Invasive Rodent May Not Have Come to California by Accident

California's latest invasive-species headache may have arrived not by accident, but by invitation. Genetic testing shows the state's resurging nutria—hefty, orange-toothed rodents that tear up wetlands and threaten levees—are closely related to a population in central Oregon, not to the nutria that once lived in California before being wiped out in the 1970s, reports Smithsonian. This development points to a more recent, illegal human-assisted reintroduction, the California Department of Fish and Wildlife announced earlier this month.

The how and why remain murky. A CDFW geneticist tells SFGate the animals couldn't realistically have walked to where they were rediscovered in 2017, especially as no nutria were found in between the two areas. Theories on the perps range from homeowners seeking a natural way to clear aquatic plants to those with a simple fondness for the rodent—or maybe even individuals intent on causing some sort of damage.

Since that first pregnant female turned up in Merced County nine years ago, officials have removed 7,800-plus nutria and now spend about $5 million a year chasing them across hundreds of thousands of acres in the Central Valley and Sacramento-San Joaquin Delta. Residents may legally kill nutria that wreak havoc on property, but they're urged to double-check IDs: Most "nutria" sightings reported to the state turn out to be muskrats.