The social environment in which an individual lives can have profound impacts on numerous aspects of its biology, including fitness, physiology, and gene expression. Long-term field and laboratory studies of the colonial tuco-tuco (Ctenomys sociabilis) indicate that whether a yearling female lives alone or with conspecifics impacts each of these parameters. To better understand the effects of the social environment, comparative data from other, independently evolved examples of ctenomyid sociality are required. To date, however, few additional species of tuco-tucos have been studied with regard to social structure; of those species for which appropriate data are available, the majority (N = 7 of 9 species) have been shown to be solitary. Here, we present information indicating that, in addition to C. sociabilis, at least two other species of ctenomyids – C. opimus and C. rionegrensis - display evidence of some degree of sociality. Based on analyses of mark-recapture and radiotelemetry data, we demonstrate that spatial and thus presumably social relationships differ markedly among these species. The distribution of these species within the genus Ctenomys suggests that they represent independent origins of non-solitary behavior. Collectively, these analyses indicate that patterns of social structure in ctenomyid rodents are more diverse than previously suspected, thereby creating exciting new opportunities for comparative analyses of the causes and consequences of patterns of social behavior.