Nutria and muskrats are often confused due to their similar appearances and semi-aquatic lifestyles. Both are medium-sized, brown-furred rodents found in wetlands. Despite these resemblances, they are distinct species with unique ecological impacts.
Understanding Their Differences
Nutria (Myocastor coypus) are considerably larger than muskrats (Ondatra zibethicus). An adult nutria typically weighs between 11 to 22 pounds and can measure up to 2 feet in body length, with an additional 12-18 inches for its tail. In contrast, muskrats are much smaller, generally weighing 2 to 4 pounds and having a body length of about 10-14 inches, plus an 8-11 inch tail.
A distinguishing feature lies in their tails. Nutria possess a round, sparsely haired tail that resembles a rat’s tail, often tapering to a point. Muskrats, however, have a flattened, vertically compressed tail that is scaly and nearly hairless, acting like a rudder for swimming.
Their incisors also offer a clear distinction. Nutria are recognized by their prominent, bright orange or reddish-orange incisors that protrude noticeably even when their mouth is closed. Muskrat incisors, while present, are less conspicuous and typically appear yellowish or off-white. The color difference is due to iron pigmentation in nutria enamel.
When examining their hind feet, nutria exhibit fully webbed toes, aiding their strong aquatic locomotion. Muskrats, while also adapted for water, have only partially webbed hind feet. Furthermore, the snout of a nutria is broad and often appears somewhat blunt, whereas a muskrat’s snout is more pointed and slender.
Nutria often prefer larger, more open water bodies like marshes, lakes, and wide rivers, often seen grazing on emergent vegetation along banks. They construct burrows into riverbanks and levees. Muskrats typically inhabit smaller ponds, streams, and canals, building dome-shaped lodges from vegetation in shallow water or burrowing into banks.
Shared Characteristics
Nutria and muskrats share several characteristics that contribute to their frequent misidentification. Both are medium-sized rodents with dense, brown fur that insulates them in aquatic environments.
Both species are semi-aquatic, spending significant portions of their lives in and around water. They thrive in wetland habitats, including marshes, ponds, lakes, rivers, and slow-moving streams.
Their diets also overlap considerably, as both are primarily herbivorous. They feed on a variety of aquatic vegetation, including roots, stems, and leaves of plants like cattails, sedges, and reeds.
Ecological Impact
The ecological roles of nutria and muskrats diverge significantly, largely due to their native status. Muskrats are native to North America and play an integral role in their ecosystems. They create “lodges” and channels that provide habitat and pathways for other wetland species, contributing to the biodiversity and health of marshlands.
Nutria, however, are not native to North America, having been introduced from South America for the fur trade in the late 1800s and early 1900s. In many regions, they are considered an invasive species. Their aggressive feeding habits lead to significant environmental damage, particularly the destruction of wetlands.
Nutria consume the entire plant, including the root systems, leading to widespread “eat-outs” where large areas of vegetation are completely denuded. This destruction of root mats destabilizes soil, contributing to severe erosion and the conversion of productive marshland into open water. They also damage agricultural crops like sugarcane and rice, and infrastructure such as levees, through their extensive burrowing.
Consequently, management strategies for these animals differ greatly. Muskrat populations are often managed to maintain ecosystem balance. Nutria control programs are focused on eradication or population reduction to mitigate their destructive ecological impact.