Cats in US kill billions of birds and mammals, study finds

Domestic cats in the United States kill up to 3.7 billion birds and as many as 20.7 billion mice, voles and other small mammals each year, biologists estimated on Tuesday.

Cats are probably the biggest human-induced killer of these species, outstripping better-known culprits such as habitat loss, agricultural chemicals or hunting, they said in a study published in the journal .

A team led by Scott Loss at the Smithsonian Conservation Biology Institute in Washington looked at published research into the predation habits of cats.

Cats that have outdoors access kill between 30 and 47 birds apiece in temperate parts of Europe and North America each year, and between 177 and 299 mammals, according to past investigations.

The next step was to get an estimate of the number of cats in the United States.

Loss’s team calculated there were around 84 million cats with owners, of which a couple of million are unlikely to have outdoor access or go hunting.

Added to that are between 30 and 80 million “unowned” cats – animals that are wild or free-ranging but without an owner and survive on goodwill.