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Leslie A. Lyons, an assistant professor at the School of Veterinary Medicine at the University of California, Davis, explains.
Over the course of evolution, purring has probably offered some selective advantage to cats. Most felid species produce a "purr-like" vocalization. In domestic cats, purring is most noticeable when an animal is nursing her kittens or when humans provide social contact via petting, stroking or feeding.
Although we assume that a cat's purr is an expression of pleasure or is a means of communication with its young, perhaps the reasons for purring can be deciphered from the more stressful moments in a cat's life. Cats often purr while under duress, such as during a visit to the veterinarian or when recovering from injury. Thus, not all purring cats appear to be content or pleased with their current circumstances. This riddle has lead researchers to investigate how cats purr, which is also still under debate.
Scientists have demonstrated that cats produce the purr through intermittent signaling of the laryngeal and diaphragmatic muscles. Cats purr during both inhalation and exhalation with a consistent pattern and frequency between 25 and 150 Hertz. Various investigators have shown that sound frequencies in this range can improve bone density and promote healing.
This association between the frequencies of cats' purrs and improved healing of bones and muscles may provide help for some humans. Bone density loss and muscle atrophy is a serious concern for astronauts during extended periods at zero gravity. Their musculo-skeletal systems do not experience the normal stresses of physical activity, including routine standing or sitting, which requires strength for posture control.
Because cats have adapted to conserve energy via long periods of rest and sleep, it is possible that purring is a low energy mechanism that stimulates muscles and bones without a lot of energy. The durability of the cat has facilitated the notion that cats have "nine lives" and a common veterinary legend holds that cats are able to reassemble their bones when placed in the same room with all their parts. Purring may provide a basis for this feline mythology. The domestication and breeding of fancy cats occurred relatively recently compared to other pets and domesticated species, thus cats do not display as many muscle and bone abnormalities as their more strongly selected carnivore relative, the domestic dog. Perhaps cats' purring helps alleviate the dysplasia or osteoporotic conditions that are more common in their canid cousins. Although it is tempting to state that cats purr because they are happy, it is more plausible that cat purring is a means of communication and a potential source of self-healing.
Answer originally published on January 27, 2003.
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47 Comments
Add CommentI think that cats , being born blind & deaf use their purring to find the mother , & when they feed they indicate to the mother that everything is good. The mother purrs so the kitten can locate her. There is also the self healing theory & purring when near death. I think that it depends on the circumstances the cat is in , a happy cat purrs when it is receiving attention , or purrs when it is injured etc. I think it would stand to reason that a cat purrs for many different reasons , depending on the situation the cat is in.
Reply | Report Abuse | Link to thisBelieve or not my nephew, who was born into a household with two cats, learned to purr before he learned to talk. After he started talking he soon lost the ability to purr...and he hasn't stopped talking since then! :-)
Reply | Report Abuse | Link to this" I just think cats purr because they are VERY jealous they cant bark and dont understand commands like a dog does ( sit,stay,play dead) i think its their last ditch effort in getting one over on their enemies ( dogs) and as foolish as it sounds its true i am a veternarian who spent countless years studying this"
Reply | Report Abuse | Link to thisWell Animal Specialist...My Cats will sit on command. They use the potty... and not a litter box... They will even give commands back to be in their own way. They come when called (Each to their own name) and are actually a lot smarter than my dog is. My siamese cat Allie will even offer her paw and shake on command. So I do not buy into your theory about being jealous about not being able to follow commands.
and you have an affinity for goats just like Rob as well, am i right? am i right?
Reply | Report Abuse | Link to thisBravo! Great response! My thoughts exactly!
Reply | Report Abuse | Link to thisHmmm, interesting. Makes me give a second thought to the chanting involved in some meditation techniques.
Reply | Report Abuse | Link to thisveterinary legend holds that cats are able to reassemble their bones when placed in the same room with all their parts. Purring may provide a basis for this feline mythology.
Reply | Report Abuse | Link to thisWhat the hell is this comment supposed to mean ?
My thoughts exactly. I don't think this article belongs in Scientific American, as it is only a lump of maybies. And not to mention a poorly written lump. It does convey the message, but is illogical in some places and constructed poorly.
Reply | Report Abuse | Link to thisSeriously? Animal Specialist, huh? I assume those was one massive troll, because no one could possibly be that incoherently retarded. I also agree with the more intelligent commenters that the article itself was dubious and, in fact, borderline incorrect. Do most "scientific" articles have fallacious arguments? So, lemme get this straight, even though cats purr mostly when they are content, because they sometimes, occasionally, maybe, purr when they are scared or dying, the answer is that cats DON'T purr because they are happy? How 'bout cats don't JUST purr when they are happy, they also purr to self-soothe, like when people hum to themselves when they are nervous. "It is more plausible to state that cat purring is a means of communication..." Uh, yeah, of communicating happiness.
Reply | Report Abuse | Link to thisHey vet,sounds like you ran into a cat that was smarter than you and YOU are the one with the jealousy problem.Just for the record I had a cat for 17 years that would stand up and and extend his arms/paws and wrap them around the neck of anyone around him that was upset or crying.He responded only to his name,not kitty kitty.He could open any kind of door knob,collapsed on my head every night to kneed my hair and yes ,gasp ,purr profusely.To top it all off,if I hadn't cleaned the litter box in awhile he had the smarts to sh!t in the tub so I wouldn't have to clean it off the carpet.Sounds like cats are more self aware than you are!Put that in your hat and wear it for awhile.
Reply | Report Abuse | Link to thisyou're lying you dumbass
Reply | Report Abuse | Link to thisanimal specialist isn't a veterinarian, they are a dumbass dog lover
Reply | Report Abuse | Link to thish
Reply | Report Abuse | Link to thisI have seen my cats purr when they are happy and when they are in distress. They purr for both emotions. I suppose it's like when we cry, we can be either upset or really happy.
Reply | Report Abuse | Link to thisL
Reply | Report Abuse | Link to thisI believe that cats purr is primarily a mechanism for their mothers to know that the kitten is healthy. A really sick or dead kitten won't purr so the mother knows it must take it out of the litter so it won't make the the others sick. The mother is regularly licking and cleaning the kittens and expects this feedback.
Reply | Report Abuse | Link to thisNo you and your cats are just air head bimbos and inferior to dogs face it.
Reply | Report Abuse | Link to thismy cat is dying from leukemia. She is naturally 'talkative' and purrs a lot affectionately. Now she calls me , and when I respond with a touch or stroke she starts to purr. However I like the theory of sound healing.
Reply | Report Abuse | Link to thismy cat is very ill and mews to me .when i respond with a caress she purrs.
Reply | Report Abuse | Link to thisthank you very much for the analysis on why cats purr. its very informative and very well organized. i have referenced this piece in a school paper i am composing. i recently adopted two domestic short-haired cats from the A.S.P.C.A. i feel i have grown a bit closer to my two cats (Schmokey & Malcom) by learning more about them. i was very curious as to why they are always purring. And yes, cats do love to sleep. Is it true cats sleep 2/3 of their lives? Thats very interesting...
Reply | Report Abuse | Link to thiswas wondering if Purring could be a function for stimulating the teat in the mother while feeding...used in conjuction with kneading to increase milk flow????? Then the behavior carries over after weaning as a comfort/stress trigger?
Reply | Report Abuse | Link to thispoint of clairification....i meant that the Kitten purrs to stimulate milk flow via vibrations in the mouth when feeding....
Reply | Report Abuse | Link to thisI think cats have realised that the purring noise is attractive to humans and they do it to show that they approve of the actions performed by humans . This makes the humans encouraged to perform certain actions that the cat likes - such as petting them and feeding them. Thus the cat trains the umans to take care of them.
Reply | Report Abuse | Link to thisThat is funny.
Reply | Report Abuse | Link to thisThere is just one major flaw with your argument. Cats do not have a different type of "meow" when they are surrounded by other languages. That is, "me now" does not sound like "meow" when you translate it in different languages. If you are going to post comments like this, you need to clarify that it is your opinion or your own personal assumption. There is absolutely no scientific basis to what you commented. Please be more careful in the future.
Reply | Report Abuse | Link to this"Cats often purr while under duress, such as during a visit to the veterinarian or when recovering from injury. Thus, not all purring cats appear to be content or pleased with their current circumstances."
Reply | Report Abuse | Link to thisThe post kinda contradicts that though
Growing up we had a boxer, a beagle, and a cat. The cat taught the dogs how to purr and the dogs taught the cat how to sit up and beg. It was a crazy house anyway so they fit right in!!
Reply | Report Abuse | Link to thisIt's simple, women like purring cats because it reminds them of their vibrators. It's been more than once that my girl asked me, and my cat, to leave the room at same time.
Reply | Report Abuse | Link to thiskittens find their mother by smell perhaps?
Reply | Report Abuse | Link to thisfake ... and gay!
Reply | Report Abuse | Link to this" I just think cats purr because they are VERY jealous they cant bark and dont understand commands like a dog does ( sit,stay,play dead) i think its their last ditch effort in getting one over on their enemies ( dogs) and as foolish as it sounds its true i am a veternarian who spent countless years studying this"
Reply | Report Abuse | Link to thisthat is hands down one of the stupidest things I've ever heard.
sounds like your cat's a social climber!
Reply | Report Abuse | Link to thisCats purr to keep their staff in line. A little purring will get a human to do almost anything (I serve 2 cats).
Reply | Report Abuse | Link to thisU GO GIRL!!!! i think i have figured it out well firstly cats have special vocal cords that vibrate ALL THE TIME i have noticed this when my grandmothers cat is asleep and i put my hand on his neck i cant hear it but i can feel it. Also when you pet them or cause some stimulation they purr at a frecuency so u can hear them. Have u ever noticed that when the cat breathes his/her purr stops and changes pitch? well i have so it MIGHT be a special way of breathing so it could have something to do with the lungs and the scientists are just looking in all the wrong places
Reply | Report Abuse | Link to thisMore plausible????? What brand and potency of glue is this author sniffing?
Reply | Report Abuse | Link to thisOh it might be on the list of possibilties.... as one far-fetched wholly unsubstantiated idea worthy of some thought.
But.... as to plausible.... or MORE plausible than the obvious and perpetual observation that cats purr when things that please them occur???
This is the mental defect of the wannabe-scientist who has what might be called the Ripley-syndrome.
"Ripley-syndrome?????" you ask.
Yeah.... "Ripley's Syndrome".... the irrational need to invent some counter-intuitive interpretation of common and well-understood phenomena in order to be a candidate for inclusion in a "Ripley's Believe It Or Not" frame in the Sunday paper comics.
The willingness of the faux-educated to spew forth nonsense worthy of the now-defunct carnival sideshow circuit tells us we need carnival sideshows so the pseudoscientists and goofbrains.... as well as willing con-artists of the gentler, least exploitative sorts, would have a place to ply their trade.
well you can hear cats purr and when a kitten is born it cannot hear. do you expect it to hear the kitten hear the mother purr if it is deaph. tell me if i didnt understand correcly.
Reply | Report Abuse | Link to thisI've raised 8 cats in my life & none of them were related or the same breeds. I've noticed there's only 3 occasions when they purr.
Reply | Report Abuse | Link to this*Being combed or pet.
*Sitting next to a human or another cat after a fit of stress, like a vet trip, thunder storm, or getting back from the vet.
*When you baby talk to them in whispered tones.
The information about "various investigators" is not entirely without scientific basis. I'd point out, though, that the writer is a vet and not an expert in bone growth or biomechanics. I'd also like to point out the warning sign of unnamed researchers who published unnamed articles in unmentioned contexts.
Reply | Report Abuse | Link to thisFor those interested in learning about the whole picture, I would point you toward one of those researchers often used to support "mystical healing powers" of sound. In fact, the amplitudes that the biomechanical engineer found to increase bone density were much more powerful than a cat's purr, but much less powerful than unregulated 'medical' devices seeking to capitalize on the discovery. He references the well-documented harmful chronic effects of intense vibration and seeks to differentiate that from other, possibly beneficial effects of lower-strength, short-duration vibration that are under investigation.
http://bme.sunysb.edu/people/faculty/c_rubin.html
Conclusions about possible clinical benefits of vibration therapy were still very much up in the air in 2009, mostly owing to the wildly different techniques used by different researchers. http://www.rehab.research.va.gov/jour/09/46/4/pdf/totosy.pdf
As of 2011, it still isn't clear that it actually helps improve patient outcomes.
http://www.ncbi.nlm.nih.gov/pubmed/22084334
Simple and fact-based answer: um... we don't know exactly why cats, both large and small, purr.
Reply | Report Abuse | Link to thisHowever, we do know that many cats (including mine) have their "owners" ... very well trained:-)
I've heard that some cats purr when they sense healing energy. I'm not sure if that's true or not, but somehow it would make sense if it is.
Reply | Report Abuse | Link to thisAs I sit here with my 15 LB Bangle cat sitting on my lap and purring like a monster, I believe that he is purring because he is as content as could be. I come home and he crawls up on my lap, tries to climb me like I'm a tree then flops over in my arms like a baby with his tongue hanging out and drooling like a mad man and loving the entire experience. He purrs the entire time. The same with our crazy Siamese - Purr,purr, purr. She was taken away from her Mom too early and will kneed and purr, make full circles and try to fall asleep on my chest - Just a content kitty. You break out the turkey meat and she is in hog heaven.
Reply | Report Abuse | Link to thisHopefully you were kidding, but I guess you haven't heard that cats have more neural connections than dogs do and if you think the ability to follow commands means greater intelligence, then I would take a closer look if I were you.
Reply | Report Abuse | Link to thisMaybe it's not that a cat is purring because it's happy, but rather it's happy because it's purring.
Reply | Report Abuse | Link to thisGreat research effort. Has there been any recent research into this topic area? I visited http://www.top10thingsblog.com/2012/11/16/why-do-cats-purr/ and it gave me the top 10 reasons why cats purr and was wondering if they are all correct and accurate?
Reply | Report Abuse | Link to thisThanks
I did not know that cats purr when they are injured. It so sunrises me that sincerely I can not believe it. And I wouldn't like to see a cat injured.
Reply | Report Abuse | Link to thisIf this is true (and it should be) I have learned a new fact.
Everybody knows that when we touch a (familiar) cat, it purrs.
I foster and rehab cats and kittens, some have even been semi-feral. I have taught all of them the way I've always taught my Golden Retrievers. After 47+ cats & kittens I come to the conclusion in many ways cats are smarter then dogs. Of course their abilities are different but just the same... my cats and all fosters know what the word "share" means when it comes to their food, they all answer to their name & come running, most play fetch (yes, they bring their ball back and set it down in front of me and wait for me to throw it again), they all love my Golden. My own cat tells me when he wants to eat. If I don't get it for him, he opens the cabinet himself, selects a can and pushes it down. When he wants me to do treat toss, he comes over and opens the desk drawer for his treats. What I love most of all is, soon as my baby boy looks at me or approaches me he starts to purr. He rubs himself all over me and willingly gives me kisses.
Reply | Report Abuse | Link to thisI really don't think looking at a cat as a specimen is the same as being owned by a cat. Bring one home and fall in love with him or her and I guarantee they will start responding to you better.
That's so awesome! I said moo as my first word, but nothing similar to purring :)
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