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Dec

10

2007
 
 

Do top cats quash rats?



Island data show that mesopredators are released... sometimes island birds now flying highRemoving introduced cats Felis cattus allowed introduced rats Rattus exulans to wreak havoc on two high-altitude native island Cook’s petrel Pterodroma cookii populations, according to a study of long-term data published this week in PNAS. The University of Auckland’s Matt Rayner and fellow New Zealand biologists found that exterminating the top level predators from Little Barrier Island in 1980 resulted in a steady drop in chick production until 2004, when the rats followed the cats’ fateful footsteps. In the few years since there has been a dramatic boost in petrel numbers, freed at last from their twin alien predators. The counterintuitive, theoretically beguiling idea that removing top predators can lead to a fall in prey numbers -- a phenomenon known as mesopredator release -- has seldom been put to the test in the real world, and Rayner’s findings sound a cautious note: at another, low-altitude site, rat presence made little difference to petrel chick production, possibly because there were plenty of alternative food sources. It might be a dog eat dog world, but it's not a simple one. Source: Rayner MJ, Hauber ME, Imber MJ, Stamp RK & Clout MN (2007) Spatial heterogeneity of mesopredator release within an oceanic island system. Proceedings of the National Academy of Sciences USA DOI: 10.1073/pnas.0707414105 Related story in Conservation magazine: Us Or Them Image © Eric Preston

Filed Under Endangered species, Invasive species, Monitoring, Restoration | 

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