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

Abstract

Baeckens, S., Huyghe, K., Palme, R. and Van Damme, R. 2016. Chemical communication in the lacertid lizard Podarcis muralis: the functional significance of testosterone. -Acta Zoologica (Stockholm) 00: 000-000.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.

Environmental conditions shape the chemical signal design of lizards

“…Altering the chemical composition or the relative proportions of the compounds in the chemical signal is one way of coping with suboptimal signalling environments, but other ways are also possible. Increasing the total quantity of the deposited glandular secretions, for example, has been shown to increase the signal detectability in the lacertid lizards Podarcis muralis (Baeckens, Huyghe, et al., ), Specific site selection for secretion deposit may be another way of increasing signalling efficacy. Lizards of the species I. cyreni deposit their excrements at non‐random sites (preferring high positioned rocks) to facilitate chemical or even visual detection by others (López, Aragón, & Martín, ).…”

“…The extraction procedure is harmless, and the lizards are able to rapidly produce more secretion afterwards (e.g. Baeckens, Huyghe, Palme, Van Damme, ). We immediately placed the collected secretions in glass vials with glass inserts sealed with Teflon‐lined lids.…”

Rapid and repeated divergence of animal chemical signals in an island introduction experiment

“…We extracted secretions from both hind limbs, resulting in 2–6 mg of secretions per individual for chemical analysis. The extraction procedure is harmless, and the lizards are able to rapidly replenish the harvested secretions following their release back to the wild (Baeckens, Huyghe, Palme, & Damme, 2017). Immediately following collection, we transferred the secretions to glass vials with glass inserts sealed with Teflon‐lined lids.…”

Sexual selection and the chemical signal design of lacertid lizards

“…The extraction procedure is harmless, and the lizards are able to produce more secretion rapidly thereafter (e.g. Baeckens et al, 2017a). The samples were stored in glass vials fitted with Teflon-lined stoppers and kept at −20 °C until analysis.…”