Are Nutria Established in Illinois?

Many are familiar with semi-aquatic mammals such as the American beaver (Castor canadensis) and muskrat (Ondatra zibethicus), but the name nutria may not ring the same bell. Nutria (Myocastor coypus) are an invasive semi-aquatic mammal from South America.

Nutria were introduced into North America during the 1930s to supplement the fur trade in Louisiana, Ohio, New Mexico, Washington, Michigan, Oregon and Utah. As the demand for nutria fur diminished in the 1940s, individuals were released to the wild both intentionally and by unintentional escape. This has resulted in nutria inhabiting at least 20 states. States with dense populations, such as Louisiana and Maryland, have implemented management efforts to reduce nutria populations, each with their own set of challenges.

Characteristics of Nutria

Nutria are small semi-aquatic mammals, easily mistaken for a small beaver or large muskrat, especially by people who are unfamiliar with wildlife. Upon closer inspection, nutria have a relatively large, square head on a smaller body. Nutria will appear a bit grayer compared to beaver and muskrat and have distinct white whiskers. They have short legs that make it seem as if they are dragging their chest to the ground and walk with an arched back. Their body will measure around 24 inches long and their round tails can measure from 13 to 16 inches. The tail will be mostly hairless with a few tufts of hair at the base. The average weight for an adult is around 12 pounds, though they can grow up to 20 pounds. Nutria breed year-round and have an average litter size of 4 or 5 young. Contrary to other semi-aquatic mammals, nutria do not create dens or lodges. Instead, they rest on top of vegetation or occupy abandoned burrows. As a result, nutria are generally limited to warmer climates that do not have harsh winters.

As a generalist species, nutria take advantage of a variety of aquatic environments and therefore can be found in areas such as small farm ponds, large rivers, and everything in between. They feed on a wide range of aquatic vegetation but prefer cattails, cordgrass and bulrush. Their feeding habits are what define them as an invasive species. Nutria consume around 25 percent of their body weight each day. With such an aggressive appetite, they can quickly denude large areas, removing all vegetation, digging out the roots and exposing the topsoil to erosion. This feeding behavior causes rapid erosion, changing the plant community in important wetlands that provide habitat to multiple wildlife species. Wetlands with diverse emergent vegetation are converted to open water and habitat quality is reduced. This can have detrimental effects on many species of native plants and wildlife. Infrastructure and agriculture in areas where nutria become established can suffer as well.

Sightings of Nutria in Illinois

Over the past decade, multiple sightings of nutria have been reported in southern Illinois. While one report in 2022 was confirmed to be nutria, the physical similarities among semi-aquatic mammals create uncertainty in reports without supporting evidence. Although nutria have established populations in Kentucky and Missouri, it is unknown whether they are breeding in Illinois. It was previously thought that these areas would have too harsh a winter to support nutria. Evidence of nutria in surrounding states has proven that thought wrong and therefore prompted the need for research into their potential presence in Illinois.

Investigating the Status of Nutria

The Illinois Department of Natural Resources (IDNR) has partnered with the Cooperative Wildlife Research Lab (CWRL) at Southern Illinois University to investigate the status of nutria as well as other species of semi-aquatic mammals in southern Illinois. Current research focuses on surveying all semi-aquatic mammals, identifying the best method to detect nutria to better understand their potential distribution and guide future management efforts.

Sign surveys, camera traps, detection dogs, and environmental DNA (eDNA) sampling have been or are currently undergoing to survey for the presence of nutria in water bodies in Alexander, Pulaski, Masaac and Pope counties.

These surveys will help us determine if there is a nutria problem, and also assess which methods are most effective at detecting them – if they are present.

While research will help shed light on the status of nutria in Illinois, it is only the first step in the larger management process. This research will inform future work and, if nutria are in Illinois, we can assess any impacts to our native wetlands and native species. If negative impacts are fond, this work will be important to ensure nutria are found and removed before they become overabundant. Detecting them earlier rather than later will be crucial in preventing damage and maintaining healthy wetland systems in Illinois.

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Derek Whipkey is a master’s student in the Cooperative Wildlife Research Lab at Southern Illinois University. He is researching the distribution of semi-aquatic mammals in southern Illinois. Whipkey received his bachelor’s degree in wildlife science from Ohio State University.