Myocastor coypus
coypu
(Also: nutria)

Myocastor coypus is native to South America. Its distribution ranges from middle Bolivia and southern Brazil to Tierra del Fuego. As a result of escapes and liberations from fur farms, feral populations now occur in Europe, Asia, and North America. Woods et al. (1992)

Nutrias inhabit marshes, lake edges, and sluggish streams, especially in areas with emergent or succulent vegetation along the banks. They are chiefly lowland animals, but may range up to 1,190 meters in the Andes. Although they generally prefer fresh water, the population of the Chonos Archipelago in Chile occurs in brackish and salt water. Greer (1966), Nowak (1991).

Myocastor coypus looks like a large, robust rat. Its body is highly arched, and the head is large and almost triangular. The ears and eyes are small and are located in the upper part of the head. The incisors are broad, with orange-pigmented anterior surfaces. The legs are short. The hind feet are much longer than the forefeet, and contain five digits; the first four are connected by webbing, and the fifth is free. The forefeet have four long, flexible, unwebbed digits and a vestigial thumb. The tail is long and rounded. Females have four pairs of thoracic mammae that are situated well up on the sides of the body. The pelage consists of two kinds of hair, soft dense underfur, and long coarse guard hairs that vary from yellowish brown to reddish brown. The underfur is dark gray, and it is denser on the abdomen. The chin is covered by white hairs, and the tail is scantily haired.

Males are generally larger than females. The length of the head and body is 521 mm (472 - 575), and the length of tail is 375 mm (340 - 405).

Gosling (1977), Nowak (1991); Woods et al. (1992).

The potential longevity of Myocastor coypus is 6 years.

Myocastor coypus is semiaquatic. Individuals can remain submerged for more than 10 minutes. They are most active at night. Most of the active period is spent feeding, grooming, and swimming. They commonly make platforms of vegetation, where they feed and groom themselves. For shelter nutria construct burrows, which may be a simple tunnel or a complex system containing passages that extend 15 meters or more and chambers that hold crude nests of vegetation. Nutria also make runways through the grass and wander within a radius of about 180 meters of their dens. Myocastor coypus is highly gregarious. Groups usually consists of 2 - 13 animals and are composed of related adult females, their offspring, and a large male. Young adult males are occasionally solitary. Generally, nutrias remain in one area throughout their lives.

Nowak (1991), Doncaster and Micol (1989), Woods et al. (1992).

Home Range

Home range is fairly constant in spite of population density. The average home range for female nutria is 2.47 ha, while for males it is 5.68 ha.

Nutria probably communicate through tactile, chemical, and auditory channels. Their eyesight is limited.

Nutria are herbivorous. The diet consists largely of aquatic vegetation: stems, leaves, roots, and even bark. They may use logs or other floating objects as feeding platforms. Woods et al. (1992).

In spite of been intensively trapped for its fur, nutria are considered pests in some places because their burrows damage dikes and irrigation facilities. Burrows sometimes penetrate or weaken the river banks. Myocastor coypus may raid rice and other cultivated crops, and they compete with native fur bearing animals. Nowak (1991), Woods et al. (1992).

A demand for nutria fur developed in the early 19th century and has continued to the present. For this reason, nutria have been introduced almost worldwide. For example, Argentina exported 20,000,000 pelts between the years 1972 and 1981, obtained both from wild and captivity animals; and in Louisiana (USA) nearly 1,000,000 pelts were harvested during the 1986 - 1987 trapping season. Nutria have also been hunted by people for meat. Mares et al. (1989), Woods et al. (1992).

Mares et al. al. (1989) suggests that nutria are rapidly disappearing in many rivers and lakes of Argentina.

The higher-level classification of nutria is controversial. Though nutrias are related to echimyids and capromyids, several morphological differences argue against uniting myocastorids with either of these taxa in the same family. Therefore, currently nutria are placed in their own family, Myocastoridae. Woods and Howland (1979), Woods et al. (1992).