A December survey of the tadpole community of the Research Swamp

Abstract. Patterns of habitat use and breeding phenology of temperate-zone anuran species are well known, facilitating further study of the mechanisms that structure anuran communities. However, few studies have examined such patterns in tropical anuran assemblages. The Research Swamp site at the La Selva Biological Reserve in Northeast Costa Rica is one of the few tropical sites where the breeding community of anurans has been studied in detail. Past investigators have surveyed the larval anuran community in the pond as an indicator of the suite of species that use the pond for breeding. While adult and juvenile populations have been studied year round, surveys of larval populations have been limited to the typically wet month of July. In this study, I surveyed the tadpole community of the Research Swamp in December for comparison with the communities observed by others in July. I found fewer tadpoles (16), than in past studies, representing two species (Hyla phlebodes and Agalychnis callidryas). The significant year-to-year variability in the composition of the tadpole community shown by other studies suggests that annual variation may be as strong or stronger than seasonal variation. Because anuran reproductive cycles at this site have been shown to be influenced by rainfall, seasonal and year-to-year variability in the tadpole community is likely to correspond with annual variations in monthly rainfall. The low density of tadpoles found in this study could be the result of unusually low rainfall during September 2000, creating conditions unfavorable to breeding.