Wednesday, February 19, 2025

Invasive Rodents Spreading Across the Bay Area

So far this year, nearly 1,000 nutria – a semi-aquatic rodent that resembles muskrats or beavers – have been hunted down in the Bay Area.

Wildlife officials are also urging individuals to report sightings of the 20-pound rodents, which can grow upwards of 2.5 feet long, as cameras have shown they’ve spread to Contra Costa County, where they pose a risk to a major watershed.

A spokesperson for the Department of Fish and Wildlife’s Bay Delta Region in California and the agriculture commissioner of Countra Costa County, Matthew Slattengren, both confirmed the presence of the rodent in the Sacramento-San Joaquin River Delta.

nutria
Nutria have bright orange-yellow teeth that they use for gnawing

The 20-pound-rodent, known for its ‘wildly destructive’ tendencies, poses a major concern now that they’ve entered the delta, which channels water to farms and cities across the state. The delta will also make it easier for the animals to spread to other areas, where there’s a high chance that they will destroy the wetland habitat, which can affect local crops.

To make matters worse, the rodents are incredibly prolific breeders, with adults being able to give birth to up to 200 offspring a year. They also consume up to 25 percent of their body weight in food every day.

However, their feeding habits are known to destroy threatened and endangered species that thrive in the marshland ecosystems. Nutria also pose a risk to livestock, pets, and humans, as they can carry diseases such as septicemia and tuberculosis.

Many also carry tapeworms that can cause ‘nutria itch’, a rash that develops due to liver and blood flukes.

nutria 2
Nutrias can spread a number of diseases including tuberculosis, septicemia, and ‘nutria itch’

In March 2017, a pregnant female nutria was discovered in Merced County. It was the first time the species was found in the state. Since then, more than 5,000 of the rodents have been killed throughout California.

In 2018, an intensive survey was conducted in the Sacramento-San Joaquin River Delta after two nutrias were spotted outside of the area.

Peter Tira, a spokesperson for the California Department of Fish and Wildlife said ‘[they] cannot have [the rodents] reproducing in the delta’ as the potential consequences for the state’s economy are too great.

Anyone who spots signs of nutria, especially those on federal or state lands, should take photos of the animal and immediately report it to the agency’s invasive species program online. They can also report suspected sightings via phone by calling 866-440-9530 or by sending an email to invasives@wildlife.ca.gov.

report nutrias
Officials are urging the public to report sightings of the 20-pound rodent

If possible, the photos should include the animal’s whiskers, as it’s the easiest way to discern nutrias from muskrats and beavers, as well as an object for size reference such as a wallet or pencil.

The interagency nutria response team will be helping with the eradication effort by following up on the suspected sightings.

Brooke Carter
Brooke Carter
Freelance writer who loves dogs and anything related to Japanese culture.
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