Conspecific presence affects foraging decisions of insular and mainland Aegean wall lizards (Podarcis erhardii)

Abstract

Conspecifics often constitute a valuable source of information. For instance, animals are often attracted to a foraging site by the presence of conspecifics, a phenomenon known as ‘local enhancement’. Theory predicts that animals should engage in local enhancement only when associated benefits (efficient resource detection) outweigh the costs (increased interference competition), a trade off that depends on environmental context. Insular and mainland habitats differ in key ecological factors, such as predation pressure, competition, and food availability, which likely affect how animals use social cues while foraging. Here, we compared the local enhancement behaviour of Aegean wall lizards from three small islets, two larger islands, and two mainland sites in Greece. In the wild, lizards were offered food near a transparent container that either held a conspecific (social trials) or was empty (control). We then compared whether and how fast individuals would (1) emerge near, (2) approach, and (3) start eating the food, between social and control situations, and among habitats (mainland, island, or islet). We also looked at whether the presence of conspecifics – confined, or free-roaming when multiple lizards were attracted – provoked interference competition. Conspecific cues influenced foraging decisions in a complex manner. The presence of confined conspecifics had only minor effects, but other free roaming conspecifics accelerated or inhibited foraging activities, depending on their type (emerging, approaching, eating). Insular lizards also engaged in more aggressive interactions than mainland ones. Our results indicate that the costs and benefits of local enhancement may vary geographically, but they are inconclusive due to methodological limitations. Further research is needed to identify the environmental conditions favouring the evolution of local enhancement and social cognition.