Question

Cats as Subsidized Predators

A recent conservation study in the prestigious journal Nature became a huge story (and controversy) among animal lovers. This study showed that domestic cats in the US kill a median of 2.4 billion birds and12.3 billion mammals per year. Many of these birds and mammals are native species (not just invasive, non-native urban pests). Owned (pet) cats had less impact than unowned cats, but outdoor pet cats still caused substantial wildlife mortality.

For Week 4's discussion, consider this issue: It is likely that most of you either own a cat or know of someone who owns a cat that is allowed to roam outdoors.  Considering your scientific background and your interest in conservation, how do you feel about the results from these two studies? What are your ideas about how to address this complicated, serious problem?

Answer 1

Anthropogenic threats, such as collisions with man-made structures, vehicles, poisoning and predation by domestic pets, combine to kill billions of wildlife annually. Free-ranging domestic cats have been introduced globally and have contributed to multiple wildlife extinctions on islands. 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. Here we conduct a systematic review and quantitatively estimate mortality caused by cats in the United States. We estimate that free-ranging domestic cats kill 1.3–4.0 billion birds and 6.3–22.3 billion mammals annually. Un-owned cats, as opposed to owned pets, cause the majority of this mortality. 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. Scientifically sound conservation and policy intervention is needed to reduce this impact.