Invasion of nutria rodents in California may have been intentional: officials

California is currently being invaded by a 20-pound rodent that was previously believed to have been eradicated from the state, and officials said its reintroduction may not have been part of nature.

Officials with the California Department of Fish and Wildlife said that DNA testing of the 2.5-foot-long harmful rodent called a nutria has proven that it is connected to a population in Oregon and not to a distant population in the Golden State from the 1970s, which was believed to have been completely wiped out. 

“This study supports our long-held belief that the current invasion is the result of reintroduction rather than explosive growth of a remnant, undetected population,” Nutria Eradication Program Manager Valerie Cook said in a CDFW press release.

Nutria are semi-aquatic rodents from South America and are found near freshwater or estuaries. Because they burrow like beavers, they cause extensive damage to water infrastructure, banks, and levees, and create a hazard for people, livestock, and machine operators, per the wildlife agency. This destructive behavior classifies them as an A-rated pest.

The big question now is why? Was it by accident, or was it something more nefarious?

Michael Buchalski with the CDFW told SFGATE that “Given where nutria were rediscovered in California, it is nearly impossible that they could have migrated there on their own.”

“It’s too far of a distance and we don’t find any nutria in the areas in between. That makes human introduction the most likely scenario.” 

“Someone may have thought they could be an effective natural way to manage aquatic vegetation on their private property,” Buchalski added. “Also, some people just really like nutria. … Or it could have been malicious in hopes that they would cause environmental damage. It’s hard to know.”  

In order to prove their theory, extensive testing was conducted on the current nutria population following the discovery of pregnant nutria in the Central Valley’s Merced County in 2017. Up until that point, the rodent had been absent from the state for decades.

One theory officials were working on was that she was connected to the rodent’s distant family in the state, and that researchers had somehow just missed that they were still around.

In order to conduct the DNA testing, researchers obtained skins and skulls that were part of museums and universities across the state. In one case, they even tested a taxidermy from Butte County, in Northern California. The results were tested against populations around the world and across the US.

In the end, CDFW said “genetic research suggests California’s current nutria invasion was the result of intentional reintroduction, with the original source animals likely being transported from the central Oregon population.”

In the late 19th and early 20th centuries, nutria existed around the world and their pelts were part of the fur trade. However, when that came to an end, the rodents were set free, including in California. By the late 1970s, the feral population in the state was officially declared eradicated.

Since 2017, massive efforts have been spent trying to get rid of the beast that destroys wetlands, agriculture, and flood control infrastructure, with a total of 7,841 Nutria removed from Sacramento, San Joaquin Delta and the Central Valley since the end of March. 

The Post reached out to the CDFW for further comment.

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