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Despite these harmful effects, policies for management of free-ranging cat populations and regulation of pet ownership behaviours are dictated by animal welfare issues rather than ecological impacts 11. Mounting evidence from three continents indicates that cats can also locally reduce mainland bird and mammal populations 5, 6, 7 and cause a substantial proportion of total wildlife mortality 8, 9, 10. Free-ranging cats on islands have caused or contributed to 33 (14%) of the modern bird, mammal and reptile extinctions recorded by the International Union for Conservation of Nature (IUCN) Red List 4. Scientifically sound conservation and policy intervention is needed to reduce this impact.ĭomestic cats ( Felis catus) are predators that humans have introduced globally 1, 2 and that have been listed among the 100 worst non-native invasive species in the world 3. 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 US birds and mammals.

Un-owned cats, as opposed to owned pets, cause the majority of this mortality.

We estimate that free-ranging domestic cats kill 1.3–4.0 billion birds and 6.3–22.3 billion mammals annually. Here we conduct a systematic review and quantitatively estimate mortality caused by cats in the United States.

The magnitude of mortality they cause in mainland areas remains speculative, with large-scale estimates based on non-systematic analyses and little consideration of scientific data. Free-ranging domestic cats have been introduced globally and have contributed to multiple wildlife extinctions on islands. Anthropogenic threats, such as collisions with man-made structures, vehicles, poisoning and predation by domestic pets, combine to kill billions of wildlife annually.

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