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Nutria (myocastor coypus)


Photo credit: Stanze,

(Myocastor coypus)

Report this Species!

If you believe you have found this species anywhere in Pennsylvania, please report your findings to iMapInvasives by submitting an observation record.

Species at a Glance

The nutria, also called the coypu, is a large, semi-aquatic rodent that was brought to the United States as an important resource for the fur farming industry. When the fur market collapsed in the 1940s, nutria were released into the environment, impacting thousands of acres of coastal wetlands as they grazed on native marsh vegetation and burrowed into dikes, levees, and littoral banks.


The nutria is a furry, swimming rodent that can weigh 7-9 kg (15-20 lbs) and reach 0.6 m (2 ft) long. It is light to dark brown with a large head, short legs, and a stout body that appears hump-backed on land. Its large front teeth can range in color from yellow to orange-red. It is highly adapted for aquatic ecosystems with partially-webbed hind feet; a long round tail; and eyes, ears, and nostrils that are set high on the head, allowing them to stay above the waterline while swimming.

Similar Species

Often mistaken for beavers and muskrats, the best way to distinguish the nutria is to look at the size, tail, and head. An adult nutria is about one-third the size of an adult beaver and five to eight times larger than an adult muskrat. A beaver has a large, broad, flat tail, and a muskrat has a long narrow tail that whips back and forth when swimming. The nutria has a heavy rat-like tail thinly covered in bristly hairs that trails smoothly behind it when swimming.


This species has adapted to a wide range of freshwater, estuarine, and saltwater habitats, but is usually found in and along lakes, marshes, and slow-moving streams. It prefers habitats with an abundance of emergent vegetation, small trees, shrubs, and other succulent vegetation along the banks. It can also be found under buildings, in overgrown lots, on golf courses, and in storm drains.


The nutria was first imported into the United States for nutria “ranching”, which became very popular in the 1930s. After the collapse of the fur market, thousands of nutria were released by ranchers who could no longer afford to keep them, or they escaped into the wild. Other than fur harvesters, alligators are the only significant predator of the nutria; however, even in areas with an abundance of alligators, this species can thrive if habitat conditions are suitable.


Native to South America, the nutria was introduced into the United States in 1899. Accidental and intentional release of this species allowed it to become established in at least 16 states, including Delaware, Maryland, North Carolina, and Virginia in the Mid-Atlantic Region.


Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.

Environmental Impacts

The nutria feeds heavily on marsh grasses and aquatic vegetation, reducing diversity and abundance of native plants and impacting valuable fish and wildlife habitats. Intense grazing can destroy roots mats, increasing erosion and resulting in barren mudflats and open water. The nutria can also impact important crops like sugarcane, rice, corn, and various fruits and vegetables, resulting in substantial financial losses for farmers. Its burrowing behavior can weaken the foundations of reservoirs, dams, buildings, road beds, and flood control levees. It can also serve as hosts for several pathogens and parasites which can contaminate drinking water supplies and swimming areas.


Information for this species profile comes from the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016).

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