Chemical communication in the lacertid lizard Podarcis muralis: the functional significance of testosterone

Chemical signals are essential for intersexual communication in many animals, including lizards. While faeces have been suggested to contain socially relevant chemical stimuli, epidermal gland secretions are generally believed to be the leading source of chemosignals involved in lizard communication. Early research has shown that sex hormones affect epidermal gland activity, with androgens stimulating gland/pore size and/or gland productivity. However, the functional significance of hormone-induced glandular activity in lizard chemical communication remains unclear. In this study, we manipulated testosterone (T) concentrations in male Podarcis muralis lizards. While T-supplementation did not change pore size, it did increase secretion production substantially. Chemosensory tests showed that female conspecifics tongue-flick at a higher rate and more quickly towards the secretion of males with experimentally increased T levels than towards the secretion of control males, suggesting that females can discriminate between males with dissimilar T levels based on chemical cues of secretion alone. Based on the scent of faeces, however, females were unable to discriminate between males with differential T levels. Also, females reacted more quickly when offered larger amounts of secretion - irrespective of whether secretions were obtained from control or T-increased males. This result indicates that secretion quantity affects chemosignal detectability in Podarcis muralis.