Multiple Chemical Signals in Male Rock Lizards: Femoral Gland Secretions and Feces May Provide Information on Body Size but Using Different Compounds

Chemosensory communication in lizards may be based on multiple compounds coming from multiple sources. Both secretions from external epidermal glands, and internal cloacal glands and feces are known to convey information (sex, familiarity, body size, etc.) for conspecifics. However, although some compounds in femoral gland secretions have been characterized and their function examined, there is very little information on potential semiochemicals in cloacal products and feces. More importantly, it is not well-known whether the compounds and information from multiple sources are redundant, complementary, or different. We analyzed the lipids in femoral gland secretions and feces of male Carpetan rock lizards (Iberolacerta cyreni) and examined which compounds might predict body size. We found many compounds in feces, mainly steroids, alkanes, and branched alkanes, while the main compounds in femoral secretions were steroids and fatty acids. The body size of males was related to the proportions of some alkanes, alkenes, and terpenoids in feces, while it is related to the proportions of some steroids and fatty acids in femoral secretions. There were also differences in the chemical profiles of feces of males and females, which may allow sex recognition. Therefore, femoral secretions and feces may both inform on males' sex and body size, but the chemical bases of this information are different depending on the source.

Automated summary

Chemosensory communication in lizards involves multiple compounds from external and internal glands and feces. While femoral gland secretions contain steroids and fatty acids, feces contain steroids, alkanes, and branched alkanes. The proportions of these compounds in feces and secretions predict body size in males, while the chemical profiles in feces may allow sex recognition. Therefore, the information conveyed by feces and femoral secretions differs in terms of chemical composition and provides different information about sex and body size.