A new study published Tuesday reports that within the continental U.S. cats that roam free kill an estimated 1.4 billion to 3.7 billion birds, annually. Additionally, 6.9-20.7 billion mammals mostly mice, rabbits and shrews are killed by cats yearly. According to the American Bird Conservancy, the amount of endangered birds of the 800 species in the U.S. is approximately one third.
"To maintain the integrity of our ecosystems, we have to conserve the animals that play integral roles in those ecosystems. Every time we lose another bird species or suppress their population numbers, we're altering the very ecosystems that we depend on as humans," said Dr. George Fenwick, president of the American Bird Conservancy in a press release. He hopes that the new report will spark action.
The report was published in Nature Communications and was conducted by Peter P. Marra of the Smithsonian's Conservation Biology Institute, his colleague, Scott R. Loss and Tom Will, a U.S. Fish and Wildlife Service biologist. They concluded that reptile and amphibian populations may also be impacted by cats. The lack of studies, make this estimate difficult to determine. The authors estimate that nationwide, between 258 to 822 million reptiles and 95 to 299 million amphibians may die by cat each year. Data was taken from 21 studies conducted within in Europe, Australia, New Zealand and the United States. As reported by USA Today, "I was stunned," said Marra.
Scientists found that feral cats and stray cats, not house cats are responsible for a majority of the killings. "Our findings suggest that free-ranging cats cause substantially greater wildlife mortality than previously thought and are likely the single greatest source of anthropogenic mortality for U.S. birds and mammals," says the report. Animal activists argue that feral cats are just trying to survive in the world. "Human impact is the real threat" to birds, says Becky Robinson, president of the non-profit organization, Alley Cat Allies. Their policy of Trap-Neuter-Return is a way to protect birds without having to euthanize cats. She points out that cats are not the sole danger that birds face. Collisions with man-made objects and chemicals found in fertilizers and insecticides can also attribute to bird deaths.