Skin temperature changes in wild chimpanzees upon hearing vocalizations of conspecifics.

A growing trend of research using infrared thermography (IRT) has shown that changes in skin temperature, associated with activity of the autonomic nervous system, can be reliably detected in human and non-human animals. A contact-free method, IRT provides the opportunity to uncover emotional states in free-ranging animals during social interactions. Here, we measured nose and ear temperatures of wild chimpanzees of Budongo Forest, Uganda, when exposed to naturally occurring vocalizations of conspecifics. We found a significant temperature decrease over the nose after exposure to conspecifics' vocalizations, whereas we found a corresponding increase for ear temperature. Our study suggests that IRT can be used in wild animals to quantify changes in emotional states in response to the diversity of vocalizations, their functional significance and acoustical characteristics. We hope that it will contribute to more research on physiological changes associated with social interactions in wild animals.