Frog vocal responses to thermal variation in Hainan tropical rainforests

Amphibians, the most threatened vertebrate group, are particularly vulnerable to temperature changes due to their ectothermic nature, but the impact of distinct thermal environments on their calling behaviors remains unclear. In this study, we used a combination of human-based field surveys and passive acoustic monitoring (PAM) techniques to investigate the calling behaviors of four anurans (Microhyla fissipes, Leptobrachium hainanensis, Hylarana guentheri, and Amolops torrentis) within the confines of the Hainan Tropical Rainforest National Park. We also examined the relationship between this behavior and daily temperature fluctuations in these species. The results showed that four anurans had temporal partitioning in daily calling activities. All species exhibited a narrow preferred temperature range for calling: M. fissipes, L. hainanensis, and H. guentheri preferred [24/25°C, 29°C), while A. torrentis preferred [23°C, 26°C). The calling count of L. hainanensis was unaffected by environmental temperature; however, the calling activity of the other three species either increased or decreased as temperatures rose. Furthermore, temperature had no impact on the call durations of two terrestrial species (M. fissipes and L. hainanensis), but had a significant influence on those of two water species (H. guentheri and A. torrentis). These results suggest that four anurans are sensitive to changes in the environmental temperature and respond differently to daily temperature variations. This study enhances our understanding of how poikilothermic animals’ vocalisations respond to specific thermal environments and provides insights into the impact of global warming on amphibians.