Nutria
Myocastor coypus

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.

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Nutria. (Photo courtesy of Steve Kendrot/USDA APHIS Wildlife Services)

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Appearance

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.

Feeding

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.

Predators

No natural predators in the Chesapeake Bay watershed.

Voice

Nutria are social animals that can often be heard calling to each other in mooing or pig-like grunts. Their vocalizations are generally used to indicate feeding times or as a way to attract mates.

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.

Did you know?

  • Nutria is a Spanish word for “otter.” They are also known as coypu.
  • They are semi-aquatic, spending time both on land and in the water. Primarily nocturnal, feeding around midnight and resting during the day.
  • 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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