Unintended Consequences

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Science  04 Feb 2000:
Vol. 287, Issue 5454, pp. 769
DOI: 10.1126/science.287.5454.769e

The introduction of alien species is one of the principal threats to biodiversity, especially in island ecosystems, but despite decades of research our understanding of the ecology of invasions is still very patchy. Of the many injurious aspects of species introductions, the phenomenon of hyperpredation is one of the potentially more devastating. Under hyperpredation, populations of indigenous prey species become especially vulnerable to extinction following the introduction of a non-native prey species, because of a concomitant increase in the population of an introduced predator.

Yet the evidence for hyperpredation on islands is largely circumstantial; there are no detailed field studies. Does hyperpredation work in theory? Courchamp et al. have modelled the population dynamics of a system involving introduced cats (predator), introduced rabbits (prey), and indigenous birds (prey) in an island context. Their models confirm the destructive potential of hyperpredation on the indigenous species, even in the absence of direct competition between indigenous and introduced prey. This work identifies hyperpredation as a factor that should always be considered in island conservation programs. Just as importantly, it is a step toward a better understanding of the processes that follow invasions of alien species.—AMS

J. Animal Ecol.69, 154 (2000).

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