Female chimpanzees giving first birth in their natal group in Mahale: attention to incest between brothers and sisters

Chimpanzee societies generally show male philopatry and female dispersal. However, demographic data on wild chimpanzee from long-term study sites have revealed that some females give birth in their natal group (i.e., “remaining females”). Here, we report two remaining the M Mahale, Tanzania, compare cases with previous reports to explore social ecological factors lead group. The results neither traits of nor they experienced showed a coherent trend. found multiple, non-mutually exclusive potential may influence decision by remain group: decrease indirect feeding competition, support mothers or allomothers care offspring aggressive interactions other individuals, close relationships females, short adolescent infertility period. Additionally, observed copulating her older brother, which was first observation brother–sister incest Mahale. Although DNA analysis infant not product inbreeding, pair copulated frequently latter half estrus period, suggesting did avoid behaviorally inbreeding. Furthermore, there no hard evidence avoided mating maternal avoidance be proximate factor responsible for