Escape Behavior and Predation Risk of Mainland and Island Spiny-tailed Iguanas (Ctenosaura hemilopha)

Abstract

We investigated the relationships between predator avoidance behavior and predation risk by comparing the wariness of iguanas (Ctenosaura hemilopha) belonging to an island population with few predators with that of iguanas belonging to a mainland population under high predation pressure. We predicted that island iguanas would be less wary than mainland ones. Island iguanas allowed the closer approach of potential predators before their first reaction and fleeing. The responses of both sexes did not differ statistically, except for the frequent displays shown by males as the first reaction. These results suggest that island iguanas, which were probably introduced onto the island by man, have modified their behavior in response to a decline in predation risk, supporting the hypothesis that predation pressure can contribute to intraspecific variation in antipredator behavior. The results also quantify the tameness of prey on islands without terrestrial predators, and their consequent vulnerability if foraneous predators are introduced. No significant difference was found between the populations in the time needed by frightened iguanas to resume their normal activity, suggesting that the island iguanas could learn to recognize predators and develop a suitable antipredator behavior