Age-dependent self- and individual chemosensory discrimination in male Psammodromus algirus lizards is based on lipids and proteins from their scent

Self- and individual discrimination are needed to maintain social relationships. However the extent of precision of these abilities may depend on the social strategy of each individual, which may vary with ontogeny. Many animals use chemical cues to discriminate conspecifics. For example, many lizards use femoral gland secretions, which are composed of lipids and proteins, but it is not well known the role of each of these chemical classes in conspecific discrimination. We examined whether and how differences in age-dependent social strategies of male lizards Psammodromus algirus affect self- and individual chemosensory discrimination, and whether these are mediated by the lipid and/or protein fraction of femoral secretions. In this lizard species, there are two age categories of males that adopt alternative reproductive strategies; dominant and territorial “old” males and “young”, but reproductively mature, satellite-sneaker males. We examined chemosensory responses to separated lipid and protein fractions of femoral secretions. Both young and old males discriminated both their own lipids and proteins from those of conspecific males of their same age category. With respect to individual discrimination, only old males distinguished different unfamiliar old males based on their lipids alone, but not on proteins, while they do not discriminate between different individual young males. In contrast, young males do not show individual discrimination in any case. Therefore, our results show age-related differences in chemical social discrimination abilities in male P. algirus lizards that could be explained by their different age-dependent social strategies. Significance statement Self and individual discrimination is crucial in modulating animal social interactions, but the level of discriminatory ability may depend on the individual advantage associated with this ability. Male Psammodromus lizards adopt age-related reproductive strategies: older males actively defend their territories (and females therein), while younger ones stealthily try to enter these territories to mate with females. Both types of males use chemical secretions (protein-lipid mixtures) for intraspecific communication. We show that lizards of all ages can discriminate their own scent, independently from the available fraction (both lipids and proteins); only old males are able to discriminate lipids from other old individuals, but only if they are old, too. Therefore, the level of discrimin