Abstract

Human vocal development and speech learning require acoustic feedback, and humans who are born deaf do not acquire a normal adult speech capacity. Most other mammals display a largely innate vocal repertoire. Like humans, bats are thought to be one of the few taxa capable of vocal learning as they can acquire new vocalizations by modifying vocalizations according to auditory experiences. We investigated the effect of acoustic deafening on the vocal development of the pale spear-nosed bat. Three juvenile pale spear-nosed bats were deafened, and their vocal development was studied in comparison with an age-matched, hearing control group. The results show that during development the deafened bats increased their vocal activity, and their vocalizations were substantially altered, being much shorter, higher in pitch, and more aperiodic than the vocalizations of the control animals. The pale spear-nosed bat relies on auditory feedback for vocal development and, in the absence of auditory input, species-atypical vocalizations are acquired. This work serves as a basis for further research using the pale spear-nosed bat as a mammalian model for vocal learning, and contributes to comparative studies on hearing impairment across species.This article is part of the theme issue ‘Vocal learning in animals and humans’.

Highlights

  • Human vocal development and speech learning require acoustic input and auditory feedback mechanisms, which allow the gradual modification of utterances to match a previously perceived auditory target [1]

  • Complementing a previous isolation study with juveniles, which focused on vocal adjustment towards playbacks of a single vocalization type [14], we investigated the effect of deafening on their vocal development

  • Three juvenile bats were deafened at less than two weeks of age, and their vocal development was studied in comparison with a control group, consisting of three age-matched, normally hearing conspecifics

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Summary

Introduction

Human vocal development and speech learning require acoustic input and auditory feedback mechanisms, which allow the gradual modification of utterances to match a previously perceived auditory target [1]. The acoustic recording of the six bats was performed at two life stages: as juveniles (within the first six months of their lives) and as adults (at about 2 years of age) (electronic supplementary material, table S1). The identity of the vocalizing animal could only be determined in the juvenile recordings, allowing exclusively descriptive statistics for the adult data (electronic supplementary material, table S4).

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Conclusion

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