How do beavers build dams across streams?

Beavers are expert ecosystem engineers. Using strong incisors that grow continuously, they fell small trees and transport sticks to the dam site. They weave branches together and seal gaps with mud, leaves, and vegetation to form a barrier that raises water levels. The pond created by the dam helps protect the beaver lodge from predators and gives the animals underwater access to food caches and entrances. Beaver dams can alter wetlands, increase biodiversity, and change the shape of local waterways.