Frequently Asked Questions (FAQs)
Nutria grooming on muskrat house
What are Nutria? Nutria are South American semi-aquatic rodents similar to our native muskrat and beaver. They weigh 15-20 pounds and are approximately 24” long from nose to base of tail. They have a 14” round tail covered in stiff bristly hair. They breed year round and can give birth to 2-3 litters of 4-9 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 escaped or released from captive populations became established in 18 states across the U.S., including Louisiana, Florida, Texas, Georgia, Alabama, Mississippi, North Carolina, South Carolina, Delaware, and Virginia.
Where are nutria found on the Delmarva Peninsula? Nutria are found throughout the Eastern Shore, concentrated in Dorchester County, and in the Potomac and Patuxent Rivers on the Western Shore.
What is the Capacity for Nutria Populations to Grow? Like most rodents, nutria are very prolific. They are ready to breed at 4-7 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 1-2 days of giving birth. Young nutria are capable of surviving without the mother after about 4 days of nursing, but most young continue to nurse for 7-8 weeks and remain with their mother 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 Olney 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.
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 four to six months. Sexually mature male nutria can breed throughout the year. Females are pregnant from 128 to 130 days, and are ready to breed within forty-eight hours after giving birth. Litters average four to five young; however, nutria can have up to thirteen young per litter and may have three litters per year. Young are born fully furred and active, weighing 8 oz. at birth. They can swim and eat vegetation shortly thereafter, still feeding on mother's milk for up to eight weeks. Within five days of life, nutria can survive away from the mother.
As an example of their proliferation: in 1938, twenty individual nutria were introduced into Louisiana and within twenty years, the nutria population exceed 20 million animals. By 1962, the nutria had replaced the native muskrat as the leading furbearer in Louisiana.
Why are they 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 NWR has seen more than 7,000 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 dykes, 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 (a farmer in Oregon was killed when his tractor toppled into a drainage ditch that had been undermined by nutria). As an invasive species, nutria also compete with native wildlife, especially muskrats, and can reduce their 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.
Left: Blackwater NWR in 1938. Right: Same area in 1989. Over 6 square miles of marsh was lost to open water because of nutria and 53% of the remaining marsh had suffered significant damage and could be lost without preventive action.
What Threat Does Nutria Pose to the Health of the Chesapeake Bay? In the past 40 years, Blackwater National Wildlife Refuge in Dorchester County has lost over 7000 acres of salt marsh 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.
This represents a significant loss of habitat for nesting waterfowl, including black ducks, which are declining in population, wetland birds, including the state-listed black rail, and a variety of song birds. Fish and crabs depend on salt marsh 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 poses 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 no natural predators to help control population growth, nutria populations in Maryland have grown rapidly. Population estimates on the inhabited 10,000 acres of Blackwater National Wildlife Refuge have grown from about 250 animals in 1968 to the most recent estimate of between 35,000 and 50,000 animals. At Tudor Farms, a 6,000-acre private wildlife management area adjacent to the refuge, population estimates between 1995 and 1998 were estimated at 17,000 to 24,000 animals. Ecologists believe that random commercial trapping has been unable to decrease the nutria population in these areas over the past decade because harvest rates have remained 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/nutrient filters, contributing to the maintenance of clean water, and serve as nurseries for young crabs and fish. Three-square bulrush (Scirpus olneyi) 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. The swim channels through the marsh also permit the saltwater tidal flooding of many isolated, interior 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 have become abundant, the muskrat have declined 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 are being degraded by nutria.
USDA Wildlife Specialist checks a trap on a prototype floating platform
What is being done about them? In 2002, the U.S. Department of Agriculture’s Wildlife Services program partnered with the U.S. Fish and Wildlife Service, Maryland Department of Natural Resources, and private landowners to determine if nutria can be eradicated from the Eastern Shore. Since then, USDA staff have implemented an integrated wildlife damage control program designed to eradicate the species from the Delmarva Peninsula. Wildlife Specialists employ traps, shooting 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 focusing on isolated pockets of individual nutria. To date over 13,000 nutria have been removed from 150,000 acres in 5 counties, including Dorchester, Talbot, Caroline, Somerset, and Wicomico counties. Damaged marsh is recovering.
Left- Nutria-damaged marsh in Somerset County in 2007. Right- Same marsh is recovered in 2009 following nutria eradication
What about wetlands restoration? Also during Phase II of the project, an initial test is being run at the refuge on both the planting of Olney three-square bulrush and the spraying of sediment to raise the eroded planting surface in the marsh destroyed by nutria. This testing will help managers assess the feasibility and cost of restoring these marshes.
Can nutria really be eradicated? Nutria were successfully eradicated from England and we have determined that with an intense population control we can eliminate nutria from more than 120,000 acres of marsh in Dorchester County. Damaged marshes and muskrat populations are now recovering in the absence of nutria. Encouraged by these results, the program is now expanding into neighboring counties which are infested by nutria.
Nutria eradication or control? In Phase II of the project, a combination of different traps and trapping strategies are being used to control nutria. A variety of trapping methods will be compared to determine trap effectiveness and to maximize the number of nutria captured. Progressive and systematic trapping will be used to cover the entire area under study. Forty-acre grids have been measured across the entire refuge and adjacent lands and trapping specialists from the U.S. Department of Agriculture's Wildlife Services are systematically setting and checking traps in one sweep across a grid. Second sweeps will be made in randomly chosen trapped sites, and surveys will be conduced in these areas to listen for nutria calls and to find evidence of recent nutria activity. In this way, biologists hope to determine whether or not it is possible to eradicate nutria in this peninsula population. This process will take two to five years.
What research has been done on the population? In Phase I, six experimental areas were chosen on these study sites. All trapping at this stage was live and all animals, except those used to study the population's overall health and reproductive status of individuals, were released with either tags for recapture to estimate populations or radio collars or transmitters to study their behavior. Nutria were marked to generate population estimates. Radio-telemetry was used to obtain data on nutria movements, behavior, and life history information essential in developing a successful eradication program. Reproductive physiology has been and will continue to be studied to assist biologists in control efforts.
Nutria damage and scat.
Why should private landowners be concerned? Nutria are a major concern to private landowners who suffer from erosion-induced loss of acreage, 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), and reduced hunting and trapping opportunities. Farmers lose crops and even in areas where nutria are not apparently causing damage, their presence threatens property and natural resources on neighboring properties as well.
What can private landowners do to protect their resources? Over half of more than 13,000 nutria taken between 2002 and 2010 have come from private lands. Landowners can protect their property by enrolling in the program. All that is required is for landowners to allow USDA 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 USDA.
Is there a cost 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 4-8 weeks to remove the nutria. After that, periodic visits every 3-12 months will be made to the property 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 USDA Nutria Project 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. USDA 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.
I hunt and/or trap on my property. Will this activity interfere?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 owner’s concerns and will respect any requests they make regarding accessing the property during hunting or trapping season.
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, providing refuge to nutria which threaten to repopulate adjacent property. This prolongs our efforts on these adjacent properties. 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 call Steve Kendrot, the USDA project leader, at 410-221-7857 or by e-mail at firstname.lastname@example.org.
How are we educating the public? A variety of communication tools have been used to cultivate an understanding, nationally and locally, of the impact nutria are having on Maryland's marshes. The project has been covered by local and state news media many times over the past four years, as well as on the Discovery Channel, the National Geographic Channel, and CNN. Presentations on the project have been made by biologists before a wide variety of audience.
How can the public help? You can help by being able to recognize nutria and their signs, and report sightings to 410-221-7857 or toll free in Maryland to 1-877-463-6497.
Call 410-221-7857 and become a partnering landowner if you own marshland, waterfront property, agricultural land, freshwater ponds, or waterfowl impoundments.
What is the Partnership? A critical element to the success of this project lies in the close partnership between several key government agencies: The U.S. Fish and Wildlife Service, the U.S. Department of Agriculture, the U.S. Geological Survey, the U.S. Army Corps of Engineers, the Maryland Department of Natural Resources, and the University of Maryland Eastern Shore. These agencies work on a "management team" to move the project forward and to keep a host of other partner organizations (26 in total) informed on its progress. This partnership works together to obtain necessary financial and other support for the project on a continuing basis. This partnership and the nutria project serve as a model for similar projects in the 15 other states impacted by nutria.
Who are the partners that make up the Chesapeake Bay Nutria Project?
- U.S. Fish and Wildlife Service
- Blackwater National Wildlife Refuge
- U.S. Department of Agriculture
- U.S. Geological Survey
- U.S. Army Corps of Engineers
- Maryland Department of Natural Resources
- University of Maryland Eastern Shore
- Patuxent Wildlife Research Center
- Tudor Farms, Inc.
What’s the latest news concerning the eradication efforts? On Nov. 17, 2004, the Washington Post reported that the Blackwater Refuge staff and their partners had eradicated the destructive nutria from Blackwater Refuge. With continued vigilance, Maryland wildlife authorities should be able to keep nutria out of the Refuge and allow the marshes to recover. Read the Post article for more details: Blackwater Refuge Now Nutria-Free.
Judas nutria efforts?
Where can I learn more about nutria? Try the following Websites:
Information about the ecological impact of nutria: http://www.pwrc.usgs.gov/resshow/nutria.htm
Information about nutria from MD DNR: http://www.dnr.state.md.us/wildlife/invnutriafaq.asp
Information about nutria from Friends of Blackwater: http://www.friendsofblackwater.org/nutria.html
Information about the Maryland Nutria Partnership: http://www.dnr.state.md.us/wildlife/invnutriaproj.asp
Information about the USDA Wildlife Services: http://www.aphis.usda.gov/wildlife_damage/