Invasive Species: Nutria
Introduction | A Historical Nuisance | Impacts on the Environment | Prevention & Control Measures | Resources
A Historical Nuisance
It is the quality of nutria fur that first inspired people to bring them from South America (Argentina and Chile) to North America in the late 1800s. Fur-farming attempts failed due to high mortality rates and low reproductive success in captivity. Accidental and intentional releases led to the establishment of wild populations of nutria in at least 15 other states. Sightings have been reported in 40 states and three Canadian provinces. While nutrias have made their way to many watersheds in the United States, Louisiana has the unfortunate distinction of hosting the largest wild population of this animal. Recent estimates put the population of nutrias in southeast Louisiana as high as 6,000 animals per square mile.
Nutrias have a body similar to a large rat and a head that resembles a beaver. They are easily identified by their hairless round tail and four large front teeth that are bright orange in color. Their soft, grayish-brown underfur is covered by coarse brown guard hairs.
The hind feet of a nutria are webbed making them excellent swimmers. Full-grown, nutrias weigh between 12 to 16 pounds. Nutrias are vegetarians and will graze upon a variety of wetland plants, including water hyacinths (another exotic species), cypress seedlings, cordgrass and duckweed. Nutria have also been known to feed on lawn grasses and shrubs in residential areas.
This large population of nutrias got its start in 1937 on Avery Island, the home of Tabasco hot-sauce magnate E. A. McIlhenny when McIlhenny imported a handful of nutria to begin a fur farm. The animals readily adapted to their new home and successfully bred in captivity. Hurricanes along the Louisiana coast in 1939 and 1940 have been given reponsibility for the escape of these animals from several fur farms in the area, including McIlhenny's. It was hoped that the alligator, the only natural predator of nutria, would keep the population in check, but within two years nutria had spread to Texas and Mississippi. The nutria population grew to tremendous numbers, an estimated 20 million animals by the late 1950s (Lowry, 1974), which supported a vibrant trapping and fur industry for several decades in Louisiana. Between 1962 and 1986 Louisiana trappers harvested more than 1 million nutria each year. Around 1986, the fur industry in Louisiana fell on economic hard times, making trapping of nutria economically unattractive. At the same time, reports of nutria damage in the coastal wetlands began to escalate.
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