Listen, who is it? A novel method for studying the nightly and annual phenologies of cave bat communities in data deficient areas of the world.

Context: Bats are the only mammals who have conquered the skies (Gunnell & Simmons, 2005; Thewissen & Babcock, 1992) and the leading mammals in terms of total biomass (Greenspoon et al., 2023) with the exception of domestic mammals. However, the ecology of bats is still a mystery, especially in poorly sampled regions such as Central Africa. Aims: We present a new method for studying the nocturnal and annual phenologies of cave bat communities in data deficient regions. Methods: In two caves (Mont Belo and Boundou) in the Republic of Congo, which are home to several species of insectivorous bats throughout the year, we set up an acoustic monitoring protocol (PAM) over a period of 19 months. In both caves, we collected a total of 2,375,956 acoustic files. We detected the presence of five distinct bat groups or species. Key results: Our results showed bimodal activity throughout the year, except during the long rainy season, when tri- or quadri-modal activity was detected. Activity distributed throughout the night is related to the period of juvenile rearing (gestation, parturition and lactation). For all acoustic groups, we also observed high activity from October to March (long rainy season, short dry season and short rainy season) and low activity during the long dry season (June, July, August). This high activity is linked to the lactation period, the independence of young bats and potentially the mating period. Finally, the reproductive activity of insectivorous bat species is synchronized with the period of high resource availability. Conclusion: This study demonstrated the great variability of activity in five acoustic groups of cave-dwelling insectivorous bats, while at the same time gathering valuable information on bat species in the Congo. These variations are strongly linked to the season and/or the biological cycle of these species. This information is relevant to understanding the mechanisms by which colonies of cave bats can merge and fission. Implications: The use of this technique can provide essential information to estimate insectivorous bat populations in habitats that have been poorly sampled using this passive acoustic monitoring protocol.