Bite and seek: bite force and exploratory behaviour of the lizard Podarcis siculus across its non-native range in the north-eastern United States

Abstract

Abstract Understanding how animals succeed in novel environments is critical to predicting the outcomes of species introductions under global change. Variation in exploratory behaviour—the willingness to investigate unfamiliar environments—has potential to influence species’ invasion success. The Italian wall lizard, Podarcis siculus, is native to southern Europe and has been introduced across Europe and North America. To compare the exploratory behaviour and bite force of individuals from three non-native populations in the United States, we conducted a laboratory experiment involving wild-caught lizards from New York City, Philadelphia, and Boston. We tested a series of hypotheses concerning the predictions that: (1) exploratory behaviour would be greatest in the most recently established population and (2) bite force—associated with competitive ability—would be greatest in the densest populations. Across populations, exploratory behaviour increased significantly with body size. Contrary to our first prediction, exploratory behaviour was not significantly greater in more recently established populations. Consistent with our second prediction, however, lizards from the low-density Philadelphia population exhibited weaker bites. Results suggest that contemporary behavioural variation reflects differences in local ecological conditions, such as resource abundance, population density, and size structure rather than establishment history. Our findings highlight the need for further research into behavioural and performance drivers of lizard invasion success.