Nutria (Coypu)

Myocastor coypus

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Nutria in wetland habitat
Invasive South American nutria in wetland habitat.
John and Karen Hollingsworth, US Fish and Wildlife Service, Bugwood.org
Invasive
Family

Echimyidae (spiny rats) or Myocastoridae (nutrias) in the order Rodentia

Description

A robust, semiaquatic rodent with a large head, small ears, small front legs having feet with unwebbed toes, large hind legs having feet with webbing between the first 4 toes, and a round tail. The tail is 12–18 inches in length and is scaly and scantily haired. The general body color is brownish.

Similar species: The nutria somewhat resembles a large muskrat or a small beaver but can easily be distinguished by the round tail (the muskrat's is vertically flattened; the beaver's is horizontally flattened). The tail shape is difficult to see, however, when the animal is swimming.

Size

Total length: 30–42 inches (tip of nose to end of tail); weight: 15–25 pounds.

Habitat and conservation

Wetlands and marshes. Nutria cannot tolerate particularly cold winters, so they will probably not establish large populations in Missouri. They have been introduced globally for fur and for meat, but neither enterprise seems commercially viable. Where nutria establish large populations, they usually become pests, destroying wetlands, wrecking irrigation systems, gnawing on human property, and displacing native species.

Foods

These herbivores feed heavily on aquatic plants. It has been noted that in captivity, the nutria's food consumption is so great that keeping them fed them causes a nutria-farming operation to be unprofitable. They consume about 25 percent of their body weight each day.

image of Nutria Coypu Distribution Map
Distribution in Missouri

In Missouri, the nutria has been occasionally trapped in the southeastern part of the state. It was first reported in Missouri in 1943.

Status

Native to South America, nutria were brought to the U.S. and other countries for the fur market. They have been raised in captivity and have been released or escaped into the wild. Where they have no predators, nutria can overgraze wetlands, exposing their fragile organic soils. In the U.S., they are most numerous, and problematic, in the marshes of Louisiana, Maryland, and Oregon.

Life cycle

Nutria burrow into the banks of streams. There can be up to 3 litters a year. Gestation lasts 130 days. A litter comprises 1–13 young. Upon birth, the young have fur, have open eyes, are able to start eating vegetation within a few hours (thus they are prococial; the same term is used for the young of chickens, which hatch already feathered and are able to run around as soon as their feathers dry). The young nurse for 7–8 weeks, after which they leave home. They can breed as early as 3 or 4 months of age. They can potentially live for up to 6 years, but in the wild most only live for about 1 year, with 3 years the usual limit.

Human connections

Nutria are only one example of the problems caused when people introduce an exotic organism into a region where it doesn't belong. They have destroyed thousands of acres of marshland, and they damage irrigation systems, gnaw on Louisianans' homes, erode river banks, and displace native animals. People must go to great efforts and expense to control them.

Ecosystem connections

While they are not much of a problem in Missouri, nutria wreak havoc on marsh ecosystems in Louisiana and other southern states, where their foraging on emergent aquatic plants and digging into the banks for roots denudes large patches of ground, thus damaging wetland habitats. They are such a problem that in many places eradication efforts are under way.