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Mesopredator release and avifaunal extinctions in a fragmented system

Abstract

Mammalian carnivores are particularly vulnerable to extinction in fragmented landscapes1, and their disappearance may lead to increased numbers of smaller carnivores that are principle predators of birds and other small vertebrates. Such ‘mesopredator release’2 has been implicated in the decline and extinction of prey species2,3,4,5,6. Because experimental manipulation of carnivores is logistically, financially and ethically problematic6,7, however, few studies have evaluated how trophic cascades generated by the decline of dominant predators combine with other fragmentation effects to influence species diversity in terrestrial systems. Although the mesopredator release hypothesis has received only limited critical evaluation8 and remains controversial9, it has become the basis for conservation programmes justifying the protection of carnivores6. Here we describe a study that exploits spatial and temporal variation in the distribution and abundance of an apex predator, the coyote, in a landscape fragmented by development. It appears that the decline and disappearance of the coyote, in conjunction with the effects of habitat fragmentation, affect the distribution and abundance of smaller carnivores and the persistence of their avian prey.

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Acknowledgements

We thank L. Angeloni, D. Bolger, T. Case, J. Crooks, D. Doak, J. Estes, R. Fisher, S.Hathaway, D. Menendez, S. Minta, P. Raimondi, B. Rice, and A. Suarez for their valuable help with this research, and C. Bell for illustrating Fig. 1 . This work was funded by D. Brimm, an NSF Graduate Research Fellowship, an EPA STAR Fellowship and an American Society of Mammalogist grant (K.R.C.).

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Correspondence to Kevin R. Crooks.

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Figure 1: Model of the combined effects of trophic cascades and island biogeographical processes on top predators (for example, coyote), mesopredators (domestic cat) and prey (scrub-breeding birds) in a fragmented system.

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