Intergroup Transfer and Inbreeding Avoidance in Bonobos

Abstract

We examined the 20-years records of female transfer of wild bonobos at Wamba, D. R. Congo. Most females left their natal group between 6 and 9 years old, and immigrated into new groups between 10 and 12 years. Females seemed to travel several groups before settling in a new group. After settling down, they start reproduction and will not transfer to other groups for the rest of their life. We examined average of coefficient of consanguinity of males with whom females may copulate in new groups. The probability of inbreeding drastically decreases when a female transfers groups, and it decreases according to the amount of intergroup travel. Differences in female transfer pattern between bonobos and chimpanzees seem to be due to the differences in the risks of traveling alone, such as predators, social relationships between females, and high social status of females. The balance between cost and benefit of intergroup transfer may determine philopatric social structure in chimpanzees and bonobos.