nutria have escaped from commercial fur farms and are a threat to Virginia's marshes
Source: US Fish and Wildlife Service, Nutria
Nutria (Myocastor coypus) are nocturnal rodents weighing up to 20 pounds that thrive in marshes. They are native to South America, not to Virginia. Nutria were originally introduced into Louisiana by commercial fur farmers in 1899. Farmers on the Delmarva Peninsula released thousands of animals in the mid-1900's, when fur farming became no longer economically viable.
On the western side of the Chesapeake Bay, nutria migrated north of the North Carolina border after World War II. After 50 years, they have finally extended their range beyond the blackwater swamps in the Coastal Plain to the Chickahominy River.
Nutria have a high reproductive rate, producing up to three litters annually. Nutria are outcompeting native muskrats, and destroy entire plants when feeding rather than harvest just a portion like other grazing animals. By digging up the roots, nutria destroy marshes and trigger conversion to open water habitat.
Wildlife managers in Virginia consider nutria to be a serious threat to coastal wetlands:1
nutria eat so many roots that they trigger erosion which converts marshes into open water habitat
Source: US Fish and Wildlife Service, Nutria in water and Nutria damage
Nutria were introduced into the Blackwater National Wildlife Refuge in Maryland in the 1940's. The Chesapeake Bay Nutria Eradication Project required 20 years and $27 million to eliminate 14,000 of them from the Delmarva Peninsula. That extirpated the invasive manmmals from the eastern side of the Chesapeake Bay, but nutria are still present on the western side.2
If nutria manage to expand north of the Chickahominy River into the rest of Virginia, the invasive animals will thrive in the coastal rivers. Excessive amounts of emergent vegetation in marshes will be uprooted and mudflats will be left unprotected by roots. If phragmites does not quickly cover a new mudflat, then currents and storms will wash away the soil and convert former marshland into open water habitat.
Marshes with natural vegetation are more ecologically valuable than mudflats with phragmites or open water, so Department of Wildlife Resources biologists use "conservation dogs" to smell where nutria are present and then set traps to kill them.3
traps are baited with carrots and apples to capture nutria and prevent their spread north of the Chickahominy River
Source: US Fish and Wildlife Service, Baited trap used to capture nutria and Caged Nutria
nutria have expanded their range into multiple states
Source: US Geological Survey (USGS), NAS - Nonindigenous Aquatic Species
Source: Discover, Nutria Hunted to Save Wetlands