The social life of eastern water dragons: sex differences, spatial overlap and genetic relatedness

Abstract

Understanding the ways individuals socialize with each other and how they differ temporally, spatially and phylogenetically is key to unravelling the evolutionary processes that shape social evolution. Our current knowledge of social evolution in vertebrates, however, has primarily come from bird and mammalian studies. Despite being largely understudied, reptiles remain an important piece of the puzzle in our study of social evolution; they represent a major class of vertebrates and, similar to mammals and birds, many are gregarious. Increasing our understanding of sociality in reptiles is important given that it would allow for comparisons across phylogenetically distinct vertebrate classes. In this study, we investigated the social structure of the eastern water dragon, Intellagama lesueurii, and found that males and females showed both preference and avoidance for members of either sex. Furthermore, we found sex differences in the extent of individual sociability: females generally formed stronger associations with one another than any other sex class (e.g. male–male, male–female). Although association patterns correlated to some extent with home range overlap, we found no evidence of a correlation with kinship. Overall, our study presents additional evidence that sociality can evolve outside the realm of kin selection.