Why Do Cats Purr?

Why Do Cats Purr?

Dr Jane BicksAs a veterinarian, I am commonly asked “Why do cats purr?” Most people believe cats purr when they are content or happy. While cats do purr when they are content, researchers attempting to uncover the answer to this 3,000-year-old mystery are finding the answer more complicated than previously thought. All domestic cats purr, as well as many wild cats, like pumas, ocelots, lions and cheetahs. Purring can occur in a variety of situations. When cats purr in the presence of other unknown cats or kittens, the behavior may serve to convey submissiveness or a friendly greeting. While it is true that cats purr contentedly while on their pet parent’s lap, they also purr when they give birth, when they are frightened, severely injured and even while dying. Because kitties clearly cannot be content in all these situations, contentment or friendliness cannot be the only reason they purr.

So why else would they purr?

Perhaps it is helpful to look at purring in the context of natural selection. Natural selection tells us that a particular behavior or trait will persist from generation to generation only if it is beneficial to an animal’s survival. For purring to exist in both domestic and wild cats, there must be something vital about the behavior. Purring is created by the vibration of the cat’s larynx and diaphragm, and therefore requires an expense of energy. If a kitty is sick, they would not use precious energy to purr unless there was a very good benefit.

Researchers have found certain types of purrs are meant to communicate with their people. In 2009, researchers discovered a high-pitched cry, similar to that of a human infant, embedded in the purrs of cats soliciting food. They were using the purr to signal their human caretakers that they needed something. Those sneaky kitties!

I’m sure you have heard the expression that “cats have nine lives”. Similarly, veterinarians have an old saying that if you put a cat who has broken bones in a room with other cats, the breaks will heal. In fact, cats are amazing self-healers: they have fewer post-operative complications than dogs, have a lower incidence of bone and joint disease than dogs, and 90% of cats survive high-rise falls – I’m talking falls from 5 story buildings! (Robinson, et. al 1976) What could possibly account for these facts?

One theory is that the purr has healing properties. Researchers have found that vibrations in the frequency range between 25 and 50 hertz promote bone strength, stimulate healing of fractures, provide pain relief, and help heal tendons and muscles. In 2001, National Geographic reported a study where chickens grew stronger bones after been placed on a vibrating plate for 20 minutes daily. Bioacoustic researchers have recently studied purring in 47 cats, both wild and domestic. They studied the frequency, pitch, loudness and duration of purring in relation to the cat’s behavior, and guess what they found? The domestic house cat purrs in the range of 25 and 50 Hz: the exact range associated with healing properties such as increased bone density.

Maybe this has something to do with a cat’s uncanny ability to “heal by association”. Perhaps purring is part of the reason why, when we fall ill, having a cat sit on our laps can actually make us feel better. Whether it is simply the comfort of having a friend nearby, or whether it’s the vibrational frequencies of your kitty’s rumble, the joy of a cat purring on your lap is priceless.

Whatever the reason, I encourage you to take care of your cat. Keep him happy and purring and you’ll likely both lead healthier and happier lives.

Thank you for all you do to make the world a better place for your dear companions,
Dr. Jane Bicks, DVM


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Comments (7) -

  • Robin B Thatcher

    6/20/2010 1:40:42 PM |

    This is a fascinating and informative article. Thanks so much for sharing. Robin T.Owner and foster mom for two rescue groups.

  • cindy

    6/20/2010 5:15:31 PM |


    I had a rabbit that I thought was purring.  The first vet that I took daisy to, didn't say that she wasn't purring, just that she had a respitory infection.  

    So she purred and purred.  I took her to another vet and he said that rabbits don't purr and that was a respitory infection.  I had two other bunnies in sunny california and they never purred.  I thought I had a really unusual bunny.  The prob is that the vet said that there isn't much that can be done to help daisy's respitory infection.  She's on meds and has improved.  There is only one vet in the area, who deals with rabbits. And he's allergic to them.  So he may not be taking care of bunnies for much longer.  

    I just wish that I knew this sooner so I could have relieved her respitory infection.  My cats do purr alot.  Thanks for the dry food for cats.  It's kept them full and at the weight they sh/be.  They didn't like the canned food.  So I have to buy over the counter canned food.  They are very healthy and their coats are silky.  Thanks very much!  Cindy

  • Linda Covert

    6/20/2010 8:50:41 PM |

    Thank You Dr. Jane for the article about cats purring. My daughter gave me a 7 month old ragdoll named Gilbert on mothers day.  I have been grieving the passing of my mom's dog today. She had been ill for 10 days.  After the news, I cried and cried. Gilbert jumped on my bed and purred me into a peaceful sleep. He is so beautiful.
    I have been feeding my pets Life's Abundance for years.  
    I do have a questions? How do I prevent Gilbert from trying to escape.  I have caught him when he gets out but since I live on the edge of a field, I would not want him to run into a wild animal.  I don't want to lose him.  Do you have any advice?  He is a smart ragdoll and I don't want to lose him.
    Thank You for caring for our little family members!

  • kparks

    6/21/2010 4:59:06 AM |

    I have a young cat who does not purr. Is taht a normal occurance? Her brother is a champion noise maker, but I have ner heard or 'felt' her purr.

  • Ragnhild Bundesmann

    6/21/2010 7:03:56 AM |

    Thank you, I have heard that on PRI as well.  My cats know when I am hurting.  When I hearniated my disks in my back, my last cat would not leave me, but laid on the affected leg and purred.  My current cat did the same when I tore my rotator cuff.  She did not see the MRI report, she just knew it.  And yes, my current Siamese cat has the purr with the loud pitch and then she goes to the refrigerator where she knows the roast chicken is.  My husband and I both know the purr, so does my dog who comes to sit next to the cat so she won't be left out.
    I think I better learn to purr myself!

  • Mary

    3/25/2011 11:24:47 AM |

    My big tuxedo cat curled up by my husband's head the day before he died, when he was in a coma, and purred, licked his head and would reach out and pat his face.  I am sure that Kitty knew my husband was ready to go and was telling him it was OK.  I have five other cats and two dogs and Kitty was the only one to do this.  One of my dogs would not leave my husband's side two days before he died. I know these animals have a sixth sense when it comes to things like this.  

  • Bree Culley

    8/10/2013 3:20:42 PM |

    Excellent blog post. I definitely appreciate this site. Continue the good work!

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