Nutria are almost entirely herbivorous and eat animal material (mostly insects) incidentally, when they feed on plants. Freshwater mussels and crustaceans are occasionally eaten in some parts of their range. Nutria are opportunistic feeders and eat approximately 25% of their body weight daily. They prefer several small meals to one large meal.
The succulent, basal portions of plants are preferred as food, but nutria also eat entire plants or several different parts of a plant. Roots, rhizomes, and tubers are especially important during winter. Important food plants in the United States include cordgrasses (Spartina spp.), bulrushes (Scirpus spp.), spikerushes (Eleocharis spp.), chafflower (Alternanthera spp.), pickerelweeds (Pontederia spp.), cattails (Typha spp.), arrowheads (Sagittaria spp.), and flatsedges (Cyperus spp.). During winter, the bark of trees such as black willow (Salix nigra) and bald cypress (Taxodium distichum) may be eaten. Nutria also eat crops and lawn grasses found adjacent to aquatic habitat.
Because of their dexterous forepaws, nutria can excavate soil and handle very small food items. Food is eaten in the water; on feeding platforms constructed from cut vegetation; at floating stations supported by logs, decaying mats of vegetation, or other debris; in shallow water; or on land. In some areas, the tops of muskrat houses and beaver lodges may also be used as feeding platforms.