Behavioural traits for success: comparison between two sympatric lacertid lizard species

Invasive species are a major threat to biodiversity especially because of their influence on native species. Their behaviours, including those in nonsocial contexts, significantly influence species fitness, drive invasion processes and can result in the competitive exclusion of less dominant species. Understanding these behavioural patterns is vital for the protection of native species and the control of invasive species spread. There is still a controversy regarding the success of invasive species, whether it is attributed to inherent behavioural traits or to adaptations to new environments. This study focused on native populations of two sympatric lizard species in Croatia: a lizard known for its invasiveness, Podarcis siculus, and the eastern Adriatic endemic Podarcis melisellensis. We evaluated nonsocial behaviour associated with competition, including food consumption, exploratory behaviour and risk-taking behaviours, using two primary apparatuses: an open field and a radial maze. Podarcis siculus exhibited higher levels of exploratory behaviour, reduced risk-taking behaviours and greater food consumption than P. melisellensis. These behavioural traits are consistent with behaviour observed in invasive populations of P. siculus, suggesting that they may be intrinsic to the species. Our results indicate that a successful invader is more likely to explore and at the same time be more cautious. Research on behavioural traits in native populations sheds light on preadaptive features of invasive species that could characterize a successful invader, highlighting the importance of researching invasive species in their native range.