LIFE-HISTORY CONSEQUENCES OF SOCIAL COMPLEXITY - A COMPARATIVE-STUDY OF GROUND-DWELLING SCIURIDS

We examined life-history consequences of increased social complexity I n ground-dwelling sciurid rodents. We derived a continuous metric of s ocial complexity from demographic data. Social complexity increased wi th 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 lift-history variables that could be attributed to phylogenetic similarity. Analyses that incorporated e stimates of phylogeny generated consistent results. As social complexi ty increased, a smaller proportion of adult females bred, there was a greater time to first reproduction, litter size decreased, and there w as greater first-year offspring survival. Social complexity influenced neither gestation nor lactation time. Thus, social complexity has cos ts in terms of a reduction in the annual per-capita number of offsprin g produced but benefits in terms of enhanced offspring survival.