Keeping a cool mind: head-body temperature differences in the common wall lizard

Evidence of head–body temperature differences are known for many species of medium‐ to large‐sized reptiles, but are scanty for small lacertid lizards. In this study, we heated 48 individuals of Podarcis muralis (19 males and 29 females) in order to investigate their ability to achieve and maintain local temperature differences between body parts. Lizards were put into polystyrene boxes and heated with incandescent lamps. Temperatures were measured with both an infrared thermometer and an infrared camera at four different body points every 20 min for 2 h. We found a statistically significant thermal gradient from the tip of the nose, the coolest part of the body, to the trunk, the warmest area, whereas the head achieved an intermediate temperature. We therefore hypothesize that P. muralis is able to physiologically regulate the heat distribution across its body. Podarcis muralis is sexually dimorphic, but neither sex nor body size are associated with temperature differences between individuals. The two measurement devices used responded differently to insulating material and to living animals, possibly indicating that infrared camera is able to detect dermal heat, while infrared thermometer detects mainly epidermal heat. This study shows for the first time that P. muralis can achieve and maintain temperature differences between the head and the body.