Why Do Cats Purr?

Scientists don’t know exactly why cats purr, but some of the possible reasons are pretty cool.

By Avery Hurt
Jan 3, 2022 8:15 PMJan 3, 2022 8:30 PM
Happy Kitty
Credit:(Denis Val/Shutterstock)


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Can you think of anything more relaxing than having a purring cat curled up in your lap? (OK, if you’re a dog person, maybe you can. But stick with me here because this gets cool.) A cat’s purr is often interpreted by humans as a sign that the cat is content. And that may be true — sometimes. But there’s much more to purring than just happy vibes.

Feed Me Now!

Kittens are born deaf and blind, but they can mew and purr almost right away. Purring is how helpless little kittens get the attention of their moms, explains Autumn Vetter, DVM, Clinical Assistant Professor in the School of Veterinary Medicine at the University of Georgia. Little kittens purr to tell their mom they’re hungry. If your cat purrs when it’s time to fill the food dish, you’re probably hearing the “Mommy, please feed me” purr.

But purring may not always signal a request, much less contentment. Cats purr when they’re anxious or stressed, too. A trip to the vet or just being placed in a cat carrier can set off a bout of purring in some cats. Cats also might purr when they’re in pain. Vetter notes that sometimes cats purr when they’re being euthanized. “I’ve had them start to purr at the very end to self soothe,” she says. A 2009 study in Current Biology found that the different types of purrs sound different, too. Human subjects found the purrs of cats asking to be fed much more “urgent and less pleasant” than the purrs of cats who weren’t asking for anything. An acoustical analysis of the purrs backed this up. Embedded in the low-pitched purr was something much more insistent: a high-frequency cry. Interestingly, that cry sounds somewhat like the cry of a human infant in distress. Somewhere along the evolutionary path, it seems, cats learned one of the most reliable ways of catching the attention of humans.

Emotional and Physical Benefits of Purring

There is also some evidence that purring may do more than indicate emotional arousal or hunger. A 2001 paper published in the Journal of the Acoustical Society of America found that cats (including big cats such as cheetahs and pumas) produce purrs at frequencies that have been shown to promote wound healing.

It’s also possible that cats purr for preventive health — to keep their bones strong and their muscles from deteriorating. When humans rest too much (for example, when they’re ill or injured or just because they’re really into television), their muscles deteriorate and their bones get thin. Purring could be cats’ way of avoiding this unpleasant outcome of a lifestyle that involves long stretches of sitting very still waiting for prey to scurry by. By creating vibrations with their purring, cats may stimulate their bones and muscles enough to keep them from going soft from lack of use. 

Purr Translation

So how do you know what your cat is trying to get across with their purrs? Is it time for lunch? Do you need to call the vet? Or is your beloved kitty just doing routine maintenance? Like most human-pet communication, it takes time and attention to learn the lingo. If you know your cat well, you can probably tell what they’re trying to get across to you. But if you’re stumped, reading a cat’s body language can help. Vetter points out that if a cat is lying on their side with their legs open and eyes partially closed, the purr is probably one of contentment. If their limbs are close to their body and eyes are wide open and dilated, the purr is more likely to be a nervous purr.

Cats probably purr for several reasons, and not always to get messages through to humans. When purrs are messages to us, they could range from something as simple as “I’m happy now” to something a bit more complex: “Has anyone around here noticed that it’s dinner time?” But it’s when they’re not talking to us that purrs become trickier to diagnose.

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