Cats in US Kill Billions of Animals Annually

Cats in the United States kill between 1.4 billion and 3.7 billion birds and up to 20.7 billion small mammals every year, finds a new study.

Researchers from the Smithsonian Conservation Biology Institute (SCBI) and the U.S. Fish and Wildlife Service have found that cats (both domesticated ones and feral strays) are the leading cause of deaths of small mammals, unlike better-known causes such as habitat loss, hunting or agricultural chemicals.

Study co-author Pete Marra, an animal ecologist with the SCBI, and his colleagues analyzed previous studies on bird deaths and the predation habits of cats. They estimated that around 84 million domesticated cats live in the country, and most of them are allowed to roam outdoors.

"A lot of these cats may go outside and go to 10 different houses, but they go back to their house and cuddle up on Mr. Smith's lap at night," Marra told LiveScience.

In addition, there are between 30 and 80 million wild or free-ranging cats without an owner.

Each of those kitties kills between 23 and 46 birds a year, and between 129 and 338 small mammals. In total, cats kill up to 3.7 billion birds and between 6.9 and 20.7 billion small mammals like mice, chipmunks, squirrels, meadow voles and rabbits. Native birds such as the American Robin are at a greater risk, said the researchers. They point out that the feral cats kill about three times as many as domesticated cats. 

"Our study suggests that they are the top threat to US wildlife," Marra said.

The report comes on the heels of a recent debate in New Zealand, where businessman-turned-philanthropist Gareth Morgan is encouraging pet owners to make their current cats their last, in a bid to protect the endangered native bird species. This new report by Marra and colleagues, published in the journal Nature Communications, adds to mounting evidence showing that cats are significantly contributing to or causing the extinction of some birds, mammals and reptiles.

According to the International Union for Conservation of Nature (IUCN), cats are responsible for the global extinction of 33 species.