One in four adults in the UK owns a cat, according to the UK’s leading vet charity. That adds up to 11.1 million cats, many of whom free-roam over great distances. With so many felines prowling the country and with British wildlife in a precarious state, it begs the question, how harmful are domestic cats to the species they prey on?


The Mammal Society, a charitable organisation concerned with the welfare and conservation of mammals, surveyed cat owners to find out just that. Over the course of five months, on average a single cat brought home 11 prey items, which included all manner of animals from house sparrows to grass snakes. This may not seem like much, but with millions of cats in Britain, this could mean that some 274 million dead animals are dropped on owners’ doorsteps each year.

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In the face of such startling figures, what is a responsible cat lover to do? There’s one obvious answer: keep these cuddly killers indoors, permanently.

But the solution isn’t quite that straightforward, says Dr John Bradshaw, who has studied domestic cats since the mid-1980s. “In this country, the evidence that cats are causing any serious depletion in wildlife populations is pretty flimsy,” he explains. “That’s not to say they aren’t killing things. There are plenty of surveys that show they are. But the long-term effects of that have been difficult to find.”

Most species targeted by domestic cats will have lots of offspring, to counter the expectation that many will die before they reach adulthood.

“Cats aren’t very efficient hunters,” adds Bradshaw. Their prey is most likely already in a poor condition, dead or dying, when they catch it. “Really, focusing on the cat is counterproductive.”

To demonise cats, Bradshaw suggests, would distract from the real dangers to wildlife in the UK: loss of habitats, reduced availability of food and the increased use of pesticides and fertilisers. These threats were identified in the UK’s State of Nature report in 2016, which brought together data from more than 50 different organisations. Though Mittens may not be public enemy number one on our shores, elsewhere in the world cats aren’t off the hook.

In 2013, an American review found that pet cats allowed to roam free could be linked to the death of 684 million birds in the US each year. This was three times the figure for birds killed by cars and 12 times as many as killed by wind turbines.

Scott Loss, one of the authors of the study, wants to make one thing clear: “It’s not an issue relating to the cats themselves. It’s a human issue. The key is getting people to realise the negative impacts that free-roaming cats have, and adjusting their behaviours regarding cat ownership. We’re not blaming cats.”

Yes, cats kill wildlife. If that bothers you, perhaps consider keeping Tiddles indoors © Getty Images
Yes, cats kill wildlife. If that bothers you, perhaps consider keeping Tiddles indoors © Getty Images

For owners worried about wildlife, Loss recommends keeping their pet cats indoors. Or, if they’re outdoors, to have them restrained in some way, either by installing ‘catios’ – outdoor cat enclosures that enable them to run around but separate them from wildlife – or even walking them on a lead. “Often, those suggestions don’t go over well with cat owners. They say ‘my cat isn’t a problem’ so they don’t think it’s worth restraining them.” says Loss. If you don’t have the space for a ‘catio’ and can’t imagine your furry friend happily taking to a leash, then Bradshaw has some advice.

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First off, to dissuade your cat from the hunt, check their food bowl. “The first thing to look at is their cat food. Is your cat getting all the nutrition it needs? If not, then you’re almost giving it an excuse to go hunting.” Bradshaw explains.

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Otherwise if you want a pet cat, but can’t put up with its murderous tendencies, Bradshaw suggests getting a kitten who has never been out, or a cat that’s always been kept indoors. Bringing a cat inside who has previously explored the Great Outdoors can have its challenges, and their individual personalities will determine how well they’ll adapt to life in captivity.

Is there anything then that owners can do to keep Tiddles happy and healthy during the transition from the great outdoors to the living room? Dr Lynn Bahr, a feline vet in the United States, creates products and toys that enrich the lives of indoor cats. Bahr says that giving cats an opportunity to play is essential. “Keeping them active, exercised mentally and physically is extremely important,” Bahr stresses. “I hide toys and treats around the house for my cats, so they have to go and forage for them as they would do in the wild.”

Though she warns that life on the inside poses a range of health risks for cats: obesity, diabetes, depression, to name just a few. That isn’t to say there aren’t dangers outdoors – car accidents, cat fights, feline HIV, ticks and fleas all threaten to end a pet’s life prematurely.

For those concerned about their pet’s happiness and the state of nature, Bradshaw suggests looking into the wildlife in the area and finding out if there are vulnerable or endangered species nearby. If there are, restrict your cat’s outdoor activity. “But making habitats for wildlife – feeding birds, building log piles at the bottom of your garden for mice – is actually much better for nature than locking your cat away.”

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Amy ArthurEditorial Assistant, BBC Science Focus

Amy is the Editorial Assistant at BBC Science Focus. Her BA degree specialised in science publishing and she has been working as a journalist since graduating in 2018. In 2020, Amy was named Editorial Assistant of the Year by the British Society of Magazine Editors. She looks after all things books, culture and media. Her interests range from natural history and wildlife, to women in STEM and accessibility tech.