12-16-2002 - Biodiversity

sagar: Author=’Beverly Wachtel’ program=’3633′ video=”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”:http://www.fs.fed.us/ and the “National Fish and Wildlife Foundation”:http://www.nfwf.org/ – supporting the conservation of native fish, wildlife, plants, and their habitats. I’m Joel Block, with Deborah Byrd, for Earth and Sky.

Written by EarthSky