The Role of Bioacoustic Signals in Koala Sexual Selection: Insights from Seasonal Patterns of Associations Revealed with GPS-Proximity Units
William Ellis1☯*, Sean FitzGibbon1☯, Geoff Pye2☯, Bill Whipple2‡, Ben Barth1‡, Stephen Johnston1‡, Jenny Seddon3‡, Alistair Melzer4‡, Damien Higgins5‡, Fred Bercovitch6☯
1 School of Agriculture and Food Science, The University of Queensland, Brisbane, Queensland, 4072, Australia,
2 San Diego Zoo Global, P.O. Box 120551, San Diego, California 92112–0551, United States of America,
3 Faculty of Veterinary Science, The University of Queensland, Brisbane, Queensland, 4072, Australia,
4 CQUniversity, Koala Research Centre of Central Queensland, School of Medical and Applied Sciences, Rockhampton, Queensland, 4702, Australia,
5 Faculty of Veterinary Science, The University of Sydney, Sydney, Australia,
6 Kyoto University Primate Research Institute & Wildlife Research Center, 41–2 Kanrin, Aichi, Inuyama, 484–8506 Japan
☯ These authors contributed equally to this work.
‡ These authors also contributed equally to this work.
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.