Social Bonds and Genetic Ties: Kinship, Association and Affiliation in a Community of Bonobos (Pan Paniscus)

Abstract

SummaryStudies of captive populations of bonobos suggest that females are more gregarious than males. This seems to contradict assumed sex-differences in kinship deriving from a speciestypical dispersal pattern of female exogamy and male philopatry. Here we present data on spatial associations and af liative relations among members of one wild community (Eyengo) for which genetic relationships were identi ed by analysing mitochondrial and nuclear DNA. Our data from Lomako con rm the existence of spatial associations among resident females. In addition, they reveal strong social bonds between males and females. While most female-female associations did not last longer than one eld season, long-term associations occurred predominantly between mixed-sex dyads and involved both close kin and unrelated individuals. Differences in social grooming appeared to be related to patterns of spatial association rather than to kinship. It is suggested that under natural conditions social organisation of bonobos is characterised by strong inter-sexual bonds. Males may bene t from bonding with females by increased reproductivesuccess via rank acquisition. For females bene ts may derive from inclusive tness and reduced food competition. Preliminary evidence suggests that females also may bene t from protection by resident males against male intruders.

Social structures in Pan paniscus: testing the female bonding hypothesis

“…This confirms the findings for wild bonobos at Lomako Hohmann et al 1999;Hohmann and Fruth 2002). In two groups, we found a tendency for females to associate preferably with other females, but grooming was not more pronounced between these females.…”

“…However, it has been stated that this tendency of female bonding in bonobos may be a side effect of captivity (Stanford 1998;Franz 1999;Hohmann et al 1999), similar to the stronger female bonding of captive chimpanzees (de Waal 1994;Baker and Smuts 1994). Although female-female relations are indeed well developed in wild bonobos, several studies found that intersexual bonds are stronger (Kuroda 1979(Kuroda , 1980Kano 1982;Furuichi and Ihobe 1994;Muroyama and Sugiyama 1994;Hohmann et al 1999).…”

“…While this is true for many species, especially cercopithecine monkeys (Smuts et al 1987), bonobos, Pan paniscus, seem to be an exception to this rule. In the wild, females are the migrating sex and are generally unrelated to other females in their community (Kano 1982(Kano , 1992Furuichi 1989;Hashimoto et al 1996;Furuichi et al 1998;Gerloff et al 1999;Hohmann et al 1999;Hohmann and Fruth 2002). However, several studies have reported that close bonds develop between these females (Badrian and Badrian 1984;White 1988;Furuichi 1989;Parish 1996).…”

“…Although female-female relations are indeed well developed in wild bonobos, several studies found that intersexual bonds are stronger (Kuroda 1979(Kuroda , 1980Kano 1982;Furuichi and Ihobe 1994;Muroyama and Sugiyama 1994;Hohmann et al 1999). Since bonds between mothers and their grown sons are very close (Kano 1982(Kano , 1992Furuichi 1989Furuichi , 1997Ihobe 1992), this effect is partly due to relatedness.…”

“…Thus, it has been suggested that, in the wild, bonds between female bonobos are present, but are not equivalent to the strong male-male bonding in chimpanzees. Instead, bonobos live in a society based on interactions between females and their grown sons, and between males and unrelated females Hohmann et al 1999).…”