Teams work to eradicate marsh-destroying nutria rodents
WICOMICO RIVER, Md. — On the wall of the nutria eradication team’s drab office at the Blackwater National Wildlife Refuge, there’s a large whiteboard with names and numbers on it. They’re bets in a long-running pool: How many nutria will the team find in the marshes of the Wicomico River?
“The people that guessed 90, 70, 120, they’ve already lost,” says Stephen Kendrot as he drives along a Wicomico County back road.
It’s an overcast April afternoon with a long-awaited bit of warmth in the air. The nutria project leader is coming back from a site in Quantico, where four of his trappers are roaming the Wicomico River in jon boats. They’ve killed about 120 nutria there so far and found a few more this particular morning.
The river is the site of the final battle in the long-running quest to eradicate the beaver-like rodents (“nutria” means “otter” in Spanish) that have destroyed thousands of acres of the state’s wetlands over the past 40 years. It has taken longer than expected but the state is almost free of the invasive rodents.
Led by Kendrot, the project, administered by the U.S. Fish and Wildlife Service and implemented by the U.S. Department of Agriculture Wildlife Services, has cleared marshes up and down the Delmarva Peninsula over the past 12 years. On the Wicomico River, Kendrot’s team is after the last surviving colony.
Nutria feed on the roots and tubers of marsh plants, cutting up the root mat, a fibrous layer that holds the marsh together. Water then can flush in and out with the tide, eroding the mat. The marsh begins to sink and eventually turn to ponds.
Fish and wildlife that rely on the wetlands are displaced, and the ponds can’t support vegetation that could provide new habitats.
Marshes also act as filters to keep pollutants out of the bay, and they trap some carbon dioxide, said Doug Myers, Maryland senior scientist at the Chesapeake Bay Foundation, one of the non-governmental organizations that support the project.
Marsh loss also leaves the area more vulnerable to rising sea level, saltwater intrusion, land subsidence and groundwater withdrawal, Kendrot said.
“A marsh without nutria is somewhat resilient to all these other factors, but with nutria it doesn’t stand a chance,” he said.
The wetlands in the Chesapeake region have experienced more marsh loss than most other wetlands around the world, Kendrot said, and a study in the 1990s proved that, even with other contributing factors, nutria were largely responsible.
The semi-aquatic critters (Kendrot describes them as “a 20-pound rat with a scaly tail and buck teeth”) were brought to the U.S. from South America in the 1940s for the fur trade. They have established colonies in states throughout the Southeast and Pacific Northwest. In Louisiana, the nutria population reached 20 million in 20 years, creating a problem that is now too large for eradication.
The race against nutria in Maryland has cost between $16 million and $17 million total to date; the project receives between $1.3 million and $1.5 million a year, federal money funneled through the Fish and Wildlife Service.
Research for the project began in the mid-1990s, the program was launched in 2000, and eradication began as a pilot program in 2002. By 2010, the team was confident it could wipe the species from the state.
Their strategy combines traditional population management techniques with geographic information systems, GPS and mapping technology that help them track, trap and kill the nutria, and collected a huge amount of data on the creatures. The carcasses are studied for information like age, sex and pregnancies.
To date, the team has killed more than 13,000 nutria in Maryland, deeming 216,201 acres of the Delmarva Peninsula nutria-free with 11,357 acres to go. (Half of the peninsula’s 500,000 acres was clear of nutria from the start.)
Delmarva, which is bordered by the Chesapeake Bay, is “ground zero” for nutria, where they were first introduced in Maryland. Nine of its major watersheds were infested at the start of the project, Kendrot said.
There are probably between 200 and 500 nutria remaining in the area, Kendrot said. The goal is to get the population so low that the remaining few die off.
The 10-man team estimates that it can catch about 95 percent of nutria in a given area within four weeks, but the last 5 percent can take just as long as the first 95.
“When it gets down to the last, it gets more interesting. More challenging,” said Richard Elzey, Sr., who has been a wildlife specialist with the project since 2002.
The team will finish initial trapping by the end of 2014, but they won’t declare the state officially eradicated until 2017, after a period of surveillance to make sure new nutes don’t sneak in.
But the team’s true focus is on what happens after they leave the marsh.
“You can’t measure the efficacy of eradication by how many critters you kill. It’s what you leave behind that determines your success,” Kendrot said.
In some areas, like two sites on the Choptank River and in Somerset County, Maryland, the marsh recovered completely after the USDA team removed the nutria there, Kendrot said. But there are other places that can never fully recover.
At Blackwater Refuge, the last nutria was caught in December 2011. But the marsh, which was once so dense you could walk across it at low tide, is filled with water.
“Much of this marsh was lost by the ’70s and ’80s, so a lot of people that visit today don’t even make the connection that this isn’t a healthy ecosystem, it’s not what it should be [or] certainly what it used to be. They just see a beautiful lake with some geese swimming out in it,” Kendrot said.
In 2003, the Blackwater Refuge partnered with the Army Corps of Engineers and Baltimore’s National Aquarium, among others, to restore parts of the refuge, but it cost $300,000 for just six acres. There isn’t funding to restore the more than 5,000 acres of marsh that have been converted to open water, Kendrot said.
Elzey, who grew up near Blackwater and has watched its marshes disappear over the course of his life, said he wished the project had started in the 1970s. He trapped nutria when they were first introduced on the Delmarva Peninsula.
“I remember when it was just a creek running through. All marsh. All marsh, and I tracked it all,” he said.
Some animal cruelty groups oppose the eradication of invasive species, but there has been relatively little opposition to the nutria project compared to similar programs, Kendrot said.
Though the environment is more important than the nutria, the Bay Foundation’s Myers said he wished the dead animals didn’t go to waste.
But there is no market for nutria fur or meat, Kendrot said, as places like Louisiana learned when they tried to start up a commercial nutria meat market. Production costs would be high and Wildlife Services couldn’t ensure the safety of the meat for human consumption, anyway, he said.
Kendrot said the line of work is controversial but justified when considered in an environmental context.
“It’s a hard leap for some people to make. How can killing animals be considered conservation? But the project isn’t to kill nutria. It’s to save the marsh,” Kendrot said.