Fruth / Oral

Genito-genital-rubbing - a display of differences in social status

Barbara Fruth ¹ & Gottfried Hohmann ², Max-Planck-Institute fur Verhaltens physiology, 82319 SEEWIESEN; Max-Planck-Institute fur evolutionare Anthropology, 04155 LEIPZIG

     Mounting between females is known from insects, birds and mammals. Female bonobos (Pan paniscus) show a mounting behavior which physically differs from other primate species. They embrace each other ventro-ventrally and rub their genital swellings laterally against each other. Although many functions were suggested, so far none has been object of detailed investigation.
     Here we test five hypotheses generated by information of female-female mounting from both primate and non-primate species. These consider mounting behavior to proximately serve the (1) reconciliation of former opponents, (2) attraction of mates, (3) regulation of tension, (4) expression of social status, and/or (5) social bonding among individuals. Each hypothesis allows several predictions, which are tested with data collected during six field seasons (1993-1998; 27 months) on members of one bonobo community in Lomako (DRC).
     A total of 466 genital contacts were sampled and related to factors such as agonistic conflict, individual affiliation, party size and composition, mating, female cycle, access to food, and rank.
     No evidence was found for hypothesis (2) and (5). However, our data are in support of hypotheses (1) and (3). Wild bonobos sometimes do use genital contacts to reconcile although more often than not this behavior is unrelated to agonistic conflicts. In addition, rank related asymmetries in initiation and performance strongly support hypothesis (4): low ranking females solicit genital contacts, high ranking ones occupy more often the top position. We will discuss the potential advantages deriving from genital contacts. We suggest that in future they can be used to investigate the quality and dynamics of social relationships among female bonobos.

Fruth, B. , Hohmann, G. & W.C. Mcgrew. 1999. The Pan Species, in: The Nonhuman Primates, eds. P. Dolhinow & A. Fuentes, pp. 64-72, Mayfield Publishing Company. Gerloff, U., HArtung, B., Fruth B., Hohmann, G., & D. Tautz. 1999. Intra-community relationships, dispersal pattern and control of paternity in a wild living community of bonobos (Pan paniscus) determined from DNA analyses of faecal samples. Proceedings of the Royal Society of Britain, 266, 1189-1195.
Hohmann, G. , Gerloff, U., Tautz, D. & B. Fruth (in press), Social bonds and genetic ties: kinship, association and affiliation in a community of bonobos (Pan paniscus), Behavior.