“Bay Area Under Siege: The Rise of Invasive 20-Pound Rodents”
Close to a thousand nutria have been hunted down in the Bay Area this year alone, prompting wildlife officials to urge the public to report sightings of these invasive, 2.5-foot-long rodents. Recent camera footage has confirmed their spread to Contra Costa County, posing a significant risk to a critical watershed.
Concerns Over Nutria’s Impact on Local Ecosystems
Krysten Kellum, a spokesperson for the California Department of Fish and Wildlife’s Bay Delta Region, along with Contra Costa County Agriculture Commissioner Matthew Slattengren, confirmed the nutria’s discovery in the Sacramento-San Joaquin River Delta. Their presence is alarming, as it facilitates easier dispersal into other regions, potentially leading to widespread destruction of wetland habitats, significant crop losses, and weakened levees that could fail due to the rodents’ burrowing activities.
Nutria reproduce at an alarming rate, with the potential to give birth to as many as 200 offspring each year. Each nutria can consume up to 25% of its body weight daily, but they waste and destroy up to ten times that amount. This feeding behavior threatens rare and endangered species, as well as native plants that depend on the marshland ecosystem being eroded by their activity.
Health Risks Associated with Nutria
In addition to environmental concerns, nutria pose health risks to humans, livestock, and pets. They can carry diseases such as tuberculosis, septicemia, tapeworms, and blood and liver flukes, which can lead to infections through contaminated water exposure.
Since the first sighting of a pregnant female at a private wetland in Merced County in March 2017, over 5,000 nutria have been killed throughout California. Following the initial discovery, the California Department of Fish and Wildlife (CDFW) prepared for a thorough survey of the Sacramento-San Joaquin River Delta after spotting two nutria just outside the region.
Recent Sightings and Ongoing Efforts
Kellum reported that one or two nutria passed through Contra Costa County for the first time last year. The agency successfully hunted down two nutria on August 15 after they were found near Dutch Slough, south of Sherman Island, where another family group was seen in 2022. However, the origins and extent of their propagation remain unclear.
“We have had additional detections of nutria on camera in that area over the last month, but with no additional captures,” Kellum noted.
Reporting Sightings to Aid Eradication Efforts
Officials are calling for the public to photograph and report suspected nutria sightings or signs, especially on state or federal lands. Reports can be submitted online to the CDFW’s invasive species program, via email at invasives@wildlife.ca.gov, or by calling 866-440-9530. When possible, photos should show the animal’s whiskers, feet, or tail, alongside a size reference object like a pencil or quarter.
Residents can also report nutria 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 help in their eradication effort,” Kellum stated.
