Koala bellows and their association with the spatial dynamics of free-ranging koalas

Ellis, William A. H.; Bercovitch, Fred B.; FitzGibbon, Sean; Roe, Paul; Wimmer, Jason; Melzer, Alistair; Wilson, Robbie S.

doi:10.1093/beheco/arq216

Cited by 55 publications

(78 citation statements)

References 34 publications

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“…Koalas are polygamous and the occurrence of male bellowing is significantly higher during the breeding season (Ellis et al., ; Smith, ). Hence, the intensity of sexual selection on male koala bellowing is likely to be strong (Ellis & Bercovitch, ).…”

Section: Discussionmentioning

confidence: 99%

“…More recent studies have examined the production (Charlton, Frey, et al., ), information content (Charlton, Ellis, McKinnon, Brumm, et al., , Charlton, Ellis, McKinnon, Cowin, et al. ) and function of male koala bellows (Charlton, Ellis, Brumm, Nilsson, & Fitch, ; Charlton, Ellis, Larkin, & Fitch, ; Charlton, Whisson, & Reby, ; Ellis et al., ). Although the function of female koala vocal signals has received less attention, female koalas are known to produce bellow vocalisations during the reproductive period (Smith, ), particularly when they are in oestrous (Feige, Nilsson, Phillips, & Johnston, ).…”

Section: Introductionmentioning

confidence: 99%

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Subharmonics increase the auditory impact of female koala rejection calls

2017

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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.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Subharmonics increase the auditory impact of female koala rejection calls

2017

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“…Re-recording experiments were conducted between 0300–0500 when temperature and humidity are lowest and hence, when sound propagation is maximised [22]. The occurrence of male bellowing also remains high at these times in free-ranging koalas [36]. Recordings made on all three recording dates were analysed and the average acoustic values from each call form the basis of the results.…”

Section: Methodsmentioning

confidence: 99%

Estimating the Active Space of Male Koala Bellows: Propagation of Cues to Size and Identity in a Eucalyptus Forest

et al. 2012

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Examining how increasing distance affects the information content of vocal signals is fundamental for determining the active space of a given species’ vocal communication system. In the current study we played back male koala bellows in a Eucalyptus forest to determine the extent that individual classification of male koala bellows becomes less accurate over distance, and also to quantify how individually distinctive acoustic features of bellows and size-related information degrade over distance. Our results show that the formant frequencies of bellows derived from Linear Predictive Coding can be used to classify calls to male koalas over distances of 1–50 m. Further analysis revealed that the upper formant frequencies and formant frequency spacing were the most stable acoustic features of male bellows as they propagated through the Eucalyptus canopy. Taken together these findings suggest that koalas could recognise known individuals at distances of up to 50 m and indicate that they should attend to variation in the upper formant frequencies and formant frequency spacing when assessing the identity of callers. Furthermore, since the formant frequency spacing is also a cue to male body size in this species and its variation over distance remained very low compared to documented inter-individual variation, we suggest that male koalas would still be reliably classified as small, medium or large by receivers at distances of up to 150 m.

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“…Low frequency sound has a much greater range, a fact exploited by many mammals including elephants and koalas, and even some birds, including emus and cassowaries. Modern koalas (Phascolarctos cinereus) produce low frequency vocalisations to communicate over long distances and display to females (Ellis et al, 2011;Martin and Handasyde, 1999;Mitchell, 1990;Smith, 1980). To help hear these vocalisations, koalas have large auditory bullae (Louys et al, 2009).…”

Section: Behavioural Functions For Sinusesmentioning

confidence: 99%

A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials

Sharp¹

2016

MMV

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Sharp, A.C. 2016. A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials. Memoirs of Museum Victoria 74: 331-342.Cranial sinuses result from the resorption and deposition of bone in response to biomechanical stress during a process known as pneumatisation. The morphology of a pneumatic bone represents an optimisation between strength and being light weight. The presence of very large sinuses has been described in a number of extinct marsupial megafauna, the size of which no longer exist in extant marsupials. With advances in digital visualisation, and the discovery of a number of exceptionally preserved fossil crania, a unique opportunity exists to investigate hypotheses regarding the structure and evolution of the atypically voluminous sinuses. Sinus function is difficult to test without first obtaining data on sinus variation within and between species. Therefore, the crania of seven species of extinct and extant vombatiform marsupials were studied using CT scans to provide a volumetric assessment of the endocast and cranial sinuses. Sinus volume strongly correlates with skull size and brain size. In the extinct, large bodied palorchestids and diprotodontids the sinuses expand around the dorsal and lateral parts of the braincase. Brain size scales negatively with skull size in vombatiform marsupials. In large species the brain typically fills less than one quarter of the total volume of the endocranial space, and in very large species, it can be less than 10%. Sinus expansion may have developed in order to increase the surface area for attachment of the temporalis muscle and to lighten the skull. The braincase itself would have provided insufficient surface area for the predicted muscle masses.

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Koala bellows and their association with the spatial dynamics of free-ranging koalas

Cited by 55 publications

References 34 publications

Subharmonics increase the auditory impact of female koala rejection calls

Subharmonics increase the auditory impact of female koala rejection calls

Estimating the Active Space of Male Koala Bellows: Propagation of Cues to Size and Identity in a Eucalyptus Forest

A quantitative comparative analysis of the size of the frontoparietal sinuses and brain in vombatiform marsupials

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