California wiped out 20-pound rodents. DNA suggests someone brought them back

California once believed it had beaten nutria. The invasive semi-aquatic rodents had been wiped out in the state by the late 1970s, but decades later they reappeared in the Central Valley and a new genetic study suggests their return was not an accident of nature, but the result of human reintroduction.The finding matters because nutria are not just another nuisance species. They can damage wetlands, weaken levees, and destroy native vegetation and crops, which is exactly why California has spent years trying to remove them again.What nutria areNutria, also known as coypu, are large South American rodents that are built for water. Adult nutria typically weigh about 15 to 20 pounds, have a stout body, partially webbed hind feet, and a heavy rat-like tail covered in bristly hairs.They are often mistaken for beavers or muskrats, but nutria are a separate species with their own ecological problems.