Anuran call properties as reliable indicators of environmental suitability for reproduction

Abstract

The annual onset of breeding activity by animals in seasonal environments is often accompanied by auditory signals such as stridulations in insects and vocalizations in birds, mammals, and anurans. In ectotherms, the seasonal timing of such activity by males signals to females the general favorability of environmental conditions for reproduction. Complementary to this, the acoustic characteristics of male auditory signals are presumed to indicate, primarily, the status or quality of males as mates or territorial competitors. Here, using male anurans as a case study, we present the novel hypothesis that characteristics of auditory signals that are modulated by temperature may also serve as bioclimatic indicators of the suitability of proximal abiotic conditions for reproduction by females. According to this hypothesis, thermal constraints on characteristics such as call rate and duration that are insuperable by males may imbue their calls with features that facilitate tracking of environmental conditions by females independently of information intended for communication by males. We integrate findings from empirical studies spanning multiple fields of ecology and evolution to demonstrate how temporal variation in call properties may directly influence female reproductive behavior and physiology. Finally, we outline how this proposed mechanism may enable environmental tracking, provide guidelines for future research to experimentally test this hypothesis, and discuss how findings from this research can translate into actionable conservation management for species of concern.