Quality versus quantity: do weak bonds enhance the fitness of female baboons?

Abstract

There is growing evidence that social bonds have adaptive consequences for individuals in many mammalian species, including savannah baboons. While the majority of studies have shown that the strength of social bonds and the extent of social integration enhance female fitness, several other investigations have suggested that the number of social bonds may sometimes may be more important than the strength or quality of females' social relationships. Here, we examine the impact of the number of strong and weak social bonds on female fertility and longevity in a population of chacma baboons,Papio ursinus. We find no evidence that the number of social bonds consistently affects fertility or infant survival to 1 year, but offspring of females with more weak social bonds lived longer than offspring of other females. After discussing several methodological issues that may influence the analyses of the effects of the number of social bonds, we re-examine the relationship between the number of weak and strong social bonds and reproductive performance using procedures that avoid these problems. Again, we find no evidence that the number of weak or strong social bonds affects females' fertility, survival to 1 year. The effects of the number of weak social bonds on infant longevity disappear, and appear to be an artefact of the relationship between the number of weak social bonds and the number of females in the group.