What can echolocation recordings reveal about the species composition, habitat specificity and structure of mangrove bat communities in the Northern Territory?

In June 2021 we used ultrasonic recorders to inventory zoophagic bats at mangrove patches in three bioregions on the Northern Territory coast: Darwin Coastal, Arnhem Coast and Gulf Coastal. All species could be separated in terms of their search-mode echolocation sequences using tropical Western Australian and Northern Territory reference libraries based on pulse peak frequency (F _peak), fineness-of-tuning (Q _{− 6dB}), repetition-rate and shape. Twenty-five of the 27 species that comprise the 'Top End' zoophagic bat fauna are now known to occur in its mangroves, an average of 21.3 ± 0.3 (s.e.) species per bioregion. Northern Territory and Western Australian populations of all but three species show few discernable differences in the four echolocation metrics assessed. Unlike the tropical bioregions in Western Australia, no bat species is confined to mangroves in the Northern Territory. Even so, analysis of data from these and adjacent bioregions shows that bat community structures throughout tropical north-western Australia are adapted to their environmental setting. In this paper we discuss how to recognise 'Top End' bats from their echolocation sequences, data needed for rapid inexpensive survey and monitoring programmes that inform conservation planning. We present the results of the first systematic survey of the bats occupying Northern Territory mangrove forests. More broadly, we identify environmental controls influencing the species composition and structure of tropical bat communities across north-western Australia. [ABSTRACT FROM AUTHOR]