According to the California Department of Fish and Wildlife, nutria have extremely destructive feeding habits that often lead to severe soil erosion, in some cases converting marsh to open water. Nutria also burrow into banks and levees, creating complex dens that extend as much as 6 meters deep and 50 meters into the bank, often causing severe streambank erosion, increased sedimentation, levee failures, and roadbed collapses. The rodents, which can weigh more than 20 pounds and are often mistaken for beavers or muskrats, were introduced to California for the fur trade in the early 20th century, but were eradicated by the 1970s. In 2017 a reproducing population was discovered in the San Joaquin Valley and nutria have now been confirmed in Stanislaus, Tuolumne, Merced, and Fresno counties, including an area near Grayson that is only about 25 miles south of the Delta. They could reach the Delta all too easily: A single female nutria can have 200 offspring, which can disperse as far as 50 miles. CDFW has launched an eradication program and is asking the public to report sightings to CDFW’s Invasive Species Program.