MUSKRATS.... in California
In California, the native distribution of muskrats is along the Colorado River by the Arizona border. Native populations also exist in scattered locations with suitable habitats on the arid side of the Sierra Nevada from Mono to Lassen County. The muskrat is a native to Eagle Lake but was not historically present less than 50 miles from suitable habitat on the Pit River in Modoc County. Movement of muskrats from their native habitat along the Colorado River into irrigation ditches and drainage canals began in 1901 when a canal from the Colorado River to the Imperial Valley was completed. Soon after, there were reports by the Imperial Irrigation District of extensive damage to canal banks. A high demand for fur during the 1920’s resulted in the release of muskrats elsewhere. Muskrats now occupy canals, ponds, and irrigation ditches throughout most of the Sacramento and San Joaquin Valleys.
In Shasta County, muskrat populations along the Fall River, Pit River and lower Hat Creek drainage are the result of escapees from the Mount Shasta Fur Farm established in 1931 on Mud Lake, 4 miles north of McArthur. Muskrats have been implicated as the cause of several levee breaks that have resulted in flooding and loss of pasture, as well as a major cause of bank erosion and collapse along the Fall River. There are concerns that the associated increase in sedimentation of the river and effect on stream channel morphology may have a detrimental effect on the wild trout fishery and the threatened Shasta crayfish.