The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

Don’t judge a female by her swelling: variability in the timing of ovulation in relation to sexual swelling patterns in wild female bonobos (Pan paniscus)


Department of Primatology, Max Planck Institute for Evolutionary Anthropology

March 28, 2015 2:00, Grand Ballroom E/F/G Add to calendar

Variability in the timing of ovulation in relation to female sexual swelling patterns differs across the primate order, impacting a male’s ability to pinpoint ovulation and thereby affecting male mating strategies. We examined how endocrine parameters that are indicative of ovulation are associated with sexual swellings in wild female bonobos (Pan paniscus) and the temporal relation between the maximum swelling phase (MSP) and ovulation. Data were collected at the Luikotale field site, Democratic Republic of Congo, spanning 36 months from 2010 to 2013. Observational data on female sexual swellings (n=14 females) were used to characterise female swelling cycles. Furthermore, we combined urinary oestrone and pregnanediol analysis using LC-MS to determine the timing of ovulation in 34 cycles from a subset of 9 females. Duration of the MSP was highly variable, lasting from 2 to 30 days. Timing of ovulation varied considerably in relation to the onset of the MSP, resulting in a low probability of ovulation occurring on any particular day of a female’s MSP. Our results suggest that sexual swellings in wild female bonobos are not reliable indicators of ovulation, and that the temporal inflation and variability of these visual sexual signals in relation to ovulation may constrain mate guarding efforts by males.

This research is funded by the L.S.B. Leakey Foundation and the Max Planck Society.