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.
Beaver damage varies by type, magnitude, and region.
In the West, beaverdamage mostly effects gravity flow water delivery, drain systems, andstructures, such as chewing through stoplogs or plugging culverts. Pasturesand agricultural fields that are adjacent to riparian areas which containwillows or other preferred foods can be flooded from beaver dams. In areas where beavers are causing damage, a number of beaver control measurescan be employed. Poisons have been shown to be unproven on wild beaverpopulations. Trapping or shooting have both been shown to be highly effectivein controlling nuisance beavers.