Interspecies play behavior in captive black-and-white ruffed lemurs (Varecia variegata) and ring-tailed lemurs (Lemur catta)

Social play is a widespread behavior across the animal kingdom. Although its ultimate function remains debated, it likely contributes to establishing and maintaining social bonds. Hence, it is not surprising that many group-living animals engage in social play with conspecifics, with playfighting being the most common form. More puzzling, however, are cases of interspecific play behavior, as firstly, playfighting in particular requires effective communication between partners to ensure that both parties perceive the interaction as play behavior rather than aggression. Secondly, the choice of a heterospecific partner over a conspecific raises questions about the social and ecological factors that influence this behavior. Here, we describe multiple instances of playfighting between adult black-and-white ruffed lemurs ( Varecia variegata ) and juvenile ring-tailed lemurs ( Lemur catta ). We observed multiple behaviors consistent with play from both species. To the best of our knowledge, this is the first documented case of such behavior between the two species. Although interspecific play is rare and difficult to study systematically, it offers valuable insights into the evolution of social play and communicative signaling.