Socially integrated female chimpanzees have lower offspring mortality.

In humans and other social mammals, more socially connected females often have higher fitness. Yet evidence linking female sociality to offspring survival remains inconsistent, and is limited to a handful of primate species in which females depend on close female kin for social status. Here, we examine the relationship between female social integration and offspring survival in eastern chimpanzees. We find that females that were more socially integrated with other females in the year before giving birth had higher offspring survival to age 1 (the period of highest mortality) and age 5 (the approximate age of weaning). Furthermore, social integration remained a strong predictor of offspring survival among females without close female kin. Our results thus add to a small set of studies linking sociality with offspring survival, here in the dispersing sex. As in humans, more socially connected female chimpanzees have higher offspring survival, despite primarily residing with non-kin.