NUTRIA: AN INVASIVE RODENT PEST OR VALUED RESOURCE?

Nutria or coypu (Myocastor coypus), semi-aquatic rodents native to southern South America, are an invasive species having detrimental impacts mainly in the southern and eastern United States. Nutria were introduced into the U.S. in 1899 for fur farming and became established in several states. Nutria dispersals resulted primarily from releases by fur farmers, escapes during hurricanes or rising floodwaters, or as translocations in an attempt to control nuisance aquatic vegetation. The ravenous appetite of these herbivores can cause damage to agricultural crops and aquatic vegetation, and can alter aquatic ecosystems. Their burrowing habits can weaken irrigation structures and they are a host for some diseases. Eradication is desired in areas such as national wildlife refuges, but can be difficult due to the nutria's extensive suitable range of habitat, the logistical challenges posed to land managers associated with these habitats, their efficiency in dispersal, and their high, year-round reproductive ability. Control is more practical in some areas and is facilitated by periods of cold temperatures and sustained lethal control. An example of an eradication strategy was implemented by USDA/Wildlife Services at Blackwater National Wildlife Refuge, Maryland, during 2002-2004 where systematic intensive control depopulated nutria from the Refuge. An example of long- term management of nutria was implemented by the Louisiana Department of Wildlife and Fisheries where an incentive payment is distributed to registered trappers and hunters on a per nutria basis. Louisiana continues to recognize nutria as a beneficial natural resource, such as fur and food, and manages for a low population. To offset negative attributy Blackwater National Wildlife Refuge recognizes only the negative impacts of this invasive species and has implemented an eradication strategy. Research efforts continue to develop efficient methods for nutria control, including detection and monitoring techniques, attractants for bait delivery of toxicants or fertility control materials, lures for improved capture rates, and improved capture devices.