Imported for fur, giant rodent now devastates US wetlands

Two hundred years ago, you wouldn't have been able to find them outside of South America. But since then, Nutria, one of the world's largest rodents, has taken over US. These rodents were initially brought to North America in the late 19th and early 20th centuries, primarily for fur farming, since their soft underfur was valuable in the fur trade.They first took hold when they were brought to Avery Island, a swampy coastal part of Louisiana 30 miles south of Lafayette and the production site for Tabasco brand hot sauce. Many were bred and kept in fur farms or released and regularly trapped.But when the fur market collapsed after the 1940s, many were released or escaped into the wild, establishing feral populations. The invasive creatures began damaging the environment, prompting state officials to take action to curb the population. The species was declared eradicated from California by the late ’70s.After that, officials did not detect any evidence of nutria in the state for years. Then, in 2017, they found a pregnant female in Merced County. Concerted eradication efforts have been underway ever since, with wildlife managers using visual observation surveys, motion-detection cameras and scat-detection sniffer dogs to locate and trap the creatures. Since the rediscovery, they’ve captured 7,841 nutria. The state says it’s now spending about $5 million per year on eradication efforts.Nutria: The illegal immigrantsNutria are such prolific breeders that one female can lead to 200 offspring in just a year. Unlike animals that take a year or longer to reach sexual maturity, nutria are ready to make babies at about four to six months. Females have anywhere from five to seven babies in a litter, and they have several litters every year.The rodents thrive in marine environments and quickly spread through rivers into coastal wetlands. They feed on the roots, leaves and stems of marsh plants which kills the vegetation instead of just trimming it. This destroys the root mats that hold the wetland soil together, leading to erosion, conversion of marsh into open water and loss of habitat for the native species.They also pose a risk to agricultural production and burrow into river banks, levees, and earthen dams, weakening infrastructure and accelerating bank collapse. In the United States, sugarcane and rice are the primary crops damagedby the nutria. Grazing on rice plants can significantly reduce yields, with severe localised loss. Other cropsdamaged by the nutria include corn, milo, sugar and table beets, alfalfa, wheat, barley, oats, peanuts, various melons, and a variety of vegetables. This depredation can lead to significant losses, especially for small farmers.They also pose a risk for public health and safety. The rodents can serve as hosts for several pathogens, including tuberculosis and septicemia, which can infect people, pets and livestock. In addition, they can carry parasites, such as blood flukes, tapeworms, liver flukes and a nematode known to cause a rash called "nutria itch."A major hurricane in the late 1940s helped spread nutria across coastal Louisiana and southeast Texas. Today, they’ve been reported in at least 40 states and parts of Canada. The Gulf Coast, especially Louisiana, has been hit hardest with Nutria having destroyed tens of thousands of acres of coastal marsh there. They have also spread to states like Maryland, Oregon, Washington, North Carolina and parts of California and Texas.In terms of identification, they are approximately two feet long, with a large head, short legs, and a stout body that appears hump-backed on land. They are dark brown, large, buck-toothed, web-footed rodents that can grow larger than 20 pounds.Control effortsWhile they may look cute, nutria cause serious damage to wetlands and crops like rice and sugarcane, leading to over $1 million in losses each year, when all impacts are combined.In the early 2000s, Louisiana's wildlife department tried encouraging people to eat Nutria by asking chefs to create recipes inspired by the rodent. There was even a campaign to bring their fur back in fashion, with a tagline: "Look fabulous while helping to save the wetlands."Taking a more direct approach, Maryland's wildlife department staged an eradication project in Chesapeake Bay's Blackwater refuge area, where tens of thousands were removed from the wetlands over a 15-year period. Within twoyears, the eradication team had nearly eliminated nutria from the Blackwater National Wildlife Refuge, and by 2006, they expanded the eradication zone into surrounding counties. By utilising specialised detector dogs, hair snares, and intensive trapping, federal and state agencies successfully eradicated nutria from Maryland.Louisiana runs a bounty program called the Coastwide Nutria Control Program, paying trappers per tail to reduce populations. The Louisiana Department of Wildlife and Fisheries offers a $6 per tail bounty to registered hunters and trappers to remove up to 400,000 nutria per season.