Coypu (Myocastor coypus) — identification, habitat & look-alikes

The nutria, also called the coypu, is a large South American rodent that has become a serious wetland pest in the U.S., especially along the Gulf Coast. It looks like a big rat with a round, nearly hairless tail and bright orange front teeth. The name "nutria" comes from the Spanish word for otter.

Appearance

Appearance: Body 16–24 in (40–60 cm) long plus a 12–18 in (30–45 cm) tail; adults usually weigh 9–20 lb (4–9 kg). Brown fur, white whiskers and muzzle, large orange-yellow incisors, and partly webbed hind feet.

Look-alikes

American beaverCastor canadensis

A beaver is much bigger, with a broad, flat, paddle-shaped tail and fully webbed hind feet. A nutria's tail is round and rat-like.

Why they get mixed upBoth are large brown swimming rodents with orange teeth.

MuskratOndatra zibethicus

A muskrat is much smaller, about 2–5 lb (0.9–2.3 kg), and its tail is flattened side to side. A nutria has white whiskers and a round tail.

Why they get mixed upBoth live in marshes and swim with only the head showing.

Where it lives

Typical habitats: Freshwater marshes
Bayous and canals
Farm ponds
Coastal marshes
Range: Native to southern South America. Brought to the U.S. for fur farming starting in 1899; it has been recorded in about 30 states, with well-known populations along the Gulf Coast in Louisiana and Texas and in Washington and Oregon.
Preferred conditions: Prefers shallow edges of freshwater marsh with dense plants, but also uses bayous, rivers, drainage canals, swamps, and brackish marshes. Severe cold is thought to be the main limit on how far north it can spread.

Behavior

Diet: Mostly wetland plants; it digs up roots, rhizomes, and tubers, especially in winter, and eats about a quarter of its body weight each day.
Activity: Mostly active at night when food is plentiful, but often out by day when food runs short. A strong swimmer.

Life cycle

Gestation: About 130 days.
Litter size: 1–13 young, about 4 on average. Females can breed again right after giving birth.
Time to maturity: Can breed as young as 3–4 months old.
Lifespan: Wild nutria rarely live past 3 years; captive ones can reach about 6.

Conservation

IUCN Red List: LCLeast ConcernLow risk of extinction
Threats: Heavy feeding strips marsh plants and can turn marsh into open water, and burrows weaken levees, canals, roads, and foundations.

Culture and stories

Culture and stories: Nutria were in Louisiana for fur farming by the 1930s, and releases around 1940 let them take hold along the coast. When demand for nutria fur faded in the 1980s, trapping dropped off and numbers grew.

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