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Behaviour & communication

Discrimination of sex and reproductive state in koalas, Phascolarctos cinereus, using chemical cues in urine

Charlton, BD 2014, Animal Behaviour, vol. 91, no. 1, pp. 119-125.

Koalas can determine both the sex and oestrous stage of other individuals by detecting unique chemical cues in their urine. During their breeding season, male and oestrus female koalas at Lone Pine Koala Sanctuary demonstrated a higher interest in the urine of males than did nonoestrus females, which avoided male urine. Male koalas investigated the urine of an oestrus female, but not that of a nonoestrus female.

  The chemosensory ability of koalas to determine the sex of other individuals informs both male and female social behaviour. Males can identify potential mates by detecting the presence of females, and can avoid the threat of a rival male if his presence is detected nearby. Females can either detect potential mates during oestrus or avoid the threat of an aggressive male when not in oestrus. Similarly, the chemical cues in female urine that signal her reproductive state are likely to improve the reproductive success of both male and female koalas. Males can enhance their mating success by targeting oestrus rather than nonoestrus females, while the advertisement of her oestrus status may benefit a female by encouraging competition between males, thereby improving her chances of attracting a high-quality mate.

  In mammals, this type of olfactory communication is essential for shaping social behaviours and organisation. Chemical communication is particularly important for solitary species like the koala, as chemical cues in urine assist in the detection and assessment of potential mating partners over large distances. This means that individuals can establish relationships without the need for any direct contact, which is critical to the reproductive success of this largely sedentary species.

  The ability of male koalas to determine the reproductive state of females, as well as of females to signal their oestrous stage to males, is likely to be a key factor affecting the reproductive success of males and females alike. The findings of this study not only improve our understanding of koala communication but may also be the first to provide evidence of the use of chemical cues to advertise and assess female reproductive states in marsupials.


Summarised by Joanna Horsfall


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