Variation in Abundance and Efficacy of Tadpole Predators in a Neotropical Pond Community

Variation in predation risk plays an important role in shaping prey behavior, morphology, life history, population dynamics, and community structure in freshwater systems. Anuran larvae are important prey in freshwater communities and spatiotemporal variation in risk can arise from changes in the number and identity of predators; however, our understanding of variation in abundance, identity, and foraging rates for natural predator assemblages in tropical pond communities is limited. We surveyed ponds near Gamboa, Panama in 2004 and 2010 to estimate variation in predator communities of tadpoles over space and time. We also conducted short-term predation trials with the 10 most common predators using hatchling tadpoles of two widespread Neotropical frog species, Red-Eyed Treefrogs (Agalychnis callidryas) and Pantless Treefrogs (Dendropsophus ebraccatus). Predator abundance varied nearly threefold across ponds within a single year and as much as 19-fold within a pond across years. Dominant taxa also varied, with backswimmers (Notonectidae), poeciliid fish, or libellulid dragonfly naiads being the most common depending upon pond and year. Predation trials revealed that prey-specific predation rates differed among predator taxa. Some presumed predators did not consume hatchlings, whereas others consumed >90% of prey. The smaller D. ebraccatus hatchlings generally experienced higher predation rates; however, large invertebrate predators like aeshnid dragonfly naiads, giant water bugs, and fishing spiders consumed more A. callidryas. These results suggest that strong but variable larval-stage risk may be an important selective factor shaping tadpole communities and phenotypes in Neotropical ponds.