Heart rate responses to social interactions in free-moving rhesus macaques(Macaca mulatta): A pilot study

Heart rate telemetry was explored as a means to access animal emotion durin g social interactions under naturalistic conditions. Heart rates of 2 middl e-ranking adult females living in a large group of rhesus macaques (Macaca mulatta) were recorded along with their behavior. Heart rate changes during 2 types of interactions were investigated, while controlling for the effec ts of posture and activity. The risk of aggression associated with the appr oach of a dominant individual was expected to provoke anxiety in the approa chee. This prediction was supported by the heart rate increase after such a n approach. No increase was found when the approacher was a kin or a subord inate individual. The tension-reduction function of allogrooming was also s upported. Heart rate decelerated faster during the receipt of grooming than in matched control periods.