Rodents of unusual size are no longer just something from the movies. These swamp rats known as nutria are a scourge spreading across Contra Costa and Solano counties, and they’re a risk to our crops, livestock, and water supply.

In the autumn of Moo Deng, California is dealing with an invasive outbreak of rodents that could be considered the anti-Moo Deng: they’re not cute, they’re not in captivity, and they’re dangerous on a number of levels. We’re talking about nutria, sometimes called “swamp rats,” who can measure up to two feet long and weigh up to 20 pounds, and are recognizable for their bright orange front teeth.  

And these damned things are trouble. “Nutria have devastating impacts on wetland habitats, agriculture, and water conveyance/flood protection infrastructure,” according to the California Department of Fish and Wildlife (CDFW). “Nutria consume up to 25% of their body weight in above- and below-ground plant material each day. Due to their feeding habits, up to 10 times the amount of plant material consumed is destroyed, causing extensive damage to the native plant community, soil structure, and nearby agricultural crops.”

The nutria (which is Spanish for “otter”) had been eradicated from California for decades, but the invasive little suckers turned up again in Merced County in 2017. Their population has exploded since, and the CDFW says they were seen in Solano County last year, where their population has already grown to the hundreds. Now the Chronicle recently reported that nutria had turned up in Contra Costa County’s Sacramento-San Joaquin River Delta.

And they’re a risk to damage the delta’s levees.

"The Nutria is an invasive species that can be destructive to wetland habitat, crops, and can weaken levees to the point of failure,” Contra Costa County agricultural commissioner Matthew Slattengren told KTVU. “With Nutria in the Delta, it is easier for it to disperse into other regions."

And they’re also carriers for tuberculosis and tapeworm, which can spread to humans, livestock, and pets. Additionally, nutria can infect swimming areas and drinking water with blood and liver flukes.

Yes, the CDFW recommends killing them (as long as you own the property on which they are found). You can also contact the CDFW, who will handle the deed in humane fashion.

Any Contra Costa County residents who see a nutria are asked to report the sighting to the county’s agriculture department at (925) 608-6600. If outside Contra Costa County, CDFW officials ask that you send them pictures and the location to [email protected], or call (866) 440-9530, or fill out the online invasive species sighting report.

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Image: Petar Milošević via Wikimedia Commons