Variable response of anuran calling activity to daily precipitation and temperature: implications for climate change

Long-term monitoring of frog populations is needed to understand the effects of global change. To better understand the relationships between climate variation and calling activity, we monitored an anuran assemblage in a Puerto Rican wetland by sampling the acoustic environment for one minute every 10 minutes, for 41 months. By automating data collection using passive acoustic monitoring hardware, we collected more than 110,000 recordings. These recordings were analyzed using species-specific identification algorithms of four Eleutherodactylus species. The peak calling activity of E. coqui (>0.3 detection frequency) and E. cochranae (>0.2) occurred between April and September, and there was a clear decline in activity during the dry months of January-March. There was no clear annual pattern in E. brittoni or E. juanariveroi, but E. juanariveroi did show a significant decline in calling activity over the 41-month study (similar to 0.5 to similar to 0.35). Calling activity of E. coqui and E. cochranae was positively correlated with temperature, while E. brittoni and E. juanariveroi responded negatively to temperature and precipitation. This difference in response to temperature and precipitation could be related to differences in body size and the location of calling sites among the four species. For example, E. brittoni and E. juanariveroi are small species that call from the tips of the vegetation. High temperatures and intense precipitation may cause them to retreat into the vegetation, and reduce calling activity. In contrast, E. coqui and E. cochranae call lower in the vegetation and from leaf axils where they are more protected. Based on these findings, future scenarios of climate change could pose a threat for the survival of the populations of these four species. New climate regimes could negatively affect the calling activity, and thus diminish reproductive events.