Beavers build dams for two good reasons, food and protection. They begin by cutting larger trees and placing them with the branches facing upstream. The branches catch other debris in addition to the sticks and mud placed there by the beaver. Some dams can be quite large, others very small. Sometimes, beavers will build a series of dams down a stream.
Beavers are strict vegetarians, and the aquatic vegetation that grows in ponds supplies summer food.
The favorite plants of the beaver are duckweed, pickerel weed, cattails, and spatterdock. Since beavers are slow moving on land, they are much safer swimming in the beaver pond they create by building a dam. Beavers have many uses for the trees that they cut down. They cut the trees by standing on their hind legs, using their tails for balance. A ring is chewed around the tree using the upper incisors.