Investigating Multimodal (Visual, Acoustic, and Thermal) Ovulatory Signaling in a Non-Human Primate Species...

In primate species, females communicate their reproductive status through multiple sensory channels, with visual signals such as swelling size being well documented. We investigated whether thermal (swelling temperature) and auditory (acoustic structure of copulation calls) modalities are also informative about the timing of ovulation in red-capped mangabeys (Cercocebus torquatus). Over 4 months, we collected standardized photographs, thermal images, audio recordings, endocrine (progesterone) and behavioral data from a captive group of six adult females and one resident male. We analyzed variation in swelling size, swelling skin temperature, and temporal and spectral parameters of female copulation calls according to the timing of ovulation (N = 15 cycles). Swelling size, but not temperature, varied with the likelihood of ovulation. Copulation calls produced close to ovulation were hoarser, showing a lower harmonic-to-noise ratio and higher entropy. We found no evidence that thermal or auditory traits influenced male inspection toward females or the likelihood that they engaged in a second mating. These findings suggest that, in this population, ovulatory signaling is primarily unimodal (visual), although such a system could operate within a broader multimodal framework of female reproductive signaling. Our study, while deserving further extension, provides novel insights into the relative contribution of different modalities to ovulatory communication in non-human primates.