Wildlife Damage Management, Internet Center for

 

Title

Beavers

Date of this Version

July 1994

Abstract

The beaver (Castor canadensis) is the largest North American rodent. Most adults weigh from 35 to 50 pounds (15.8 to 22.5 kg), with some occasionally reaching 70 to 85 pounds (31.5 to 38.3 kg). Individuals have been known to reach over 100 pounds (45 kg). The beaver is a stocky rodent adapted for aquatic environments. Many of the beaver’s features enable it to remain submerged for long periods of time. It has a valvular nose and ears, and lips that close behind the four large incisor teeth. Each of the four feet have five digits, with the hind feet webbed between digits and a split second claw on each hind foot. The front feet are small in comparison to the hind feet. The underfur is dense and generally gray in color, whereas the guard hair is long, coarse and ranging in color from yellowish brown to black, with reddish brown the most common coloration. The prominent tail is flattened dorsoventrally, scaled, and almost hairless. It is used as a prop while the beaver is sitting upright and for a rudder when swimming. Beavers also use their tail to warn others of danger by abruptly slapping the surface of the water.The beaver’s large front (incisor) teeth, bright orange on the front, grow continuously throughout its life. These incisors are beveled so that they are continuously sharpened as the beaver gnaws and chews while feeding, girdling, and cutting trees. The only way to externally distinguish the sex of a beaver, unless the female is lactating, is to feel for the presence of a baculum (a bone in the penis) in males and its absence in females.

Exclusion: Fence small critical areas such as culverts, drains, or other structures. Install barriers around important trees in urban settings.
Cultural Methods and Habitat Modification: Eliminate foods, trees, and woody vegetation where feasible. Continually destroy dams and materials used to build dams. Install a Clemson beaver pond leveler, three-log drain, or other structural device to maintain a lower pond level and avoid further pond expansion.
Frightening: Shooting of individuals or dynamiting or other continued destruction of lodges, bank dens, and dams, where legal, will occasionally move young colonies out of an area.
Repellents: None are registered; however, there is some evidence that repellents may be useful.
Toxicants: None are registered.
Trapping: No. 330 Conibear® traps. Leghold traps No. 3 or larger (including coil-spring types with equivalent jaw spread and impact). Basket/suitcase type traps are primarily used for live trapping. Snares can be useful, particularly in dive sets and slides where legal.
Shooting: Rarely effective (where legal) for complete control efforts and can be dangerous to humans.
Other Methods: Other methods rarely solve a beaver damage problem and may increase risks to humans and nontarget species.