Nutria (Myocastor coypus) are an invasive, semi-aquatic South American rodent first introduced in Maryland (USA) in 1943. In the absence of natural population control mechanisms, subsequent population increases and range expansion have resulted in established populations in eight Maryland counties located east of the Chesapeake Bay. Nutria foraging behaviour damages or destroys existing root mat that binds and secures structural components of functional marshlands. When this fibrous network is compromised by nutria activity, emergent marsh is quickly reduced to unconsolidated mudflats. These areas in turn are highly susceptible to erosional processes and are eventually converted to open water.

Rapidly increasing nutria populations coupled with significant wetland losses has prompted the formulation of a complex partnership representing 21 governmental agencies and private organizations. This group has produced a comprehensive pilot project proposal that focuses on development of techniques necessary to remove this noxious exotic species from Maryland's native ecosystems. Additionally, wetland restoration techniques that may reverse severe marshland degradation will also be evaluated.

A research project to evaluate the practicability of eradicating nutria is taking place in Maryland. Rapid expansion of nutria range is occurring and they are now present and causing habitat degradation in 15 states of the United States.

In 1943 artificial farming of this exotic furbearer was initiated on Blackwater National Wildlife Refuge in Dorchester County, Maryland to enhance an already vibrant fur industry. This quickly proved unprofitable and the remaining project nutria either escaped or was inadvertently released. Nutria are a foreign species with no natural controls. Population increases and range expansion have now resulted in established populations in at least eight counties east of Chesapeake Bay and an increasing number of isolated individuals have been verified on the western shore.

Population estimates on a 10,000-acre parcel located in Dorchester County have expanded from less than 150 nutria in 1968 to an estimated 35,000 - 50,000 animals currently.

Still today the fur industry contributes millions of dollars to the local economy of Maryland which, historically, the muskrat has contributed heavily. Due to loss of habitat and the fact that nutria out-compete muskrat, the muskrat population has suffered greatly.

Individual nutria has been recorded to exceed 35 pounds in weight. An average Maryland nutria weighs 16 pounds.

Nutria are approximately three feet long from the nose to the tip of the tail.