What size of Neotropical frogs do spiders prey on?

Abstract

Interactions between vertebrates and invertebrates at similar trophic levels can shape community diversity and interactions, being frogs acting as prey and predators. Although spiders are a common dietary item for anurans, reports of frog predation by spiders are increasingly common in the literature. Anurans are preyed by several arthropod taxa, and spiders are, by far, the most important invertebrate predator for the group. Herein we report six new predation events by spiders on frogs and, based on a literature review, we analyzed the relationship between frog and spider sizes, and on prey niche overlap between frog and spider families for the Neotropics. Records of predation increased substantially in the last decades, especially after 2005. We recovered a relationship between frog and spider sizes, with the spider predator similar-sized or smaller than frogs. Most anuran prey ranged from 15 to 25 mm in body size, while most spiders were about 53% smaller than the frogs. Spiders were not specialized in any anuran family. Large cursorial spiders were involved in most of the reports, especially Ctenidae spiders, and Hylidae was the most frequently predated frog family. Since this prey-predator relationship is often determined by size, spiders may avoid larger frogs, explaining the pattern of our recovered reports of predation on smaller frogs. Although common, we suggest that future reports on spider-frog predation events should include more information, such as prey/predator sizes and identification, antipredator strategies, time for capture and ingestion, anuran stage, and habitat characteristics.