island in the middle of the pond. The lodge has two or more underwater entrances and an above-water platform where beavers can sleep, eat and groom themselves. When the snow falls on the lodge during the winter, this strong structure gets even more insulation. When the wind is blowing and it is -30 degrees in the forest, a beaver lodge could be 30 degrees above zero with no wind chill. That plus beaver’s warm fur coats keep them warm all through the winter.

But the most important preparation that beavers make for winter is their food cache (pronounced “cash”). Throughout the summer and fall, beavers gather branches of quaking aspens, paper birch and speckled alder trees and bury their ends underwater in the mud. When the lakes freeze and it is more difficult and dangerous for beavers to leave the water in search of food, they just swim over to their underwater twig pile and get a meal.

If you are snowshoeing or skiing on a pond and see a beaver lodge, enjoy it from a distance. Beaver activity and swimming around the lodge usually means that the ice is thinner near a beaver lodge. But if you look carefully, you might see the tips of branches sticking through the ice. Its just another example of how northwoods animals get ready for winter.

The Ely Timberjay