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Don’t let their fluff fool you: Your cat was built for murder. Felines, no matter how chonky, eepy, or boopable, are remarkably adaptable obligate carnivores, down to eat just about anything that fits in their mouth.
Well-intentioned (or … threatening?) gifts of dead birds, rats, and lizards are familiar to outdoor cat owners—even my shockingly uncoordinated indoor cat has killed a spider or two in her day. But an analysis published today in Nature Communications, led by Auburn University ecologist Christopher Lepczyk, reveals that there’s shockingly little that cats don’t eat.
Compiling evidence from a century of research from across the globe, Lepczyk’s team identified over 2,000 animal species eaten by cats—and that’s only what scientists have recorded so far. Of those species, 347 are at risk of extinction, and 11 have since been listed as extinct in the wild (or for good). Scientists have known for ages that feline predation is an ecological nightmare, but “it’s a challenging problem that we still have yet to deal with,” says Peter Marra, dean of the Earth Commons Institute and biology professor at Georgetown University, who was not involved in this study.
My cat slept through Marra’s video call, barely out of frame, blissfully ignorant of the ecological damage she caused in her wayward youth. She’s a sweet, perfect angel baby, and many doting cat parents feel the same about their own kitties. Could the solution to this environmental problem … really be to get rid of them? “Cats are embedded in our culture,” Marra continues. “It gets confusing when we start to talk about taking one life to save another.”
Since they were domesticated in the Middle East nearly 10,000 years ago, cats have traveled pretty much everywhere humans have. To thrive in so many different environments, felines became opportunists. While some animals, like pandas and koalas, stick to a limited menu of specific foods, “cats are not diet specialists,” says Marra. “They’re just trying to make ends meet.”
Lepczyk has spent the last two decades compiling evidence of what cats eat—first as a curiosity-driven side project, then as a full-blown scientific endeavor. Hundreds of peer-reviewed journal papers, doctoral dissertations, government reports, and magazine articles over the past century contain reports of cat diets around the world, but until now, the information had never been fully synthesized and laid out. So his team, comprising researchers from North America, Europe, Australia, and New Zealand, pulled every report of cats eating things they could find, and added each species listed as cat food to a database. “It’s not rocket science that we’re doing here,” Lepczyk says. “But it was needed.” Finding out exactly what animals are affected by cats will inform future conservation and policy, hopefully keeping both at-risk species and loving pet owners happy.
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There’s more than one way to monitor a cat’s diet. Over the years, scientists have examined the contents of cat vomit and litter box turds, and conducted surveys asking pet owners to report the critters brought home by their outdoor fur babies. Lepczyk says that, especially when it comes to feces, it’s tricky to distinguish between things that the cat killed and things that the cat scavenged. Elizabeth Gow, a research scientist with Environment and Climate Change Canada and an adjunct professor at the University of Guelph, who was not involved with this study, gets around this problem by fitting cats with GoPro-like cameras to record what (and how) they hunt when humans aren’t watching. Among other wonders, Gow has captured film of a cat taking down a rabbit larger than itself.
With millions of predatory felines roaming around, both feral and domestic, “their need for food causes enormous harm to the environment,” Marra says. The notion that outdoor cats wreak havoc on bird populations has simmered in the back of pet owners’ minds for years, and the scientific evidence linking cats to bird deaths is incriminating. Given that other facts of urban development, like light pollution and habitat loss, are already driving populations down, birds “really can’t afford to have more things hurt them—especially things that we can control,” says Gow. “Cats are something that we can partly control.”
But birds aren’t even the half of it. Lepczyk’s team found that while birds (981 species, or nearly 10 percent of all types of bird known) make up about 47 percent of species eaten by cats, the feline global diet also includes 463 reptiles, 431 mammals, 119 insects, 57 amphibians, and 33 other critters like spiders and crabs. And the number of species identified is still rapidly increasing with every paper published, suggesting that the number of species reported in this new research is an underestimate. “We have a snapshot of what they’re eating, but it’s not leveling off,” Lepczyk says. “We haven’t gotten everything.”
Still, he says, the results are fairly conclusive and unsurprising, given the massive pile of evidence this work drew from. Scientists have known for ages that feline predation is an ecological nightmare—this paper simply demonstrates that cats eat a lot of things we weren’t aware of. From a conservation perspective, that’s concerning. “We’re all single threads in a tapestry that is the Earth,” Marra says. “Every time we lose a species, or populations are impacted, the integrity of that tapestry is compromised.”
Such damage may be spread unevenly across the world. The paper compiles data from across the globe, but stray felines disproportionately ravage islands where native species evolved in relative isolation. They have terrorized Australia since they were introduced to the island by Europeans in 1788. Cats spread across the continent very quickly, and Australian fauna were unequipped to deal with such an undiscriminating predator. Tanya Plibersek, Australia’s minister for the environment and water, declared war on feral cats in September 2023. “We have the biggest mammal extinction record of modern times by a country mile, and cats are responsible,” says Sarah Legge, a professor at Australian National University and member of the country’s Biodiversity Council, who was not involved in this study.
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The level of insight into cat diets also varied from place to place. Studies from regions outside of North America and Australia were greatly underrepresented in this meta-analysis, despite large, well-documented feral cat populations in places like Istanbul, Rome, and Houtong, Taiwan. It’s been harder to draw as strong a line between cats and biodiversity loss in other countries, Legge says. While there’s plenty of evidence correlating the presence of free-ranging domestic cats to population decline of other species, figuring out whether they really cause prey species loss would require “impossible experiments,” she says, like removing cats from a whole suburb to see what happens.
Mikel Delgado, scientist and certified cat behavior consultant, thinks the problem extends far beyond felines. Human behaviors like deforestation, intensive farming, urban development, and burning fossil fuels also hurt native species. “The focus on cats,” she believes, “is a bit of a scapegoat for a much bigger problem about our ecological landscape.” If we’re not yet willing to meaningfully change our behavior, she continues, “I’m not sure why we’d be motivated to do anything to a species that we have a very close relationship with.”
A universal approach to curtailing cat predation probably wouldn’t work either—cultural attitudes toward cats differ widely across the world. Legge says that there’s a lot of support for pet containment in Australia, because the public is relatively well educated about the ecological impact of free-ranging cats and other invasive species. Regional laws that would require owners to keep their pet cats indoors wouldn’t be such a radical step in Australia as they would in the US or Europe, Legge says, where people often feel like cats need the freedom to roam outdoors to be happy.
It’s true—some cats are an absolute terror when they’re cooped up inside. But Delgado says that cats usually act up indoors because their environment isn’t properly set up to let them do all the natural cat things they’d otherwise enjoy outdoors: exploring, climbing, hunting, scratching. In many ways, Marra says, we’ve owned our responsibility with respect to dogs much better than we have with cats, and that’s a shame. Educating people on responsible cat ownership, Lepczyk says, can help them give their kitties enriching, safe, and ecologically friendly lives. Building an enclosed outdoor “catio,” training your cat to wear a harness, or taking them out in a pet stroller (my personal preference) can all give pets outside time where they can’t kill birds, get into fights, or get hit by cars.
Lepczyk, a longtime cat lover who’s parented fur babies throughout his 26-year marriage to study coauthor Jean Fantle-Lepczyk, gets it. “I understand why people love cats,” he says. “And I think that makes it a really challenging issue.” Legge suspects that no amount of meta-analysis will convince outdoor cat lovers to change their behavior. “The issue is more about what people think is fair to the cat,” she says. “I suspect it’s a social science issue, not an ecological one.” Delgado agrees that there isn’t a good solution that will make everybody happy. Killing stray cats is widely perceived as distasteful, but TNR (trap-neuter-return) approaches, often taken as a no-kill alternative, aren’t effective unless you neuter a huge percentage of the total cat population, Delgado says. “At this point, the cat is already out of the bag.”
But Lepczyk believes that continuing to encourage people to keep their cats indoors can address at least part of the problem. “We will never solve having outdoor cats if we don’t try to work on responsible pet ownership,” he says. “There’s no single way to solve it. But the more we can encourage responsibility, the better.”
