Bat echolocation in South Asia

The study of echolocation traits can assist in developing robust tools for the detection and monitoring of bats. The advent of non-invasive and passive acoustic monitoring techniques has increased the availability of echolocation data including in highly diverse regions, such as South Asia, where 145 of the 155 extant bat species are known to use laryngeal, nasal, or lingual echolocation. However, information remains disperse with no existing review of the state of echolocation knowledge in this region. Here we present a review that collates and catalogues echolocation data to facilitate access and reveal general patterns and knowledge gaps. We conducted a systematic review that returned 35 peer-reviewed publications containing echolocation data to which we added ~6,000 unpublished recordings from various collections (including the open-source ChiroVox database). We created a foundational database reporting on six standard echolocation functional traits to be used in identification. The dataset provides data for ~60% (n = 86) of the echolocating bat species in South Asia, with 299 distinct observations (unique combinations of recording techniques, equipment, and conditions for a given species). Mapping data locations we describe spatial biases and propose priority regions for future work in areas where species richness is high, but echolocation knowledge is limited or completely absent. These priority regions largely fell within the Western Ghats and Eastern Ghats of India, northeastern India, and Sri Lanka, with smaller clusters in peninsular, western, and eastern India. Our review offers a first assessment and a ready-to-use echolocation dataset for bats in South Asia. We hope this motivates an appraisal of functional trait data collection in diverse and data-poor regions and facilitates future research.