Methods beavers use to survive the winter months

Beavers have survived frigid winters since their evolution during the Miocene Epoch 23.5 million years ago. Beavers are large, nocturnal, and semi-aquatic rodents that are closely related to squirrels. While most people consider rodents pests, the beaver is one of the most valuable mammals on earth.

Second only to humans, beavers have extraordinary abilities to change and influence the earth’s environment, thus making them tremendous assets to the wetlands. Beavers are monogamous, mate for life, and live in a family consisting of one male, one female, and two to four kits.

To survive winters and to have protection from predators, beavers build dams in bodies of water creating ponds. Working at night, beavers carry mud, stones and timber as they build the dams. Beavers also build canals which are used to float building materials that are too difficult for them to carry across land. Dams must be strong enough to hold enough water so that the bottoms of the ponds do not freeze in winter, as this would eliminate their winter food supply.

Once the pond is established, beavers build their homes which are called lodges. Building from the inside out, lodges are created from severed tree branches, grasses and mud. The lodges are strategically placed in the middle of the pond so that they can only be reached by underwater entrances. Every autumn, beavers cover their lodges with fresh mud. The mud freezes when the temperature drops low enough to cause frosts. The mud becomes nearly hard as stone and cannot be penetrated by predators. A beaver’s lodge has underwater entrances and typically consists of two dens. One den is used for drying off after they exit the water. The second den is drier and this is where the family lives. Lodges insulate the beavers allowing them to survive winters.

When the pond freezes over, beavers swim in the water underneath the ice to their food piles. Beavers keep their fur waterproof by rubbing their fur with an oily substance called castoreum. Castoreum is produced by their scent glands. They have a thick undercoat and a thick layer of fat beneath their skin which also provide insulation for the beaver. With their large webbed feet, beavers can swim powerfully underwater. Their large flat tails help steer them through water.

Beavers can stay underwater for up to 15 minutes because of their specially adapted lungs. They have clear eyelids that allow them to see underwater. The openings to their ears and nostrils close when beavers are in water to prevent intake of water. The kits learn to swim within 30 minutes of birth. If they get tired in the water, the mother carries them on her back.

Beavers do not hibernate so they must have a food source during winter. Beavers are herbivores so they store sticks and logs in a pile in their ponds. Some of their food pile is left above water so that it accumulates snow. The snow acts as insulation helping to keep water from freezing in and around their food pile. The food piles also give the beavers a place to breathe when they are outside of their lodges.

When winter ends, beavers emerge from their lodges at night to repair dams and build a new food supply for the next winter. Beavers have strong incisors that are as powerful as chisels. With these incisors they can take down trees. Their incisors can grow up to four feet per year. A pair of beavers can take down 400 trees each year. Despite the warm temperatures, beavers return to their lodges each day after working so that they can rest and be safe from land predators such as wolves.

Beavers are intelligent, industrious mammals that are second only to man with their abilities to change the world’s environment by creating wetlands with their dams. To survive winter, beavers build underwater lodges that provide insulation and safety from predators, and by building food piles in the middle of the pond for winter food.