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Subharmonics increase the auditory impact of female koala rejection calls
journal contribution
posted on 2017-08-01, 00:00 authored by B D Charlton, Darcy Watchorn, Desley WhissonDesley WhissonAlthough non-linear phenomena are common in human and non-human
animal vocalisations, their functional relevance remains poorly understood. One theory posits that non-linear phenomena generate unpredictability in vocalisations, which increases the auditory impact of vocal signals, and makes animals less likely to habituate to call repetition.
Female koalas (Phascolarctos cinereus) produce vocal signals when they reject male copulation attempts that contain relatively high levels of non-linear phenomena, and thus may function as attention grabbing vocal signals during the breeding season. To test this hypothesis, we used playback experiments: firstly, to determine whether female rejection calls induce heightened behavioural responses in free-ranging male
koalas during the breeding season, and secondly, to examine how the relative amount of non-linear phenomena in rejection calls influences male behavioural response. The results show that male koalas look for longer towards speakers broadcasting playback sequences of male bellows followed by a series of female rejection calls than those
broadcasting only male bellows. In addition, female rejection call sequences with more subharmonics, higher harmonics-to-noise ratios, and less biphonation produced the greatest male looking responses. Our findings support the hypothesis that female koala rejection calls function to grab male attention during the breeding season, and indicate that subharmonics are the main acoustic feature that increases the auditory
impact of these vocal signals.
animal vocalisations, their functional relevance remains poorly understood. One theory posits that non-linear phenomena generate unpredictability in vocalisations, which increases the auditory impact of vocal signals, and makes animals less likely to habituate to call repetition.
Female koalas (Phascolarctos cinereus) produce vocal signals when they reject male copulation attempts that contain relatively high levels of non-linear phenomena, and thus may function as attention grabbing vocal signals during the breeding season. To test this hypothesis, we used playback experiments: firstly, to determine whether female rejection calls induce heightened behavioural responses in free-ranging male
koalas during the breeding season, and secondly, to examine how the relative amount of non-linear phenomena in rejection calls influences male behavioural response. The results show that male koalas look for longer towards speakers broadcasting playback sequences of male bellows followed by a series of female rejection calls than those
broadcasting only male bellows. In addition, female rejection call sequences with more subharmonics, higher harmonics-to-noise ratios, and less biphonation produced the greatest male looking responses. Our findings support the hypothesis that female koala rejection calls function to grab male attention during the breeding season, and indicate that subharmonics are the main acoustic feature that increases the auditory
impact of these vocal signals.
History
Journal
EthologyVolume
123Issue
8Pagination
571 - 579Publisher
Wiley-BlackwellLocation
Chichester, Eng.Publisher DOI
ISSN
0179-1613Language
engPublication classification
C Journal article; C1 Refereed article in a scholarly journalCopyright notice
2017, Wiley-BlackwellUsage metrics
Keywords
koalasmammal vocal communicationbob-linear phenomenaSocial SciencesScience & TechnologyLife Sciences & BiomedicinePsychology, BiologicalBehavioral SciencesZoologyPsychologynon-linear phenomenaMEERKAT ALARM CALLSPHASCOLARCTOS-CINEREUSNONLINEAR PHENOMENAVOCALIZATIONSBEHAVIORAROUSALBELLOWSBIPHONATIONLEVELSOUNDEvolutionary BiologyZoology
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