Nutria
The nutria or coypu is an herbivorous, semiaquatic rodent from South America.
Classified for a long time as the only member of the family Myocastoridae, Myocastor has since been included within Echimyidae, the family of the spiny rats.
The nutria lives in burrows alongside stretches of water and feeds on river plant stems.
Native to subtropical and temperate South America, it was introduced to North America, Europe and Asia, 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 in the United States. Nutrias also transmit various diseases to humans and animals, mainly through water contamination.
Etymology
The genus name Myocastor derives from the two Ancient Greek words 'rat, mouse', and 'beaver'. Therefore, the name Myocastor literally means 'mouse-beaver'.Two names are commonly used in English for Myocastor coypus. The name nutria is generally used in North America, Asia, and throughout countries of the former Soviet Union; however, in most Spanish-speaking countries, the word nutria refers primarily to the otter. To avoid this ambiguity, the name coypu or coipo is used in South America, Britain and other parts of Europe. In France, the nutria is known as a ragondin. In Dutch, it is known as beverrat 'beaver-rat'. In German, it is known as Nutria, Biberratte 'beaver-rat', or Sumpfbiber 'swamp-beaver'. In Italy, instead, the popular name is, as in North America and Asia, nutria, but it is also called castorino 'little beaver', by which its fur is known in Italy. In Swedish, the animal is known as sumpbäver 'marsh/swamp-beaver'. In Brazil, the animal is known as ratão-do-banhado 'big swamp-rat', nútria, or caxingui.
Taxonomy
The nutria was first described by Juan Ignacio Molina in 1782 as Mus coypus, a member of the mouse genus. The genus Myocastor was assigned in 1792 by Robert Kerr. Geoffroy Saint-Hilaire, independently of Kerr, named the species Myopotamus coypus, and it is occasionally referred to by this name.Four subspecies are generally recognized:
- M. c. bonariensis: northern Argentina, Bolivia, Paraguay, Uruguay, southern Brazil
- M. c. coypus: central Chile, Bolivia
- M. c. melanops: Chiloé Island
- M. c. santacruzae: Patagonia
Phylogeny
Comparison of DNA and protein sequences showed that the genus Myocastor is the sister group to the genus Callistomys. In turn, these two taxa share evolutionary affinities with other Myocastorini genera: Proechimys and Hoplomys on the one hand, and Thrichomys on the other hand.Appearance
The nutria somewhat resembles a very large rat, or a beaver with a small, long and skinny hairless tail. Adults are typically in weight, and in body length, with a tail. It is possible for nutrias to weigh up to, although adults usually average. Nutrias have three sets of fur. The guard hairs on the outer coat are three inches long. They have coarse, darkish brown midlayer 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. They have approximately 20 teeth with four large incisors that grow during the entirety of their lives. The orange discoloration is due to pigment staining from the mineral iron in the tooth enamel. Nutrias have prominent four inch long whiskers on each side of their muzzle or cheek area. The mammary glands and teats of female nutrias are high on her flanks, to allow their young to feed while the female is in the water. There is no visible distinction between male and female nutria. Both are similar in coloring and weight.A nutria 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 nutria is round. It can also be mistaken for a small beaver, as beavers and nutrias have very similar anatomies and habitats. However, beavers' tails are flat and paddle-like, as opposed to the round tails of nutria.
Life history
Nutrias can live up to six years in captivity, but individuals rarely live past three years old in the wild. According to one study, 80% of nutrias die within the first year, and less than 15% of a wild population is over three years old. A nutria is considered to have reached old age at four years old. Male nutrias 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 nine 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. The average nutria reproduction is four offspring. Female nutrias will mate within two days after offspring are born. The years of reproduction cycle by litter size. Year one might be large, year two litter size will be smaller and year three the litter size will be another larger size. Females can only produce six litters in her life, rarely seven litters. A female on average will have two litters a year.Nutrias generally line nursery nests with grasses and soft reeds. Baby nutrias are precocial, born fully furred and with open eyes; they can eat vegetation and swim with their parents within hours of birth. A female nutria 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 nutrias nurse for seven to eight weeks, after which they leave their mothers. Nutrias have been known to be territorial and aggressive when caught or cornered. They will bite and attack humans and dogs when threatened. Nutrias are mainly crepuscular or nocturnal, with most activity occurring around dusk and sunset with highest activity around midnight. When food is scarce, nutrias will forage during the day. When food is plentiful, nutrias will rest and groom during the day.
Distribution
Native to subtropical and temperate South America, its range includes Chile, Argentina, Uruguay, Paraguay and the southern parts of Brazil and Bolivia. It has been introduced to North America, Europe and Asia, primarily by fur ranchers.The distribution of nutrias outside South America tends to contract or expand with successive cold or mild winters. During cold winters, nutrias often suffer frostbite on their tails, leading to infection or death. As a result, populations of nutria often contract and even become locally or regionally extinct as in the Scandinavian countries and such U.S. 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, nutrias were first introduced to the United States in California, in 1899 by William Franklin Frakes., they had spread to the San Francisco Bay Area, where their digging threatened storm levees, and the California Department of Fish and Wildlife had an active eradication program.
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 nutrias 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 nutrias to escape into the wild. According to the Louisiana Department of Wildlife and Fisheries, nutrias were also transplanted from Port Arthur, Texas, to the Mississippi River in 1941 and then spread due to a hurricane later that year.
Habitat and feeding
Besides breeding quickly, each nutria consumes large amounts of aquatic 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 nutria averages in weight, but they can reach as much as. They eat the base of the above-ground stems of plants, and often dig through soil for roots and rhizomes to eat. Nutrias eat parts and whole plants, and go after roots, rhizomes, tubers and black willow tree bark in the winter. 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 wetlands and marshes. Nutrias eat the following plant varieties: cattail, rushes, reeds, arrowheads, flatsedges, and cordgrasses. Commercial crops that nutrias also eat are lawn grasses, alfalfa, corn, rice, and sugarcane.Nutrias are found most commonly in freshwater marshes and wetlands, 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. Nutrias live in partially underwater dens. The main chamber is not submerged underground. Nutrias are considered to be a species that lives in colonies. One male will share a den with three or four females and their offspring. Nutrias use "feeding platforms" which are constructed in the water from cut pieces of vegetation supported by a structure like a log or branches. Muskrat dens and beaver lodges are also often used as feeding platforms.