Myocastor coypuscoypu(Also: nutria)

Geographic Range

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).

  • Range elevation
    1190 (high) m
    3904.20 (high) ft

Physical Description

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).

  • Sexual Dimorphism
  • male larger
  • Range mass
    5.000 to 10.000 kg
    11.01 to 22.03 lb
  • Range length
    472 to 575 mm
    18.58 to 22.64 in


Myocastor coypus is polyestrus. The length of the estrus cycle is variable; intervals between cycles may range from 5 to 60 days. Nutrias are nonseasonal breeders. The gestation period is long, varying from 127 to 139 days. There is a post-partum estrus within 2 days of parturition. Mean litter size in general varies from three to six, although it may range from 1 to 13. Factors affecting reproductive potential of nutria are food type and availability, weather conditions, predators and disease.

Sexual maturity is attained when young are only 6 months old.

Gosling (1981), Gosling and Baker (1981), Woods et al. (1992).

  • Breeding interval
    Nutrias may breed repeatedly throughout the year, the interval will depend on climate and nutritional status of the mother.
  • Breeding season
    Breeding may occur throughout the year.
  • Range number of offspring
    3 to 12
  • Average number of offspring
  • Average number of offspring
  • Range gestation period
    126 to 141 days
  • Average weaning age
    54 days
  • Average age at sexual or reproductive maturity (female)
    6 months
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    152 days
  • Average age at sexual or reproductive maturity (male)
    6 months
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    152 days

Females care exclusively for the young. Newborns are fully furred, and have their eyes open. They weigh approximately 225 grams each, and rapidly gain weight during the first 5 months. The lactation period extends for about 8 weeks.

  • Parental Investment
  • no parental involvement
  • precocial
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female


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.

Communication and Perception

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

Food Habits

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).

  • Plant Foods
  • roots and tubers
  • wood, bark, or stems

Economic Importance for Humans: Positive

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).

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

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).

Conservation Status

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

Other Comments

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).


Tanya Dewey (editor), Animal Diversity Web.

Guillermo D'Elia (author), University of Michigan-Ann Arbor.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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living in the southern part of the New World. In other words, Central and South America.

World Map


living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map


uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.


uses smells or other chemicals to communicate


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


an animal that mainly eats leaves.


A substance that provides both nutrients and energy to a living thing.


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


mainly lives in water that is not salty.


An animal that eats mainly plants or parts of plants.


referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


marshes are wetland areas often dominated by grasses and reeds.


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scrub forest

scrub forests develop in areas that experience dry seasons.


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


uses touch to communicate


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

young precocial

young are relatively well-developed when born


Doncaster, C. P. and T. Micol. 1989. Annual cycle of a coypu (Myocastor coypus) population: male and female strategies. Journal of Zoology 217:227-240.

Gosling, L. M. 1977. Coypu. Pp. 256-265 in Corbet, G. B. and H. N. Southern (eds.). The handbook of British mammals, 2nd edition. Blackwell Scientific Press, Oxford.

Gosling, L. M. 1981. Climatic determinants of spring littering by feral coypus, Myocastor Coypus. Journal of Zoology 195:281-288.

Gosling, L. M. and S. J. Baker. 1981. Coypu (Myocastor coypus) potential longevity. Journal of Zoology 197:285-312.

Greer, J. K. 1966. Mammals of Malleco Province Chile. Publications of the Museum, Michigan State University Biological Series 3:49-152.

Mares, A. M., R. A. Ojeda, and R. M. Barquez. 1989. Guia de los Mamiferos de la Provincia de Salta, Argentina. University of Oklahoma Press, Norman.

Nowak, R. M. 1991. Walker's Mammals of the World. Johns Hopkins university Press, London.

Woods, C. A. and E. B. Howland. 1979. Adaptive radiation of capromyid rodents: anatomy of the masticatory apparatus. Journal of Mammalogy 60:95-116.

Woods, C. A., L. Contreras, G. Willner-Chapman, and H. P. Whidden. 1992. Myocastor coypus. Mammalian Species 398:1-8.