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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.


  • Dense, gray undercoat guarded by long, coarse hairs that vary in color from yellowish-brown to dark brown
  • Large, bright orange front teeth
  • Short legs with large, webbed hind feet that can be nearly 6 inches long
  • Thin tail that can be 12-18 inches long
  • Small eyes and ears that are located high on the head
  • Grows to 2 feet long and weighs 12-15 pounds, but can weigh as much as 20 pounds


  • Lives in fresh and brackish marshes, swamps, impoundments, farm ponds and other wetlands
  • Semi-aquatic, meaning it spends time both on land and in the water
  • Primarily nocturnal, feeding around midnight and resting during the day


  • 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
  • Eradicated from Blackwater National Wildlife Refuge on Maryland’s Eastern Shore in 2004 after contributing to alarming losses of marshes at the refuge
  • Also reported in the Potomac and Patuxent rivers in Maryland and in the Rappahannock River and Back Bay National Wildlife Refuge in Virginia
  • Native to South America, including Argentina, Bolivia, Chile, Paraguay, Uruguay and southern Brazil


  • Feeds on roots, rhizomes, tubers and young shoots of marsh plants such as cattails, saltmeadow cordgrass and Olney threesquare
  • Will also eat crops and lawn grasses near its marsh habitat
  • Consumes approximately 25 percent of its body weight every day
  • 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, producing 2-3 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 128-130 days
  • Each litter averages 4-5 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 7-8 weeks and remain with their mother for about 10 weeks
  • Reaches sexual maturity at 4-6 months old

Other Facts:

  • Nutriais a Spanish word for “otter.”
  • Also known as coypu
  • Can be mistaken for muskrats or beavers. Nutria can be distinguished by their rounded tail and orange front teeth.
  • During winter, nutria have been observed gathering in piles to keep warm.

Sources and Additional Information:


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