Beaver Dam
A beaver gathers material for a dam. Photo © 2000 Don Getty.
DB: This is Earth and Sky, with a question from a listener. He writes, “Why do beavers build dams?”
JB: Beavers build dams for many of the same reasons humans do – mainly to transform and control their environment. Beavers are natural swimmers, with their webbed feet and sleek fur, and they like to live near streams and ponds. But shallow water doesn’t offer beavers much protection from natural predators such as wolves. So beavers build dams in order to raise the water level. The deeper water gives the beavers a good place to hide. It also slows down the water’s speed, which lets beavers build stable lodges to house their families.
DB: Scientists think that it’s actually the sound of running water that gives the beaver the urge to build dams in the first place. If the stream’s bed is made of dirt, beavers will push it up in the direction of the sound. They’ll go on building where the water pours over the barrier. Beavers will keep building until they can’t hear the sound of pouring water anymore. Although they prefer to build their dams from rocks and twigs, beavers aren’t too particular. They’ll use whatever they can grab – from cornhusks to hubcaps – when they hear the water calling.
JB: To ask your science question, come to earthsky.org. Today’s show was made possible by the U.S. Forest Service and the National Fish and Wildlife Foundation – supporting the conservation of native fish, wildlife, plants, and their habitats. I’m Joel Block, with Deborah Byrd, for Earth and Sky.
If you enjoyed this show, the following websites, books and articles may be of further interest to you:
Wilsson, Lars. My Beaver Colony. NY: Doubleday, 1968.
Rue, Leonard Lee III. The World of the Beaver. Philadelphia: J.B. Lippincott Co., 1972.
The Minnesota Zoo’s beaver web site
Author’s notes:
It’s believed that long before our human ancestors were even living in caves, beavers had mastered the art of dam building. They stick to sound engineering principles, such as building the base much wider than the top, and taking advantage of natural obstructions like boulders and trees.
Running water’s not the only sound that gets the beaver building. Any oscillating sound will do, even an electric razor (Wilsson, p. 146).
Additional Teacher Resources
Alaska Department of Fish & Game, Division of Wildlife Conservation: Beaver Fun Facts
Did you know that beavers are second only to humans in their capacity to manipulate the environment? By building and maintaining dams, beavers can completely change the vegetation, animal life, and other components of the watersheds in which they live. This site provides such fun facts, as well as links to more information about busy beavers.
Wisconsin Department of Natural Resources, Environmental Education for Kids, Critter Corner: The Beaver
This site provides a natural history of the beaver in Wisconsin in a format easily understandable to younger students, it also provides links to external information on the beaver and its role as a keystone species in its ecosystem.
