They really do move in herds: evidence of group living in an aquatic turtle

Sociality is a key aspect of the ecology of many species, and it has important implications for conservation. Nevertheless, research on vertebrate sociality has focused predominantly on mammals and birds, while reptiles have been largely neglected. Here we present some of the first evidence of group living in freshwater turtles outside of resource use or reproduction contexts. We monitored the movements of clusters of juvenile Central American river turtles, Dermatemys mawii, and used simulations to compare our results to the null hypothesis of no social association. We found that turtles moved together nonrandomly and formed tighter clusters than would be expected by chance. Indeed, in several cases, two juveniles were monitored moving closely together, apparently following one another. This work was conducted in an area with uniform habitat and little or no structure, and the results cannot adequately be explained by habitat selection, foraging behaviour or mating behaviour, thus leaving social clustering (i.e. group living) as the most parsimonious interpretation. This suggests that turtles are more social than generally assumed and expands our understanding of the contexts and taxa in which sociality arises.