Automated Acoustic Recogniser Reveals Spatial Variation in Seasonal Calling of the Range-Restricted Magnificent...

Frog species worldwide are particularly vulnerable to the effects of climate change and are the most endangered vertebrate group. To identify and mitigate impacts, it is necessary to have a method to monitor activity, particularly breeding activity, to detect changes over time. To this end, this study examined the breeding phenology of the poorly known magnificent broodfrog (Pseudophryne covacevichae) across its disjunct distribution in upland sclerophyll forests of the Wet Tropics of Australia. Using a species-specific acoustic recogniser, we processed near continuous recordings from November 2022 to November 2023, across ten sites, spanning parts of the species' disjunct ranges, the Atherton Tablelands region and Paluma Range. Recorders sampled nightly for 5 min of every hour and detected ~350,000 advertisement calls using a 95% accuracy threshold. Despite a geographic separation of under 200 km, the timing and duration of calling varied markedly among sites and regions. Atherton Tablelands populations exhibited relatively synchronous, wet season calling, whereas Paluma Range populations had delayed and more prolonged calling periods, extending into the mid to late dry season. Climate window analyses indicated that calling was influenced by antecedent environmental conditions, but the time scale and effect differed between regions. In the Atherton Tablelands, calling intensity was positively associated with high rainfall accumulation over multiple weeks, high minimum temperatures and low humidity over the preceding month. In contrast, in the Paluma Range, calling intensity declined with higher rainfall over the previous 2 weeks and was associated with cooler, but more humid nights in the week prior. The intraspecific variation in calling activity suggests that local hydrological conditions may mediate reproductive timing and duration, with rainfall either facilitating or suppressing calling, depending on the region. Understanding such fine-scale intraspecific variation in breeding may assist in identifying populations more at risk to the effects of future climate change.