Bats increase vocal amplitude and decrease vocal complexity to mitigate noise interference during social communication
Natural background noises are common in the acoustic environments in which most organisms have evolved. Therefore, the vocalization and sound perception systems of vocal animals are inherently equipped to overcome natural background noise. Human-generated noises, however, pose new challenges that can hamper audiovocal communication. The mechanisms animals use to cope with anthropogenic noise disturbances have been extensively explored in a variety of taxa. Bats emit echolocation pulses primarily to orient, locate and navigate, while social calls are used to communicate with conspecifics. Previous studies have shown that bats alter echolocation pulse parameters in response to background noise interference. In contrast to high-frequency echolocation pulses, relatively low-frequency components within bat social calls overlap broadly with ambient noise frequencies. However, how bats structure their social calls in the presence of anthropogenic noise is not known. Here, we hypothesized that bats leverage vocal plasticity to facilitate vocal exchanges within a noisy environment. To test this hypothesis, we subjected the Asian particolored bat, Vespertilio sinensis, to prerecorded traffic noise. We observed a significant decrease in vocal complexity (i.e., an increased frequency of monosyllabic calls) in response to traffic noise. However, an increase in the duration and frequency of social calls, as have been observed in other species, was not evident. This suggests that signal simplification may increase communication efficacy in noisy environments. Moreover, V. sinensis also increased call amplitude in response to increased traffic noise, consistent with the predictions of the Lombard effect.
KeywordsAcoustic communication Noise Vocal plasticity Social calls Bats
We would like to thank Guanjun Lu for his assistance with collecting the bats in the field. This research was supported by the National Natural Science Foundation of China (Grant No. 31470457, 31872680, 31670390, 31500314, 31700331), and Fund of Jilin Province Science and Technology Development Project (Grant No. 20180101024JC). The Biomedical Graduate Research Organization at the Georgetown University Medical Center provided support to J.S.K. We would like to thank LetPub (http://www.letpub.com) for providing linguistic assistance during the preparation of this manuscript.
TJ Designed the study, collected the data, implemented most of data analysis, and wrote the initial draft of the manuscript. XG Performed the experiments. AL and HW Assisted with experiments. CS Analyzed the vocal amplitude data, and composed the text in the Methods section. JF Assisted with study design, provided laboratory space and some funding. JSK Assisted with data analysis and revised the manuscript.
Compliance with ethical standards
Conflict of interest
The authors have no competing interests to declare.
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