The coypu (from Spanish coipú, from Mapudungun kóypu), (Myocastor coypus), also known as the river rat or Nutria, is a large, herbivorous, semiaquatic rodent and the only member of the family Myocastoridae. Originally native to subtropical and temperate South America, it has since been introduced to North America, Europe, Asia, and Africa, primarily by fur ranchers. Although it is still valued for its fur in some regions, its destructive feeding and burrowing behaviors make this invasive species a pest throughout most of its range.

Coypus live in burrows alongside stretches of water. They feed on river plants, and waste close to 90% of the plant material while feeding on the stems.

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