Information Last Reviewed Spring 2007
The nutria (a semi-aquatic rodent native to temperate South America) was introduced into North America in the hopes of bolstering the fur industry, but the quality of the pelt proved to be poor. Feral populations are the result of numerous accidental and intentional introductions. Foraging nutria have significantly impacted many wetland plant communities, reducing biodiversity, and altering marsh habitats. Their burrowing activity has resulted in damage to a variety of manmade structures.
Class: Mammalia or Sarcopterygii
Family: Echimyidae or Capromyidae*
* Although nutria exhibits traits of both the Echimyidae and Capromyidae families, distinguishing characteristics place it in its own subfamily (Myocastoridae).
Similar in appearance to the muskrat (Ondatra zibethicus) and the beaver (Castor canadensis) (Fig. 2), the nutria may be most easily distinguished by the following:
Adult body size
Muskrats typically obtain a body length of 31 cm (smaller than that of the nutria)
Beavers obtain an average body length of 81 cm (larger than that of the nutria)
Shape of the tail (Fig. 3)
The tail of the muskrat is higher than it is wide and vertically flattened
The tail of a beaver is large, horizontally flattened, and paddle-like
The tail of a nutria is long, thin, and rounded
Young are born fully furred and active, in litters of 4-6 (up to 13 young per litter are possible), and weighing approximately 227 g
Capable of swimming with their mother and eating plant matter within 24 hours after birth
Capable of survival without the mother after five days
Weaning most often occurs 5-8 weeks after birth
Sexual maturity is reached at 4-8 months of age
Average life span of 3 years in wild populations and 15 or more years in captive populations
Annual mortality is between 60 and 80% of the population
Females come into heat every 14-28 days, with a duration of 1 to 4 days
Gestation lasts between 128 and 132 days
Females come into estrous (i.e., are ready to breed) within 48 hours after giving birth
Fresh and brackish waters
Semi-aquatic habitats occurring at the boundaries of land and permanent water, but may inhabit any of the following:
Wetlands, marshes, and swamps
Shorelines of lakes and ponds
Canals, rivers, large ditches, and bayous
Underground burrows are utilized throughout most of the year, but nutria may also inhabit:
Dense vegetation (particularly during summer months)
Flattened circular platforms of vegetation in shallow water
Range expansion limited by extremely cold climate
Capable of inhabiting saltwater environments
Temperate South America (Argentina, Bolivia, Brazil, Chile, Paraguay, and Uruguay)
North American Distribution
See Fig. 4
Probable Means of Introduction
Imported and released to control undesirable vegetation (e.g., alligator weed, arrowweed, cattail, water hyacinth, water lily) and enhance trapping opportunities for the fur industry
Varied diet consists primarily of marsh and swamp vegetation (e.g., alligator weed, bullwhip, cattail, duck-weed, saltmarsh hay, smooth cordgrass, and three-cornered grass), but may include crops, lawn grasses, and ornamentals adjacent to their habitats
Consume approximately 25% of their body weight daily
Re-ingest fecal pellets (to maximize digestion and assimilation during periods of rest)
Cause loss and degradation of wetlands (marsh loss removes habitat for native wildlife species; e.g., waterfowl, wading birds, and muskrats)
Threaten biodiversity by eliminating valuable food resources (consumption of desirable vegetation also reduces invertebrate populations, a component of the diet of migrating and wintering waterfowl)
Threaten biodiversity by altering habitat (elimination or reduction of habitats suitable for sheltering young crabs and fish, creation of swim channels, which allow saltwater tidal flooding to occur and increase salinity and turbidity, disruption of freshwater habitats supporting native species)
Consume roots and rhizomes of sea oats (which are of critical importance to the stabilization of sand dunes on Mississippi’s barrier islands)
Damage crops (e.g., rice, sugarcane, and soybean), lawn grasses, and ornamental plantings
Interfere with restoration and planting projects
Cause damage to, and weakening of, manmade structures (e.g., culverts, highway bridges, berms, irrigation dikes, docks, and wharves) via their extensive burrowing
Break levees in rice and sugarcane fields
Provide vectors for wildlife disease (e.g., parathypiod and parasitic infection, tuberculosis, false tuberculosis, septicemia)
Carry the nematode (Strongyloides myopotami), which can affect humans who handle nutria
Consume undesirable vegetation
Create habitat for millet (which supports waterfowl) by opening dense stands of vegetation
Provide pelts for use in the fur industry
Install bulkheads to deter burrowing
Fence off levees and farmland during the winter months while populations are concentrated in other locations
Wrap sheet metal around manmade structures (the wood and styrofoam of docks and wharves) to reduce the likelihood of burrowing activity
Erect wire mesh fencing around stands of newly planted seedlings or areas of concern
Use hardware cloth tubes, rather than plastic, to protect individual seedlings
Reduce standing water in drainages
Manipulate water level (reduce water level during the summer months, increase during the winter months), as this may result in unfavorable living conditions; stressing out nutria and exposing them to predators, reducing available food resources, and increasing competition for space
Use floating platforms to lure nutria to an area which has been prebaited with sweet potatoes - once grazing has become established, bait with zinc phosphide
Trapping and shooting have also been successfully used to reduce populations
Borgnia, M., Galante, M. L., and Cassini, M. H. 2000. Diet of the coypu (Nutria, Myocastor coypus) in agro-systems of Argentina Pampas. Journal of Wildlife Management 64(2):354-361.
Carter, J. and Leonard, B. P. 2002. A review of the literature on the worldwide distribution, spread of, and efforts to eradicate the coypu (Myocastor coypus). Wildlife Society Bulletin 30(1):162-175.
Chabreck, R. H. 1962. Daily activity of nutria in Louisiana. Journal of Mammalogy 43(3):337-344.
Choate, J. R., Jones, J. K., Jr., and Jones, C. 1994. Handbook of Mammals of the South-Central United States. Louisiana State University Press. Baton Rouge, Louisiana. 304 pp.
Conniff, R. 1989. Keeping an immigrant in check. National Wildlife 27(1):43-44.
Doncaster, C. P. and Micol, T. 1989. Annual cycle of a coypu (Myocastor coypus) population: Male and female strategies. Journal of the Zoological Society of London 217:227-240.
Griffo, J.V., Jr. 1957. The status of the nutria in Florida. Quarterly Journal of the Florida Academy of Sciences 20(3):209-215.
Howerth, E. W., Reeves, A. J., McElveen, M. R., and Austin, W. 1994. Survey for selected diseases in nutria (Myocastor coypus) from Louisiana. Journal of Wildlife Diseases 30(3):450-453.
Nowak, R. M. 1991. Walker's Mammals of the World. The Johns Hopkins University Press. Baltimore, Maryland. 1629 pp.
Trillin, C. 1995. The nutria problem. Atlantic Monthly 275(2):30-32, 40-42.
Waldo, E. 1962. The Louisiana Nutria Story. Louisiana Wildlife and Fisheries Commission. New Orleans, Louisiana. 16 pp.
Whitaker, J. O., Jr. 1988. The Audubon Society Field Guide to North American Mammals. Alfred A. Knopf, Inc. New York, New York. 745 pp.
Willner, G. R., Chapman, J. A., and Pursley, D. 1979. Reproduction, physiological responses, food habits, and abundance of nutria on Maryland marshes. Wildlife Monograph 65:43.
Wolfe, J. L. 1981. Nutria: Our newest furbearer. Mississippi Outdoors 44(5):9.
Species summary for Myocastor coypus Kerr, 1792
Myocastor coypus (Nutria, Coypu)
The Mammals of Texas Online Edition - Nutria (Myocastor coypus)
This report was prepared by Danielle M. Crosier and Daniel P. Molloy (New York State Museum).