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The nutria (Myocastor coypus) is a large, dark-colored, semiaquatic rodent that is native to southern South America. At first glance, a casual observer may misidentify a nutria as either a beaver (Castor canadensis) or a muskrat (Ondatra zibethicus), especially when it is swimming. This superficial resemblance ends when a more detailed study of the animal is made. Other names used for the nutria include coypu, nutria-rat, South American beaver, Argentine beaver, and swamp beaver.
The original range of nutria was south of the equator in temperate South America. This species has been introduced into other areas, primarily for fur farming, and feral populations can now be found in North America, Europe, the Soviet Union, the Middle East, Africa, and Japan. M. c. bonariensis was the primary subspecies of nutria introduced into the United States.
Exclusion: Protect small areas with partially buried fences. Wire tubes can be used to protect baldcypress or other seedlings but are expensive and difficult to use. Use sheet metal shields to prevent gnawing on wooden and styrofoam structures and trees near aquatic habitat. Install bulkheads to deter burrowing into banks.
Cultural Methods and Habitat Modification: Improve drainage to destroy travel lanes. Manage vegetation to eliminate food and cover. Contour stream banks to control burrowing. Plant baldcypress seedlings in the fall to minimize losses. Restrict farming, building construction, and other “high risk” activities to upland sites away from water to prevent damage. Manipulate water levels to stress nutria populations.
Repellents: None are registered. None are effective.
Toxicants: Zinc phosphide on carrot or sweet potato baits.
Fumigants: None are registered. None are effective.
Trapping: Commercial harvest by trappers. Double longspring traps, Nos. 11 and 2, as preferred by trappers and wildlife damage control specialists. Body-gripping traps, for example, Conibear® Nos. 160-2 and 220-2, and locking snares are most effective when set in trails, den entrances, or culverts. Live traps should be used when leghold and body-gripping traps cannot be set. Long-handled dip nets can be used to catch unwary nutria.
Shooting: Effective when environmental conditions force nutria into the open. Night hunting is illegal in many states.
Other Methods: Available control techniques may not be applicable to all damage situations. In these cases, safe and effective methods must be tailored to specific problems.