They feed on river plants, and waste close to 90% of the plant material while feeding on the stems.
The coypu (from the Mapudungun, koypu) or nutria (Myocastor coypus), is a large, herbivorous, semiaquatic rodent and the only member of the family Myocastoridae. Originally native to temperate South America, it has since been introduced to North America, Europe, Asia, and Africa, primarily by fur ranchers.