Nutria

Nutria (Myocastor coypus) are prolific aquatic rodents native to South America. Their habit of digging out and feeding on the roots of marsh grasses has caused substantial wetland losses in Maryland, particularly at the Blackwater National Wildlife Refuge (NWR) on the Eastern Shore.

How were nutria introduced to the Bay watershed?

Nutria were first introduced in the United States in California in 1899, and then to the southern states in the early 20th century, for fur farming and weed control. When nutria farming collapsed during World War II, the animals were translocated to a number of other states in the hope they would control undesirable vegetation and enhance trapping opportunities.

In 1943, the federal government introduced nutria to Dorchester County, Maryland, to establish an experimental fur station at the Blackwater NWR. The fur station soon proved unprofitable, and the remaining project nutria escaped and/or were released. These animals were the origin of the overwhelming populations in the state at the beginning of the 21st century.

Why are nutria considered to be invasive?

Nutria excavate and feed on the roots of marsh grasses, creating circles of mud called “eat outs.” Without plant roots to stabilize the soil, water moves in and washes the exposed soil away, quickly eroding marshes and converting them to open water. Since their introduction, nutria have destroyed over 7,000 acres of marsh at the Blackwater NWR—nearly half of the refuge's marsh acreage.

Nutria also fragment marshes by creating deep swimming channels. These channels:

• Trap marsh-dependent, less mobile species into small areas of marsh.
• Create more edges that can be exposed to wave action and cause further erosion.

As more marsh plants are removed, damage to wetlands from sea level rise, land subsidence, tidal flooding and salt water increases because there are fewer plants to act as a buffer against erosion. Wetlands serve as habitat for numerous native Bay animals, including valuable fish, shellfish and waterfowl species.

Nutria have also been known to eat agricultural crops and dig large burrows into river banks, dykes and other structures, causing damage to agricultural land and possibly residential areas in flood-prone zones.

A recent economic study estimated that nutria-related destruction of Bay region wetlands would cost Maryland over $200 million in social, economic and environmental damages over the next 50 years, if not addressed.

What is being done to manage nutria?

Since 2000, the U.S. Fish and Wildlife Service has administered the Maryland Nutria Project, which is responsible for eradicating nutria from the Bay region. Nutria eradication has resulted in the recovery and protection of several hundred thousand acres of marshland in Maryland.

• In 2004, nutria were successfully removed from the Blackwater NWR after a concentrated two-year effort.
• Work to eradicate the animal from state and private lands continues. Nutria still remain on the lower Eastern Shore and around the Potomac and Patuxent rivers; however, their numbers continue to dwindle.

Nutria have also been spotted in wildlife refuges in Delaware and Virginia, but populations are limited.