1 year and 410 nutria later, the war against California's giant swamp rats rages on

A giant 20-pound rodent with the ability to destroy roads, levees and wetlands has been discovered in Stanislaus County. A giant 20-pound rodent with the ability to destroy roads, levees and wetlands has been discovered in Stanislaus County. Photo: CA Department Of Fish And Wildlife Photo: CA Department Of Fish And Wildlife Image 1 of / 20 Caption Close 1 year and 410 nutria later, the war against California's giant swamp rats rages on 1 / 20 Back to Gallery

It's been one year since the California Department of Fish and Wildlife launched a formal effort to eradicate nutria from the state's wetlands.

After not being seen in California since the 1970s, nutria, an invasive and destructive rodent, were rediscovered in the San Joaquin Valley in 2017. So far 410 nutria have been killed, but the Department of Fish and Wildlife warns that the war is far from over.

Nutria can grow to be as large as 20 pounds, and pose a "triple threat" to California. Fish and Wildlife spokesperson Peter Tira said Nutria pose a threat "as a top-rated agricultural pest, a destroyer of critical wetlands needed by native wildlife, and a public safety risk as their destructive burrowing jeopardizes the state's water delivery and flood control infrastructure."

The vast majority of the eradicated nutria (330) came from Merced County. Sixty-five came from San Joaquin County, 12 from Stanislaus County, 2 from Mariposa County and 1 from Fresno County. There have also been confirmed nutria sightings in Tuolumne County.

Going forward, the Department of Fish and Wildlife is planning a number of new ways to hunt and exterminate the swamp rats, including enlisting the help of dogs and "Judas nutria."

"Detection dogs" would help the department locate nutria and confirm their absence from certain areas. The "Judas nutria" project would work to capture and sterilize nutria, instead of killing them. After the nutria are sterilized, they will be "outfitted with radio telemetry collars and released back into the environment to lead biologists to other nutria."

The nutria eradication force has prioritized a known population in the Sacramento-San Joaquin River Delta, since the region is critical for California's agricultural infrastructure.

"Our goal is to keep the nutria out of the delta as much as possible," Tira told SFGATE in August. "That's the epicenter of our water control and flood control in California."

Of the 65 nutria taken from San Joaquin County over the past year, 64 were captured near Manteca, which is where the known population is. Fortunately, survey crews have not detected nutria anywhere else in the Sacramento-San Joaquin Delta.

Over the past year, the nutria eradication force has set up 487 camera stations, conducted more than 1,600 camera checks and deployed 995 trap sets. In addition, San Joaquin Valley farmers have donated five tons of sweet potatoes to be used as nutria bait.

"[The Department of Fish and Wildlife] has received widespread public support for its eradication efforts," Tira said.

According to Tira, Fish and Wildlife received 357 nutria reports from the public during the first year of the war.

"While most of these have turned out to be false reports — either sightings of other wildlife mistaken for nutria or reports that lack enough information to confirm — public reporting will continue to be important to determine the full extent of the infestation," he said.

Armed with $3 million in state and federal grants, $1.2 million from the Sacramento-San Joaquin Delta Conservancy, $600,000 over three years from the California's Wildlife Conservation Board and $1.25 million over three years from the U.S. Fish and Wildlife Service's State Wildlife Grant Program, the nutria eradication force hopes to step up its efforts in 2019.

The Department of Fish and Wildlife believes that public education and outreach are key components of eradication efforts going forward, and have created a nutria identification pocket guide for the general public.

The guide can be viewed here. Nutria sightings can be reported to (866) 440-9530 or invasives@wildlife.ca.gov.

Eric Ting is an SFGATE staff writer. Email him at eting@sfchronicle.com and follow him on Twitter

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