Life history consequences of social complexity: A comparative study of ground-dwelling sciurids

Abstract

We examined life-history consequences of increased social complexity in ground-dwelling sciurid rodents. We derived a continuous metric of social complexity from demographic data. Social complexity increased with the number of age-sex 'roles' that interacted in a social group. Data were analyzed by computing phylogenetically independent contrasts and by using phylogenetic autocorrelation to estimate and then remove the maximum amount of variation in life-history variables that could be attributed to phylogenetic similarity. Analyses that incorporated estimates of phylogeny generated consistent results. As social complexity increased, a smaller proportion of adult females bred, there was a greater time to first reproduction, litter size decreased, and there was greater first-year offspring survival. Social complexity influenced neither gestation nor lactation time. Thus, social complexity has costs in terms of a reduction in the annual per-capita number of offspring produced but benefits in terms of enhanced offspring survival.