Nutria, also known as coypu, are large, semi-aquatic rodents that originated in South America. They are often mistaken for other aquatic mammals, leading to questions about their natural behaviors and environmental impact. This article clarifies common misunderstandings about nutria, particularly their building habits.
Understanding Nutria Structures
Nutria do not build dams. They construct extensive burrow systems for shelter, nesting, and protection from predators. These burrows consist of tunnels and dens dug into riverbanks, levees, dikes, and other earthen structures. Burrows can range from simple, short tunnels to complex systems with multiple entrances and chambers, some extending up to 150 feet. The main den chamber is usually above the waterline and may be lined with plant debris.
In marshy areas, nutria may also create surface nests or flattened platforms from vegetation, used for resting, feeding, grooming, and giving birth. These platforms are temporary and differ from beaver dams.
Environmental Impact of Nutria Activities
Nutria activities primarily impact the environment through their burrowing and feeding habits. Their extensive burrowing causes significant bank erosion and destabilizes shorelines, leading to the collapse of infrastructure like levees, dikes, and roads. This damage increases flood risks and requires costly repairs.
Nutria are voracious herbivores, consuming substantial amounts of aquatic vegetation. They can eat up to 25% of their body weight daily, leading to widespread destruction of plant life. This feeding behavior often results in “eat-outs,” where healthy wetlands are converted into open water or barren mudflats, destroying habitat for other wildlife.
Nutria Versus Beavers
The question of whether nutria build dams often arises from confusion with beavers, which are the primary dam-building rodents in North America. Beavers construct elaborate dams using wood, mud, and rocks to create deep-water ponds, which provide refuge from predators and facilitate access to food. This behavior contrasts sharply with nutria, who do not build dams and instead rely on burrows for shelter.
Several physical differences distinguish nutria from beavers. Nutria are generally smaller, typically weighing between 10 to 20 pounds, while beavers can weigh 25 to 60 pounds or more. A noticeable distinction is their tails: nutria have a round, sparsely haired, rat-like tail, whereas beavers possess a broad, flat, paddle-like tail. Nutria also have bright orange incisor teeth and partially webbed hind feet, which aid their semi-aquatic lifestyle. In contrast, beavers have fully webbed hind feet, suited for their highly aquatic and dam-building activities.