The beaver is a large rodent that builds dams out of wood and mud to create deep-water ponds that provide a defensive barrier for their homes. Beavers are found in North America, Europe and Siberia. They live in and around forest rivers, feeding on bark, twigs, roots and leaves. Their back feet are webbed for swimming and their coats are sleek and waterproof. They use their large, flat tails as rudders for steering as they swim.

Builders

Beavers are known for building dams across streams in order to create their own ponds. With their strong teeth, they gnaw through tree trunks which they use to build a dam across a stream, forming a pond. In so doing, the beaver creates a wetland, an ecosystem that is lived in by many other species of animal.

In the pond that forms behind the dam, the beavers construct a lodge out of mud and sticks. The chamber inside the mound is reached by several tunnels, each with an underwater entrance. The lake around the lodge protects the family from predators. The beavers are careful to make the lake deep enough so it does not freeze to the bottom in winter. Before winter sets in, beavers cover their lodges with mud. This freezes when frost occurs. The mud hardens, making it impossible for predators, such as wolves or wolverines, to break in.

Repair work

The beavers' dam is often weakened by winter weather. It may be further damaged when snows melt upstream in the spring, making the waters run higher and faster. Young beavers, born last spring, help their parents out, using their sharp teeth to fell small trees, and filling cracks in the dam with mud from the lake bed. Beavers work hard to repair their dams: they can even rebuild one overnight.