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                                                                                BEHAVIOR, Page 50

Apes That Swing Many Ways


By Eugene Linden


    In a forest clearing near Wamba in equatorial Zaire, a group
of bonobos, or pygmy chimpanzees, approaches a juicy stash of
sugarcane laid out by Japanese researchers. As the animals draw
near the sweets, they begin an astonishing series of sexual
interactions. Some females embrace, rubbing their genitals
against each other; males rub rumps, and sometimes briefly enter
into what looks like mating. There is plenty of heterosexual
sex too, as well as adult-infant encounters and enough mixing
and matching to offend every puritanical sensibility.
Scientists have observed similar orgies when bonobos converge
on fig trees ripe with the sticky fruit.

    This is not typical ape behavior. In similar situations,
the bonobo's cousin, the common chimpanzee, might engage in
greetings and dominance interactions with far less libido in
evidence. Why then do the bonobos launch into extended orgies
of polymorphous perversity?

    One feature of the bonobo's forest environment offers a
possible clue: fruit trees that produce an unusual abundance of
food in a small area. This brings large numbers of bonobos into
closer social contact than is typical for common chimpanzees.
The presence of food can stimulate competition among the apes,
and the larger the group the greater the danger of conflict.
Frances White of Duke University argues that at these crucial
times, sexual encounters reinforce bonds, particularly among
females, helping individual apes to maintain access to food.
Frans de Waal, the author of Chimpanzee Politics: Power and Sex
Among Apes, believes the varied sex reduces tensions and fosters
conciliation among these intensely social animals.

    Bisexual behavior may serve a similar function for another
highly intelligent mammal: the dolphin. "Sometimes male dolphins
use homosexual sex to assert dominance over other males, and
other times they use it in a friendly way, but always they are
negotiating relationships," says Richard Connor, a biologist at
Woods Hole Oceanographic Institution.

    With both dolphins and bonobos, however, bisexual behavior
appears to be more ritualistic than erotic (quite often,
male-male encounters do not lead to ejaculation). Thus such
behavior may have little to do with sexual orientation. Instead
it may be viewed as a counterpart of the ceremonial sex seen in
some human cultures.