A cat-astrophe? Cats eat over 2,000 species worldwide, study finds

The simple housecat, as it turns out, will kill and eat just about any tasty-looking creature it comes across and is a threat to biodiversity when allowed to roam outdoors, a new study found.

They don't call those paws "murder mittens" in certain corners of the internet for nothing.

A study published this week in Nature Communications examined the global impact of free-ranging domestic cats' diets and found they eat more than 2,000 species of rodents, insects, birds and more, including at least 347 that are "of conservation concern."

Their proliferation around the world and disruption to ecosystems make them "amongst the most problematic invasive species in the world," the study authors write.

Why the housecat is 'problematic' to biodiversity

Cats were first domesticated over 9,000 years ago and spread by humans across the globe, the study authors write. They now inhabit every continent except Antarctica.

They are "opportunistic predators and obligate carnivores," meaning they will change their diet depending on what is available to them, and they require a diet of animal flesh. Cats also kill animals they don't consume afterward, unrelated to their diet, the study says.

Domesticated cats have disrupted many ecosystems, the study authors say. They spread novel diseases, including to humans; out-compete wild cats; prey on animals in their environments; and have caused many species to become extinct. Just the presence of cats alone in an environment can cause fear and affect native species' foraging and breeding behaviors, according to the authors.

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What's on your furry friend's menu when it goes out to eat?

In total, cats – unowned and owned with access to the outdoors – eat about 981 species of birds, 463 species of reptiles, 431 species of mammals, 119 species of insects and 57 species of amphibians, according to the study. The results of the study show an increase in the species that had been thought to be consumed by cats.

The most commonly identified animals in a cat's diet were the house mouse, European rabbit, black rat, house sparrow and brown rat. Cats also feast on carcasses that can be scavenged.

Useful though cats may be at deterring pests from our abodes, they are predators to several species that are near-threatened or threatened, including some that have endangered status or are extinct. More than 7% of birds, 4.9% of mammals and 2.7% of reptiles of conservation concern are on the cat's menu.

"We found records of cats consuming 11 species from Australia, Mexico, the United States of America, and New Zealand that have since been listed as extinct in the wild (EW) or extinct (EX)," the authors wrote.

The study also notes that known estimates are conservative, and the true number of species eaten by cats remains unknown.