Stress and Play Fluctuation in wild Lemur catta

Strepsirhines have been neglected in the study of animal play. Yet, data from a wide array of primate taxa are needed to understand role, functions and social determinants of play. We investigated play behaviour in wild ringtailed lemurs (Lemur catta) at the Berenty Reserve (Madagascar) where two other sympatric lemur species, and potential resource competitors, live (Propithecus verreauxi and Eulemur fulvus). We followed two groups of ringtailed lemurs (9 and 16 individuals) from November 2006 to February 2007. We evaluated play fluctuation during possible stressful conditions, such as the presence of neighbour groups of conspecifics (C), the presence of groups of other lemur species (NC). We considered the absence of any other group (A) as the control condition. We first verified whether the presence of other groups did increase stress levels in the study groups. Stress levels were measured via scratching, which previous studies have proven as a reliable indicator of anxiety in human and non-human primates. Scratching rates in the study animals were higher in presence of other groups (C+NC) rather than in their absence (A). Overall play rates were highest when other groups were nearby. In presence of NC groups, play rates decreased as NC groups approached the study groups. Instead, when only C groups were in sight, play rates increased as the distance between the study groups and other conspecifics decreased. Moreover, play was highest during extra-group aggressive encounters (involving C groups) whereas it was suppressed during intra-group fights. Our results suggest that play fluctuate in response to different stressful conditions and may be used as a mechanism to cope with anxiety.