Genetic Analysis of Migration Pattern of Female Bonobos (Pan paniscus) Among Three Neighboring Groups

Relationships between females of different groups in female philopatric species are typically antagonistic, whereas those in female dispersing species can be more moderate. Such nonantagonistic relationships among females of neighboring groups may allow immigrant females to minimize dispersal costs by migrating into those groups, whereas the frequency of female migration among neighboring groups is little understood in female dispersing species. Bonobos (Pan paniscus) are a species in which females disperse and often show affinitive interactions between groups during intergroup encounters. We examined the frequency of female migration into neighboring groups in bonobos using genetic and demographic data. We studied 27 immigrant female bonobos in three neighboring groups at Wamba, Democratic Republic of the Congo. We estimated the frequency of female migration into neighboring groups using the following formula: the number of females that migrated into any neighboring group/the number of females that migrated into any nonnatal group. We estimated the number of females that migrated into any neighboring group using genetic evidence for female migration among the three groups, and the number of neighboring groups for the three groups. We estimated the number of females that migrated into any nonnatal group using the age of subject females, age of first birth, interbirth intervals, and mortality. The estimated frequency of female migration into any neighboring group was 60% (4.5/7.48). Our results suggest that female bonobos do not disperse far from their natal groups, which may be because they usually transfer between groups during intergroup encounters.