If a frog calls in the forest: Bioacoustic monitoring reveals the breeding phenology of the endangered Richmond Range mountain frog (Philoria richmondensis)

Abstract

Amphibians are the most threatened vertebrate taxon of modern times. Baseline data and affordable methods to monitor populations are absent for many Australian frog species. Furthermore, some species are visually cryptic, and detection often relies upon male advertisement calls. Imperfect detection rates impede our ability to assess the status of populations over time. Understanding the factors that influence calling is essential to inform the timing of survey effort and increase survey efficiency. Automated recording systems offer considerable potential to determine calling phenology and establish the relationship between calling and abiotic factors. The mountain frogs (PhiloriaMyobatrachidae) of the Gondwana rainforests are considered susceptible to climate change impacts, such as shifts in the timing of calling. In order to describe the calling phenology of Philoria richmondensis, commercially available automated recording systems were deployed at five locations, and over 5000h of sound recordings were captured and analysed. Peak calling activity occurred during morning and evening periods in the austral spring. Ambient temperature was found to significantly contribute to the probability of a call occurring, with the highest frequency of calls recorded occurring between 15°C and 16°C, and there was a negative relationship between precipitation and calling activity. The results allow future surveys to be better targeted and provide a benchmark with which to detect changes in calling phenology over time.