02184nas a2200193   4500008004100000245007800041210006900119260001600188300001400204490000800218520156700226653001101793653003201804653002501836100002701861700002401888700002401912856005401936       2017                        eng d00aSubharmonics increase the auditory impact of female koala rejection calls0 aSubharmonics increase the auditory impact of female koala reject  cJan-08-2017  a571 - 5790 v1233 a<p>Although 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.</p>
10akoalas10amammal  vocal communication10anon-linear phenomena1 aCharlton, Benjamin, D.1 aWatchorn, Darcy, J.1 aWhisson, Desley, A.  uhttp://doi.wiley.com/10.1111/eth.2017.123.issue-8