Nutria (Myocastor coypus). The nutria is a rodent that is native to temperate Argentina, Bolivia, Chile, Paraguay, and Uruguay in South America (Rue 1967). In South America, the nutria is exploited for its pelt, but in the United States, the quality of the pelt is poor and the meat is unpalatable.
Will Frakes of Elizabeth Lake, California, originally brought this species into the United States in 1899 (Hodgson 1949). The animals were introduced into the wild in the United States in the 1930's when E. A. McIlhenny released six pairs on Avery Island, Louisiana, to start a commercial fur farm. Within 2 years, several individuals escaped from the island, and a viable population established itself in Louisiana (Dozier 1951). In 1940, a hurricane washed the entire colony of 150 nutria off Avery Island into other parts of Louisiana. Since the storm, the nutria population expanded to 1 million individuals in Louisiana (Griffo 1957). The nutria eventually spread throughout Alabama, Georgia, Mississippi, Texas, and--in the early 1950's--Florida through immigration and importation and release of breeders (Anonymous 1955). Already established populations north of Florida easily expanded their range by simply following water courses to the Gulf of Mexico (Tiebout 1983). Individuals that escaped from 20 or more fur farms in the 1950's contributed to the establishment of the nutria in Florida (Griffo 1957). Belfiore (1991) reported that by 1991 the nutria population increased exponentially to more than 10 million individuals. As Tiebout (1983) commented, escape rates may have increased as fur farmers' profits decreased.
Nutrias were released in Blountstown, Palatka, and St. Petersburg for the control of aquatic vegetation (Tiebout 1983). More specifically, Griffo (1957) reported seven records of feral nutrias in North Choctawhatchee Bay, East Choctawhatchee Bay, the mouth of the Apalachicola River, the mouth of the Swannee River, Cedar Keys, Otter Spring Run in Gilchrist County, and the Hillsborough River. In these areas, nutrias do not have natural predators, and they thrive in various polluted runoff canals, ponds, and barnyards of several large commercial dairies in the Brandon area (Brown 1979). Although they consumed large quantities of undesirable aquatic and shoreline vegetation, the nutrias also consumed large amounts of desirable aquatic vegetation and farm crops, competed with muskrats (Ondatra zibethicus) and waterfowl, and created extensive tunnels in pond and canal banks. The species gradually expanded its range into central Florida, and eradication was necessary when damage from tunnelling became severe (Brown 1979).
Florida has an abundance of suitable habitat for the nutria, and the nutria's fecundity of 5-8 young/litter and 2-3 litters/year is high. This combination is detrimental to the environment (Tiebout 1983). The nutria's natural South American habitat is composed of vegetation such as saw grass (Cladium jamaicense), giant cut-grass (Zizaniopsis miliacea), southern bulrush (Scirpus californicus), and maidencane (Panicum hemitomom; Atwood 1950). These plants are also typical in Florida and point toward the inevitability of a population expansion that has not yet occurred. Although the nutria occurs in the northern two-thirds of the state, including most of the panhandle, the population may be classified as stable to declining (Tiebout 1983). However, in 1959, the state passed Florida Statute 372.98 that labeled the nutria a public nuisance. Consequently, all nutria farmers have to have licenses, the release of animals is prohibited, and cage guidelines are mandated (Tiebout 1983). Smith (1969) described the nutria as an undesirable alien that residents of Florida should eliminate on sight (Tiebout 1983).
The nutria was once expected to be a good biological control agents for unwanted aquatic vegetation (Griffo 1957). However, when it was imported into Texas to control cattails (Typha spp.), arrowheads (Family Juncaginaceae), water lilies (Family Nymphaeaceae), and other noxious water weeds, it eradicated the targeted plants and everything else in the area. In a short time, the lakes were changed into denuded potholes that were not even suitable habitat for the nutria (Rue 1967). Nutrias also break levees in rice and sugarcane fields by enlarging muskrat burrows around levees or by cutting directly into the levees. The levees break and eventually crops are flooded and destroyed. (Waldo 1958). Nutrias also feed on crops of cabbage, corn, lettuce, and peas (Waldo 1958) and occasionally damage highway bridges and culverts by burrowing around them (Waldo 1958). Nutrias benefit the environment by opening dense stands of vegetation and thereby creating habitat for duck food plants such as millet.
Nurtrias may also be the vectors of wildlife diseases. Waldo (1958) noted that the diseases most commonly associated with the nutria are tuberculosis, false tuberculosis, and septicemia. Diseases associated with an abundance of nutrias and their excretions are parathypiod and parasitic infections. Transmission of the diseases by infected nutrias may harm native species.
The only reported economic impacts that the nutria has had in Florida is the marginal amount of money that can be made from the farming of the nutria for fur and the damage to crops, ornamental shrubs, irrigation dikes, and berms. However, nutria fur has never been a popular commodity in the United States, and profits from the fur have been low. Rue (1967) noted that the only people who can make money from the nutria are those who sell the breeding stock. Furs sold for less than $10/piece on the 1967 market; however, the market is highly variable. In 1943, 436 pelts were harvested; by 1950-1951; 78,422 pelts were harvested; and by 1957, more than a half million pelts were harvested and farmers began to complain about encroachment of the nutria into rice and cane fields (Waldo 1958). In the future, the nutria may become a good source of meat for consumption by humans and animals (Waldo 1958).
