Life in the fast lane

Father and young. Photo credit: wikipedia.org

 The Barbary macaque (Macaca sylvanus) are the only macaque's to live outside of Asia. They are also one of the only macaques where the males show exceptional parental care, including care towards young that are not biologically their own. The females however are rather promiscuous and will intake multiple matings with different males while in her peak fertility stage (Pfefferle et al., 2008). 

Two baby Barbary macaques. Photo credit: flickr.com

Like many animal species the females will make a particular call whilst in the midst of copulation. It was first thought that the calls were an indication to the male that the female were at a higher fertile phase but that now may not be the case (Pfefferle et al., 2008). A study has shown that the loud vocal calls made by the female during copulation are actually to help the male macaque ejaculate. Each time the female would make a call the male would increase his thrust rate during copulation, resulting in a higher rate for ejaculation. If the female didn't make any noise than the male may not ejaculate. The more intense the calls the faster the thrust from the male resulting in ejaculation (Pfefferle et al.,2008). It is believed that the vocal calls during copulation evolved by females for the purpose of sperm competition and to cause paternity confusion amongst the males. The loud vocal calls indicate to other males that ejaculation has occurred and with high levels of promiscuity by females, each male only knows that they may be the possible biological  donor. This then leads to higher paternity care from the males towards young that may not be their own (Pfefferle et al., 2008). 




References:
Pfefferle, D., Brauch, K., Heistermann, M., Hodges, J.K. & Fischer, J. 2008, "Female Barbary macaque (Macaca sylvanus) copulation calls do not reveal the fertile phase but influence mating outcome", Proceedings of the Royal Society B: Biological Sciences, vol. 275, no. 1634, pp. 571-578.