The coypu (from Spanish coipú, from Mapudungun koypu; Myocastor coypus), also known as the nutria, is a large, herbivorous, semiaquatic rodent. Classified for a long time as the only member of the family Myocastoridae, Myocastor is now included within Echimyidae, the family of the spiny rats. The coypu lives in burrows alongside stretches of water, and feeds on river plant stems. Originally native to subtropical and temperate South America, it has since been introduced to North America, Europe, Asia, and Africa, primarily by fur farmers. Although it is still hunted and trapped for its fur in some regions, its destructive burrowing and feeding habits often bring it into conflict with humans, and it is considered an invasive species.
Description & appearanceThe coypu somewhat resembles a very large rat, or a beaver with a small tail. Adults are typically 4–9 kg (9–20 lb) in weight, and 40–60 cm (16–24 in) in body length, with a 30 to 45 cm (12 to 18 in) tail. It is possible for coypu to weigh up to 16 to 17 kg (35 to 37 lb), although adults usually average 4.5 to 7 kg (10 to 15 lb). They have coarse, darkish brown outer fur with soft dense grey under fur, also called the nutria. Three distinguishing features are a white patch on the muzzle, webbed hind feet, and large, bright orange-yellow incisors. The nipples of female coypu are high on her flanks, to allow their young to feed while the female is in the water.
A coypu is often mistaken for a muskrat, another widely dispersed, semiaquatic rodent that occupies the same wetland habitats. The muskrat, however, is smaller and more tolerant of cold climates, and has a laterally flattened tail it uses to assist in swimming, whereas the tail of a coypu is round. It can also be mistaken for a small beaver, as beavers and coypus have very similar anatomies. However, beavers' tails are flat and paddle-like, as opposed to the round tails of coypus.
Distribution & habitatNative to subtropical and temperate South America, it has since been introduced to North America, Europe, Asia, and Africa, primarily by fur ranchers. The distribution of coypus outside South America tends to contract or expand with successive cold or mild winters. During cold winters, coypus often suffer frostbite on their tails, leading to infection or death. As a result, populations of coypus often contract and even become locally or regionally extinct as in the Scandinavian countries and such US states as Idaho, Montana, and Nebraska during the 1980s. During mild winters, their ranges tend to expand northward. For example, in recent years, range expansions have been noted in Washington and Oregon, as well as Delaware.
According to the U.S. Geological Survey, nutria were first introduced to the United States in California, in 1899. They were first brought to Louisiana in the early 1930s for the fur industry, and the population was kept in check, or at a small population size, because of trapping pressure from the fur traders.The earliest account of nutria spreading freely into Louisiana wetlands from their enclosures was in the early 1940s; a hurricane hit the Louisiana coast for which many people were unprepared, and the storm destroyed the enclosures, enabling the nutria to escape into the wild. According to the Louisiana Department of Wildlife and Fisheries, nutria were also transplanted from Port Arthur, Texas, to the Mississippi River in 1941 and then spread due to a hurricane later that year.
Coypus are found most commonly in freshwater marshes, but also inhabit brackish marshes and rarely salt marshes. They either construct their own burrows, or occupy burrows abandoned by beaver, muskrats, or other animals. They are also capable of constructing floating rafts out of vegetation.
FoodBesides breeding quickly, each coypu consumes large amounts of vegetation. An individual consumes about 25% of its body weight daily, and feeds year-round. Being one of the world's larger extant rodents, a mature, healthy coypu averages 5.4 kg (11 lb 14 oz) in weight, but they can reach as much as 10 kg (22 lb). They eat the base of the above-ground stems of plants, and often dig through the organic soil for roots and rhizomes to eat. Their creation of "eat-outs", areas where a majority of the above- and below-ground biomass has been removed, produces patches in the environment, which in turn disrupts the habitat for other animals and humans dependent on marshes.
ReproductionCoypus can live up to six years in captivity, but individuals uncommonly live past three years old; according to one study, 80% of coypus die within the first year, and less than 15% of a wild population is over three years old. Male coypus reach sexual maturity as early as four months, and females as early as three months; however, both can have a prolonged adolescence, up to the age of 9 months. Once a female is pregnant, gestation lasts 130 days, and she may give birth to as few as one or as many as 13 offspring. They generally line nursery nests with grasses and soft reeds. Baby coypus are precocial, born fully furred and with open eyes; they can eat vegetation with their parents within hours of birth. A female coypu can become pregnant again the day after she gives birth to her young. If timed properly, a female can become pregnant three times within a year. Newborn coypus nurse for seven to eight weeks, after which they leave their mothers.