Beavers Prepare for Winter

by Kevin Strauss

Now that we have had our first hard freeze and brown and yellow leaves are dropping from the trees, it is clear that winter is on the way. Homeowners are scrambling to rake up leaves, clean their gutters and cover their flower bulbs against the impending cold. Animals are getting ready for winter, as well.
Beavers have been “preparing for winter” all summer long, but now that time is short before freeze-up, beavers are busier than ever patching holes in their dams and burying quaking aspen, paper birch and speckled alder branches underwater.

Dam repairs are even more critical in the fall than they are the rest of the year. Researches believe that one of the primary reasons that beavers build dams is to maintain beaver ponds that are at least five feet (about 1.75 meters) deep. This water depth is critical for beavers who don’t want to be trapped in their lodges all winter. On cold winters, northland lakes can put on up to 3 feet (1 meter) of ice. Since beaver lodges have underwater entrances, if a beaver pond is only three feet deep, it would freeze to the bottom and trap the beavers inside. By maintaining a water depth of at least five feet, beavers can always enter and exit their lodge in the winter.

One of the reasons that beavers leave their lodges in the winter is to retrieve stored food, tree branches from their “food caches.”

These branch caches are not just for convenience, the way that we might stock up our freezer with hamburger and pizzas for the coming winter, they are a matter of survival. Before their lakes or ponds freeze, beavers can enter and leave the safety of the water from a hundred different places on the shore. But once lakes freeze, beavers rely on just a few exit holes that they keep open in the ice. Should a beaver leave the water in search of tasty birch branches, a predator like a wolf or coyote needs only to find the beaver’s exit hole and wait their for the beaver to return. On land (or ice) a beaver is no match for a wolf.
This brings us back to the food cache. By having dozens of branches buried in the mud under the ice, a beaver needs only to dive through the underwater entrance to its lodge, swim over to the food cache, cut off a branch and take it back to the lodge for dinner. While wolves and coyotes might easily eat a beaver on land, I haven’t heard any reports of them trying to chase a beaver into deep water. Beavers can easily outdive and outswim their canine predators.

To find where beavers are preparing for winter in your area, look for the pointed stumps of “beaver chewed” trees, a beaver dam and a rounded lodge made out of sticks and mud. If a beaver lodge has light-colored (newly cut) branches on it, it is probably in use. If the lodge is made up of old grayish or dark brown sticks or covered in grass, it has probably been abandoned by the beavers.

The Ely Timberjay