Restoration through Eradication: Neutralizing Nutria in the Chesapeake Bay

Contact: Steve Kendrot, USDA | 410-221-7857

Restoration through Eradication: Neutralizing Nutria in the Chesapeake Bay

ANNAPOLIS, MD (April 3, 2009) – In the nearly 70 years since nutria (Myocastor coypus) were introduced into the marshes at Blackwater National Wildlife Refuge in Dorchester County, Maryland, these invasive aquatic rodents have wreaked havoc in the Chesapeake Bay. Originally brought to the area for its luxurious fur, this South American species found the brackish and freshwater marshes in Dorchester County an ideal habitat and began multiplying like Mickey Mouse’s brooms in Fantasia. Slowed only by periodic severe winters, the nutria population at Blackwater NWR swelled to an estimated 35,000 animals from a handful of original escapees. MISC has named nutria the April Invader of the Month.

Unable to cope with the voracious eating habits of thousands of these 15-pound invaders, which dine primarily on marsh grasses and sedges, freshwater marshes in Dorchester County began to disappear at an alarming rate. Nearly half of Blackwater’s original marsh has disappeared and the trend repeated itself as nutria spread outward from their point of origin. Although many factors influence the rate of marsh loss, studies conducted to measure the relative impact of nutria demonstrated that nutria-free marshes were more resistant to the changes caused by sea level rise, salt water intrusion, and land subsidence.

In 2002, a partnership of state, federal and private agencies led by the US Fish and Wildlife Service, Maryland Department of Natural Resources and USDA Wildlife Services embarked on a campaign to eradicate this destructive species from the Delmarva Peninsula. Beginning at Blackwater NWR and its surrounding state and privately owned lands, the eradication team worked out a systematic procedure for removing entire populations of nutria and preventing their recurrence. By applying intensive trapping and hunting pressure in a systematic and progressive manner, and sweeping trapped-out areas regularly with trained detection dogs and other methods, the 17 full-time wildlife specialists employed by the project removed 10,000 nutria from 100,000 acres of infested marshes in Dorchester County. In 2007, the program expanded, and began to attack known high density populations in Wicomico and Somerset Counties. In 2008, the program shifted its focus to the tidal freshwater marshes of the Choptank River. To date, we have cleared approximately 150,000 acres out of 1/2 million acres of Delmarva wetlands of nutria.

The good news is that eradicating nutria is a sound investment in marsh restoration. Researchers, sportsmen, land managers and others have noticed and documented the recovery of damaged marshes in areas where nutria have been removed. While marsh that has converted to open water is irreversibly lost without intensive and costly restoration efforts, partially damaged marshes can be restored simply by removing nutria. In fact, when compared to the cost of rebuilding marsh, which can cost thousands of dollars per acre, the cost of protecting marsh through nutria eradication averages between $60 and $70 dollars per acre and makes good economic sense. It makes even more sense when compared to the cost of doing nothing. If allowed to repopulate, nutria could destroy another 35,000 acres of marsh; the economic ripple effects would be felt throughout the region, to the tune of $35 million a year. Hunting, fishing, ecotourism and commercial fishing are vitally important to the economy of the Chesapeake Bay area and healthy marshes are the foundation of this ecosystem. In addition to these economic values, wetlands provide coastal residents protection against flooding and play a critical role in cleaning the Chesapeake Bay by filtering storm runoff and absorbing excess nutrients. This is certainly a case where an ounce of prevention is worth a pound of cure.

Restoration through Eradication: Neutralizing Nutria in the Chesapeake Bay
Restoration through Eradication: Neutralizing Nutria in the Chesapeake Bay

Nutria in captivity at Blackwater. Photo: C. Holko, MDA

Despite the success the program has achieved so far, our work is far from over and reaching our goal is not a foregone conclusion. The status of nutria populations in remaining marshes is unknown, but given the distribution of tidal waterways, drainage ditches, ponds and waterfowl impoundments throughout the Delmarva peninsula, it is likely that nutria remain in hundreds of locations, waiting for an opportunity to reinvade the marshes that gave them a foothold in establishing themselves. Nearly 350,000 acres of habitat on the Delmarva Peninsula remain to be inspected and thousands of acres will need to be trapped. Our goal is to complete this stage by 2013. However, every acre that is added to the nutria-free zone is an additional acre that needs to be carefully and routinely monitored and spreads our staff more thinly. Continued success will require consistent funding, a dedicated staff, careful planning, and the cooperation of private landowners throughout Delmarva.

Residents of Maryland, Delaware and Virginia’s Eastern Shore can help us reach our goal by spreading the word, enrolling their land, and reporting sightings. Questions and sightings can be referred to Steve Kendrot, USDA project leader at 410-221-7857.

For more information about this and other Invasive Species of Concern, visit

Nutria in captivity at Blackwater 
C. Holko, MDA