Nutria Facts (Copyu)

The nutria or coypu (Myocastor coypus) is a large, semi-aquatic rodent. It resembles the beaver and muskrat, but a nutria has a rounded tail, while a beaver has a paddle-shaped tail and a muskrat has a flattened ribbon-like tail. Beavers and nutrias have webbed back feet, while muskrats lack webbed feet. While once raised for their fur, nutrias have become a problematic invasive species.

Description

The nutria looks like an unusually large rat. It has coarse brown outer fur and soft gray under fur, which is called nutria. It is distinguished from other species by webbed hind feet, a white muzzle, white whiskers, and large orange incisors. Female nutrias have nipples on their flanks so they can feed their young in the water. Adults range from 16 to 20 inches in body length, with 12 to 18 inch tails. The average adult weighs between 8 and 16 pounds, but some specimens weigh up to 37 pounds.

Habitat and Distribution

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Raccoon Facts

By Anne Marie Helmenstine, Ph.D.

Originally, the nutria was native to temperate and subtropical South America. It was hunted for food, but primarily for its fur. In the late 19th and early 20th century, numbers dwindled in the original habitat and fur ranchers brought the species to North America, Europe, Africa, and Asia. Accidentally or intentionally released nutrias rapidly adapted to new habitats and expanded their range. The range is limited by the mildness or severity of winters, as the nutria is susceptible to tail frostbite, which can lead to death. Nutrias always live close to water. Common habitats include river banks, lake shores, and other freshwater wetlands.

Diet

A nutria eats 25% of its body weight in food each day. For the most part, they dig out rhizomes and aquatic plant roots. They supplement their diet with small invertebrates, including mussels and snails.

Behavior

Nutrias are social animals that live in large colonies. They are excellent swimmers and can remain submerged up to five minutes. Nutrias are nocturnal; they forage at night and retire to burrows near the water to stay cool during the day.

Reproduction and Offspring

Because they live in warm climates, nutrias can reproduce year-round. Usually, a female has two or three litters per year. Nutrias line their nests with reeds and grasses. Gestation lasts 130 days, resulting in one to 13 offspring (usually five to seven). The young are born with fur and their eyes open. They nurse for seven to eight weeks, but also begin eating grass with their mother within a few hours after birth. Females can become pregnant again the day after they give birth. Females become sexually mature as early as 3 months of age, while males mature as early as 4 months of age. Only 20% of nutrias survive their first year, but they can live three years in the wild and up to six years in captivity.

Conservation Status

The International Union for Conservation of Nature (IUCN) classifies the nutria conservation status as "least concern." While nearly extinct and protected in its native habitat, the species is so invasive it is not considered to be at risk. Overall, the population size is decreasing due to eradication measures. Within its original habitat, the species is threatened by habitat degradation and persecution by ranchers.

Nutrias and Humans

Nutrias are kept for fur and meat and sometimes as pets. However, they are best known for the ecological threat they pose outside their natural range. They displace other species and cause significant erosion of wetland soil. Their feeding and burrowing opens wetlands to flooding, damages roads and bridges, and destroys crops. Since they are hunted as an invasive species, their fur is considered ethical and more sustainable than synthetic fur, while their meat is become increasingly popular.

Sources

• Bertolino, S.; Perrone, A.; ;Gola, L. "Effectiveness of coypu control in small Italian wetland areas." Wildlife Society Bulletin 33: 714-720, 2005.
• Carter, Jacoby and Billy P. Leonard: "A Review of the Literature on the Worldwide Distribution, Spread of, and Efforts to Eradicate the Coypu (Myocastor coypus)." Wildlife Society Bulletin, Vol. 30, No. 1 (Spring, 2002), pp. 162–175.
• Ford, Mark, and J. B. Grace. "Effects of Vertebrate Herbivores on Soil Processes, Plant Biomass, Litter Accumulation and Soil Elevation Changes in a Coastal Marsh." Journal of Ecology 86(6): 974-982, 1998.
• Ojeda, R.; Bidau, C.; Emmons, L. Myocastor coypus. The IUCN Red List of Threatened Species 2016: e.T14085A121734257. Errata version published in 2017.
• Woods, C. A.; Contreras, L.; Willner-Chapman, G.; Whidden, H.P. Mammalian Species: Myocastor coypus. American Society of Mammalogists, 398: 1-8, 1992.