How do beavers build dams?

Beavers are among the best-known ecosystem engineers because their dam-building changes the shape of streams and wetlands. Using strong teeth, they fell trees and drag woody material into waterways, then seal gaps with mud and vegetation. The resulting pond provides deeper water around the lodge entrance, which helps protect them from predators. These structures can also create habitat for fish, amphibians, birds, and insects. In North America and Europe, beaver activity can significantly influence local hydrology and biodiversity.