Coypus

(Myocastoridae)

Class Mammalia

Order Rodentia

Suborder Hystricognathi

Family Myocastoridae

Thumbnail description
Large, semi-aquatic rodent with a reddish to yellowish brown outercoat and a thick, gray undercoat

Size
Head and body length 1.4–2.1 ft (43.0–63.5 cm), tail 0.8–1.4 ft (25.5–42.5 cm), weight 11–22 lb (5–10 kg), can occasionally reach 37 lb (17 kg), with males generally larger than females

Number of genera, species
1 genus; 1 species

Habitat
Prefers remote, shallow inland bodies of water such as ponds, slow-moving rivers, lakes, and swampy or marshy areas

Conservation status
Not threatened

Distribution
Native to southern South America, introduced to Europe, Asia, Africa, and North America

Evolution and systematics

The coypu (from the native South American Araconian word koypu) is also known as the nutria (from the corrupted Spanish word lutra, meaning "otter"). It is sometimes also referred to as the South American beaver. The geological range is the late Oligocene epoch (about 38 million to 24 million years ago) to the Recent in South America.

Originally considered a subfamily of the Hutias (Capromyidae), coypus have more recently been distinguished from the other rodents due to their large size and strong, broad, orange-colored incisors.

The taxonomy for this species is Myocastor coypus (Molina, 1782), Rio Maipo, Santiago Prov., Chile.

Physical characteristics

The stout body of the coypu is highly arched. Its four legs are relatively short and hairless, with the two hind feet much longer than the two forelimbs. The hind feet each contain five digits, with webbed toes except between the

fourth and fifth toes (the skinless fifth toe is used for grooming the fur), while the forefeet each have four long, flexible, non-webbed toes and a non-functioning thumb. Its strong claws are sharp. The tail is scaly and sparsely haired, except at and around the base. The coypu is often confused with the muskrat, but it is much larger and has a terete (cylindrical) tail as opposed to the laterally compressed (flat) tail of the muskrat.

Its coat consists of two types of hair: (1) an outercoat (or outer fur) that is soft, dense, reddish brown to yellowish brown in general coloration, containing long, coarse bristles (or guard hairs) that are coarser in texture on the back; and (2) an undercoat (or under fur) that is thick, dark gray in color, and denser on the abdomen, also called nutria (the fur that is valuable as pelts). Also on the lower parts of the body is the stomach fur, which is pale yellow and is not as coarse as that of the upper parts. The outercoat almost completely hides the undercoat.

The head is large and sturdy, and somewhat triangular in shape. The facial features include 20 strong teeth ([I1/1 C0/0 P1/1 M3/3] × 2 = 20). Its large, broad, and conspicuously orange-colored front incisors continue to grow, while the extremely high-crowned cheek teeth are semi-rooted and decrease in size as they converge toward the front. The coypu can close its lips behind the incisors, thus allowing it to gnaw while underwater. Its small black eyes are set near the upper part of the head. The coypu has small, rounded ears and well-developed auditory senses. Near the chin and around the nose and mouth is white fur, and on each side of the face are a few whiskers that are longer and more sensitive than the adjoining white fur. Fat glands (used for lubrication while grooming) are located at the corner of the mouth and near the anus.

A female coypu has four pairs of thoracic mammae. These are located high on the sides of the body so that the mother can lie on her stomach while in the nest as she nurses her

young, or to allow them to nurse while she is feeding in shallow water.

Distribution

The coypu is native to the temperate zones (southern parts) of South America ranging from central Bolivia and southern Brazil to Paraguay, Uruguay, and Tierra del Fuego in Chile and Argentina. It was introduced to North America, northern Asia, eastern Africa, and Europe mostly for the value of its furs or to control evasive aquatic plant species. The animal is not well adapted to cold conditions, often becoming more active during the warmer days (rather than during the colder nights) and tending to huddle together in burrows with other coypus on cold nights.

Habitat

The coypu lives in rainforests, temperate deciduous forests, grasslands, specifically in swamps and marshes and near the banks of lakes, streams, and rivers. Considered terrestrial, however it actually spends most of its time in the water, being an excellent swimmer and diver. The coypu lives in burrows that are built in and around the water. It is especially fond of areas with abundant vegetation along the banks. The coypu normally prefers freshwater, but it will inhabit brackish and saltwater (such as the population of the Chonos Archipelago in Chile).

Behavior

Coypus usually live together in pairs, although they frequently form large colonies of two to 13 animals usually consisting of related adult females, their offspring, and a large

male. A young adult male may be occasionally solitary. Both the male and the female will generally remain in the same territorial area for their entire lives. A coypu can swim well due to webbed toes on the hind feet, and spends most of its time in the water. It is able to remain underwater for as many as

five to 10 minutes. On a regular basis, it carefully cleans and lubricates its fur with its fore feet, wiping the fat glands at the corners of its mouth. It then grooms and arranges the fur throughout its body.

The coypu often takes over the hole of other animals, usually muskrats. When it digs its own burrow, it prefers a location near water along a sloping bank that is usually at a 45–90% inclination. Self-built burrows can be simple tunnels 4–10 ft (1.2–3.0 m) long or complex systems that contain branching passages that extend 50 ft (15 m) or more and chambers that hold simple nests composed of various types of vegetation. The burrow's entrance is built above the water level. When unable to dig its burrow in the ground, the coypu carefully builds a simple surface nest of reeds, either on land or in shallow water. It builds winter resting platforms near dense vegetation that are 20–30 in (51–75 cm) wide and 6–9 in (15–23 cm) above the water level. It also makes runways through the grass in order to wander on numerous, curvy trails up to 590 ft (180 m) from its den. The average territorial range for a female is about 6 acres (2.5 ha), while for a male it is about 14 acres (5.7 ha); however, home ranges can vary anywhere from 6 to 445 acres (2.5–180 ha). The population density is usually 1.1–6.4 animals per acre (2.7–16.0 animals per ha), but can be smaller or much larger than these values.

The coypu is most active at night just before sunset and a few hours before dawn, where its main activities are feeding, grooming, and swimming; during the day it is commonly seen but is not so active. It is a very shy and fearful creature at the first sign of the smallest disturbance, which quickly sends it

seeking shelter in the water, in its burrow, or in other hiding places. When in a safe environment, the coypu is gregarious and very social to other members of its community.

Predators of the coypu include wild cats, large birds of prey (such as bald eagles), red wolves, large snakes (like the anaconda and cottonmouth), alligators, and humans. Turtles, snakes, birds of prey, and other swamp animals may eat juvenile coypus. When confronted with an enemy, it will dive into the water, being more graceful in water than on land (where it is sometimes awkward and clumsy). If unable to quickly reach water when confronted with danger, it can run and jump fast for short periods of time.

Feeding ecology and diet

The coypu will eat almost any available terrestrial or aquatic green plant. It has been called "an eating machine" for its huge appetite for all types of plants. The coypu is primarily an herbivore, feeding on aquatic plants such as rushes, spikerush, arrowhead, pickerel week, smartweed, bur reed, three-cornered grass, cattail, bullwhip, alligator weed, and duckweed. It also eats leaves, roots, stalks, and stems, along with bark, clover, and cultivated crops (if available nearby) such as rice, sugar-cane, soybeans, and corn. It forages for food on land and in the water. A Maryland (United States) study determined that roots are its most important food. The coypu will also eat insects, bivalve mollusks, mussels, snails, and earthworms (but seemingly only in England and South America). It is fond of foods that can be gnawed and chewed, which wears down its teeth. The animal eats about one-fourth of its own weight in

food each night, munching throughout most of the night rather than eating large meals. The digestive organ easily breaks down cellulose particles, which are then adapted for use in the body. When preparing to eat, the coypu often brings its food to a feeding site. It usually sits on a riverbank while holding food in its fore feet before transfering it to its mouth. In other cases, it uses vegetation, branches, and other floating materials as a platform to sit upon while eating (and resting and grooming). It also competes for food with native fur-bearing animals such as the muskrat, beaver, and various waterfowl. In its native habitat of South American marshes and coastal lakes, the coypu is well adapted to regular periods of flood and drought. Its ability to breed quickly allows its populations to stabilize well after frequent environmental upsets caused by drought and flood cycles. However, without these regular cycles to regulate its population size, the number of coypus can quickly grow out of control.

Reproductive biology

The coypu is generally polyestrous in captivity and sometimes in the wild, where mating occurs usually two or three times during the year. It is a very successful procreator. The estrous cycle is variable but generally lasts for about 24–26 days, with a period of receptivity lasting one to four days. The intervals between estrous cycles last from five to 60 days. Ovulation may be induced. The gestation period is long, lasting a little over four months (specifically, 127–139 days). In Chile, the young are born in the spring and in the summer. There is a post-partum estrus within one to two days of giving birth. A female usually give birth to a litter of three to six young (with an average of five, and with one to 13 having been recorded). Factors influencing the size of the litter include availability and type of food, weather conditions, enemies, and diseases. Miscarriages are unusually high in this female rodent, with about one-third of the litters being lost during pregnancy.

A well-developed newborn is born with hair and teeth, open eyes, and able to swim as soon as it dries off (usually within a few hours). Birth weight is about 7.9 oz (225 g) and a newborn is able to survive on its own after about five days of nursing, but usually remains dependent on its parents for six to 10 weeks. The youngster rapidly gains weight during the first five months. The mother's lactation period lasts some eight weeks. A young coypu is sexually mature at about three to four months if born in warmer months and at about six to seven months if born during cooler months. In the wild, there is an 80% mortality rate in the first year of life, and only a few animals live more than two to three years. However, its life span can be six to nine years and some animals have been reported to live for 10 years.

Conservation status

Generally coypus are common, with no special status. The coypu population was severely reduced in the past, mainly during the early nineteenth century as a result of intensive hunting for its valuable, velvet-like undercoat. Demand for its fur continues to the present, but not as much as in the past because its fur is no longer considered as attractive as it used to be. It is rapidly disappearing along many rivers and lakes in Argentina. The species became rare in many of its natural habitats during the height of its being hunted for its fur, but by the early 1900s, efforts were started to regulate hunting and to establish captive breeding farms. Such farms were established within its natural habitat and in other parts of the world. Some animals escaped or were deliberately introduced in such areas as the United States (especially the Gulf coast states, along the West coast to Washington, and the East coast to Maryland), Canada (mostly the southern parts), England, Holland, France, Germany, Scandinavia, Japan, Asia Minor, the Caucasus, and central Asia. By the 1950s, the capture of coypus was prohibited in Argentina and Uruguay, and the nutria pelt trade also became illegal. (The name nutria is generally used when referring to its pelt.) Coypu populations in those countries started to recover following these actions. Most of the present fur trade is presently supplied by nutria farms, and by coypus that have become wild in North America, England, and Russia.

Significance to humans

The fur of a farm-bred coypu is valued because of its luxurious, fine, soft undercoat, which is processed by furriers (by first removing the coarser bristles in order to leave the undercoat exposed). It is also hunted for its meat mostly in its native lands, although farm-raised meat is much more convenient. There is no direct benefit from coypu populations in its non-native habitat. Some were introduced in some habitats to control invasive aquatic plant populations, but its appetite for all plant species made its presence at those areas more damaging than beneficial.

The coypu is considered a pest in some places because its burrows often damage dikes, irrigation facilities, and natural plant communities. Burrows can also weaken riverbanks. The coypu population often competes with native wildlife, and also eats and sometimes destroys cultivated crops such as rice. Parasites from coypus have been reported such as trematodes, cestodes, nematodes, biting lice, and mites. Diseases and viruses from coypus have also been reported, such as leptospirosis, hemorrhagic septicemia, and paratyphoid. In wetlands, its large appetite has severely damaged many habitats. On barrier islands where coypu feed on sea oats, the stability of sea dunes has been threatened.

In the 1930s, coypus were introduced to fur farms in southeast England. Escaped individuals adapted quickly to the new habitat and caused considerable damage to riverbanks and root crops. An eradication campaign in the 1960s resulted in the extermination of most of the wild population (approximately 40,000 animals caught), but a string of mild winters in the 1970s brought significant growth. A more committed eradication campaign in the early 1980s resulted in 35,000 captured individuals, with the last coypu caught in England in 1989.

Resources

Books

Burt, W. H. A Field Guide to Mammals: North America North of Mexico. 3rd ed. The Petersons Field Guide Series. New York: Houghton Mifflin Company, 1980.

Feldhemer, G. A., L. C. Drickamer, S. H. Vessey, and J. F. Merritt. Mammalogy: Adaption, Diversity, and Ecology. Boston: WCB McGraw-Hill, 1999.

Gould, E., and G. McKay, eds. Encyclopedia of Mammals. 2nd ed. San Diego: Academic Press, 1998.

Grzimek's Encyclopedia of Mammals. Vol. 3. New York: McGraw-Hill Publishing Company, 1990.

Macdonald, D. The Encyclopedia of Mammals. New York: Facts on File Publications, 1984.

The National Geographic Book of Mammals. Vol. 1. Washington, DC: National Geographic Society, 1981.

Nowak, R. M. Walker's Mammals of the World. Vol. 2, 6th ed. Baltimore and London, U.K.: Johns Hopkins University Press, 1999.

Whitaker, J. O., Jr., and W. J. Hamilton Jr. Mammals of theEastern United States 3rd ed. Ithaca, NY: Comstock Publishing Associates, 1998.

Whitfield, P. Macmillan Illustrated Animal Encyclopedia. New York: Macmillan Publishing Company, 1984.

Wilson, D. E., and D. M. Reeder, eds. Mammal Species of theWorld. 2nd ed. Washington, DC and London, U.K.: Smithsonian Institution Press, 1993.

Other

Coypu, Nutria—Myocastor coypus. America Zoo. <http://www.americazoo.com/goto/index/mammals/218.htm>

D'Elia, Guillermo. Myocastor coypus: Nutria, Coypu. Animal Diversity Web, Museum of Zoology, University of Michigan. <http://animaldiversity.ummz.umich.edu/accounts/myocastor/m._coypus>

Nutria (Coypu). EnchantedLearning.com. <http://www.enchantedlearning.com/subjects/mammals/rodent/Nutria.shtml>

William Arthur Atkins