Shadows of Forgotten Ancestors

Despite their apparently unrestrained sexual behavior, chimps get jealous. A male who rejected the solicitation of a female in estrus, but instead copulated with her daughter, was slapped in the face by the outraged mother. Cruising migrant females from the next territory are threatened or attacked by the local females—especially if the visitors go so far as to groom with one of the resident males. The male may also blaze with sexual jealousy over a particular female’s behavior—but, almost without exception, only when she is vividly pink and swollen and able to conceive. High-ranking males will then chase away aroused lower-ranking males. Although it’s unlikely he’s thought this out, his motive, it seems very clear, is to monopolize her around the time of ovulation so that no one but he can father her children.* As far as he’s concerned, the rest of the time she can do as she pleases.

Possessiveness is hard to maintain, though, at the core of the territory where the chimp population density is high. Even the most vigilant and high-ranking males will be distracted—by hunting, say, or challenges from lower ranks, or insufficient deference, or by grooming, or by the necessity of adjudicating disputes. And during such an intervention—it may last only a few minutes—other males, patiently awaiting their chance, pounce on the off-limits female, especially if she’s in estrus. Kleptogamy is on their minds. In zoos a female will, as soon as the alpha male is removed from her cage, present herself to lower-ranking males, even if this requires adroit positioning so the act can be performed through the bars of two adjacent cages. Both in the wild and in captivity, when the cuckolded male discovers what has happened, he attacks the female. Perhaps he knows that she was all too willing. Besides, it’s much safer than attacking a rival male.

Even when the alpha is present, a subordinate male may catch the eye of a female who strikes his fancy and then gaze pointedly toward some nearby bushes. Nonchalantly, he then ambles off, often followed after a discreet interval by the female. Sometimes their infidelity is observed. Motivated by jealousy or by the wish to ingratiate himself to the leader, the informer rushes up to the alpha in great excitement, takes his arm, points, and leads him to the treacherous couple. At other times the female may inadvertently reveal what is going on by uttering a high-pitched scream at the moment of her orgasm. After being discovered in this way more than once, females do not usually abandon the risky practice of clandestine rendezvous; instead, they learn to suppress the scream, converting it into a kind of husky pant.

Frans de Waal reports that, following a long grooming session between a high-ranking and a low-ranking male,a subordinate male may invite the female and enjoy a copulation without interference by the others. These interactions give the impression that males obtain “permission” for an undisturbed mating by paying a price in grooming currency … Perhaps sexual bargaining represents one of the oldest forms of tit for tat, one in which a tolerant atmosphere is created through appeasing behavior.⁹

To achieve reliable sexual monopoly during her estrus, the ardent male must usher the female away from the multitude. Scientists who study chimps call this “consortship,” and distinguish it from “courtship.” The proposition is put to the female as follows: He takes a few steps away and looks at her over his shoulder. If she does not instantly follow, he shakes a nearby branch. If this provides insufficient inducement, he will chase her and, if need be, attack her. More often she goes quietly, especially if he’s high-ranking. Then, off somewhere alone in the forest, he has her to himself. It is a distant intimation of monogamy.

Consortship typically lasts for weeks, and is not without its perils. The happy couple may be attacked by predators or patrols from the neighboring territory; and the male’s status in the dominance hierarchy may be undergoing active review during his absence. Jane Coodall reports a few cases in which the young female’s mother invites herself along on the consortship; “as far as the male is concerned,” she is a “most unwelcome chaperone.” Here, where conception is most likely, the incest taboo is particularly vivid—no case is known of a male chimp ever inviting his own mother or sister to be his consort.