Killer Kitties

Jan. 30, 2013—Is Fluffy's feline tribe an invasive species laying waste to native animal populations? Definitely—and a new study shows the carnage is much worse than previously thought. Research by Smithsonian's Migratory Bird Center and the U.S. Fish and Wildlife Service published this week in Nature Connections finds that cats kill between 1.4 and 3.7 billion birds in the U.S. each year and anywhere from 6.9 to 20.7 billion small mammals. The figures scientists used to cite were more like 500 million. Big difference.

The clincher? Most of those birds and mammals are native species, not unwelcome nonnatives like Norway rats and starlings. Seems America's 80 million pet cats and 80 million more feral cats prefer to dine on North America's indigenous protein sources. They do this at different rates, however; pets account for about a third of bird killings and about 10 percent of mammal slaughter. The rest is the doing of feral cats.

The cats' impact on native species is a matter of concern to bird lovers and conservationists. The International Union for the Conservation of Nature, which publishes the annual Red List of Threatened Species, has long listed felix catus among the top 100 worst invasive species in the world. If set loose on islands, particularly fragile environments, feral cats can wreak havoc; they're implicated in 14 percent of bird, mammal and reptile extinctions worldwide.

The issue is shining a light on feral cat colonies, a regular feature of urban life. Cities like Austin and Washington, D.C. have hundreds of feral cat colonies where well-meaning citizens have done trap-neuter-release actions to at least prevent cat proliferation. But if the cats are harming native species, should they be re-released? Tough questions...

Read more at, National Geographic and the New York Times.