Nutria

The nutria ( ) or coypu ( ) (Myocastor coypus) is an herbivorous, semiaquatic rodent native to 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 mainly on aquatic and riparian vegetation. In its native range it forms part of South American wetland food webs and can contribute to the dispersal of aquatic plants and spores. 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, introduced populations can damage wetland vegetation and infrastructure through feeding and burrowing, and the species is considered invasive in several countries. Some populations can carry some zoonotic pathogens, including pathogenic Leptospira, although their epidemiological significance is scarce and region-specific.

The nutria ( ) or coypu ( ) (Myocastor coypus) is an herbivorous, semiaquatic rodent native to 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 mainly on aquatic and riparian vegetation. In its native range it forms part of South American wetland food webs and can contribute to the dispersal of aquatic plants and spores. 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, introduced populations can damage wetland vegetation and infrastructure through feeding and burrowing, and the species is considered invasive in several countries. Some populations can carry some zoonotic pathogens, including pathogenic Leptospira, although their epidemiological significance is scarce and region-specific. Coypu (Myocastor coypus coypus) feeding Tricao.jpg|M. c. coypus feeding; in Chile Coypu (Myocastor coypus coypus) swimming Tricao.jpg|The species is native to South America ==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 of age. 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 pups. Female nutrias will mate within two days after giving birth. 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. ==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. ==Commercial use and issues== ==Control efforts== As a global alien species, nutrias are monitored and managed throughout the world. Many countries have attempted eradication efforts with varying degrees of success. Nutrias are predicted to expand their range northward over the next century as global temperatures increase. ==== Great Britain==== In the UK, nutrias escaped from fur farms and were reported in the wild as early as 1932. There were three unsuccessful attempts to control the nutria in East Anglia between 1943 and 1944. Nutria population and range increased, causing damage to agriculture in the 1950s. During the 1960s, a grant was awarded to rabbit clearance societies that included nutria. This control allowed for the removal of 97,000 nutria in 1961 and 1962. From 1962 to 1965, 12 trappers were hired to eradicate as many nutrias as possible confining the remaining population within the Norfolk Broads. The campaign used live traps allowing non-target species to be released while any nutrias caught were shot. Combined with cold winters in 1962 to 1963, almost 40,500 nutrias were removed from the population. Although nutria populations were greatly reduced after the 1962–1965 campaign ended, the population increased until another eradication campaign began in 1981. This campaign succeeded in fully eradicating the nutria in Great Britain. The trapping areas were broken into eight sectors leaving no area uncontrolled. The 24 trappers were offered an incentive for early completion of the 10-year campaign. In 1989 nutrias were assumed eradicated, as only three, all male, were found between 1987 and 1989. ===New Zealand=== Nutrias are classed as a "prohibited new organism" under New Zealand's Hazardous Substances and New Organisms Act 1996, preventing it from being imported into the country. ===United States=== ====Atlantic Coast==== An eradication program on the Delmarva Peninsula, between Chesapeake Bay and the Atlantic Coast, where nutrias once numbered in the tens of thousands and had destroyed thousands of hectares of marshland, had nearly succeeded by 2012. In September 2022, government officials announced that nutrias had been completely eradicated on the Maryland Eastern Shore. ====California==== The first records of nutrias invading California dates from the 1940s and 1950s, when the species was found in the agriculture-rich Central Valley and the south coast of the state, but by the 1970s the animals had been extirpated statewide. They were found again in Merced County in 2017, on the edge of the San Joaquin River Delta. State officials are concerned that they will harm infrastructure that sends water to San Joaquin Valley farms and urban areas. In 2019, the California Department of Fish and Wildlife (CDFW) received nearly $2 million in Governor Gavin Newsom's first budget, and an additional $8.5 million via the Delta Conservancy (a state agency focused on the Delta) to be spent over the course of three years. The state has adopted an eradication campaign based on the successful effort in the Chesapeake Bay, including strategies such as the "Judas nutria" (in which individualized nutrias are caught, sterilized, fitted with radio collars, and released, whereupon they can be tracked by hunters as they return to their colonies) and the use of trained dogs. The state has also reversed a prior "no-hunting" policy, although hunting the animals does require a license. California has a restriction on importation and transportation without a permit. If nutrias are found or captured in the state of California, local authorities must be notified right away and the nutrias cannot be released. Licensed hunters in the state of California may hunt nutrias as a non-game animal. Bounty programs are not advised in California due to native species of muskrat and beaver being misidentified. ====Louisiana==== The Louisiana Coastwide Nutria Control Program provides incentives for harvesting nutria. Starting in 2002, the Louisiana Department of Wildlife and Fisheries (LDWF) performed aerial surveys just as they had done for the Nutria Harvest and Wetland Demonstration Program, except under a different program title. Under the Coastwide Nutria Control Program, which also receives funds from CWPPRA, 308,160 nutrias were harvested the first year (2002–2003), revealing damage and totaling $1,232,640 in incentive payouts to those legally participating in the program. Essentially, once a person receives a license to hunt or trap nutria, that person is allowed to capture an unlimited number. When a nutria is captured, the tail is cut off and turned in to a Coastal Environments Inc. (CEI) official at an approved site. As of 2019, each nutria tail is worth $6, which is an increase from $4 before the 2006–2007 season. Nutria harvesting increased drastically during the 2009–2010 season, with 445,963 nutria tails turned in worth $2,229,815 in incentive payments. Each CEI official keeps record of how many tails have been turned in by each individual per parish, the method used in capture of the nutria, and the location of capture. All of this information is transferred to a database to calculate the density of nutrias across the Louisiana coast, and the LDWF combines these data with the results from the aerial surveys to determine the number of nutrias remaining in the marshes and the amount of damage they are inflicting on the ecosystem. Another program executed by LDWF involves creating a market of nutria meat for human consumption, though it is still trying to gain public notice. Nutria is a very lean, protein-rich meat, low in fat and cholesterol with the taste, texture, and appearance of rabbit or dark turkey meat. Few pathogens are associated with the meat, but proper heating when cooking should kill them. The quality of the meat and the minimal harmful microorganisms associated with it make nutria meat an "excellent food product for export markets". Several desirable control methods are ineffective for various reasons. Zinc phosphide is the only rodenticide registered to control nutria, but it is expensive, remains toxic for months, detoxifies in high humidity and rain, and requires construction of expensive floating rafts for placement of the chemical. It is not yet sure how many nontarget species are susceptible to zinc phosphide, but birds and rabbits have been known to die from ingestion. Therefore, this chemical is rarely used, especially not in large-scale projects. Other potential chemical pesticides would be required by the US Environmental Protection Agency to undergo vigorous testing before being acceptable to use on nutria. The LDWF has estimated costs for new chemicals to be $300,000 for laboratory, chemistry, and field studies, and $500,000 for a mandatory Environmental Impact Statement. Contraception is not a common form of control, but is preferred by some wildlife managers. It is also expensive to operate– an estimated $6 million annually to drop bait laced with birth-control chemicals. Testing of other potential contraceptives would take about five to eight years and $10 million, with no guarantee of FDA approval. Also, an intensive environmental assessment would have to be completed to determine whether any non-target organisms were affected by the contraceptive chemicals. Neither of these control methods is likely to be used in the near future. In Louisiana, a claimed environmentally sound solution is the killing of nutrias to make dog food treats. ==Gallery== Nutria heart. (Myocastor coypus).jpg|Nutria heart Nutriaschädel.jpg|Skull from various perspectives Nutria (Myocastor coypus) in a partially frozen river Ljubljanica.jpg|By the river Ljubljanica Coypus.jpg|Feral nutria in Oise river in France File:Myocastor coypus 2016 G2.jpg|10-day-old baby nutria File:Tropy nutrii.jpg|Track ==References== ==Further reading== Sandro Bertolino, Aurelio Perrone, and Laura Gola "Effectiveness of coypu control in small Italian wetland areas" Wildlife Society Bulletin Vol. 33, No. 2 (June 2005) pp. 714–772. Carter, Jacoby and Billy P. Leonard: "A Review of the Literature on the Worldwide Distribution, Spread of, and Efforts to Eradicate the Coypu (Myocastor coypus)" Wildlife Society Bulletin, Vol. 30, No. 1 (Spring, 2002), pp. 162–175. Carter, J., A.L. Foote, and L.A. Johnson-Randall. 1999. "Modeling the effects of nutria (Myocastor coypus) on wetland loss". Wetlands 19(1):209–219 Lauren E. Nolfo-Clements: Seasonal variations in habitat availability, habitat selection, and movement patterns of Myocastor coypus on a subtropical freshwater floating marsh. (Dissertation) Tulane University. New Orleans. 2006. Sheffels, Trevor and Mark Systma. "Report on Nutria Management and Research in the Pacific Northwest" Center for Lakes and Reservoir Environmental Sciences and Resources, Portland State University. December 2007. Available on-line: [https://web.archive.org/web/20100605003204/http://www.clr.pdx.edu/docs/CLR_nutria_report.pdf]

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