Data from: Estimating colony sizes of emerging bats using acoustic recordings

The decline of bats demands more widespread monitoring of populations for
conservation and management. Current censusing methods are either prone to
bias or require costly equipment. Here, we report a new method using
passive acoustics to determine bat count census from overall acoustic
amplitude of the emerging bat stream. We recorded the video and audio of
an emerging colony of Mexican free-tailed bats from two cave locations
across multiple nights. Instantaneous bat counts were calculated from the
video frames, and the bat stream’s acoustic amplitude corresponding to
each video frame was determined using three different methods for
calculating acoustic intensity. We found a significant link between all
three acoustic parameters and bat count, with the highest R2 of 0.742
linking RMS pressure and bat count. Additionally, the relationship between
acoustics and population size at one cave location could accurately
predict the population size at another cave location. The data were
gathered with low-cost, easy-to-operate equipment, and the data analysis
can be easily accomplished using automated scripts or with open-source
acoustic software. These results are a potential first step towards
creating an acoustic model to estimate bat population at large cave
colonies worldwide.