The nutria, or coypu (Myocastor coypus), is a large, semi-aquatic rodent native to South America. This animal, which can weigh up to 20 pounds, resembles a large rat with a long, sparsely-haired tail and distinctive bright orange incisor teeth. Nutria were intentionally introduced globally for the international fur trade. When the fur market collapsed, thousands of nutria escaped or were released, establishing them as an invasive species in at least 20 U.S. states. Understanding the nutria’s diet is necessary to grasp the environmental consequences caused by this species.
Nutria’s Preferred Diet and Feeding Habits
Nutria are almost entirely herbivorous, feeding mainly on vegetation found in their aquatic habitats. They are opportunistic feeders but strongly prefer the succulent, basal portions of aquatic plants, specifically underground structures. These food sources include the roots, rhizomes, and tubers of plants like cattails, cordgrasses, bulrushes, and arrowheads.
The nutria’s feeding behavior involves a high consumption rate, with an individual eating approximately 25% of its body weight in vegetation daily. They often clip and discard the above-ground stems to access the nutrient-rich underground parts. This preference for below-ground material is pronounced during winter when above-ground vegetation is scarce.
Nutria are adaptable and will consume other materials when necessary. They may eat the bark of trees such as black willow and bald cypress. Occasionally, they consume small amounts of animal matter, such as insects, mussels, and crustaceans, though this is incidental to their primary diet.
The Primary Ecological Impact: Wetland Destruction
The nutria’s focused feeding on underground plant parts causes severe ecological damage in wetlands. Marsh plants rely on dense root and rhizome mats to hold the saturated soil together. By grubbing for these roots and tubers, the nutria severs the cohesive structure that binds the marsh soil.
This destructive feeding creates an “eat-out,” an area where the majority of plant biomass has been removed. Once the root mat is chewed through, the exposed marsh soil is highly susceptible to erosion. Tidal currents and storm events easily wash away the destabilized soil, leading to rapid land loss.
The removal of the root mat converts productive marshland into open water areas, a process that can be irreversible. This loss intensifies coastal erosion and eliminates natural buffers that protect inland areas from storm surge. The destruction of marsh habitat reduces ecosystem biodiversity and removes essential areas for native wildlife.
Impact on Agriculture and Native Ecosystems
The feeding habits of nutria result in economic and ecological repercussions outside of wetlands. Nutria are opportunistic foragers and readily move from aquatic habitats into adjacent fields to consume commercial crops. They graze on various agricultural products, with rice and sugarcane being particularly vulnerable to damage in the Gulf Coast states.
High nutria populations impact native species by competing for food resources, such as muskrats competing for shared aquatic plants. The nutria’s extensive consumption of vegetation also alters the habitat structure. This negatively affects native bird and fish populations that depend on intact marsh plants for nesting and shelter.
A related consequence stems from their burrowing activities along waterways. Nutria dig extensive burrow systems up to 50 feet long into the banks of ditches, canals, and levees. These burrows compromise the structural integrity of flood-control levees, roadbeds, and irrigation systems, leading to undermining and breaches that cause substantial infrastructure damage.