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Why do Cats Purr?

Cats purr for a myriad of reasons, from expressing contentment to self-healing. This soothing vibration can signify happiness, but it's also a cat's way of comforting themselves when in pain. Intriguingly, the frequency of purrs may even promote bone density and healing. What other secrets does this feline behavior hold? Join us as we unravel the mysteries of a cat's purr.
Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

Most people are familiar with the sound of a cat's purr, and the sound is often referenced as an indicator of contentment or well being. However, as most cat owners are aware, the purr is not restricted to periods of contentment, but will also manifest during times of stress or pain. The physiology and reasons for the noise are not completely understood, although there are several hypotheses as to the reasons for the feline purr.

Most cat species, large and small, purr. Zookeepers have recorded instances of big cats such as leopards purring, and even some unrelated species such as raccoons are also capable of making a distinctive purring noise. It is believed the sound is caused by the vibration of vocal cords, and is a voluntary act on the part of the animal. When purring, the muscles of the voice box can act as a valve, causing air traveling in both directions to vibrate, which creates the illusion of continuous sound.

Raccoons make a purring noise too.
Raccoons make a purring noise too.

As anyone who has held a purring cat knows, the whole body of the animal vibrates, and the noises come in varying intensities. The purr can also be combined with a meow, although the result is sometimes comic. The purr is generally considered to be a soothing sound, and cats are sometimes used as therapy animals for this reason.

Originally, it was thought the noise was simply an expression of an emotional or physical state of contentment, safety, and well being. It is true that happy cats will purr, and that when cats mutually groom or cooperate on a task they will frequently purr. While it was a pleasant theory, the clearly demonstrated fact that cats will make the sound when they are not happy suggested that there was more to it than that.

Even large, undomesticated cats, including leopards, have been known to purr in captivity.
Even large, undomesticated cats, including leopards, have been known to purr in captivity.

The vibrational frequency of the purr ranges from 25-130 Hertz. This happens to be a frequency which promotes healing of bones and eases muscle pain, suggesting that perhaps cats are actually healing themselves with the mechanism. This suggestion has been borne out by studies which show that cats tend to have faster healing bone fractures than other animals, and suffer less from osteoarthritis and other bone disease.

Large cats like tigers cannot purr.
Large cats like tigers cannot purr.

Cats will often purr when they are tired, which could be considered a waste of energy unless the action is serving a physiological function. Cats may be massaging themselves from within after a long day, easing muscle soreness, inflammation, shortness of breath, and exhaustion.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments

amypollick

I don't always know why cats purr, but I do know it's one of the most comforting sounds ever. That sound means peace and happiness to me.

anon159203

Cats absolutely purr when they are distressed. They do it to make themselves feel better. Many cats purr on their death beds. It's a myth that cats only purr when they are happy.

anon76735

I've never known an unhappy/agonizing cat/kitten to purr. i agree that there are healing powers to a purr but i believe it simply because of the peaceful contentment; it soothes. i know it does that for me, so i can only imagine it does that for them. when you feel bad don't you think about things that soothe you? if it is true that a cat/kitten does this when they don't feel right then; does it not make sense that this is why they do it at those times? i think it is a good/happy feeling/moment that creates the "purr"!

anon65526

Cats purr because they're happy. if they cry they're usually not happy about something.

anon4595

how do cats purr? and where do the sound of a purr come from?

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    • Raccoons make a purring noise too.
      By: Eric Isselée
      Raccoons make a purring noise too.
    • Even large, undomesticated cats, including leopards, have been known to purr in captivity.
      By: Yulia Romanova
      Even large, undomesticated cats, including leopards, have been known to purr in captivity.
    • Large cats like tigers cannot purr.
      By: hitdelight
      Large cats like tigers cannot purr.
    • Cats often purr when they're tired.
      By: dashabelozerova
      Cats often purr when they're tired.