Diet and resource partitioning in Patagonian bats (Chiroptera: Vespertilionidae and Molossidae)

Partitioning of food resources is one of the main drivers of bat community organization. We investigated the trophic structure of the Patagonian bat ensemble which comprises eight insectivorous species classified in the families Vespertilionidae and Molossidae. Natural history studies, particularly those of diet and resource use, are scarce for these species and for bats of harsh environments generally. Here, we report the analysis of 140 dietary records from the eight Patagonian species sampled in 23 Western Central Patagonian localities in Chubut Province, Argentina. We estimated the dietary composition, both as percentage volume and as frequency of occurrence, of each dietary item, which was identified to the level of order. Trophic-niche breadth and average prey hardness were calculated for each bat species. We applied a principal components analysis for volume dietary data and correspondence analysis for frequency data. We recorded six insect orders (Coleoptera, Lepidoptera, Trichoptera, Diptera, Neuroptera, and Hemiptera) in different proportions across species. The latter also diverged in average prey hardness and trophic-niche breadth. This study provides the first quantitative picture of trophic organization in bats from Patagonian habitats. While Myotis species mainly consumed Coleoptera, followed by Lepidoptera and Diptera, Lasiurus species took chiefly Lepidoptera; Histiotus predominantly hunted for Coleoptera, and T. brasiliensis captured chiefly Lepidoptera, Coleoptera, and Diptera. These different dietary combinations indicate resource partitioning among three vespertilionid and one molossid genera, as well as a degree of niche organization in Patagonian bats, which help to understand their ecosystem role as insect predators.