• Female giant panda (Ailuropoda melanoleuca) chirps advertise the caller's fertile phase

      Charlton, Benjamin D.; Keating, J. L.; Rengui, L.; Huang, Y.; Swaisgood, Ronald R.; (2010)
      Although female mammal vocal behaviour is known to advertise fertility, to date, no non-human mammal study has shown that the acoustic structure of female calls varies significantly around their fertile period. Here, we used a combination of hormone measurements and acoustic analyses to determine whether female giant panda chirps have the potential to signal the caller's precise oestrous stage (fertile versus pre-fertile)….
    • Koala bellows and their association with the spatial dynamics of free-ranging koalas

      Ellis, William A.; Bercovitch, Fred B.; FitzGibbon, S.; Roe, P.; Wimmer, J.; Melzer, A.; Wilson, R. (2011)
      Acoustic communication mediates sociality in a variety of animals. One of the more ubiquitous vocal signals to have evolved is the sexual advertisement call of males. Koala (Phascolarctos cinereus) males emit a sonorous bellow call during the breeding season, but no detailed studies of the calling context appear to have been published. We used a novel remote sound detection network to monitor koala bellowing while simultaneously collecting koala behavioral data using collar-mounted GPS units. Our approach enabled us to examine fine scale temporal variation in vocalization and spatial movements of free-ranging koalas without direct behavioral observations. Bellow occurrence was susceptible to weather conditions, with fewer calls occurring when wind speed and temperatures were high. The number of bellow vocalizations recorded during an annual period mirrored breeding activity, with nearly all male bellows recorded during peak mating season. The distance traveled by koalas and the occurrence of koala bellows both peaked around midnight, but only female travel distance during the breeding season was temporally correlated with bellow occurrence. We conclude that environmental factors might trigger male bellowing to launch the breeding season and that these male vocal signals function more to attract females than to repel males. Female mate selection is probably an important component of male reproductive success in koalas, which is partly mediated by male bellow characteristics.
    • Social context mediates testosterone's effect on snort acoustics in male hyrax songs

      Weissman, Yishai A.; Demartsev, Vlad; Ilany, Amiyaal; Barocas, Adi; Bar-Ziv, Einat; Geffen, Eli; Koren, Lee (2019)
      Testosterone affects physical and motivational states, both of which may strongly influence vocalization structure and acoustics. The loud complex calls (i.e., songs) of male rock hyraxes (Procavia capensis) are used as honest signals for advertising physical and social states. The snort, a low frequency, noisy element of the song, encodes information on the singer's age and social rank via harshness, as measured by jitter (i.e., acoustic frequency stability) and duration; suggesting that the snort concomitantly advertises both vocal stability and aggression. Our past findings revealed that testosterone levels are related to both vocal elements and social status of male hyraxes, suggesting that hormonal mechanisms mediate the motivation for aggressive and courtship behaviors. Here we examined whether long-term androgen levels are related to snort acoustics and song structure by comparing levels of testosterone in hair with acoustic and structural parameters. We found that songs performed by individuals with higher testosterone levels include more singing bouts and longer, smoother snorts, but only in those songs induced by external triggers. It is possible that hyraxes with higher levels of testosterone possess the ability to perform higher-quality singing, but only invest in situations of high social arousal and potential benefit. Surprisingly, in spontaneous songs, hyraxes with high testosterone were found to snort more harshly than low-testosterone males. The context dependent effects of high testosterone on snort acoustics suggest that the aggressive emotional arousal associated with testosterone is naturally reflected in the jittery hyrax snort, but that it can be masked by high-quality performance.
    • The role of bioacoustic signals in koala sexual selection: Insights from seasonal patterns of associations revealed with GPS-proximity units

      Ellis, William A.; FitzGibbon, Sean; Pye, Geoffrey W.; Whipple, Bill; Barth, Ben; Johnston, Stephen; Seddon, Jenny; Melzer, Alistair; Higgins, Damien; Bercovitch, Fred B. (2015)
      Despite being a charismatic and well-known species, the social system of the koala (Phascolarctos cinereus—the only extant member of the family Phascolarctidae) is poorly known and much of the koala’s sociality and mating behaviors remain un-quantified. We evaluated these using proximity logging-GPS enabled tracking collars on wild koalas and discuss their implications for the mating system of this species. The frequency and duration of male-female encounters increased during the breeding season, with male-male encounters quite uncommon, suggesting little direct mating competition. By comparison, female-female interactions were very common across both seasons. Body mass of males was not correlated with their interactions with females during the breeding season, although male size is associated with a variety of acoustic parameters indicating individuality. We hypothesise that vocal advertising reduces the likelihood of male-male encounters in the breeding season while increasing the rate of male-female encounters. We suggest that male mating-season bellows function to reduce physical confrontations with other males allowing them to space themselves apart, while, at the same time, attracting females. We conclude that indirect male-male competition, female mate choice, and possibly female competition, mediate sexual selection in koalas.
    • Vocal cues to male androgen levels in giant pandas

      Charlton, Benjamin D.; Keating, Jennifer L.; Kersey, David; Rengui, Li; Huang, Yan; Swaisgood, Ronald R. (2011)
      Little is known about the potential of non-human mammal vocalizations to signal information on the hormonal status of the caller. In the current study, we used endocrine data and acoustic analyses to determine whether male giant panda bleats provide reliable information about the caller's current androgen levels. Our results revealed significant relationships between acoustic features of male giant panda bleats and the caller's faecal androgen metabolite concentrations….
    • Vocal repertoire and signal characteristics of 'Alalā, the Hawaiian Crow (Corvus hawaiiensis)

      Tanimoto, Ann M.; Hart, Patrick J.; Pack, Adam A.; Switzer, Richard A. (2017)
      The critically endangered Hawaiian Crow or ′Alalā (Corvus hawaiiensis) is currently extinct in the wild and the remaining 115 individuals are being captively managed on Hawai′i and Maui Islands by the Zoological Society of San Diego. Here we provide the first comprehensive analysis of the vocal repertoire of this species....