Influence of introduced predators and natural stressors on escape behavior and endocrine mechanisms in an island species, the Galápagos marine iguana (Amblyrhynchus cristatus)

Abstract

Low wariness in terrestrial island species is attributed to low predation pressure. However, we know nothing of its physiological control and little of its flexibility in the face of predator introductions. Marine iguanas on the Galápagos Islands are an excellent model to study the physiological correlates of low wariness. They have lived virtually without predation for 5 to 15 million years until some populations were confronted with feral cats and dogs beginning some 150 years ago. I tested whether and to what extent marine iguanas can adjust their behavior and endocrine stress response to novel predation threats. Indeed, the results provide evidence that naïve island species show behavioral and physiological plasticity associated with actual predation pressure, a trait that is presumably adaptive. However, the adjustments are not sufficient to cope with the novel predators. I suggest that low behavioral and physiological plasticity in the face of introduced predators may drive many island species to extinction.