# Nutria — Facts, Threats & Conservation

*Myocastor coypus (Molina, 1782) — family Myocastoridae*

> The nutria or coypu (Myocastor coypus) is a large semiaquatic rodent Least Concern in native South America but listed among the world's worst invasive species after fur-farm escapes — it destroys wetlands, undermines banks and was eradicated from Britain by 1989.

**IUCN status:** Least Concern in native South America — among the world's worst invasive mammals elsewhere  ·  **WARN range:** Native: South America, Invasive: North America, Europe, Asia and Africa

## Quick facts
| Fact | Value |
| --- | --- |
| Body length | About 40–65 cm plus tail |
| Weight | About 5–9 kg |
| Diet | Aquatic vegetation — roots and stems |
| Habitat | Freshwater marshes, rivers, reed beds |
| Lifespan | About six to eight years in the wild |
| Native range | South America |
| Britain status | Eradicated by 1989 |

## Scientific classification
- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Mammalia
- **Order:** Rodentia
- **Family:** Myocastoridae
- **Genus:** Myocastor
- **Species:** Myocastor coypus

## Conservation status
- **Status:** Least Concern in native range — invasive elsewhere
- **Population:** Abundant in South America; variable in introduced range
- **Trend:** Stable in native range; managed or increasing in many introduced areas
- **Assessed:** 2016
- **CITES:** Not listed
- Listed among the 100 world's worst invasive alien species. EU invasive species of Union concern. Britain eradicated coypu by 1989; Louisiana and other regions fund ongoing control.

## Key facts: Nutria
- Nutria are Least Concern in South America but among the 100 worst invasive species globally.
- Fur-farm escapes and releases established populations across North America, Europe and Asia.
- Feeding and burrowing destroy reed beds, river banks and flood infrastructure.
- Britain eradicated coypu by 1989 after a ten-year trapping campaign removing roughly 35,000 animals.
- Louisiana and Maryland run ongoing control programmes costing millions — Maryland declared eradication in 2022.
- EU invasive species of Union concern since 2016 — import and release banned.
- Same fur-trade introduction pattern as American mink and muskrat.

## Native rodent, global invader
In the wetlands of Argentina, Chile, Uruguay and southern Brazil, coypu are a normal part of the food web — prey for caimans, jaguars and raptors, grazing aquatic vegetation in balance with the ecosystem. The IUCN lists Myocastor coypus as Least Concern because populations remain secure across native range.

Outside South America the same animal destroys habitat. Nutria consume roughly a quarter of their body weight in vegetation daily, preferring roots and stems of marsh plants. Reed beds that took years to establish can be stripped in a season. Burrows in river banks and levees cause collapses and flooding. The damage pattern matches what island ecosystems suffered from introduced mammals — a theme WARN covers in extinct profiles such as the dodo, where introduced pigs and rats did to nesting birds what nutria do to wetlands.

## Fur farms and the escape epidemic
Nutria fur was fashionable in the early twentieth century. Farms across North America, Europe and Japan held captive breeding stock; when fur prices collapsed — notably in the 1940s in Louisiana — ranchers released animals they could no longer afford to feed. Each release seeded a population with high reproductive output: females can produce two litters a year with four to six young, and reach breeding age within months.

Spread followed river systems and coastal marshes with suitable vegetation. In East Anglia, coypu established after 1920s farm escapes and took decades to remove. In Louisiana, nutria became so abundant that wetland loss accelerated coastal land subsidence — vegetation that held marsh soil together was eaten faster than it could regenerate.

## Britain's eradication — a completed campaign
Coypu damaged sugar beet, cereals and reed beds across Norfolk and Suffolk and burrowed into flood defences. Early trapping in the 1960s failed because effort was misdirected; a cold winter in 1962–63 reduced numbers temporarily but did not eliminate them. The final campaign from 1981 deployed 24 trappers full-time for ten years, using cage traps and population modelling to work inward from range edges.

An incentive scheme paid trappers a bonus for early eradication — addressing the problem that successful trappers would otherwise work themselves out of employment. The last wild coypu was caught in 1989. Britain remains coypu-free, demonstrating that mainland eradication is possible with sustained resources, accurate population biology and political commitment — conditions rarely replicated elsewhere.

## Ongoing battles in Louisiana and the Chesapeake
Louisiana runs one of the largest nutria control programmes in the world, paying bounties for tails during open seasons and linking harvest to wetland restoration funding. The Chesapeake Bay Nutria Eradication Project removed the last nutria from Maryland by 2022 — a milestone for Atlantic coastal marsh recovery. Other US states and European countries continue control without eradication as the goal.

Japan's nutria population, introduced in 1939 for food and fur, persists despite decades of control — a contrast with Britain's success that reflects different geography, climate and programme duration. The EU banned coypu as an invasive species of Union concern in 2016. Where nutria remain, management is permanent rather than a one-time fix.

## What WARN does
WARN publishes free, sourced species education for invasive-species cases where global IUCN status misleads. Nutria are Least Concern in the Pantanal and a wetland crisis in Louisiana — fur farming moved the problem, and control costs persist decades later.

If this guide helps you understand wildlife and the pressures it faces, a gift to WARN supports habitat protection and free public education in our partner countries.

## Frequently asked questions: Nutria
### What do nutria eat?
Aquatic and semi-aquatic vegetation — roots, stems and leaves of reeds, rushes and marsh plants. They consume roughly a quarter of their body weight daily and can strip reed beds that support nesting birds and fish.

### Where do nutria live?
Native to subtropical and temperate South America. Introduced populations occupy wetlands across North America, Europe, Asia and parts of Africa — anywhere with slow water, banks to burrow and vegetation to graze.

### Are nutria dangerous to humans?
Nutria are shy and usually flee. They can bite if cornered and may carry parasites transmissible through contaminated water, but unprovoked attacks on people are not documented. The main harm is ecological and infrastructural.

### How long do nutria live?
About six to eight years in the wild where predators and control allow; up to about ten years in captivity. High reproduction means populations turn over quickly.

### How big is a nutria?
Body length about 40–65 cm, tail about 30–45 cm. Adults typically weigh about 5–9 kg — beaver-sized, though the tail is round rather than flat.

### Are nutria still in Britain?
No. The last wild coypu was removed from East Anglia in 1989 after a ten-year eradication campaign. There have been no confirmed wild populations since, though occasional escapees are reported and investigated.

### What is the difference between nutria and muskrat?
Both are semiaquatic rodents introduced for fur, but nutria are much larger — up to about 9 kg versus roughly 1.8 kg for muskrats — with round tails and orange incisors. Both burrow into banks; nutria graze vegetation more destructively at scale.

## Sources
- [IUCN Red List — Myocastor coypus](https://www.iucnredlist.org/species/14085/115112242)
- [IUCN Global Invasive Species Database — coypu](https://iucngisd.org/gisd/species.php?sc=99)
- [Science — Vanquishing Nutria: Britain's eradication (1999)](https://doi.org/10.1126/science.285.5435.1838)

---
Full guide: https://worldanimalrescuenetwork.org/wildlife-guides/nutria