Sexual intercourse plays a major role in bonobo society observed in captivity, being used as what some scientists perceive as a greeting, a means of conflict resolution, and post-conflict reconciliation. Bonobos are the only non-human animal to have been observed engaging in all of the foll...owing sexual activities: face-to-face genital sex, tongue kissing, and oral sex. (Although a pair of Western Gorillas have been photographed performing face to face genital sex) In scientific literature, the female-female behavior of touching genitals together is often referred to as GG rubbing or genital-genital rubbing.

The sexual activity happens within the immediate family as well as outside it. Bonobos do not form permanent relationships with individual partners. They also do not seem to discriminate in their sexual behavior by sex or age, with the possible exception of abstaining from sexual intercourse between mothers and their adult sons; some observers believe these pairings are taboo. When Bonobos come upon a new food source or feeding ground, the increased excitement will usually lead to communal sexual activity, presumably decreasing tension and allowing for peaceful feeding.

Bonobo males frequently engage in various forms of male-male genital behavior (frot). In one form, two males hang from a tree limb face-to-face while "penis fencing". Frot also may occur when two males rub their penises together while in face-to-face position. A special form of frot called "rump rubbing" occurs to express reconciliation between two males after a conflict, when they stand back-to-back and rub their scrotal sacs together. Takayoshi Kano observed similar practices among bonobos in the natural habitat.

Bonobo females also engage in female-female genital behavior, possibly to bond socially with each other, thus forming a female nucleus of Bonobo society. The bonding among females allows them to dominate Bonobo society—although male Bonobos are individually stronger, they cannot stand alone against a united group of females. Adolescent females often leave their native community to join another community. Sexual bonding with other females establishes the new females as members of the group. This migration mixes the Bonobo gene pools, providing genetic diversity.

Source: http ://en.wikipedia.org/wiki/Bonobo#Sexual_social_behavior