This paper reflects on the social organization of a lizard species, the Australian sleepy lizard, Tiliqua rugosa. Our knowledge of this species has arisen from over 35 years of intimate and detailed study, and our study has been set in the broader context and wider understanding of the ecological consequences of social organization. Specifically, we have been interested in the conditions that promote the stable cohesion of groups of two or more conspecific individuals, and the structuring of wider social networks within a population. The benefits of social living have been recognized for a long time (Alexander, 1974) and include shared vigilance against predators, reduced predation from a dilution effect and from predator confusion, shared defense against competitors, information sharing and cooperation in hunting and foraging, and maintaining body warmth in aggregations. The balancing costs include higher levels of competition within groups for resources and mates, easier detection by predators, and the transmission of pathogens and parasites among group members in frequent contact with each other. In his overview of social behavior across animal taxa, Wilson (1975) documented multiple examples of social behavior in birds, mammals, fish and hymenopteran insects, but fewer examples, and of less-advanced forms of sociality within some other taxa, such as reptiles.