Close to a thousand nutria have been hunted in the Bay Area this year, and wildlife officials are urging residents to report sightings of these invasive, 2.5-foot-long rodents. Recent camera captures indicate that nutria have spread to Contra Costa County, posing a significant threat to a vital watershed.
Krysten Kellum, a spokesperson for the California Department of Fish and Wildlife (CDFW), and Matthew Slattengren, Contra Costa County agriculture commissioner, confirmed the rodents’ presence in the Sacramento-San Joaquin River Delta to SFGATE, following initial reports by the San Francisco Chronicle.
The destructive nature of nutria is a growing concern. With their arrival in the delta—an essential water channel for cities and farms throughout California—they could easily disperse to other regions, further damaging wetland habitats, leading to substantial crop losses, and “weakening levees to the point of failure” due to their burrowing, Slattengren noted in an email.
Nutria reproduce rapidly, with the potential to produce up to 200 offspring annually. Each rodent can consume up to 25% of its body weight daily, but they waste and destroy up to ten times that amount, threatening rare and endangered species as well as native plants that rely on the marshland ecosystem.
In addition to their ecological damage, nutria pose health risks to humans, livestock, and pets, carrying diseases like tuberculosis, septicemia, tapeworms, and flukes, which can cause infections through exposure to contaminated water.
The species was first discovered in California in March 2017, when a pregnant female was found in a private wetland in Merced County. Since then, over 5,000 nutria have been eradicated across the state. Following the initial discovery, the CDFW initiated an extensive survey of the Sacramento-San Joaquin River Delta after two nutria were spotted near the area.
“We cannot have nutria reproducing in the delta,” said Peter Tira, a spokesperson for CDFW. “The threat to California’s economy is too great.”
Kellum explained that only one or two nutria passed through Contra Costa County last year, but two were captured on August 15 after being spotted near Dutch Slough, south of Sherman Island, where another family group was seen in 2022. The source of the new sightings and the extent of their spread remain unknown.
“We have had additional detections of nutria on camera in that area over the last month, but with no additional captures,” Kellum reported.
Officials are asking the public to photograph and promptly report any suspected nutria sightings or signs, especially on state or federal lands, through CDFW’s invasive species program online, by emailing invasives@wildlife.ca.gov, or by calling 866-440-9530. If possible, photos should capture the animals’ whiskers, feet, or tails, along with a size reference such as a pencil, quarter, or wallet.
Residents can also report sightings to Contra Costa County staff by calling 925-608-6600.
“Reports will be followed up on by the interagency nutria response team and will aid in their eradication efforts,” Kellum added.
