Frequently Asked Questions
Nutria grooming on muskrat house. USDA photo.
What are nutria? Nutria are South American semi-aquatic rodents similar to our native muskrat and beaver. They weigh 15 to 20 pounds and are approximately 24 inches long from nose to base of tail. Their 14 inch-long tail is round and covered in stiff bristly hair. They breed year round and can give birth to 2 to 3 litters of 4 to 9 young each year. They are considered an invasive species due to their detrimental impacts on the Chesapeake Bay environment.
Why were nutria introduced? Maryland’s nutria population was established when nutria escaped or were intentionally released from fur farms near Blackwater National Wildlife Refuge in Dorchester County. Nutria were brought to the area as a furbearer to be trapped, however, today their pelts are virtually worthless and there is no commercial value to the species on Delmarva.
Where are nutria found in the United States? Animals that have escaped or been released from similar captive populations throughout the U.S. have become established in 16 states, including Louisiana, Florida, Texas, Oklahoma, Arkansas, Tennessee, Georgia, Alabama, Mississippi, North Carolina, South Carolina, Maryland, Delaware, Virginia, Washington, and Oregon.
Where are nutria found on the Delmarva Peninsula? Nutria have been found throughout the Eastern Shore. Nutria populations are concentrated in Dorchester County, but they have also have been found in Talbot, Caroline, Wicomico, and Somerset Counties, Maryland, and Kent County, Delaware.
What is the capacity for nutria populations to grow? Like most rodents, nutria are very prolific breeders. They are ready to breed at 4 to 7 months of age and may breed throughout the year. Nutria can produce up to three litters of four offspring each year, but litter sizes can reach 13 young. After mating, females give birth in a little over 4 months and are ready to breed again within 1 to 2 days of giving birth. Young nutria are capable of surviving independently 5 days after birth, but most young continue to nurse for 7 to 8 weeks and remain with the female for about 10 weeks.
Mortality, or the percentage of animals that die in a population each year, is estimated to be 80% during the first year of life, and few animals live more than 2 or 3 years. Predators of nutria in the Chesapeake Bay include humans, bald eagles, and carnivorous mammals.
What do they eat? Nutria are vegetarians and feed on roots, tubers, shoots, and leaves of marsh plants such as three-square bulrush, cattails, and spartina. Nutria will also feed heavily on agricultural crops such as corn, soybeans, and clover.
Nutria tracks showing tail drag. USDA photo.
How fast do nutria reproduce? Nutria are highly prolific and breed all year. Reproductive peaks occur in late winter, early summer, and mid-autumn. Reproduction and survival may be influenced by extreme weather conditions. Nutria reach sexual maturity at 4 to 7 months. Sexually mature male nutria can breed throughout the year. Females are pregnant from 128 to 130 days, and are ready to breed within 2 days after giving birth. Litters typically contain 4 to 9 young; however, they can have up to 13 young per litter and may have three litters per year.
As an example of their proliferation: In 1938, twenty nutria were introduced into Louisiana and within twenty years, the nutria population exceeded 20 million animals. By 1962, nutria had replaced the native muskrat as the leading furbearer in Louisiana.
Why are nutria a problem on the Delmarva Peninsula? The nutria’s destructive feeding habits have resulted in the loss of tens of thousands of acres of marsh to erosion throughout the Chesapeake Bay. Blackwater National Wildlife Refuge has seen more than 5,000 acres of marsh converted to open water that no longer supports the diverse array of wildlife that depends on the marsh. Loss of marsh habitat also results in increased flooding; the filling of ditches, streams and river channels by sediments lost to erosion; and timber die-off as salt water from the Bay intrudes further inland. Nutria also burrow into dikes, berms, roads, water control structures, and stream banks which often collapse, resulting in erosion, costly repairs, damage to equipment, and threats to human health and safety. As an invasive species, nutria also compete with native wildlife, especially muskrats, and can reduce muskrat numbers significantly. Nutria will defend themselves vigorously when cornered, and many pet owners have incurred costly vet bills when their dogs have encountered nutria. Many farmers have suffered extensive damage to corn and soybean crops where nutria inhabit streams and drainage ditches in agricultural lands.
What threat do nutria pose to the health of the Chesapeake Bay? In the past 40 years, Blackwater National Wildlife Refuge has lost over 5,000 acres of saltmarsh from a combination of nutria feeding activity, sea level rise, and erosion of soil that supports marsh plants. Marsh is also being lost on state and private conservation lands at equally alarming rates. This represents a significant loss of habitat for nesting waterfowl, including American black ducks, which are declining in population; wetland birds, including the state-listed black rail; and a variety of songbirds. Fish and crabs depend on the saltmarsh for shelter and protection from predators and as a source of food, since the plants and sediment support many insects and other invertebrates. The loss of these species, in turn, reduces the value of these areas for commercial fisheries and for local ecotourism, which brings $15 million each year from visitors to Blackwater National Wildlife Refuge alone.
Nutria pose a significant threat not only to the health of the Chesapeake Bay, but also to the very conservation purposes for which state, federal, and private conservation refuges were purchased and are maintained, with both public and private funds.
How has their population increased? With few natural predators to help control population growth, nutria populations in Maryland have grown rapidly. Populations on Blackwater National Wildlife Refuge were estimated to have increased from about 250 animals in 1968 to between 35,000 and 50,000 animals by the late 1990’s. At Tudor Farms, a 6,000-acre private wildlife management area adjacent to the refuge, populations between 1995 and 1998 were estimated at 17,000 to 24,000 animals. Biologists believe that random commercial trapping did not decrease the nutria population in these areas prior to the establishment of the Chesapeake Bay Nutria Eradication Project because commercial harvest rates were only between 5,000 to 10,000 nutria on each area every year.
What are nutria’s impacts on other species? Marsh loss removes habitat for native wildlife species, such as waterfowl, wading birds, and muskrats. Healthy marshes also function as sediment and nutrient filters, contributing to the maintenance of clean water, and serve as nurseries for young crabs and fish. Three-square bulrush is an especially valuable food resource for wintering waterfowl. The loss of this plant removes it as food for these birds and reduces invertebrate populations, which migrating waterfowl also feed on. Nutria create swim channels through the marsh which allows saltwater tidal flooding into many isolated, interior marsh ponds that support submerged aquatic vegetation. The increase in salinity and turbidity limits the growth of submerged aquatic vegetation, important for making dissolved oxygen and serving as food and shelter for many native species. Submerged aquatic vegetation is an important food source for migrating and wintering waterfowl, especially American black ducks, a species of priority concern in the Atlantic Flyway. Some investigators reported that nutria have negatively affected native muskrat populations. Where the larger, more aggressive nutria become abundant, the muskrats decline due to competitive displacement. Maryland has lost over 73% of its original wetlands, making the remaining wetlands vital to maintaining the health of the Chesapeake Bay ecosystem. Unfortunately, large expanses of Maryland's marshes have been degraded by nutria.
USDA Wildlife Specialist checks a trap on a prototype floating platform. USDA photo.
What is being done about nutria? In 2000, the Chesapeake Bay Nutria Eradication Project, led by the U.S. Fish and Wildlife Service, Maryland Department of Natural Resources, U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) Wildlife Services, Tudor Farms, and the University of Maryland, began as a pilot study to determine the feasibility of eradicating nutria. In 2002, taking what was learned in the pilot study and using funding provided by Congress through the U.S. Fish and Wildlife Service, APHIS Wildlife Services implemented an integrated wildlife damage control program designed to eradicate the species from the Delmarva Peninsula. APHIS Wildlife Specialists employ traps, firearms, and detection dogs to systematically seek out and remove nutria from infested wetlands. High tech computer mapping software and global positioning devices are used to apply intensive population control in strategic areas.
What have our accomplishments been so far? The project has successfully reduced the original population and is now monitoring areas to locate possible residual nutria. To date over 13,000 nutria have been removed from more than 150,000 acres in 5 counties in Maryland, including Dorchester, Talbot, Caroline, Somerset, and Wicomico counties, as well as in Kent County, Delaware. Population delineation surveys determined that an additional 100,000 wetland acres were nutria-free. Following removal of nutria, much of the nutria-damaged marsh is recovering.
What about wetland restoration? Damage to these essential habitats must be repaired to conserve fish and wildlife populations and sustain commercial and recreational activities. The health of marsh habitats on the Delmarva Peninsula is being evaluated and prioritized for conservation and restoration efforts. Biologists from Maryland, Delaware, and Virginia; federal agencies; and non-government organizations are partnering with coastal engineers to use the newest scientific techniques for marsh restoration and protection. By restoring lost shallow water and marsh habitat, we will improve the economic returns from activities such as fishing, hunting, and wildlife viewing.
Can nutria really be eradicated? Nutria were successfully eradicated from England, and we have determined that with an intensive eradication program we can eliminate nutria from the Delmarva Peninsula. The Chesapeake Bay Nutria Eradication Project has removed nutria from every nutria infested watershed on Delmarva, and is now engaged in revisiting previously trapped watersheds to find and remove any remaining animals and to verify eradication.
Nutria eradication or control? In Louisiana, it is estimated that there are 20 million nutria scattered over hundreds of thousands of acres of marsh. Complete eradication under Louisiana’s scenario is impossible, so they have instituted a control program that will need to be funded and implemented indefinitely. Total eradication on the Delmarva Peninsula is possible because the nutria population is much lower than in Louisiana and the Delmarva Peninsula is effectively an island, surrounded by water on three sides and inhospitable terrain to the north. Once nutria are eradicated, the need for continued funding will be eliminated.
What research has been done on the population? In 2000, six experimental areas were chosen for research to determine the feasibility of eradication. Only live trapping was used and all animals, except those used to study the population's overall health and reproductive status, were released with either tags for recapture to estimate populations, or radio collars with transmitters to study their behavior and movement.
Nutria damage and scat. USDA photo
Why should private landowners be concerned about nutria? Nutria are a major concern to private landowners who suffer from erosion-induced loss of marshland, reduced access to remaining marsh (damaged marsh is very difficult to walk on and erosion has filled in many creeks that were once navigable by boat), reduced hunting and trapping opportunities, and destruction of agricultural crops.
What can private landowners do to protect their resources? Over half of the more than 13,000 nutria taken between 2002 and 2016 have come from private lands. Landowners can protect their property from nutria damage by enrolling in the program. All that is required is for landowners to allow APHIS Wildlife Services staff access to their property to inspect for nutria damage, remove any infestations, and periodically monitor the property for reinvasion. This voluntary agreement is established by an “Agreement for Control of Wildlife Damage” form provided to the landowners by APHIS Wildlife Services.
Is there a cost for landowners to participate in the program? This service is provided free to the landowner.
How long will nutria project personnel need to be on my property? Depending on the size of the property and the severity of the nutria infestation, project staff will require access for 4 to 8 weeks to remove the nutria. After that, periodic visits every 3 to12 months will be made to the property during the life of the project to prevent the establishment of new populations.
I have concerns about “strangers” or the government accessing my property. Many landowners are rightfully concerned about unknown people on their property. As Federal Wildlife Specialists, all APHIS Wildlife Services staff undergo extensive criminal background checks. We realize the importance of private landowner cooperation to the success of our program, and our staff are highly respectful of private property owners. APHIS Wildlife Services is a non-regulatory agency and has no authority to enforce environmental or game laws. We respect the confidentiality of our agreements with private landowners. We have established hundreds of agreements with private landowners without incident, and in fact, many landowners have requested that we inform them of any unauthorized activity on their property.
Will nutria eradication efforts interfere with hunting and trapping on my property? No. Your cooperation is voluntary and you can stipulate when, where, and how we access your property on the agreement form. We like to obtain as liberal access as possible because we have hundreds of thousands of acres of marsh to cover and scheduling our work is easiest when we don’t have access restrictions. However, we understand owners’ concerns, and will respect any requests they make regarding accessing property during hunting or trapping seasons.
Are other landowners participating? Hundreds of private landowners have allowed nutria project staff access to their property. Only a small number of landowners have refused to allow access. Such landowners are providing refuge to nutria, which threaten to repopulate adjacent properties. This prolongs our efforts and increases project costs. Fortunately, landowner refusal has not been widespread, and the vast majority of landowners have enthusiastically supported the program.
Who can I call if I have additional concerns or problems? You can contact Marnie Pepper, the APHIS Wildlife Services Project Leader, at (410) 901-2118 or Margaret.A.Pepper@aphis.usda.gov.
How are we educating the public? A variety of communications tools have been used to cultivate an understanding, nationally and locally, of the impact nutria have had on Chesapeake Bay marshes. The project has been well covered by local, state, and national news media many times over the past 16 years, including the Discovery Channel, the National Geographic Channel, and CNN. Presentations on the project have been made by biologists before a wide variety of audiences.
How can the public help? You can help by being able to recognize nutria and their sign (tracks, scat), and reporting sightings to (410) 901-2118 or toll free in Maryland to 1-877-463-6497.
Call (410) 901-2118 and become a partnering landowner if you own marshland, waterfront property, agricultural land near the water, freshwater ponds, or waterfowl impoundments.
What is the Chesapeake Bay Nutria Eradication Partnership? The Chesapeake Bay Nutria Eradication Partnership is a coalition of 26 private, local, state, and federal partners that is critical to the success of the nutria eradication project. The partners work together to obtain necessary financial and other types of support for project operations. A “management team,” composed of representatives from the U.S. Fish and Wildlife Service, the Maryland Department of Natural Resources, U.S. Department of Agriculture’s APHIS Wildlife Services, Delaware Department of Natural Resources and Environmental Control, Virginia Department of Game and Inland Fisheries, and Tudor Farms, Inc., oversees the project. APHIS Wildlife Services supervises daily operations and implements the partner’s Strategic Operations and Management Plan. This partnership and the nutria project serve as a model for similar projects in the 16 other states and other countries impacted by nutria.