How Do Beavers Build Dams?

Beavers are water animals whose diet is tree bark. They are excellent swimmers and wood cutters, and they use the trees they chew down not only for food, but also for building lodges and dams.

Beavers live together in groups. They cut down trees together - one beaver chews while the other rests, and then the second beaver chews while the first rests. The beaver family builds its dam with logs, branches, plants, and rocks plastered together with mud. Building up from the bottom, the beavers use poles to strengthen the dam. Then they add more twigs, brush, water plants, and mud. When finished, the top of the dam is above water.

Beavers constantly repair their dams and lodges, and the dams grow to be very large. They even dig canals from wooded areas to the water to transport logs that are too heavy to carry over land.

One beaver dam in Montana measured 2,140 feet long!