Social networking in baboons

Everyone knows that primates are highly social. Savannah baboon troops typically consist of several unrelated males and one or more matrilineal dominance hierarchies. Female baboons interact with all members of the troop, but their closest and longest lasting interactions are shared with a few related females or peers. Females belonging to high-ranking matrilines (lines of female descent) enjoy priority access when it comes to foraging sites and reproduction, and reduced stress from aggression relative to females belonging to lower ranking matrilines. The short-term benefits of forming social bonds with other females are clear, but does it enhance a female’s fitness?


Figure 1. A pair of mother baboons with their infants. (Photo by Mara1)

Joan Silk and colleagues (2009) studied chacma baboons (
Papio cynocephalus) in Botswana over a 15-year period to answer this question. In this study, the researchers carefully controlled for factors that might bias female fitness as measured by offspring survival. Their results demonstrate that offspring from adult females that formed strong bonds with other females had greater life expectancy. More importantly, they were able to show that females that formed strong social networks with their mother and adult daughters had higher rates of offspring survival regardless of dominance rank of the mother. The benefits of strong social bonds among females include reduced exposure to predators while foraging and reduced social stress. Furthermore, these benefits extend to the offspring of females with strong social networks.

References

Silk, J.B., Beehner, J.C., Bergman, T.J., Crockford, C., Engh, A.L., Moscovice, L.R., Wittig, R.M., Seyfarth, R.M., and D.L. Cheney. 2009. The benefits of social capital: close social bonds among female baboons enhance offspring survival.
Proceedings of the Royal Society B, 276:3099-3104.