Free-ranging domestic cats in the United States kill many more birds and mammals than previously thought, making them possibly the top anthropogenic killer of US wildlife.
Scott Loss at the Smithsonian Conservation Biology Institute, Washington DC, and his colleagues conducted a systematic review of studies on cat population sizes and predation behaviour. They analysed the data to estimate mortality caused by US domestic cats — including those living on farms, pet cats that spend at least some of their time outdoors, stray cats fed by humans and feral felines. The researchers estimate that these cats kill 1.4 billion to 3.7 billion birds and 6.9 billion to 20.7 billion mammals annually, possibly exceeding other human-related causes of death such as habitat destruction or collisions with vehicles or buildings.
These numbers suggest that cats could be endangering some species in certain regions, the authors say.