The nutria (Myocastor coypus) is a large, semi-aquatic rodent native to South America. It was introduced to North America for the fur trade in the late 19th and early 20th centuries. After the fur market collapsed in the 1940s, escaped or released nutria established invasive populations across at least 20 U.S. states. Nutria are a significant nuisance because their feeding and burrowing habits cause extensive environmental and property damage. They damage crops, degrade wetlands, and threaten structural integrity near waterways, making control necessary for affected landowners.
Identifying Nutria and Assessing Property Damage
Nutria are distinguished from native species like beavers and muskrats by several physical characteristics. An adult nutria typically weighs 12 to 20 pounds and can be up to three feet long, including its tail. A defining feature is its pair of large, bright orange-yellow incisors, colored by iron in the tooth enamel.
The nutria has a long, round, and sparsely-haired tail, unlike the flat tail of a beaver or the flattened tail of a muskrat. When swimming, the nutria’s tail remains largely still, while a muskrat’s tail undulates. The presence of nutria is often confirmed by the damage they cause, which is divided into structural and vegetative destruction.
Extensive burrowing is a major concern, as tunnels can extend up to 150 feet in length. This severely weakens the banks of streams, canals, levees, and ditches. Tunneling creates weak points that can collapse, leading to erosion, damage to roadbeds, and potential failure of flood control structures.
Agriculturally, nutria consume up to 25% of their body weight daily, feeding on roots and rhizomes. This causes significant economic losses to crops like rice and sugarcane. Their feeding habits can also completely denude marsh vegetation, converting wetlands into open water, a phenomenon known as “eat-outs.”
Non-Lethal Control: Habitat Modification and Exclusion
Initial control efforts should focus on making the property unattractive or physically inaccessible. Habitat modification involves removing sources of food and shelter near aquatic environments. Eliminating dense brush, thickets, and weed lines adjacent to ditches and waterways removes cover used for traveling and resting.
Landscaping changes can discourage new burrowing activity. Contouring stream banks to less than a 45-degree slope is effective, as nutria prefer steeper banks for den construction. Restricting high-value crops away from the immediate edge of water bodies reduces feeding incentives. Draining standing water where possible also eliminates travel lanes and potential home sites.
Exclusion methods use physical barriers to block access to vulnerable areas like gardens and lawns. A low fence, approximately four feet tall and constructed of two-inch wire mesh, can be effective if properly installed. The bottom of the fence must include an apron buried at least six inches deep and extending outward by 12 inches to prevent burrowing underneath. Chemical or scent-based repellents are generally considered ineffective for long-term control, and none are currently registered for this purpose.
Direct Removal Methods and Legal Considerations
When non-lethal methods are insufficient, direct population reduction through trapping and shooting is necessary. Trapping is the most common and effective method, utilizing either live traps or lethal body-gripping traps. Live cage traps, sized for raccoons, are effective when baited with preferred vegetables like sweet potatoes or carrots.
For lethal control, body-gripping traps (e.g., Conibear® traps or double long-spring foothold traps) are placed along active travel trails, den entrances, or in culverts. Trapping success is enhanced by placing traps on floating rafts or bait boards anchored near water. For live traps, a short line of bait leading into the entrance increases the chances of capture.
Shooting is a viable control measure, particularly where permitted in rural areas. Control is most effective when performed at night with a spotlight, though local ordinances often restrict night shooting or firearm discharge near dwellings. Small caliber rifles, such as a .22 rimfire, or a 12-gauge shotgun can be used. In some situations, shooting can remove up to 80% of a local population.
Before implementing direct removal, understanding the legal context is crucial, as regulations vary widely by state and municipality. Nutria are often classified as an unprotected invasive species that can be taken at any time. However, some states classify nutria as furbearers, requiring a license or specific season for trapping. Landowners should contact their state wildlife agency, such as USDA Wildlife Services, to confirm specific regulations regarding trap types, bait use, and the legality of shooting.