Dario Maestripieri: University of Chicago Professor of Comparative Human Development, Evolutionary Biology, Neurobiology, and Psychiatry

Post-copulatory sexual selection operates through two main mechanisms: sperm competition and post-copulatory female choice. Little is known about the role of female behavior in inciting sperm competition or in the expression of post-copulatory choice. Little is also known about signals that occur after, rather than before, mating. The vocalizations that primate females give shortly after mating may be sexually selected signals that play an important role in both sperm competition and post-copulatory female choice. In recent papers, we have argued that female copulation calls have two immediate functions: to encourage mating attempts by other males and to increase mate guarding by the consort male. These vocalizations may have evolved under the selective pressures of risk of infanticide and sperm competition. When male mate guarding is effective, copulation calls allow females to concentrate paternity in dominant males and benefit from their protection against the risk of infanticide. When mate guarding is ineffective, copulation calls bring genetic benefits to females through facilitation of sperm competition. In this seminar, I will present a quantitative model in which variation in female promiscuity associated with social or ecological factors affects the extent to which dominant males can monopolize females and predicts female tendency to use copulation calls in conjunction with mating. The model predicts that in species with little female promiscuity, copulation calls should be rare and occur only after mating with dominant males. In species in which females are highly promiscuous, copulation calls should be frequent and occur after mating with any males regardless of their dominance rank. Consistent with the model, I will present data showing that female copulation calls are rare or absent in primate species in which male infanticide does not occur and sperm competition is absent or weak, whereas variation in female promiscuity in species in which male infanticide or sperm competition occurs accurately predicts the extent to which mating is accompanied by copulation calls. I will also present behavioral data from captive baboons showing that female copulation calls are most likely to occur after mating with dominant males and are effective in encouraging post-copulatory mate guarding.
http://www.bec.ucla.edu/DarioPaper.pdf