NUTRIA

(Myocastor coypus)

Nutria are swimming rodents similar to beavers and muskrats with long, thin tails. These rodents have not been sited in Pennsylvania but a risk of invasion is possible from neighboring states.

ORIGIN
South America.

HABITAT
Nutria inhabit fresh and brackish marshes, rivers, bayous, farm ponds, freshwater impoundments, drainage canals, swamps and various other types of wetlands. Although now found in more than 15 U.S. states, their native range includes Argentina, Chile, Bolivia, Uruguay, Paraguay and southern Brazil.

IDENTIFICATION
Nutria may weigh up to 9 kg (20 lb), but on average weigh between 5.5 to 7 kg (12-15 lb), with males slightly larger than females. They have dense, grayish underfur overlaid by long glossy guard hairs that vary in color from dark brown to yellowish brown. Their large front teeth are yellow-orange to orange-red on the outer surface. The forepaws have four well-developed clawed toes and one non-functional toe. The hind feet have five clawed toes: four webbed and one that hangs free.

SPREAD
Nutria were intentionally brought to America for fur ranching. During World War II fur prices collapsed and many ranchers lost interest and released animals into wild marshes where they quickly became established. Nutria are now reported in every Maryland Eastern Shore county and are found from Bombay Hook National Wildlife Refuge in Delaware through the Delmarva Peninsula to Virginia's Eastern Shore. They have also been reported on the western shore of Maryland in the Potomac and Patuxent Rivers and in Virginia as far south as the Northern Neck near the Rappahanock River.

Nutria are highly prolific and breed all year. Litters average four to five young; however, nutria can have up to thirteen young per litter and may have three litters per year. Young are born fully furred and active. They can swim and eat vegetation shortly thereafter, still feeding on mother’s milk for up to eight weeks. Within five days of life, nutria can survive away from the mother.

As an example of their proliferation: in 1938, 20 individual nutria were introduced into Louisiana and within 20 years, the nutria population exceed 20 million animals. By 1962, the nutria had replaced the native muskrat as the leading furbearer in Louisiana.

2010 Distribution of Nutria

IMPACTS
Nutria feed primarily on marsh vegetation that extends above the waterline. They are opportunistic feeders with an extremely varied diet. They consume about 25 percent of their body weight daily. Nutria use their beaver-sized incisors and powerful forefeet to dig under the marsh surface to feed directly on the root mat, leaving the marsh pitted with holes and deep swim canals. Areas devoid of vegetation are called "eat outs" and the swim canals are called "runs."

Nutria can easily convert productive grassy marsh into unproductive open water by attacking the very structure that holds the marsh together, the vegetative root mat. Once the nutria chew through the mat and expose the mud, tidal currents and wave action lead to erosion. The marsh surface sinks and the vegetation is lost to flooding. Areas destroyed by nutria become permanent, open water ponds.

In addition to destroying areas of marshland, they compete for habitat and food with native muskrat species and carry a parasite that causes marsh itch in humans.

PREVENTION AND CONTROL
Louisiana has instituted a Nutria Control Program (along with promotion of nutria meat as a high protein low fat food source). “The Coastwide Nutria Control Program” consists of an economic incentive payment of $4 per nutria tail delivered by registered participants to collection centers established in coastal Louisiana. The goal of the Program is to encourage the harvest of up to 400,000 nutria annually from coastal Louisiana.

To read more, view the Pennsylvania Sea Grant Nutria fact sheet.

FOR MORE INFORMATION ON NUTRIA

• Chesapeake Bay Program- Nutria General Information
• Species Profile- Nutria
• Wildlife and Fisheries of Louisiana
• Florida State University
• Nutria Damage Prevention and Control Methods

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