Nutria, also known as coypu, are large, semi-aquatic rodents native to South America. These animals, which can weigh up to 20 pounds and measure around two feet in length, are highly adaptable to various aquatic environments. Nutria were first brought to the United States in 1889 for commercial fur farming. After the fur market declined in the 1940s, many nutria escaped or were intentionally released. Some releases were also carried out with the hope that nutria could control aquatic vegetation.
Where Nutria Are Found Across the US
Nutria have established populations in at least 16 to 18 states across the United States. Highest concentrations are in Gulf Coast states, including Louisiana, Texas, and Florida. Louisiana hosts the largest wild nutria population, causing extensive damage to coastal wetlands. Nutria are also prevalent in the Pacific Northwest, with populations in Oregon and Washington.
The spread of nutria across the US primarily occurred through escapes and intentional releases from fur farms, as well as subsequent natural migration through interconnected waterways. For example, early introductions in California in 1899 initially failed to reproduce, but later successful introductions led to their presence in the Central Valley and South Coast by the 1940s and 50s. While California previously eradicated its nutria populations by the 1970s, a reproducing population was discovered in the San Joaquin Valley in 2017, prompting ongoing eradication efforts.
On the Atlantic Coast, nutria populations are found in states such as Maryland, North Carolina, and Virginia. Maryland successfully removed all known nutria populations from the Delmarva Peninsula in 2022 through a comprehensive eradication project. This effort, spanning over two decades, demonstrates that localized eradication is possible with dedicated programs. Despite these successes, nutria continue to pose challenges in other regions, adapting to diverse aquatic habitats like rivers, lakes, ponds, and both fresh and brackish marshes.
Why Nutria Are a Problem
The presence of nutria in non-native environments poses environmental and economic challenges. Their destructive feeding habits are a concern; nutria are voracious herbivores, consuming up to 25% of their body weight in vegetation daily. Unlike native rodents, they consume the entire plant, including the roots, rhizomes, and tubers, which prevents regrowth and leads to habitat degradation. This grazing converts vegetated marshes into open water, reducing biodiversity and destroying habitats for native wildlife.
Nutria also contribute to soil erosion through their feeding and burrowing activities. By removing the root systems that stabilize wetland soils, they weaken shorelines and riverbanks, making these areas more susceptible to erosion and land loss. Their extensive burrow systems, which can extend up to 150 feet, undermine infrastructure such as levees, dams, roads, bridges, and irrigation canals. This damage can lead to structural failures, cave-ins, and increased flooding risks, impacting both public safety and agricultural operations.
Beyond environmental and infrastructural harm, nutria can cause substantial economic losses for agricultural industries. They damage important crops like sugarcane, rice, corn, milo, beets, and various vegetables, leading to reduced yields and financial strain for farmers. Furthermore, nutria can act as vectors for several pathogens and parasites that can be transmitted to humans, livestock, and pets. These include bacteria like Salmonella and those causing tuberculosis and septicemia, as well as parasites such as blood flukes and the nematodes responsible for “nutria itch,” which can contaminate water sources through their urine and feces.