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Myocastor coypus

Nutria can be distinguished by their large, bright orange front teeth. (Peleg/Wikimedia Commons)
Nutria can be distinguished by their large, bright orange front teeth. (Peleg/Wikimedia Commons)

Nutria are large, brown, semi-aquatic rodents that live in marshes and wetlands on the Delmarva Peninsula and other parts of the Chesapeake Bay watershed. They are an invasive species.


The nutria has a dense, gray undercoat guarded by long, coarse hairs that vary in color from yellowish-brown to dark brown. It has large, bright orange front teeth and small eyes and ears that are located high on its head. It has short legs with large, webbed hind feet that can be nearly 6 inches long. Its thin tail can be 12 to 18 inches long. Nutria grow to 2 feet long and weigh 12 to 15 pounds, but can weigh as much as 20 pounds.


Fresh and brackish marshes, swamps, impoundments, farm ponds and other wetlands. Semi-aquatic, spending time both on land and in the water. Primarily nocturnal, feeding around midnight and resting during the day.


Native to South America, including Argentina, Bolivia, Chile, Paraguay, Uruguay and southern Brazil. Found throughout the Delmarva Peninsula, concentrated in Dorchester County, Maryland, but ranging from Bombay Hook National Wildlife Refuge in Delaware to Virginia’s Eastern Shore. Reported in the Potomac and Patuxent rivers in Maryland and in the Rappahannock River and Back Bay National Wildlife Refuge in Virginia.


The nutria feeds on roots, rhizomes, tubers and young shoots of marsh plants such as cattails, saltmeadow cordgrass and Olney threesquare. It will also eat crops and lawn grasses near its marsh habitat. A voracious eater, it consumes approximately 25 percent of its body weight every day. It uses its large front teeth and powerful feet to dig into the marsh and feed on the root mat, causing significant erosion and damage to marshes.


No natural predators in the Chesapeake Bay watershed.

Reproduction and Life Cycle:

Reproduction peaks in late winter, early summer and mid-autumn. Highly prolific breeders, nutria produce 2 to 3 litters per year. Some nutria dig shallow dens into the mud of marsh banks. Dens have a nesting chamber inside. Female nutria are pregnant for 128 to 130 days. Each litter averages 4 to 5 young nutria, though some litters can have up to 13 young. Females can breed again within two days of giving birth. Young nutria mature quickly. They are able to swim and eat plant material one day after birth and can live on their own after just five days of nursing. Most young nutria continue to nurse for 7 to 8 weeks and remain with their mother for about 10 weeks. Nutria reach sexual maturity at 4 to 6 months old.

Other Facts:

  • Nutria is a Spanish word for “otter.” They are also known as coypu.
  • Nutria can be distinguished from muskrats and beavers by their rounded tail and orange front teeth.
  • During winter, nutria have been observed gathering in piles to keep warm.
  • Nutria were eradicated from Blackwater National Wildlife Refuge on Maryland’s Eastern Shore in 2004 after contributing to alarming losses of marshes at the refuge.

Sources and Additional Information:


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