Nutria, or coypu (Myocastor coypus), were first documented in Virginia as early as 1956 in the area now encompassed by the Back Bay National Wildlife Refuge . Populations expanded until the 1970’s when a period of extreme cold was believed to have reduced nutria numbers substantially . Until about 2000, nutria persisted at relatively low numbers in southeastern Virginia but the distribution remained relatively static. More recently, however, nutria appear to be expanding their range in Virginia, posing a threat to valuable wetland systems north of the James River and in river habitats west of the Great Dismal Swamp. In 2019, nutria were confirmed in the Chickahominy River system north of the James River bringing a new urgency for control and eradication efforts to protect critical wetland systems in Virginia.
Nutria are social animals and are frequently found in groups. Photo by C. Johnson
The continued expansion of nutria in Virginia will certainly result in the destruction and degradation of Virginia tidal marshes and make eradication increasingly difficult. A broad-scale analysis of nutria habitat in Virginia showed increasing habitat suitability for nutria along the Western Shore of the Chesapeake Bay due to increasing climate suitability and availability of wetlands . Therefore, every river basin within the Chesapeake Bay watershed is at-risk. Further, it is likely this continued expansion will threaten the eradication efforts in Maryland, where re-infestation can be expected should spread from southeastern Virginia continue. This progression would cost millions of dollars in damage and require renewed and additional eradication efforts in Maryland.
Nutria destroy marshes through their foraging, eating native marsh vegetation and then excavating the roots, resulting in the replacement of these productive and fundamental components of the Chesapeake estuary with mud flats. This is significant ecological degradation, and the ecological value of tidal wetlands for water quality, coastal flood protection, and wildlife and fisheries habitat are well documented.
Nutria damage to marsh vegetation. Photo by E. Anton