Predators increase the risk of catastrophic extinction of prey populations

Abstract

There has been considerable research on both top-down effects^1,2 and on disturbances^3,4,5 in ecological communities; however, the interaction between the two, when the disturbance is catastrophic, has rarely been examined⁶. 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 characteristics^8,9 in a way that increases the vulnerability of prey species to extinction. We show that a major hurricane in the Bahamas led to the extinction of lizard populations on most islands onto which a predator had been experimentally introduced, whereas no populations became extinct on control islands. Before the hurricane, the predator had reduced prey populations to about half of those on control islands. Two months after the hurricane, we found only recently hatched individuals—apparently lizards survived the inundating storm surge only as eggs. On predator-introduction islands, those hatchling populations were a smaller fraction of pre-hurricane populations than on control islands. Egg survival allowed rapid recovery of prey populations to pre-hurricane levels on all control islands but on only a third of predator-introduction islands—the other two-thirds lost their prey populations. Thus climatic disturbance compounded by predation brought prey populations to extinction.