The effects of environmental cues on chorusing onset in a tropical frog assemblage

There are extensive studies on frog calling behaviours, including the effects of environmental variables, however, there are no known studies to explore the specific proximate cues that stimulate the onset of calling in an individual on a given night. The aim of this study is to identify and quantify the species-specific set of environmental variables that stimulate males to produce mating calls under natural conditions. Call surveys were conducted at an active breeding pond on the edge of Parque Nacional Soberanía, Panama, during the breeding seasons of 2009 and 2010. Observations were made on 20 anuran species at the study site and we examined the onset of calling in nine species that were active and most consistently present during breeding seasons. We used logistic and linear regression models to investigate environmental conditions that affect calling for each species. The initiation of chorusing differed by species and key factors included ambient light, rainfall, and lunar cycle. Our data define the margins of a behavioural-environmental envelope that is species-specific and is not related to calling behaviour itself but is rather defined by physiological constraints related to environmental exposure.