The nutria, also known as the coypu, is a large, semi-aquatic rodent that now thrives on multiple continents far from its original home. This species has become an established invasive species in many parts of the world, including the United States. The nutria’s establishment outside of its native range was not accidental but the result of a deliberate, profit-driven enterprise. This article explores the historical reasons and methods behind the animal’s global translocation, which led to its current invasive status.
Native Range and Basic Biology
The nutria is originally native to the temperate and subtropical wetlands of South America, with its natural range spanning countries such as Argentina, Bolivia, Uruguay, and Chile. This rodent is a robust creature, typically weighing around 12 pounds and measuring about two feet in length, not including its long, rounded tail. Nutria are strictly herbivorous, preferring to inhabit areas near permanent bodies of water, such as swamps, marshes, and riverbanks.
Nutria biology supports rapid population growth. Females are prolific breeders, capable of producing multiple litters annually after a gestation period of approximately 130 days. The young are born precocial, fully furred with open eyes, and can swim and consume vegetation within hours of birth. This high reproductive rate allows populations to multiply quickly when introduced into new habitats with few natural predators.
The Economic Incentive for Introduction
The primary reason for the nutria’s global spread was the international fur trade of the late 19th and early 20th centuries. Its pelt, often marketed as “nutria fur” or “coypu fur,” was valued for its fine, dense undercoat and waterproof outer layer, similar to that of a beaver or otter. This commercial interest led entrepreneurs to establish nutria farms, or ranches, outside of South America to meet the growing demand for luxury furs.
The first attempts at nutria farming in the United States occurred as early as 1889 in California, but larger-scale commercial imports began in the 1930s. These enterprises were driven by the promise of profit, as native fur-bearing animals were being over-harvested. The establishment of these fur farms was not limited to North America; similar operations were launched across Europe and Asia, ensuring the species had a presence on multiple continents.
Mechanisms of Release and Establishment
The nutria transitioned from a captive livestock animal to a widespread feral species through two main pathways: accidental escape and deliberate release. Ranches established to house the rodents often proved inadequate for containing the semi-aquatic, burrowing animals. Poor enclosure maintenance, combined with natural events like floods and hurricanes, allowed many nutria to escape into the wild, particularly in coastal areas. A significant example occurred in Louisiana in the 1940s, where a major hurricane scattered stock from coastal farms, inadvertently seeding the surrounding marshlands.
Many nutria were deliberately released when the fur market collapsed in the 1940s. As the demand for nutria pelts plummeted, ranchers faced the financial burden of feeding and housing thousands of animals that no longer held economic value. Rather than incur the cost of euthanization, many farmers simply opened their gates, freeing their stock into local waterways. Some nutria were also intentionally released in certain regions to control aquatic vegetation, an attempt at biological control that expanded their range.
Environmental Impact of the Invasive Nutria
The successful establishment of nutria populations has resulted in ecological damage to their non-native wetland habitats. Their destructive impact is primarily due to their feeding habits, which target the below-ground parts of marsh vegetation. Nutria consume large amounts of plant material daily, specifically focusing on the roots, rhizomes, and tubers that hold marsh soil together.
This intensive feeding causes what are known as “eat-outs,” areas where the marsh is completely stripped of vegetation. When the root mat is removed, the soil becomes unstable and quickly erodes, leading to the conversion of productive marshland into open water. This loss of coastal wetlands reduces habitat for native species and compromises the natural storm protection provided by the marsh ecosystem. Their burrowing activity also weakens human infrastructure, undermining levees, roadbeds, and drainage canals, which exacerbates flood risk in low-lying areas.