Are island lizards more catholic? A comparison of diet preferences and food neophilia of mainland and island lizards

Abstract

Insular animals often display broader dietary niches than their mainland counterparts, driven by ecological release, as well as unpredictable or limited resource availability on islands. For instance, insular lizards are known to consume atypical prey, varying from fruits and seeds to dangerous prey, such as scorpions and centipedes. However, systematic comparisons of mainland and insular lizards' feeding habits and preferences are scarce. In this study, we experimentally tested mainland, island, and islet Aegean wall lizards' dietary flexibility and preferences. In two setups-sequential feeding and a simultaneous 'cafeteria' choice test-we offered lizards typical prey (mealworms, crickets), animal-based (eggs, fish) and plant-based (fruits, leaves, capers) foods, and dangerous arthropods (scorpions). We recorded their willingness to inspect and consume each item, along with their neophilic (latency to inspect) and stress-related behaviors (tail waving, foot shakes, and startles) upon encounter. As predicted, island and islet lizards incorporated a wider variety of food items in their diet but maintained the same preference for typical prey as the mainland ones. Nevertheless, island and islet lizards also showed an increased inclination toward fruit consumption, especially watermelon, probably due to its high water content. Interestingly, mainland lizards exhibited stronger stress responses, particularly when encountering dangerous prey (scorpions). These findings highlight how insularity shapes dietary flexibility and behavioral responses in lizards.