A new study published in the American Journal of Primatology (Vol. 75(7), pp. 774-787) shows that ovulation in olive baboons (Papio anubis) is advertised through a complex set of sexual signals and cues displayed in several modalities.
The study, which was conducted by CICASP PhD student Lucie Rigaill and her colleagues, used data on variations in male and female sexual behaviors, copulation calls, male olfactory inspections of the anogenital area and size and color of the sexual swelling to determine fertile phase in female olive baboons in a semi-free ranging troop (CNRS Primatology Station, France). The authors found that, whereas all males may have information on the fertile window through behavioral, auditory and visual (i.e. swelling size) signals, only consorting males may have access to additional cues, i.e. olfactory cues, which may contain more accurate information about the timing of ovulation. They also showed that swelling color did not vary according to cycle phase. Altogether, these results suggest that a complex framework of ovulatory cues and signals may allow males and females to establish different mating strategies. The use of multiple cues by females may consist of a tradeoff between the costs of ovulatory signaling and the benefits of mating; males may gain more information about the probability of ovulation by combining multiple cues, and thus could reduce the time and energy spent in inspecting females and the risks of mate choice errors.
This research was conducted while Lucie was a Master’s student at the Dynamics of Human Evolution laboratory of the French National Center for Scientific Research in Paris. Lucie is now developing her PhD research at the Primate Research Institute of Kyoto University which will investigate if females Japanese macaques (Macaca fuscata) express their fertile status through multiple signals of ovulation. This work will be conducted on a wild population living in Koshima Island (Japan). These two related studies will lead to a greater general understanding of the evolution of sexual signaling in primates.