The Chesapeake Bay Nutria Eradication Project was formed with a mission to completely eradicate nutria from the Delmarva Peninsula.The project began in 2002, after nutria had caused millions of dollars in damage and destroyed thousands of acres of wetlands during the forty years prior. The goal was not a reduction or controlled level, but the complete eradication of nutria. The project was overseen by a Nutria Management Team of seven specialists from various backgrounds including private organizations as well as the federal and state government. For more about the team, visit the Project Partnerspage of the website hosted by the U.S. Fish and Wildlife Service. Despite originally aiming to eradicate nutria by 2017, nutria may be fully eradicated by 2015.
What are nutria? Nutria (Myocastor coypu) are semi-aquatic plant eating rodents found in wetlands. Although often compared to the muskrat, they are physically more similar to beavers and only share similarities of their tail with muskrats. Although they average about fifteen pounds, they can weigh up to twenty pounds. For a comparison of nutria to species it is often confused with, visit the U.S. Fish and Wildlife Service page on nutria eradication.
How did they get here? Nutria are native to South America but were intentionally brought to North America for their valuable fur. Eventually, this demand disappeared, but due to their lack of predators in the United States, the species did not. They became an invasive species across the U.S., infiltrating twenty two states.
Nutria are most easily distinguished from other species by their bright orange teeth. Photography by Timo Sack
Photography by Sharon Cockerline
This image shows a muskrat hut overtaken by nutria, evident by the hole in the top of the hut. Muskrats enter their huts underwater whereas nutria, who are more adapted to the land, simply burrow directly into the hut.
How do they affect the Wicomico? Despite nutria being herbivores, they negatively impact nearly all life in wetlands. They eat a quarter of their weight in vegetation daily. Nutria only eat the roots of plants, killing and wasting a large amount of vegetation. This eliminates the potential of regrowth because they've destroyed the root and destroyed the current food source that other species rely on. Not only do they consume more per individual than most species, they waste more than any other species. Destruction of the root system causes any living vegetation remaining to sink into the marsh, drowning it. Underground vegetation is critical for holding the wetlands together, preventing soil erosion, and supporting plant and animal life of both native and migrating species, thus affecting species far beyond the realm of the Chesapeake Bay.
When nutria take over these habitats, they disrupt muskrats more than
any other animal. Muskrats and nutria are in indirect competition. Both
species consume the same types of vegetation. However, muskrats eat the stalks of plants. This allows the remainder of the plant to stay rooted in the ground, preserving the habitat. Nutria tend to eat only the roots, killing large amount of vegetation despite that they are not eating it. Nutria also eat more vegetation overall. Muskrats make their own
lodges, but nutria take over muskrat houses as their
own. Many other species that relied on muskrat as a food source were
not able to capture larger nutria, once again affecting the ecosystem.
Nutria's devastating impact is worse because of their population
size. They have virtually no predators in the Chesapeake Bay
watershed beyond the occasional dog or vulture. This lack of
predators allows for unrestricted, exponential population growth. Nutria begin reproducing only six months after they are born. They
can get pregnant less than two days after giving birth, making it
possible for them to give birth to five litters of twelve nutria per
litter in only two years. For a better understanding of how nutria affect each section of the ecosystem, view the nutria food web.
About the project The team leading the eradication project included Stephen Kendrot of the U.S. Department of Agriculture, who took the time to show us nutria habitats, lodges, and traps throughout the Wicomico River. The Wicomico River and Ellis Bay were the final destinations for the ten field specialists who traveled throughout the watershed setting traps and monitoring nutria. They began this section of the watershed in the spring of 2014, at which time the team expressed confidence that nutria would be eradicated by 2015, two years ahead of the original goal. The main motivation to start the project came from the intense wetland destruction at Blackwater National Wildlife Refuge. $2.8 million worth of damages were done at Blackwater alone. As nutria consumed and destroyed all the vegetation, the soil washed away and the thriving marsh dwindled into a mucky stream threatening the health of the refuge as well as the Chesapeake Bay. The project goals were not simply to eradicate nutria but also to restore wetlands. By May 2014, over 13,000 nutria had been killed allowing the team to declare over 216,000 acres to be nutria free with only about 10,000 acres to go.
What makes eradication so difficult? The ideal eradication project would occur on a remote island, providing barriers to prevent further spread of the invasive species. Unfortunately, the watershed provided virtually no barriers for the nutria, only for the eradication team. Property rights dividing the nutria habitat posed a potential threat to the eradication of the species. Many landowners immediately allowed the team to work on their property because they understood how much of their property they would have otherwise lost. Although some were initially hesitant, nearly all land owners eventually agreed. Kendrot points out that the project never would have made it as far as it had without this compliance.
Photography by Sharon Cockerline
Pictured is a nutria trap on a marsh in the Wicomico River. The trap is easily identified by anyone passing by due to the broken stick with the orange flag on it. Breaking the stick prevents birds from perching on them. The muskrat hut is actually a man-made pushup with a trap inside. The trap is not small enough to capture muskrats or any animals besides nutria.
Many people use the words eradication and control interchangeably but Kendrot stressed the differences. Due to their lack of predators and rapid reproduction, control would have been an infinite project. Other areas in the United States, such as Louisiana, have attempted to control nutria with little avail, making it clear that eradication, although far more strenuous and time intensive, is necessary. Eradication requires the capture of every single specimen. "It's a tremendous amount of work," he admitted. "The last ten percent of the population takes ninety percent of the effort." He estimated that at each marsh they captured the first ninety to ninety five percent of nutria during their first week there, but the remaining nutria took three to four more weeks. Kendrot credits their integrated approach as one of the largest contributing factors to the eradication. How do they know when one river was free of nutria? Once a nutria was captured and killed, the eye lenses were removed and dehydrated. This indicates the nutrias age which was recorded with its weight, length, sex, and other data. This information allowed for more efficient population estimates and helped to indicate when the project was complete. During the process, different surveys were completed to get more accurate estimates of how many nutria were in each area. Platform surveys, platforms in the water, were set up for nutria to haul-out on. If signs of nutria exist, a trap will be set on the platform. Going through the marsh slowly from a boat allowed them to see the amount of vegetation, muskrat huts, and scat. Land surveys were also common and exposed hauled-out nutria, scat, and tracks. The areas must still be surveyed for several years following the death of the last nutria in order to guarantee eradication. Although the goal will likely be met by 2015, the eradication will not be declared until Kendrot and his team are sure that nutria could not repopulate and infiltrate the Chesapeake Bay watershed. Kendrot modestly explained that the 13,000 nutria caught was not the important number. When dealing with eradication of such a harmful species, what the team leaves behind is the only matter of importance. Because of their diligence, the team will leave behind no nutria, just an unprecedented impact on the Chesapeake Bay's watershed.