Feeding ecology of Elachistocleis bicolor in a riparian locality of the middle Paraná River

Elachistocleis bicolor is a poorly known South American microhylid frog. Although it has been claimed to be an ant specialist, there have been no detailed studies of ontogenetic diet change and prey selectivity in this species. We analysed the diet of 114 individuals of this frog through the post-metamorphic ontogeny. We also studied the anurans’ morphometric relationships to prey size, and compared diet with prey availability, estimating predation tactics. All prey categories were consumed out of proportion relative to their availability in the environment. The results suggest that the three stages of E. bicolor are selective foragers with a strong preference for ants, although the prey spectrum includes other taxa. The diet of subadults was more similar to that of juveniles, and had the widest diet overlap. Juveniles ate smaller prey, and this could be reducing food competition with older stages. Although the three stages are selective ant foragers, as frogs grow up, there is a partial and gradual change in prey category captured.Instituto de Botánica "Dr. Carlos Spegazzini