Beaver Dam. Photo: © Carolyn Duckworth 2004

Beaver and Their Dams

Beaver Lake, in Yellowstone National Park, is mute testimony to the industry of beavers and the ultimate result. This lake is now more meadow and mud than a body of water. But you can still see the long dam built by beavers at least a century ago. Their dam slowed the flow of stream water and created a wetland.

The Intermountain West held thousands of beaver-created wetlands until the beaver were wiped out by trappers supplying the fashion industry in the early 19th century. In Idaho alone, beaver were gone in less than ten years.

Today, beaver populations are steadily increasing and are welcome residents in many natural areas. In some places in Idaho, beaver are doing so well that hunting is allowed again. The Idaho Department of Fish and Game plans these trapping seasons in order to manage beaver populations.

Because beaver have played such a large part in shaping and even creating wetlands in the past, biologists throughout the US are using beaver to restore wetland habitats. First, the beaver are trapped and transplanted from either healthy wetlands or urban areas to the damaged wetland. After some time, the beaver dams can re-create the natural hydrology of the area by slowing water and causing streams to overflow their banks. This is important for many species of wetland plants and animals who depend on flooding to deposit fresh soil and nutrients on the floodplain and to create many small pools of water where insects and amphibians may lay their eggs. Beaver may also have a revitalizing effect on some willows and red-osier dogwood. Idaho Biologist Mabel Jankovsky-Jones of Idaho's Conservation Data Center says "Maintaining beaver populations is a critical element in sustaining natural wetland complexes."

A beaver dam backs up water on a stream, diversifying the habitat for other animals and plants.

Back