Maryland has eliminated these invasive 20-pound swimming rodents Nutria helped decimate more than 5,000 acres of wetlands in Maryland. Now, after a 20-year battle, officials are declaring victory against the invasive species.
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Maryland has eliminated these invasive 20-pound swimming rodents

A cat-sized rodent that can eat a quarter of its weight each day. Animal and Plant Health Inspection Service/USDA hide caption

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Animal and Plant Health Inspection Service/USDA

It looks like a rat crossed with a beaver, with prominent orange teeth. It's an invasive swimming rodent that has wreaked havoc on wetlands of the Chesapeake Bay for the better half of a century, and now, officials say, the nutria has been driven out of Maryland.

"It was not an easy task by any means," says Marcia Pradines Long, refuge manager of the Chesapeake Marshlands National Wildlife Refuge Complex. "Over two decades and $30 million later, we can proudly say that we have eradicated nutria from Maryland."

Nutria were first brought to the U.S. from South America in starting in 1889, with the idea to use them for fur farming. But nutria coats didn't have the same cachet as mink apparently (though some in Hollywood, including Greta Garbo and Elizabeth Taylor, reportedly wore nutria back in the day).

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The nutria fur industry collapsed in the 1940s, and thousands of the rodents made their escape or were set loose by farmers who could no longer care for them. Since then, the creatures have spread to at least 20 states.

In Maryland, nutria ground-zero was at the Blackwater National Wildlife Refuge near Cambridge, formerly the site of a nutria fur farm. By the 1990s, there were an estimated 50,000 nutria in the refuge, munching away at the native vegetation that make up a healthy wetland ecosystem. Refuge officials estimate nutria have helped destroy more than 5,000 acres of wetlands in the refuge.

"Being a an invasive non-native species, they didn't use the ecosystem like a native species would," says Kevin Sullivan, state director for USDA Wildlife Services in Maryland. "They didn't graze on the marsh. They destroyed the marsh."

Aerial photographs of Blackwater National Wildlife Refuge show a dramatically different landscape before and after the introduction of nutria. Animal and Plant Health Inspection Service/USDA hide caption

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Animal and Plant Health Inspection Service/USDA

Nutria, with their long orange teeth and sharp claws, acted like a rototiller mowing through the vegetation, Sullivan says. "They ate everything above ground, and then they started eating the floating root mats of the marsh."

The destruction can happen quickly: nutria voraciously feed on the roots and shoots of marsh plants, consuming as much as a quarter of their body weight a day. And they are prolific breeders, producing two to three litters a year, with four or five nutria babies in each one.

Nutria aren't the only cause of wetland destruction in the Chesapeake in recent decades, but Pradines Long says they're in the top three. The other big factors threatening wetlands are sea level rise and land subsidence, and other invasive species, especially phragmites, a nonnative reed from Europe that crowds out other plants without providing food for wildlife.

In 2002, a coalition of federal and state agencies came to rid Maryland of nutria, creating the Chesapeake Bay Nutria Eradication Project. "It was an all hands effort," says Sullivan. "We threw everything and the kitchen sink at this problem."

The team used traps as well as nutria sniffing dogs, trained to detect the rodents or their scat. "We systematically went across the landscape in a very scientific way," says Sullivan. "It wasn't Whac-A-Mole."

On patrol for nutria. Animal and Plant Health Inspection Service/USDA hide caption

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Animal and Plant Health Inspection Service/USDA

Over two decades, 70 employees worked on the project, scouring 250,000 acres of wetlands, including on the property of 500 private landowners. Some 14,000 nutria have met their maker as a result.

The last individual found in Maryland was in 2015; since then, the team has been working to verify that none remain before finally declaring victory this week.

"All you need is two, you know — one male, one female — and you've got the problem all over again," says Pradines Long.

The eradication of nutria in Maryland is a rare success story in the never-ending fight against invasive species.

Chris Moore, an ecosystem scientist with the Chesapeake Bay Foundation, calls the project a "shining example" of a successful environmental restoration partnership.

"When we look at the bay, there are numerous non-native invasive species that we work on that we know we're never going to have the luxury of eradicating," Moore says. Some 200 invasive species are thought to live in the Chesapeake watershed.

One reason for success in the case of nutria — besides large amounts of federal cash — is that the animals in Maryland were confined to the Delmarva Peninsula, bordered by the bay, the ocean, and up north, a narrow neck.

There is reason to fear nutria could return — populations exist in Virginia and they appear to be spreading north. The largest concentrations of nutria in the U.S. are along the Gulf Coast, though there are also nutria in the Pacific Northwest. Their range is limited by their intolerance for cold — their rat-like tails can get frostbite and fall off.

While nutria have not (yet) colonized the immediate D.C. area, there is habitat here that could be inviting for the giant rodents. For example, the area around Kingman Island, which has undergone years of marsh restoration.

"Wetlands like that would be very suitable for nutria," Sullivan says. "They would they would thrive there."

On the other hand, nutria don't generally migrate long distances, particularly if it means crossing inhospitable habitat, such as mid-Atlantic suburbia. Sullivan says the nutria team plans to transfer some of the resources used to fight nutria in Maryland to battling the rodents in Virginia.

"We are aware of how far they can move, and when they move, and and we will keep track of that. We're going to protect our southern border," he says.

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