Bay Journal

Delmarva down to its last few nutria thanks to eradication project

  • By Kathy Reshetiloff on July 01, 2016
When nutria were introduced to the Delmarva Peninsula in the 1940s for fur trading, no one had any idea of the havoc they would wreak on wetlands. (Christine Eustis,  
fws.gov/chesapeakenutriaproject/) A nutria detector dog demonstrates its skills at Blackwater National Wildlife Refuge.  (Pamela Boehland, USDA/fws.gov/chesapeakenutriaproject/ )

There is a light at the end of the tunnel as the fight to eradicate nutria from the Delmarva Peninsula nears the final phases. Nutria, South American aquatic rodents about the size of small beavers, were introduced to the Maryland part of the peninsula in the 1940s for fur trading.

Since their introduction, nutria have wreaked havoc on thousands of acres of marshland on the peninsula through their destructive feeding habits. Nutria literally consume wetlands, eating roots and plants and ripping out vegetation to create resting platforms. These voracious rodents create circles of mud flats, called “eat outs,” which eventually become open water.

Nowhere has this been more evident than at Blackwater National Wildlife Refuge in Dorchester County, MD, which has lost 5,000 acres of wetlands through a combination of nutria, sea-level rise and land subsidence. Nutria accelerated and exacerbated the impacts of the other forces by their appetite for wetland plants, especially the roots that hold the marsh together.

Wetlands on the Delmarva Peninsula provide habitat for migratory birds, including wintering habitat for waterfowl; protect nursery areas for blue crabs, fish and other aquatic species; and filter water running off the land and into rivers and the Chesapeake Bay.

Although eagles, foxes and coyotes may prey on nutria, these predators simply could not control nutria because of their prolific nature. Nutria produce up to three litters per year. So in 2002, the Chesapeake Bay Nutria Eradication Project began. Its goal: Rid the Delmarva Peninsula of invasive nutria. First working on the refuge’s 28,000 acres, the project area expanded to 250,000 acres as surveys confirmed that nutria lived beyond the refuge’s boundaries.

Major partners in the project include the U.S. Fish and Wildlife Service, U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS)-Wildlife Services, the privately owned Tudor Farms, and the natural resource agencies of Maryland, Delaware and Virginia.

Nutria are harvested by trapping and hunting. With the voluntary cooperation of public and private landowners, the eradication project has employed multiple techniques to detect and remove nutria. Fully half of the nutria captured during the project have been on private lands.

Now the eradication program moves into its final stages — searching for the last few remaining nutria. Using specially trained detection dogs has proved particularly important in confirming the absence of nutria in previously trapped areas. APHIS trains the dogs to track only nutria. Monitoring platforms with hair snares placed in rivers and creeks adjacent to wetlands have also been an invaluable tool, eliminating the need for the project’s small field staff to continuously search thousands of acres to detect the presence of nutria.

The project has completed what is known as the “knockdown” and “mop-up” phases of eradication. The large known concentrations of nutria have been eliminated and the nutria-infested watersheds have been revisited to remove any animals that were missed.

It is now in the “verification phase,” which involves surveying six saturation monitoring zones across the Delmarva Peninsula for remaining signs of nutria. As nutria are detected, mop-up efforts are re-employed with a subsequent return to verification monitoring. Each monitoring zone is surveyed a minimum of three times after each detection/ removal effort to confirm complete eradication in that zone.

In 2009, international invasive species experts identified three components critical to the successful eradication of nutria: access to private lands, developing methods to put all nutria at risk throughout the Delmarva Peninsula, and maintaining support for the program. Since then, the project has 99 percent private landowner cooperation; innovative detection and removal techniques have put all nutria at risk; and support continues.

If funding continues, the verification phase should be completed by early 2019. At that point, the project will enter a “biosecurity” phase for three to five years with a smaller team that will respond to nutria sightings and continue a scaled-down search. After a biosecurity phase with no detections, the project will be fairly certain that nutria have been eradicated from the Delmarva Peninsula.

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About Kathy Reshetiloff

Kathryn Reshetiloff is with the U.S. Fish and Wildlife Service’s Chesapeake Bay Field Office in Annapolis.

Read more articles by Kathy Reshetiloff

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