by Sandra C. Mitchell, DVM
Why do cats purr? Do they only purr when you pet them? Many people think of purring as the sign of a happy, contented cat. But did you know that cats also purr when they’re in pain or frightened?
Here’s what we know about cat purring—how cats purr, why they do it, and how you can tell what your cat’s purring means.
How Do Cats Purr?
When cats purr, signals are sent to the muscles of the voice box as well as the diaphragm, which expands the chest when breathing.
These signals stimulate a cat’s vocal cords to vibrate. So as the cat breathes in and out, the air moves across these twitching muscles, resulting in a purring sound.
Cats purr during both inhalation and exhalation, so the sound is nearly continuous.
Purring may have developed as a mechanism to keep a cat’s bones and muscles in peak condition. This is helpful during the long periods of inactivity in their style of hunting, which is to wait for prey to come by and then ambush it.
Why Do Cats Purr?
Many different situations can cause domestic cats to purr, which leads to multiple theories as to why they do it.
Here’s a breakdown of the commonly accepted reasons why cats purr.
Your Cat Is Content
Cat owners have seen their cat purr when they are content and happy, similar to how dogs wag their tails.
When your cat is sitting on your lap and getting pets and scratches, they are probably purring as well, and maybe even kneading your leg or a blanket. This nonverbal form of communication tells you that life is good and that your cat is very happy with the current situation.
Cats probably also associate their purrs with positive interactions with you. When they purr, you continue to pet them. It’s almost as if they are training you.
Your Cat Is Self-Medicating
But what about a cat that is purring during labor? What does cat purring mean then?
Believe it or not, cats also use purring as a form of self-medication and pain control.
According to studies, cats purr at frequencies that help to stimulate healing, particularly of bones and tendons. The frequency may also serve to reduce pain, ease breathing, and build muscles, among other health benefits.
Your Cat Is Calming Down
And what about cats that purr at the veterinary hospital? Well, that seems to have a logical reason, too.
Cats are thought to use purring as a mechanism for self-calming and stress reduction—sort of the kitty version of repeating a mantra to keep calm.
Frightened cats are often seen to be purring almost “to themselves.” You might see this in shelters where cats are scared and anxious.
Your Cat is Guiding her Kittens
Additionally, the vibrations that occur during purring help lead kittens to their mother. Kittens are born blind and deaf, and they depend on the mother cats to provide first milk (called colostrum).
How Can You Tell Why Your Cat Is Purring?
So how do you know what it means when your cat purrs? Look at the context of your cat’s behavior and the situation your cat is in.
A cat that’s on the exam room table in the veterinary hospital is way more likely to be scared than happy. If your cat is purring at home but acting different than normal and is not as engaged with you, they may be frightened and hurting.
When your cat is quietly sitting next to you getting their daily dose of human time, they’re probably content and encouraging your affectionate behavior with their purrs.
If your cat is not acting like they normally do, especially if they are also purring, contact your veterinarian.