The Secret Beneath the Ice
When Michigan's ponds freeze over, the beavers seem to disappear. But what really happens beneath the ice? Follow the clues to their winter lodges and uncover how these remarkable engineers survive the coldest months.
Where do beavers go in the winter? They don’t go anywhere. Beavers spend the entire winter inside the dry chambers of their cone-shaped lodges. They don’t hibernate; they stay awake and active all winter long. The walls of the lodges are very strong due to the layers of mud and sticks. In cold weather, the mud and sticks covering the lodge freeze solidly like concrete, keeping out predators.
A beaver family consists of two parents, who mate for life, one to three yearlings, and one to three kits. They all live together inside the lodge, using their combined body heat to stay warm. The parents usually mate inside the lodge from January to early March, but the embryos’ develop slowly, so the kits aren’t born until April or May. In the summer, the parents drive off the yearlings, who must find suitable spots to start a new home.
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Beavers are pure vegetarians. They will chew on any species of tree, but prefer alder, aspen, birch, cottonwood, maple, poplar, and willow – but just the outer layers of the bark, not the inner wood. They also like aquatic plants, such as cattails, water lilies, sedges, and rushes. They do not eat fish or other animals.
Beavers start building up their winter food supply in the fall before the water freezes. They pile up a raft of tree branches and logs underwater to eat when they’re stuck under the ice. All winter long, they swim out through underwater tunnels to grab the stored food and bring it back inside.
Beavers do not apply mud to the peak of their lodges, thereby creating ventilation shafts through which they can breathe fresh air. If you stand near a beaver’s lodge and listen carefully, you might be able to hear the beavers inside. You might even see steam rising on very cold days.