Beavers occur throughout continental North America from coast to coastincluding the Alaskan peninsula. In California, they are found primarily inthe northern two-thirds of the state. Optimum habitat includes riparian,riverine, lacustrine, and emergent wetlands. In spring and summer, beavers eatgrasses, leaves, and aquatic vegetation, such as tules and cattails. Inwinter, they eat the bark and cambium of trees, primarily willow, aspen, alder,and cottonwood.
Muskrats are common and widely distributed throughout the U.S. and Canada.
Muskrats occur sporadically in California, but are continuously distributedthroughout the Central Valley. Muskrats are mainly herbivorous, eating aquaticplants, especially roots and basal stems of cattails and tule bulrush. Because beavers and muskrats will den in the banks of rivers and lakes, andbecause of the beaver's dam building activity, wetland management for beaversand muskrats is primarily concerned with damage to, and alteration of, leveesand water control structures. To a lesser extent, management concerns alsoinclude vegetation changes from herbivory. For example, beavers can easilyruin a newly restored riparian area.