The guild structure of animalivorous leaf-nosed bats of Barro Colorado Island, Panama, revisited

(Uploaded by Plazi for the Bat Literature Project) We examined data sets on dietary composition of a rich (15 species) assemblage of animal-eating Neotropical leaf-nosed bats (Phyllostomidae: Phyllostominae) that occur syntopically on Barro Colorado Island, Panama. Our aim was to test previously postulated trophic structure of phyllostomines in the light of alternative analytical techniques and new data. The trophic structure of this assemblage, according to new results from Correspondence Analysis, has two main trends of variation: a gradient of increased carnivory (axis 1) and a gradient involving plant and arthropod consumption (axis 2). This rejects previous hypotheses of this guild in which the structure was described as a complex of many independent discrete resources. Although all data sets agree that coleopterans as a group are an important food item for most species, Phyllostominae bats are not typically durophageous; i.e., they lack cranial and dental adaptations for rapid processing of hard-shelled arthropods as found in other bat families. Furthermore, insectivory varies inversely with body size, and is gradually replaced by carnivory in association with increasing mass and limited dental modifications. Together with CA results, this suggests that carnivory is an extreme of animalivory rather than a qualitatively distinct feeding habit among Phyllostominae bats. This conclusion fits biomechanical data that indicate that carnivorous bats are bigger and only modestly modified versions of soft-insect specialists.