Thermal Responses of Peak Calling Activity in Forest Ponds: When the Optimal Time is for Encountering Anuran Amphibians

다국어 초록 (Multilingual Abstract)

Changes in anuran population dynamics can be assessed by monitoring the advertisement calls that males emit to attract females during the breeding season. Using the Population Size Index (PSI) — a modification of the Call Index from the North American Amphibian Monitoring Program, along with autonomous recording devices, we indirectly quantified the abundance of four anuran species by analyzing their daily nocturnal call patterns. In both the northern and southern regions of the Republic of Korea, three pond-dwelling anuran species — Rana uenoi, Bombina orientalis, and Hyla japonica — showed a right-skewed PSI distributions throughout the night. Their calling activity increased from evening until around 21:00 to 22:00 hours, then gradually declined to dawn. In contrast, Pelophylax nigromaculatus maintained peak calling activity until early dawn. Notably, the timing of peak calls varied slightly among cohabiting species within the same forest pond, indicating species-specific differences in peak calling periods. Rana uenoi began and ended its peak calling activity earlier than the other three species. Regardless of geographic region, all species exhibited distinct, species-specific PSI distribution patterns throughout the night. These findings suggest that monitoring nocturnal call phenology with autonomous recording devices can help human surveyors determine efficiently optimal time for recognizing nocturnal species and estimating their abundance in Korean forest ecosystems.