why do cats purr?

Question

my cat seems to purr a lot whenever i pick him up and hold him in my arms or whenever i brush his fur? what does it mean?

Answer 1

Actually, no one knows why they purr, except, presumably, the cats themselves. In fact, no one really seems to know how they purr either. You might assume that it's some kind of vibration in the larynx, as one science columnist suggests.

However, others, such as biologist Kelleen Flanagan of the MAD Scientist Network, subscribe to the notion that the sound is created by the vibration of blood vessels.

But regardless of the method, the question remains: What causes cats to purr, whether voluntarily or involuntarily? At this point, theories are all we've got to go on. Carol Merkle, in a paper titled "Behavior and Language of Cat", offers some possibilities that she culled from print and online research. These include the oft-cited happiness as well as pain, fear and the more subtle "waiting for happiness."

For a list of other theories about purring, check out this page from UselessKnowledge.com.

If all else fails, try Pounce.
When your cat climbs into your lap, tucks in his paws under himself, and begins to purr, all is right in his world. This is one of the things we love about our cats; that feeling of contentment they share with us. When cats become soft purring bundles of warm reassuring fur, we feel calmer and more peaceful ourselves. We may not always hear the purring – a soft vibrating rumble – but we can feel it. But why do cats purr? And what produces this characteristic sound?

According to veterinarian Bruce Fogle, author of The Cat’s Mind, the original function of purring was to enable a kitten to communicate with his mother that things are well. A kitten is able to purr by the second day of life, and although he can’t meow and nurse at the same time, he can purr and nurse. And the mother cat often purrs back, probably to reassure the kitty.

There are many theories to explain how the purr is generated. One study determined that purring involves activation of nerves within the voice box. These nerve signals cause vibration of the vocal cords while the diaphragm serves as a piston pump, pushing air in and out of the vibrating cords, thus creating a musical hum. Veterinarian Neils C. Pederson, author of Feline Husbandry, believes that purring is initiated from within the central nervous system and is a voluntary act. In other words, cats purr only when they want to.

Purring is an integral part of the feline communication system and occurs for a variety of reasons. It is classified with the “murmur vocalization” group, which involves sounds produced by a cat while the mouth is closed. In addition to purring, this group of sounds includes grunting, calling, and acknowledgment murmurs. Domestic cats and some wild cats, like pumas and mountain lions (almost any big cat that cannot roar), are all able to purr.

As the cat matures the meaning of the purr changes. Some cats purr to indicate contentment or pleasure, but badly frightened cats and severely ill cats also purr, and so do females while they are delivering their kittens. It is not uncommon for cats to purr when they are close to death. This final purring may indicate a state of anxiety or possibly euphoria, states that have also been described in terminally ill people.

Animal behaviorists believe that when cats purr under stressful circumstances, they are reassuring or comforting themselves, much as humans may sing to themselves or hum when they are nervous. Frightened cats may purr to communicate submissiveness or non-aggressive intentions. A feral cat may purr to signal that he will not attack and other cats need not feel threatened. Older cats may purr when they play or approach other cats, signaling that they are friendly and want to come closer.

A more recent theory about purring is that it is caused by the release of nature’s own morphine-like substances (endorphins) in the brain. Since endorphins are released under circumstances of pain and pleasure, this would explain the seemingly ambiguous expression of purring. This theory jives with Pederson’s reasoning, that purring is initiated in the brain, and is also compatible with the more mechanical explanations for purring, as endorphins activate one of the main action systems in the brain (so thought is translated into movement). Whatever the explanation for purring, it seems to indicate cats’ contentment and is associated with improvement in their affect at times of stress. Purring is one of cats’ most endearing qualities.
Cats don't purr just when they're feeling chipper--they also purr when they're frightened or badly hurt. Purring doesn't have any specific emotional connotation; rather it seems to be a kind of homing device. Cats learn the signal in the first few days of kittenhood, when they can't see, hear, or smell very well. The mother cat purrs to call the kittens to nurse--unable to hear the sound, the kitten can feel the vibrations.

There are two schools of thought on exactly how a cat purrs. One theory traces the vibrations to a set of "false vocal cords," a bundle of membranes that lies above the genuine vocal chords and seems to have no other clear function. The other opinion locates the purr in the vibrations of the hyoid apparatus, a series of small bones connecting the skull and the larynx that nominally serves to support the tongue. Since it's very difficult to induce a cat to purr while you are examining his hyoid apparatus, the truth may never be known.
No one knows for sure why a domestic cat purrs, but many people interpret the sound as one of contentment. Our understanding of how a domestic cat purrs is becoming more complete; most scientists agree that the larynx (voice box), laryngeal muscles, and a neural oscillator are involved.

Kittens learn how to purr when they are a couple of days old. Veterinarians suggest that this purring tells ‘Mom’ that “I am okay” and that “I am here.” It also indicates a bonding mechanism between kitten and mother.

As the kitten grows into adulthood, purring continues. Many suggest a cat purrs from contentment and pleasure. But a cat also purrs when it is injured and in pain. Dr. Elizabeth Von Muggenthaler has suggested that the purr, with its low frequency vibrations, is a “natural healing mechanism.” Purring may be linked to the strengthening and repairing of bones, relief of pain, and wound healing (See Web link to Felid purr: a healing mechanism).

Purring is a unique vocal feature in the domestic cat. However, other species in the Felidae family also purr: Bobcat, Cheetah, Eurasian Lynx, Puma, and Wild Cat (Complete list in Peters, 2002). Although some big cats like lions exhibit a purr-like sound, studies show that the Patherinae subfamily: Lion, Leopard, Jaguar, Tiger, Snow Leopard, and Clouded Leopard do not exhibit true purring (Peters, 2002).”

What makes the purr distinctive from other cat vocalizations is that it is produced during the entire respiratory cycle (inhaling and exhaling). Other vocalizations such as the “meow” are limited to the expiration of the breath.

It was once thought that the purr was produced from blood surging through the inferior vena cava, but as research continues it seems that the intrinsic (internal) laryngeal muscles are the likely source for the purr. Moreover, there is an absence of purring in a cat with laryngeal paralysis. The laryngeal muscles are responsible for the opening and closing of the glottis (space between the vocal chords), which results in a separation of the vocal chords, and thus the purr sound. Studies have shown, that the movement of the laryngeal muscles is signaled from a unique “neural oscillator” (Frazer-Sisson, Rice, and Peters, 1991 & Remmers and Gautier, 1972) in the cat’s brain.

There is one sound that is music to the ears of all of us cat lovers -- the sound of our beloved cats purring softly beside us. This motor-like sound has fascinated people for centuries. In her book The Cats, Muriel Beadle relates this myth about how cats got their purr: There was a damsel in distress who was given the task of spinning ten thousand skeins of linen thread within thirty days in order to save her true love from death. Since it was impossible for her to do this all by herself, she enlisted the help of her three cats. They all worked day and night and finished the job within the thirty days. As a reward, the cats were given the ability to purr, a reminder of the whirring sound of the spinning wheel.

Well, we can be pretty sure that's not really how cats first began to purr but, on the other hand, we twentieth century people still don't know all that much about how or why cats purr. We do know that kittens begin to purr instinctively as soon as they begin to nurse and that the first kitten to suckle uses the sound to call others to begin feeding too. When they are very young, kittens purr in a monotone, but as they get older, they begin to include variations in speed, rhythm, pitch, and volume in combinations which produce many different varieties of purring sounds.

Feline behavior experts believe that purring is a communication device. Mother cats purr while nursing, possibly providing a measure of reassurance to their kittens which reminds them that their mother is there to watch over and protect them. In addition to purring when they are content, cats also purr when they are afraid, sick, in pain, or even dying. In fact, sometimes a dying cat will purr constantly for several hours while in the final stages of illness. With that in mind, purring could be a means of communicating strong sentiments, whether good or bad.

Some cats purr more than others, not unlike some people who talk more than others. And, some cats don't purr at all. The big cats, those wild and distant cousins of our domestic housecats such as lions, tigers, leopards, and panthers, do not purr. Tigers are known to make a vocal greeting called "chuffing" which is a purr-like sound, but in the wild, it is only the medium-sized cats, such as mountain lions and cheetahs, who purr.

When a cat purrs, it feels like his entire body is softly vibrating, particularly the throat and chest. Over the years there has been much speculation about where the purring mechanism is located and how it functions. There have been several theories about the physiological origin of the purring sound. One theory purported that purring was created by turbulence in a major blood vessel of the heart with the sound being transmitted through the upper air passages during inhalation and exhalation. Other theories suggested that the sound was produced when the soft palate vibrated, when the epiglottis opened and closed repetitively, or when the diaphragm muscle vibrated.

The most popular theory was that purring sounds were generated by the false (superior) vocal cords, two membranous folds located in the larynx behind the true (inferior) vocal cords. When a cat inhaled, this was believed to produce the coarser purring sounds while exhaling supposedly caused softer, smoother sounds. But, the theory which is probably the most accurate is the one which suggests that purring comes directly from the cat's voice box. This theory states that the purring sound is produced by the tensing of the vocal cords which vibrate during inhalation and exhalation.

David Rice, a biomedical engineer at Tulane University in New Orleans, studied purring along with an international team of researchers from Tulane and from the King Alexander Museum in Germany. The outcome of that research was noted in an August 1991 issue of Discover magazine: cats use only their vocal cords to purr.

Rice was quoted by Discover as saying that the vibration of the feline vocal cords by the muscles in the cat's larynx, "creates sound when the air flows through them," whether the cat is inhaling or exhaling. "The muscles create the purring vibration -- one twitch per vibration."

Why are Rice and his fellow researchers so sure that they have the right answer to the purring question? Unlike earlier researchers of purring, Rice and his team did not use restrained animals with instruments stuck inside of them. Instead, they studied unrestrained cats by using a microphone that was sensitive to low-frequency purring sounds. They moved the microphone around the cats' bodies until they determined that only the larynx was the source of the purring. They did not detect any purring activity from any other part of the body.

So, there you have it. Whether Rice and his colleagues prove to be correct about the source of purring can only be proven or refuted by future studies. But, where the sound comes from is not as important as how we cat lovers feel when we sit in our favorite chair with our feline friends curled up in our laps, motors going strong. As for the question of why cats purr, maybe they do it to comfort their human companions. It's a nice thought, isn't it?

Why do cats purr?
Kittens purr to let their mother's know that everything is ok. Adult cats purr when they feel safe and happy. Cats can purr for a long period of time without stopping.


Why do cats meow?
Cats have 4 different meanings for "meow". If you listen carefully, you can hear that each meow is different.
1. I'm hungry!
2. I want to go out!
3. Help!
4. I want attention!

A purr is a sound made by some species of felines. It varies in detail from cat to cat (e.g., loudness, tone, etc.), and from species to species, but can be characterized as a sort of tonal buzzing. Some cats purr so strongly that their entire body vibrates. Cats purr at 20 - 200 hertz. [1]

Cats produce the purring noise by vibrating their larynx, or voice box, in a particular manner. They have a timing mechanism in the brain which sends neural messages to a muscle in the larynx, rhythmically opening and closing the air passage several times per second. Combined with the steady inhalation and exhalation of air as the cat breathes, a purring noise is produced.[2]

Felines are either able to purr or to roar, one exception being the tiger which can purr but only in one direction, as well as being able to roar. In general, small felines purr, while larger ones roar, although pumas and cheetahs purr and do not roar.[3]

[edit]
Historical theories
One theory held that purring involved blood hitting the aorta. Another held that purring might have been caused by the vibrations of the hyoid apparatus, a series of small bones connecting the skull and the larynx that nominally serves to support the tongue. Yet another theory held that cats might possess a special purring organ, though none was found

[edit]
Why felines purr
Humans usually interpret the purring of a domestic cat as an expression of some type of friendliness or contentment. This assumption is based on the observation that cats often (though not always) purr when being stroked by humans, combined with the experience that human children tend to enjoy stroking by their parents and interpret it as a gesture of affection. Consequently, most humans enjoy listening to or holding a purring cat.

It is, however, not entirely clear to scientists whether this really is one of the cat's reasons for making the sound; it is well-established that a cat also purrs when it is uneasy, nervous or in great pain, perhaps to comfort itself or to express submission. Other theories suggest that a cat purrs when it wants, needs, or is receiving attention, whether it be affection or medical treatment. Purring may also reduce pain, help a wounded cat to heal, or even help to keep a cat's bones strong[4]. When cats purr while also lightly clawing the ground it may mean they are trying to relieve stress or comfort themselves. An example is when a female cat is nursing kittens; as humans may find with children, cats may also become stressed from the attention of their young and therefore start to purr and lightly claw the ground. This may also be associated with "kneading" behavior, in which the kittens' pawing helps release milk from the nursing mother's teats. Adult cats knead (also called paddy-pawing, making muffins, making bread, or treading paws) as a sign of contentment and to relax.

Ethologist Paul Leyhousen, in his book Cat Behavior, interprets purring as a signal meaning "I am not a threat" to explain the otherwise differing circumstances that elicit the sound.

[edit]
Other examples of purring
It is not clear quite how and when purring is used between cats themselves, which is probably a more important issue bearing on its primary purpose than how and why it happens when humans are involved. One speculation is that it is a signalling mechanism between mother cat and nursing kittens. Female cats are known to purr while giving birth, and this may be to reduce the pain and also assist post-natal healing. Kittens purr while nursing, presumably as an "all's well" signal to their mother.

Some cats, usually more vocal ones, are able to meow or hiss without interrupting the purring sound.

Big cats, like lions and tigers, can purr as well, but only when they are breathing out, unlike domestic cats.

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Effect on humans
A cat's purring has been shown by a number of studies to have a therapeutic effect on humans, both relieving stress and accelerating healing. [5]

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References
↑ How A Puma Purrs
↑ Cheetahs can purr.
↑ Purring for bone strength and healing
Why do Cats Purr?
Retrieved from "http://en.wikipedia.org/wiki/Purr"

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
GOOD LUCK

Answer 2

Actually, according to scientists there is no real known reason why cats purr. Cats have been known to purr when they are relaxed, scared or even injured. But it has however been proven that the sound of a cat's purr could relieve stress and high blood pressure in humans.

Answer 3

Cats will purr for two reasons: 1) They are in pain or 2) They are relaxed and happy. Yours seems to be purring for reason #2.

Answer 4

The louder the purr, the happier the cat. When I brought my cat into my house, he purred so loud under the bed that first night. He had been a street cat and was very skinny and had some cuts on him.

Answer 5

You obviously have a uniquely amazing and beautiful bond between each other. Cats tend to do this naturally when they feel comforted,relaxed and non-perplexed. They are showing their love towards you and how happy you make the cat feel. Also,it may be craving a bit of a love and seeking attention-it obviously likes you and shows excessive attention:) Licking of cats and dogs is a domestic animals way of cleaning you-sort of like a kiss.... It shows that it wants the best for you and is nurturing you :)

Answer 6

Cats Purr because They feel safe they are happy they or telling you that they love you plus they our contented

Answer 7

Because it can and it's feeling comfortable and content; the other reason why it may purr is it is feeling stressed or pain. Here are two sources with some ideas on cats purring.

Why do cats purr? Excellent question. That question has been asked by experts and lay persons alike for quite some time.

Not all species of cat purr, but all domestic kittens are born with purring ability.

Like their colors and shapes, not all cat purrs are the same, even within the same species. Although the core purr sounds all fall within a certain frequency range, even across species, the volume, type, and harmonic (additional, complimentary) sounds vary. They can range from a low rumbling sound, all the way up to a high pitched trill, depending upon the physical attributes of the cat and its mood.

Cats typically purr when they are content, and so we normally associate the act of purring with a happy cat. For example, some cats will begin purring if you just direct a glance their way for long enough. Others take a little bit of scratching or talking to, and then there it is.

It should be noted, however, that cats also purr when they are distressed, or in pain. Female cats will purr while giving birth, presumably to act as a beacon for the blind and deaf kittens that she is bringing into the world. Perhaps it is to comfort herself as well.

And that may be one part of the answer to the question, why do cats purr? It is soothing, and makes the cat, and others around her, feel good.

Over the last few years, some fairly extensive research has been compiled on the purring question as scientists ask why do cats purr? The results have been interesting.

Using data collected about the various purring cat species, and comparing that to studies done on the healing qualities of sound vibration, a connection has been made. Further comparing cats to dogs (who obviously do not purr), with respect to complications from surgery, healing time, and other health items, researchers may have found the answer to why cats purr.

It would appear that purring may be some sort of built-in survival mechanism. Purring may be a way to improve muscle tone without exercise, reduce pain, and repair fractures!

It seems that sound vibrations, in the same frequency range (including harmonic vibrations) as a cat purr, can actually act as a healing aid, reduce pain, and promote tissue growth.

That's right - everything from increased bone density, to improved muscle tone, to tendon repair, to therapeutic pain relief is aided by low frequency vibrations. Vibrations in the range of the cat purr.

So, why do cats purr? Well, on the surface it may be to express emotion, but literally the underlying reason may be that it is essential for your cat's health!

So go make your cat purr!

Most experienced "cat wranglers" now know that cats don't purr only when they are content and happy. They also purr during tense or traumatic moments. When suddenly and violently injured, even at moments near death, a cat will often purr.


I've often likened this to saying, "Please don't hurt me any more. I'll be good," but recent studies have put a more scientific spin on this seeming anomaly.
It seems that the measurable Hertz of a cat's purr lies between 25 and 150. Coincidentally (or not) it has been found that sound frequency in this range can stimilate bone growth and healing. ¹

That cats have remarkable endurance, and are quite stoic to trauma is well known to veterinary professionals; it is not unlikely that this instinct to purr under duress is directly related.

Purring under stress has more colorfully been described as the cat's mantra, e.g., a self-soothing, self-healing, relaxing, vibrating sound (sort of like the Ommmm one might hum while in the lotus position. Notice the vibration in your lips, nose and throat? I bet most of us, if we had our "druthers," would much rather be able to purr!

The Physiology of Purring

There seems to be two schools of thought here.

The most popular one is quoted here:
One study determined that purring involves activation of nerves within the voice box. These nerve signals cause vibration of the vocal cords while the diaphragm serves as a piston pump, pushing air in and out of the vibrating cords, thus creating a musical hum. Veterinarian Neils C. Pederson, author of Feline Husbandry, believes that purring is initiated from within the central nervous system and is a voluntary act. In other words, cats purr only when they want to.²

The other theory is that the sound comes more from vibrating blood vessels than in the voicebox itself. ³
The Happy Purr of a Cat

All domestic cats are born with the purring ability. A queen will purr while giving birth. It is unknown whether this is because of happy anticipation, or whether it is a relaxing "mantra." Kittens instinctively purr when nursing, and the momcat purrs right back at them. Your adult cat will purr at the drop of a hat whenever you're near, and especially when you are holding or petting him.

Cat purrs will range from a deep rumble to a raspy, broken sound, to a high-pitched trill, depending on the physiology and/or the mood of a cat. A cat will often "wind-down" when going to sleep, with a long purring sigh that drops melodically from a high to a low pitch. Does your cat's purr sometimes sound like an idling diesel engine? That's because at the lower range of 26 Hertz, the velocities are nearly the same.

The Healing Power of the Purr

Cats are often used as "therapy animals" in convalescent hospitals, or in retirement residences. It is an accepted fact that cat owners have lower blood pressure, especially in older people. The human-feline bond is never quite so close as when a person is holding and petting a purring, vibrating bundle of fur on her lap, and all is well with the world. You may even find yourself purring in response.

Resources

¹SCIENTIFICAMERICAN.com: Why do cats purr?

² PetPlace.com: Why Do Cats Purr?

³ Mad Science Network: How Does A Cat Purr, Which Cats Purr, and What Does It Mean?

Answer 8

WHY DO CATS PURR, ACTUALLY NO ONE KNOWS WHY THEY PURR EXCEPT PRESUMABLY,THE CATS THEMSELVES . SOME SCIENTIST HAVE THOUGHT THAT MAY BEA WAY OF COMMUNICATION.

Answer 9

They like to be held and they feel secure

Answer 10

telling you that it is happy and that he loves you. cats sometimes love to lay in your lap and curl up in your lap.

Answer 11

It's happy.