The largest rodent in North America north of Panama, beavers exert profound influence on the wetland and riparian habitats they occupy. A mostly nocturnal rodent, beavers build dams of sticks and mud across streams and can be found living in ponds, small lakes, streams, and rivers. A strict herbivore, the beaver eats a combination of woody and herbaceous species, such as mountain alder, aspen, and willows. While the effects of beavers occupying an area can vary, in smaller headwater stream systems beaver activities expand and maintain healthy and productive riparian and wetland habitats.
Beavers are considered a keystone species and an ecosystem engineer because they drastically modify the habitats they occupy, creating conditions that allow certain plant and animals species to inhabit an area where they may not otherwise occur. Beaver colonies within a drainage exist as a shifting mosaic of environmental conditions, dependent upon pond age and size, successional status, substrate, hydrologic characteristics, and resource inputs, providing a wide variety of habitat types in both the aquatic and terrestrial realms.
