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 the overall amplitude of the emerging bats’ acoustic 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 stream amplitude corresponding to each video frame was determined using three different methods for calculating 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 at one cave location could accurately predict the population 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.

蝙蝠种群的衰退使得更广泛的种群监测对于保护与管理而言至关重要。当前的普查方法要么易于产生偏差，要么需要使用成本高昂的设备。本文报道了一种全新的方法，该方法利用被动声学（passive acoustics）基于飞出蝠群的声学流总幅值来开展蝙蝠数量普查。我们在多个夜晚，于两处洞穴点位对墨西哥游离尾蝠（Mexican Free-tailed bats）的飞出群落进行了音视频录制。我们从视频帧中计算得到瞬时蝙蝠数量，并通过三种不同的强度计算方法，确定了与每一视频帧对应的声学流幅值。我们发现，全部三种声学参数均与蝙蝠数量存在显著关联，其中均方根压力（RMS pressure）与蝙蝠数量的关联决定系数R²最高，达0.742。此外，在一处洞穴点位得到的声学特征与种群数量的关系，可精准预测另一处洞穴点位的种群数量。本研究使用的设备成本低廉、操作简便，且数据分析可通过自动化脚本或开源声学软件轻松完成。本研究结果有望成为构建声学模型的首个可行步骤，该模型可用于估算全球范围内大型洞穴蝠群的种群数量。