The giant rodents called nutria are an invasive species of rodent that can grow to three feet from their nose to the tip of their tail.
They are a threat to agriculture because they can wipe out wetlands, disrupting water delivery and flood control systems.
The U.S. Fish and Wildlife Service says it has captured more than 400 of the animals across the San Joaquin Valley.
According to the report, 330 were caught in Merced County, two in Mariposa County and one in Fresno County.
The nutria have a weakness for sweet potatoes, so valley farmers have donated five tons worth to help lure the rodents into traps.
If you happen to spot a nutria the California Department of Fish and Wildlife has a toll-free reporting hotline: (866)440-9530.
The e-mail address to report nutria sightings is invasives@wildlife.ca.gov.