Killer Kitties: Cat Kill Billions Every Year

"The battle between cat lovers and bird lovers has been going on for a long time. Cats and birds just don't mix. But trying to get a handle on how many birds and other animals are being killed by cats isn't easy. Just figuring out how many cats there are is tough enough."

"'Cats are really hard to count,' says Pete Marra, an animal ecologist at the Smithsonian Conservation Biology Institute. He and his colleagues actually got a grant from the U.S. Fish and Wildlife Service to try to estimate the number of animals being killed by people, including through the effects of human activities, buildings and pets. They looked at things like wind turbines, cars, pesticides and — domestic cats."

"Marra says Americans own about 84 million of them. 'And of those, about 40 to 70 percent are allowed to go outside," Marra says. 'And we estimate that about 50 to 80 percent of those are actually hunters.'"