20-Pound Rodents Are Invading California


Since March of last year, more than 20 have been documented. Kamil Martinovsky/Shutterstock

Creatures are emerging from the California marshlands with orange buckteeth, webbed feet, and round, rat-like tails. They can weigh more than 9 kilograms (20 pounds) and reach lengths of up to 1 meter (3.5 feet).

No, we’re not introducing the next bad horror flick. The real-life drama starring the invasive nutria is unfolding in three of the state’s counties and it has officials concerned.


So concerned, in fact, that the California Department of Fish and Wildlife is setting up a hotline to track the animal.

“We have no idea how many there are or how they were reintroduced,” CDFW spokesman Peter Tira told NPR. “But we do know we have to get rid of them.”

In the last year, more than 20 have been spotted, one of which was a healthy, pregnant female – and that could breed trouble.

With a lifespan of up to 10 years, a breeding pair can have up to 16,000 offspring in three years under the right conditions.


Endemic to South America, the nutria was brought to the US in 1889 for its fur. When its fur market collapsed in the 1940s, ranchers released thousands into the wild. At first, it seemed like a good idea – the nutria is a voracious herbivore and initially helped control noxious weeds. However, it soon became evident that the rodent eats almost any vegetation in its path.

In North America, nutria don't have local predators to keep populations down. Since officials don’t know the scope of infestation, they say it could create a serious problem for wetlands and ecosystems.

The large rodents eat thick vegetation down to bare earth and then they go for the roots. They’ve been known to over-graze wetland habitats and collapse levees, compete with native species, and cause erosion by tunneling into streambanks.

As with most rodents, they carry dangerous pathogens and viruses that degrade water quality and contaminate drinking supplies. The parasites and diseases they carry can transmit to humans, livestock, and pets.


It’s also not the first time they’ve taken over American soil.  They have ravaged southern US wetlands and damaged marshland ecology in the Chesapeake Bay and Pacific Northwest.

They’ve been found in 22 states and have established populations in 16.

Damage caused by their insatiable appetite can be permanent. They munch on native plants that hold wetland soil together and this, paired with rising sea levels, intensifies the loss of coastal marshes.

Their range is currently limited by cold winters, but rising global temperatures could increase their populations.


To which some people say: If you can’t beat ‘em, eat ‘em (in the form of slow-cooked nutria, nutria chili, gumbo, and even sausage).

Wildlife officials have a simpler solution. If you see one, call it in.


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