Evolutionary models for the retention of adult–adult social play in primates: The roles of diet and other factors associated with resource acquisition

Abstract

What factors in animal life history facilitate or reduce the probability that a species will perform play behavior? While some relationships are known within species and across individuals, it is not obvious that such relationships can be used to explain differences and similarities in amount and type of play across large taxonomic groupings of animals, let alone transitions among them. Primates encompass a relatively large assemblage of species that differ in numerous dietary, habitat, reproductive, and physiological processes. While all juvenile primates engage in social play, far fewer primate species engage in social play as adults. Here, derived from theory and more small-scale comparisons, we explore several biological and behavioral phenomena that differ among nonhuman primates and which may explain differences in the occurrence of adult–adult social play. We used phylogenetic logistic regression to assess the correlation of adult play with various life-history, metabolic and socioecological variables. Although the main contribution of our paper is demonstrating use of phylogenetic methods in the context of play evolution, suggestive but not significant evidence was found that adult sexual and nonsexual social play is influenced by diet, habitat, reproductive, and metabolic factors, sometimes in opposite directions, that we discuss along with needed future analyses involving improved data and interactions among traits.