Nutria have bright orange teeth, stained by iron in their enamel
The nutria, or coypu, is a big South American water rodent with orange-yellow incisors coloured by iron, webbed hind feet and teats placed high on the female's sides so young can nurse while she swims. Fur farmers spread it to three other continents, where escaped populations now chew through wetlands.
Myocastor coypus is a plant-eating, semiaquatic rodent from subtropical and temperate South America. Its genus name combines Greek words for mouse and beaver. Long placed alone in its own family, it is now grouped with the spiny rats, and DNA shows its closest relatives are the painted tree-rats. Juan Ignacio Molina first described it in 1782, filing it under the mouse genus, before Robert Kerr coined Myocastor in 1792.
Its names cause confusion. North Americans call it nutria, from the Spanish for otter, but in most Spanish-speaking countries nutria means the otter itself. So South Americans and Britons tend to say coypu, from the Mapudungun language. The French call it ragondin, Dutch speakers beaver-rat, Swedes swamp-beaver, and Italians sell its fur as castorino, little beaver.
Adults typically weigh 4 to 9 kilograms, with bodies 40 to 60 centimetres long and a thin, nearly hairless tail of 30 to 45 centimetres, though exceptional animals reach 16 or 17 kilograms. The coat has three layers, including long guard hairs and a soft, dense grey underfur, which is the part the fur trade calls nutria. A white patch on the muzzle and whiskers about four inches long complete the look. Males and females are indistinguishable at a glance.
At home, nutria dig burrows beside water, feed on aquatic and bankside plants and help spread plant seeds and spores through wetland food webs. Elsewhere the story differs. Introduced to North America, Europe and Asia mainly by fur farmers, feral populations damage wetland vegetation and undermine embankments and other structures with their burrows, and the species is listed as invasive in several countries. The subspecies most often introduced is believed to come from the subtropical north of its native range. Some populations carry germs such as Leptospira, although how much this matters for human health appears limited and varies by region.
Source: Nutria
