Sex at Dawn

As it turns out, women aren’t the only female primates making a lot of noise in the throes of passion. British primatologist Stuart Semple found that, “In a wide variety of species, females vocalize just before, during or immediately after they mate. These vocalizations,” Semple says, “are particularly common among the primates and evidence is now accumulating that by calling, a female incites males in her group...”⁴Precisely. There’s a good reason the sound of a woman enjoying a sexual encounter entices a heterosexual man. Her “copulation call” is a potential invitation to come hither, thus provoking sperm competition.

Semple recorded more than 550 copulation calls from seven different female baboons and analyzed their acoustic structure. He found that these complex vocalizations contained information related both to the female’s reproductive state (the vocalizations were more complex when females were closer to ovulation) and to the status of the male “inspiring” any given vocalization (calls were longer and contained more distinct sonic units during matings with higher-ranked males). Thus, in these baboons at least, listening males could presumably gain information as to their likelihood of impregnating a calling female, as well as some sense of the rank of the male they’d find with her if they approached.

Meredith Small agrees that the copulation calls of female primates are easily identifiable: “Even the uninitiated can identify female nonhuman primate orgasm, or sexual pleasure. Females,” Small tells us, “make noises not heard in any other context but mating.”⁵ Female lion-tailed macaques use copulation calls to invite male attention even when not ovulating. Small reports that among these primates, ovulating females most often directed their invitations at males outside their own troop, thus bringing new blood into the mating mix.

Female copulatory vocalization is highly associated with promiscuous mating, but not with monogamy. Alan Dixson has noted that the females of promiscuous primate species emit more complex matin₇ calls than females of monogamous and polygynous species. Complexity aside, Gauri Pradhan and his colleagues conducted a survey of copulation calls in a variety of primates and found that “variation in females’ promiscuity predicts their tendency to use copulation calls in conjunction with mating.” Their data show that higher levels of promiscuity predict more frequent copulation calls.⁸