Diet of the coypu (Nutria, Myocastor coypus) in agro-systems of Argentinean pampas

We used microhistological analysis of feces to study diet composition and food, selection of coypu (Myocastor coypus) in 3 riparian habitats of the Pampas region of Argentina. The main food types were monocots associated with water (40-60% of diet), which were consumed significantly more than in proportion to availability. Terrestrial monocots, represented 30-35% of the diet and were consumed in proportion to availability: Coypu ate dicots (0-15%) significantly less than the proportion available. The most preferred plant species in the diet were Eleocharis bonariensis in winter and spring (15-37%), and Lemna sp. in summer and autumn (20-30% of diet). Coypu consumed <2% of each of the 6 crops available, regardless of the phenological condition of the crops. In a field experiment, we equalized availability of a terrestrial species (Lolium multiflorum) and a hygrophylic species (E. bonariensis) at 2 distances from water, and the results suggested that dietary selection was dependent on the distribution of food sources in relation to distance to shelter. We concluded that coypu did not behave as a pest of agrosystems, provided that the riparian habitat included at least a narrow fringe of natural vegetation, as occurs in most of the Pampas Plain.