A PRELIMINARY INVESTIGATION INTO HAYNE ESTIMATES OF POISON DART FROG (ANURA: DENDROBATIDAE) DENSITIES IN RECOVERING TROPICAL FOREST HABITATS, SOUTHWESTERN COSTA RICA

The global decline of amphibian populations has created a high demand for effective tools to measure how species respond to environmental change. We investigated the effectiveness of the Hayne Estimator for evaluating the population densities of Dendrobates granuliferus and Dendrobates auratus. We observed frogs in three Costa Rican lowland forest habitats with varying degrees of deforestation recovery. Population densities were highest in selectively-logged riparian forest, substantially lower in non-native bamboo plantation forest, and lowest in pasture-regrowth secondary forest. This trend corresponds to previous research on species recolonization after deforestation and subsequent regrowth. Individuals of both species tended to aggregate near water, but our study design masked this observation. Sighting frequency correlated with rainfall for D. granuliferus but not for D. auratus. Air temperature did not influence sighting frequency. Time of day, however, influenced the sighting frequencies of both species, with most frogs observed in the early morning and late afternoon. Our results appear to support the robustness of the Hayne Estimator for Poison Dart Frog monitoring and we recommend this technique as a valuable tool for dendrobatid research.