An invasive species is a plant or animal that is not native to a particular ecosystem. An invasive can throw an ecosystem out of whack by competing with native species for resources or eliminating native species. Examples include zebra mussels, Japanese knotweed, and the domestic house cat.
That’s right. When cats are introduced to an ecosystem, either for a few hours a week or because they have been abandoned, they can cause havoc.
Housecats return to their predatory instincts when allowed outside. Of greater concern is the growing feral cat population. It’s estimated that each of the 50 million or so feral cats in the U.S. kills several hundred small mammals and between 23 and 46 birds each year.
Globally, scientists have estimated that cats have been responsible for the extinction of more than 30 species of birds.
And the problem is not just the wildlife that cats directly injure or kill. Research in Great Britain shows that the mere presence of a cat near a nest raises the likelihood of nest predation by other animals, who are attracted by the alarm calls of the parent birds. Nestlings are fed less because parents stay close to the nest. And reduced feeding, over long time periods, can reduce the size of the clutch.
Well-intentioned Trap/Neuter/Release programs are meant to control the reproduction of feral cat populations. But these programs do not eliminate the problem of existing feral cats in the environment.
Housecats that are kept indoors can be wonderful companions. But they don’t belong in nature. Any animal lover should agree that free-ranging cats take too great of a toll on wildlife.
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Web links
American Bird Conservancy report on British research
University of Georgia “Kitty Cam” project
Journal Article Addresses Feral Cat Colony Programs, Cites Rabies and Disease Risks
Photo, taken on April 25, 2009, courtesy of Tomi Tapio via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY.