Why Do Cats Purr? The Reasons Behind It

Cats don't just purr when they're happy. Researchers have identified several different reasons for the rumbly feline vibrations.

Why do cats purr? Many people think that a cat purrs from contentment and pleasure. There’s no doubt that when a purring cat rubs against you, you can’t help but feel pleased with yourself. You may not know why cats knead or why cats meow, but that cute little kitty must love you if they’re purring like that! However, you may not want to move on from petting that cat to patting yourself on the back just yet. Like many cat behaviors, there’s more than one reason why cats purr.

How do cats purr?

Cat owners may find themselves wondering not only why cats purr, but how do they do it? How do they create that distinctive noise? Well, contrary to what you might think, it’s an interesting cat fact that felines don’t have a unique body part or vocal organ that allows them to purr. Instead, the sound comes from rapid movements in their voice box. “A purr starts as a signal from the central nervous system that travels to muscles in the voice box,” explains Daniel Rotman, Founder & CEO of PrettyLitter. “These muscles tighten and release very quickly while the cat inhales and exhales to make the vibrations that we can feel and hear.”

So why do cats purr, anyway?

Well, because it’s what they’re born to do. Cats start purring, and hearing purring, from infancy. Those cute kittens are blind and deaf when they’re born, so mother cats purr and the babies follow the vibrations back to mama for food and warmth. In turn, vets believe, kittens purr to show they’re okay and to help them bond with mama cat.

“As cats grow older, purrs are used [for] anything from communicating joy and contentment to soothing pain,” Rotman explains. It’s no wonder that so many species in the cat family purr: not only our housecats, but also cheetahs, bobcats, pumas, and lynx. However, studies have shown that big cats (like lions, tigers, jaguars, and snow leopards) do not purr in the same way as their smaller cousins. They do all love boxes, though.

What does it mean when a cat purrs?

So what makes a cat purr? Sure, you might hear purrs when your pet feels relaxed or friendly, but cats also purr when they’re hungry, stressed, or in pain. “All behavior depends on history, context, and expectation,” Tony Buffington, a cat expert and veterinarian at Ohio State University, told Wired. “So it’s naive to think that cats can only purr for one reason—it’s like thinking that people can only laugh for one reason.”

Like how some human guffaws are a reaction to humorous cat memes while other giggles could come from nerves, cats’ purrs are open to interpretation. Beware of the subtle signs your cat could actually be depressed.

It could mean your cat is happy—or hungry

Purrs release feel-good endorphins, so experts think cats use the vibrations to soothe themselves. You probably can’t train your cat to purr on command, but you might find them purring while enjoying some cozy cuddles from you, or it might help calm their nerves—or literally heal their pain. Mother cats have been known to purr while giving birth. Also, studies have found that whole-body vibrations of 35 to 50 Hz could help stimulate bone healing. Cats’ purr frequencies range from 25 to 150 Hz, and some suggest the vibrations could help kitties keep their skeletons strong. (Sounds crazy, but even NASA astronauts have used vibration therapy in space, where lack of gravity means no bone-healthy weight-bearing exercise.)

As for purr frequencies even higher than 150 Hz, those serve an entirely different purpose. One study in the journal Current Biology found that when cats were trying to get their owners to feed them, their purr frequency shot up to 220 to 520 Hz—awfully close to the 300 to 600 Hz of a human infant’s cry. Researchers suggest the higher frequency makes the sound harder for cat (and baby) parents to ignore. This association with dinnertime might be why your cat purrs when they see you! Bottom line: Not all cat noises are created equal.

How can you determine why your cat is purring?

Though purring isn’t only a sign of contentment, you shouldn’t launch into panic mode the next time you hear the noise. There’s a reason people associate it with happiness—it is still the primary reason you’ll find your cat rumbling away. “They may purr when they have been injured or are in pain, but among our furry companions it is more often a sign of contentment,” Rotman explains. By the way, have you ever wondered why cats are afraid of cucumbers?

The best way to figure out your cat’s message is by looking at what else is going on. If it’s dinnertime, or if the frequency of the purring is a little higher, your furry friend might have food on the brain. If kitty is purring and then bites you, she’s probably annoyed or mad. Also be listening for continuous, insistent vocalizing from your cat; if it goes on for 24 to 36 hours, this could be one of the signs your “healthy” cat is actually sick. But a cat purring away while curled up on your lap is probably just enjoying your company. You must not be making any of these mistakes cat owners should never make.

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Marissa Laliberte
Marissa Laliberte-Simonian is a London-based associate editor with the global promotions team at WebMD’s Medscape.com and was previously a staff writer for Reader's Digest. Her work has also appeared in Business Insider, Parents magazine, CreakyJoints, and the Baltimore Sun. You can find her on Instagram @marissasimonian.