Trophic interactions among plains vizcacha ( Lagostomus maximus ), greater rhea ( Rhea americana ), and cattle in a wetland of the Paraná River Delta Region, Argentina

Abstract

The plains vizcacha (Lagostomus maximus) and the greater rhea (Rhea americana) are considered to compete for forage with cattle in agroecosystems of South America. The aims of this research were to analyze the diet diversity and the trophic niche breadth of these three herbivores where they share a wetland area in Argentina, and to assess the extent of food niche overlap throughout the year. The three species all showed relatively narrow trophic niches in all seasons, which defines them as selective feeders. Vizcacha and cattle showed the highest (54.8%) mean food niche overlap throughout the year. A low overlap was observed between greater rhea and the other two herbivores, except in Winter (61.2% greater rhea and cattle). Vizcacha showed the highest mean diet diversity, and diet diversity was similar, but lower, in greater rhea and cattle. According to the results, if livestock raising increases and a scenario of competition is considered, the vizcacha is likely be the most affected species, because its foraging areas are restricted to the surroundings of its fixed burrows. On the other hand, greater rheas have an opportunistic foraging behavior and can move into areas where cattle are absent.