Skip to main content
King County logo

Beavers! Where do we begin? There is already a lot of information on the web about these largest of North American rodents. But the effects of beavers on natural systems vary across the country and across Washington. In addition to providing useful links and information on beaver biology, we wanted to present some information we consider pertinent to beavers in King County.

Currently, King County does not have an official set of policies for how it deals with beaver issues. Nor does the County hold any regulatory authority for beaver control. Dealing with any problems caused by beavers is a landowner's responsibility. Things get tricky when a beaver on one person's land causes a change in hydrology that affects another person's property. The best situation that can result is the two (or more) landowners working together towards a solution. More on that later. But first, a refresher on some biology.



General Beaver Life History

Here are some fun and pertinent facts. Beavers are:

  • the largest member of the rodent family in North America
  • found from sea level to elevations of 12,000 feet.
  • semi-aquatic animals that spend much of their lives in ponds, rivers, streams, and adjacent woodlands.
  • primarily nocturnal and active year-round.
  • monogamous and reproduce once a year. Adults usually mate in February and produce two to four kits in May.
  • territorial and only tolerate the presence of family members under the age of 2. Maximum colonies densities rarely exceed one colony for every half-mile of stream. Family groups are usually made up of five to six individuals with all members working together to build lodges and dams and gather food. Colonies consist of two adults and the young of the current and previous years. By the age of 2, young beavers leave their family group to establish a colony of their own.

Beavers form dams out of branches, logs, and mud to create deep water ponds. These ponds not only create safe areas for the beavers but the diverse wetland systems that result also support a wide variety of fish, amphibians, birds, and mammals. They build lodges made up of branches and logs plastered together by mud, though occasionally beavers will den in the banks of streams and rivers. Beavers feed close to water where they are safer from predators, and they eat the bark, leaves, and twigs of many tree species as well as herbaceous aquatic plants such as lily pads, skunk cabbage, grasses, and sedges.

The following links provide excellent information about beaver biology, ecology, and science.