Beavers

A beaver sites on the edge of a river

The beaver is a keystone species that affects habitat structure and dynamics through the damming and diverting of streams, and the felling of trees and other woody vegetation

NPS

 

The beaver (Castor canadensis) is a keystone species that affects habitat structure and dynamics through the damming and diverting of streams, and the felling of trees and other woody vegetation. The resulting ponds and flooding help create an environment favorable to willow and aspen, the beavers’ preferred winter foods and used in building their lodges. The territoriality of beavers probably deters two colonies from locating within 50 meters of each other, and most streams in the park lack either suitable vegetation or a sufficiently low gradient to provide beavers with habitat, but information about the distribution and number of beaver colonies in the park over time adds to our understanding about the long-term effects of changes in vegetation and climate. Learn More: Beaver Habitat and Population…

 

Quick Facts

Number in Yellowstone

112 colonies counted in 2011

Where to See

  • Willow Park (between Mammoth and Norris), Beaver Ponds (Mammoth area), Harlequin Lake (Madison area), and the Gallatin River along US 191.
  • In the backcountry: upper Yellowstone River (Thorofare region), Bechler River, and Slough Creek. Occasionally seen in the Lamar, Gardner, and Madison rivers.
  • Wait in areas near known beaver activity. You may see them swimming or clambering onto the bank to gnaw at trees and willows. Listen for the sound of the beaver slapping its tail on the water before it submerges to seek safety.

Behavior and Size

  • Crepuscular: active in evening and morning
  • If living on rivers, may build bank dens instead of lodges.
  • One colony may support 2–14 beavers that are usually related. Six is considered average.
  • 35–40 inches long, including tail.
  • Weighs 30–60 pounds.
  • Average life span: 5 years.
  • Male and female beavers look alike—thick brown fur, paddle-shaped tail.
  • Like wolves, beavers live in family groups, which are called colonies. Fewer than 5% of mammals live organized like this.

Other Information

  • Beavers are native to Yellowstone.
  • Yellowstone’s beavers escaped most of the trapping that occurred in the 1800s due to the region’s inaccessibility.

Did You Know?