First experimental evidence that proteins from femoral glands convey identity-related information in a lizard

Abstract

Transferring identity-related information (IRI) to conspecifics may give advantage in effectively tuning intraspecific behaviour. Some lizard species use the secretions of specialized epidermal glands (femoral or cloacal) to convey IRI. Those secretions are made of lipids and proteins, the former been suggested to inform about signaller quality, the latter suspected to communicate IRI to conspecifics. Here, we tested the hypothesis that proteins broadcast IRI by analysing the movement patterns of 28 male common wall lizards (Podarcis muralis) under strictly controlled experimental conditions. Lizards were videotaped in plastic terraria where the substrate scent was manipulated by filling it with a solution bearing (i) the proteins extracted from the secretions of the tested lizard (SELF); (ii) the proteins from a never-met donor from other nearby populations (NON-SELF); and (iii) the solvent alone. Lizards showed higher behavioural response to the NON-SELF treatment with respect to both CTRL and SELF ones. Further, protein concentration did not affect behavioural response, suggesting an all-or-nothing effect. Both results agree with the hypothesis that proteins may be used in chemical communication and convey IRI, demonstrating for the first time that they can be used as intraspecific signal.