Predators increase the risk of catastrophic extinction of prey populations

There has been considerable research on both top-down effects(1,2) and on d isturbances(3-5) in ecological communities; however, the interaction betwee n the two, when the disturbance is catastrophic, has rarely been examined(6 ). Predators may increase the probability of prey extinction resulting from a catastrophic disturbance both by reducing prey population size(7,8) and by changing ecological traits of prey individuals such as habitat character istics(8,9) in a way that increases the vulnerability of prey species to ex tinction. We show that a major hurricane in the Bahamas led to the extincti on of lizard populations on most islands onto which a predator had been exp erimentally introduced, whereas no populations became extinct on control is lands. Before the hurricane, the predator had reduced prey populations to a bout half of those on control islands. Two months after the hurricane, we f ound only recently hatched individuals-apparently lizards survived the inun dating storm surge only as eggs. On predator-introduction islands, those ha tchling populations were a smaller fraction of pre-hurricane populations th an on control islands. Egg survival allowed rapid recovery of prey populati ons to pre-hurricane levels on all control islands but on only a third of p redator-introduction islands-the other two-thirds lost their prey populatio ns. Thus climatic disturbance compounded by predation brought prey populati ons to extinction.