In social and biological reasons why cats purr.

In this lesson, we’ll look at the social and biological reasons why cats purr.

We will cover how purring can be used as a type of communication between cats and humans, between cats and other cats, as well as how it helps them self-soothe and even heal from injury.

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What Is Purring?

There’s nothing like sitting down with your furry, feline friend after a long day. As you plop down on the couch your kitty comes to greet you, purring and rubbing her head against you. You take this as a sign of affection and pet her, returning the favor.

If you’re a cat lover, this scene is familiar to you. But have you ever thought about why cats purr? Many people assume its a sign of affection, but biologists think there’s something more to purring.

How Do Cats Purr?

Purring occurs during the respiration cycle, when cats breathe in and out. Vibrations of the larynx, or vocal chords, cause the air passing through the throat and surrounding bones to vibrate as well, creating the sound we know as purring.

Cross-section of the larynx

However, not all cats purr. Larger cats, like tigers or jaguars haven’t yet been recorded purring. Only smaller cats, like domestic cats, or small wild cats like the cheetah, bobcat and lynx, can purr. Scientists think this has to do with a bone in their throat called the hyoid. In smaller cats, the hyoid bone is more rigid and connected to the skull through a series of other bones and tissues. The vibrations of the hyoid bone caused by the larynx create the purring sound.

Larger cats have a hyoid bone too, but it is less rigid and more flexible. It’s more loosely attached to the skull and that flexibility allows for the loud roar, but prevents the subtle purring that smaller cats make.Humans have a larynx too, which serves a similar function – to generate speech. But is purring a way to communicate, like speech is for humans? Scientists think this might be part of the answer, but not the full story.

Before we look at other hypotheses about the purpose of purring, let’s explore the idea that it is used for communication.


Many people see cats as aloof, or unloving pets. But, this is not true! Cats simply have other ways of showing their affection than dogs, and purring is one way they do this.Although most of us see purring as a sign that cats are happy, like when they are curled up in our lap or near the heater, this isn’t the full story.

Cats also purr when they are hurt, scared or stressed. Scientists think purring might be a way for your cat to say they need you, or have missed you. If you have a cat, you might have noticed they purr when they want to be fed, played with, or have some other need fulfilled. Although cat haters might interpret this as ‘Give me what I want now’, more likely, its your cats way of expressing their love and dependence on you.

Cats purr to express their needs to humans
cat being pet

It appears that cats don’t only do this with people.

Scientists have studied feral cat behavior, where cats live in packs. Cats are usually thought of as solitary creatures, but in the wild they group together. After being separated for the day, the cats return to their pack, rubbing against each other and purring, almost to say ‘Welcome back, brother!’

Cats also purr when together in packs
cats together


As we mentioned, cats purr when they are scared or hurt as well. Think of this like talking to yourself, humming, or maybe even quietly singing your favorite song. You might see children doing this as well in a stressful situation.

Cats seem to do the same. Purring acts like a self-care technique, relieving stress and making them feel safer.


What if you could heal a cut faster without treating it with an antibiotic cream or pain reliever? Pretty convenient, huh? Well, it turns out that purring might serve this exact function in cats. Cats purr at about 26 Hertz.

This frequency, or vibrations per second, has been known to promote bone regeneration.

Healthy bone induced by bone regeneration versus deteriorated bone
healthy bone versus deteriorated bone

In humans, impact exercise serves the same purpose. Stress on the bones from impact causes them to add cells and calcium to the bones, strengthening them. Astronauts are a great example of what happens when this function is impaired.

In low gravity, astronauts don’t experience that high impact exercise for their time in space. As a result, they have lower bone density and are more likely to develop osteoporosis.Why would cats have evolved this mechanism when they run and jump far more than astronauts in zero gravity? Well, cats in the wild spend many hours lying in wait for their prey, crouched low and completely still.

These hours normally might reduce bone regeneration, but with the healing properties of purring, bone density is still increased by the vibrations, but quietly while they stalk their prey.

Lesson Summary

Purring is the noise created by air movement over the larynx of cats in the throat. Although many cats seem to purr when happy, they also purr when distressed. Purring may be part of communication, as a sign of love or dependence, but it also serves a self-soothing purpose in cats experiencing stress. The frequency of vibrations created during purring may also enhance bone regeneration, similar to high impact exercise in humans.


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