Everyday bat vocalizations contain information about emitter, addressee, context, and behavior.

Yosef Prat,Yossi Yovel,Mor Taub

doi:10.1038/srep39419

Abstract

Animal vocal communication is often diverse and structured. Yet, the information concealed in animal vocalizations remains elusive. Several studies have shown that animal calls convey information about their emitter and the context. Often, these studies focus on specific types of calls, as it is rarely possible to probe an entire vocal repertoire at once. In this study, we continuously monitored Egyptian fruit bats for months, recording audio and video around-the-clock. We analyzed almost 15,000 vocalizations, which accompanied the everyday interactions of the bats, and were all directed toward specific individuals, rather than broadcast. We found that bat vocalizations carry ample information about the identity of the emitter, the context of the call, the behavioral response to the call, and even the call’s addressee. Our results underline the importance of studying the mundane, pairwise, directed, vocal interactions of animals.

Highlights

One might expect most social interactions in a tightly packed group, such as a fruit bat colony, to be aggressive
The spectral content of the vocalizations was represented by Mel-frequency cepstral coefficients (MFCC) which are the most common features used in human speech processing, and which were found useful in the analysis of other animal vocalizations[10,40]
Classification performance is reported as the balanced accuracy (BA), which is the number of correct classifications in each class, divided by the number of examples in each class, averaged over all classes

Summary

Results

Collected data. 75 days of continuous recordings of 22 bats (12 adults and 10 pups) yielded a dataset of. When examining each emitter alone, the identity of specific female addressees (when males were excluded from the analysis) could be recovered above chance (for all but 1 emitter, Supplementary Fig. S4), revealing significant variations between calls directed at different recipients. This implies that an eavesdropping bat is theoretically able, to some extent at least, to identify if individual A is addressing individual B or individual C.

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Discussion

Materials and Methods