The latest push to eradicate nutrias — the large, fur-bearing, aquatic rodents that have become an invasive species in California’s wetlands — has shifted from San Joaquin County to neighboring areas in the Delta.
The large rodents, which resemble beavers and are native to South America, were first discovered in the marshes of San Joaquin County in 2017. But the pests have recently been found in Solano, Sacramento and Contra Costa counties, according to reports from the California Department of Fish and Wildlife.
Weighing up to 20 pounds, nutrias thrive in wet environments, but they also can burrow into banks to create dens, causing erosion. The plant-eating animals can carry diseases and gobble up to 25% of their body weight a day. They destroy large swaths of marshland in the pursuit of a good meal, with devastating effects on wetland habitats, agriculture and water conveyance/flood protection infrastructure.
In the past eight years, more than 5,000 nutria have been killed in California, with additional animals confirmed present across Merced, Stanislaus, Fresno, Solano, San Joaquin, Fresno, Mariposa, Sacramento, Madera, Contra Costa and Tuolumne Counties, the wildlife agency reports. Some 320 nutrias have been eliminated this year alone in Solano County. Contra Costa County has reported two, and Sacramento County has had nine.
But there is some good news for San Joaquin County, which was ground zero for the nutria infestation.
“In 2024, there have not been any sightings,” the county’s agricultural commissioner, Kamal Bagri, told Stocktonia.
But, Bagri cautioned, now is not the time to ease up on monitoring.
“I’m definitely very happy, but the hope is (California wildlife officials) continue their surveillance program,” Bagri said.
The Department of Fish and Wildlife has deployed teams from Suisun Marsh in Solano County throughout the Delta and into the San Joaquin Valley.
Anyone who thinks they have seen a nutria is asked to snap photos and report the sighting to the agency’s Invasive Species Program at wildlife.ca.gov/Conservation/Invasives/report, by e-mail to invasives@wildlife.ca.gov or by phone at (866) 440-9530.
Want more? Sign up to get Stocktonia delivered to your inbox three days a week.