Bats distress vocalizations carry fast amplitude modulations that could represent an acoustic correlate of roughness

Julio C Hechavarría,Manfred Kössl,Francisco García-Rosales,M Jerome Beetz

doi:10.1038/s41598-020-64323-7

Julio C Hechavarría, Manfred Kössl + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-64323-7

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Abstract

Communication sounds are ubiquitous in the animal kingdom, where they play a role in advertising physiological states and/or socio-contextual scenarios. Human screams, for example, are typically uttered in fearful contexts and they have a distinctive feature termed as “roughness”, which depicts amplitude fluctuations at rates from 30–150 Hz. In this article, we report that the occurrence of fast acoustic periodicities in harsh sounding vocalizations is not unique to humans. A roughness-like structure is also present in vocalizations emitted by bats (species Carollia perspicillata) in distressful contexts. We report that 47.7% of distress calls produced by bats carry amplitude fluctuations at rates ~1.7 kHz (>10 times faster than temporal modulations found in human screams). In bats, rough-like vocalizations entrain brain potentials and are more effective in accelerating the bats’ heart rate than slow amplitude modulated sounds. Our results are consistent with a putative role of fast amplitude modulations (roughness in humans) for grabbing the listeners attention in situations in which the emitter is in distressful, potentially dangerous, contexts.

Highlights

Communication sounds are ubiquitous in the animal kingdom, where they play a role in advertising physiological states and/or socio-contextual scenarios
Note that in a previous study we reported that syllables containing downward frequency modulated (FM) components represent 94% of the distress vocalizations produced by C. perspicillata, SFMs amounted to ~4% of the syllables analyzed, while qCF syllables represented less than 1% of the syllables studied[24]
We tested the idea that fast amplitude fluctuations could be a generalized trait of mammalian vocalizations produced in distress contexts

Summary

Introduction

Communication sounds are ubiquitous in the animal kingdom, where they play a role in advertising physiological states and/or socio-contextual scenarios. The word “rough” has been used in several studies to describe agonistic vocalizations of animal groups including non-human primates, otters, and birds, among others[12,13,14,15,16,17] In those species, the acoustic correlates of roughness were not studied quantitatively using methods similar to those employed for characterizing the human soundscape. Roughness could be a shared feature of animal alarm and fearful vocalizations To test this idea, in this article, we searched for fast amplitude fluctuations -the acoustic correlate of roughness - in distress vocalizations emitted by bats (species: Carollia perspicillata). Bat distress vocalizations are known to evoke strong neural responses in the amygdala[31], to entrain field potentials and spiking in the auditory cortex[27,28,30], and to boost activity in the hypothalamic-pituitary axes[32,33]

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