for National Geographic News
You may have seen them wandering through parks or languishing behind restaurants. At first, these cats look domesticated. But they're really wild animals.
Feral cats are the offspring of stray or abandoned household pets. Raised without human contact, they quickly revert to a wild state and form colonies wherever food and shelter are available.
Many city and county animal control agencies are mandated only to deal with dogsnot cats. So for decades feral cats have remained untouchable.
Some feline experts now estimate 70 million feral cats live in the United States, the consequence of little effort to control the population and of the cat's ability to reproduce quickly.
The number concerns wildlife and ornithology organizations that believe these stealthy predators decimate bird populations and threaten public health. The organizations want the cats removed from the environment and taken to animal shelters, where they are often killed.
That's caused a chorus of hisses from feral cat advocates who say the cats are unjustly being blamed for killing wildlife. Thousands of volunteers and animal welfare groups throughout the country stepped forward in the early 1990s to control the wild cat population through mass sterilization programs.
Ron Jurek, a wildlife biologist for the California Department of Fish and Game, has kept a close eye on the impact feral and free-roaming domestic cats have on native species, like the California least tern, a federal endangered bird that nests along the coast.
"Cats do kill wildlife to a significant degree, which is not a popular notion with a lot of people," he said.
In urban areas, he said, there are hundreds of cats per square mile (1.6 square kilometers)more cats than nature can support.
Exact numbers are unknown, but some experts estimate that each year domestic and feral cats kill hundreds of millions of birds, and more than a billion small mammals, such as rabbits, squirrels, and chipmunks.
Feline predators are believed to prey on common species, such as cardinals, blue jays, and house wrens, as well as rare and endangered species, such as piping plovers and Florida scrub jays.
For more than ten years, Jurek says, feral and domestic cats have been a persistent problem in California, killing one or two colonies of least terns each year. The small white birds are part of an intense monitoring program with a tremendous number of volunteers who watch the colonies throughout the six-month nesting season.
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