why do cats purr?

Answer 1

Hi there...The reason is psychological as well as physiological--the two are not mutually exclusive of one another. Cat's purr whenever they feel content, extremely frightened and some will purr when they are dying as well.

How cats purr:
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 pump, pushing air in and out of the vibrating cords, thus creating a musical hum. Some veterinarians 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.

The other theory is that the sound comes more from vibrating blood vessels than in the voicebox itself. The larger the vocal chords the softer the purr whereas the smaller the louder.
Source: http://cats.about.com/cs/catmanagement101/a/why_cats_purr.htm

The Scientific Reason WHY cats purr:

Some scientists believe when cats purr the frequency of their purring will help heal damaged bones and body organs as well as help heal humans.

All the cats had purr frequencies between 20 Hz and 200 Hz. With the exception of the cheetah, which had frequencies 2 Hz from the rest, all the species had frequencies, notably 25 Hz, 50 Hz, 100 Hz, 125 Hz, and 150 Hz, that correspond exactly with the best frequencies determined by the most recent research for bone growth, fracture healing, pain relief, relief of breathlessness, and inflammation. All of the cats' purrs, including the cheetah, had frequencies 4 Hz from the entire repertoire of low frequencies known to be therapeutic for all of the ailments.

That fact that the cats in this study produced frequencies that have been proven to improve healing time, strength and mobility could explain the purr's natural selection. After a day or night of hunting, purring could be likened to an internal vibrational therapeutic system, a sort of "kitty massage" that would keep muscles and ligaments in prime condition and less prone to injury. Additionally, the purr could strengthen bone, and prevent osteodiseases. Following injury, the purr vibrations would help heal the wound or bone associated with the injury, reduce swelling, and provide a measure of pain relief during the healing process.
Source: http://www.sciam.com/askexpert_question.cfm?articleID=0005CB0D-82FC-1E31-82FC809EC5880000&catID=3&topicID=3.

Answer 2

Story time!
Why cats purr

once upon a time, there was a mouse and a cat. They were best friends for life, always respecting each other. one day, the mouse's grandfather gave him a one of a kind drum. The only way you would hear the sound was when you petted it, the sound you would hear is purrrrr-ppuurrrrrrr. The mouse went home, all happy and excited. He eventually began bragging it in front of his buddy, the cat. " Oh, i feel so sorry that you dont have a one-of-a kind drum" or " Would you like to see the drum? well, too bad cat, you see with your eyes, not with your hands", mouse would repeatdly say this in front of cat, every single day. The cat grew furious and jealous, thinking a way for revenge. One day, the mouse got sick, and the cat visited him. cat saw the drum on mouse's bedside table, so he decided to eat the mouse first, then take the drum. While the mouse was reading a get-well card, the cat took action. cat punced in front of the mouse, mouth wide open. the mouse was quick and nimble, pushing the cat to the side of the bed. The cat misplaced the mouse with a drum, so cat eventually swallowed the drum. Now, whenever you pet a cat, you hear it purr, because you are really petting a drum inside of your cat.

THE END

Answer 3

Why and How do Cats Purr?
My mailbox often brings interesting challenges, as in this morning's short question from Gideon: "Do cats purr when they are alone?" What a great question! As I replied to Gideon, it is on the order of, "If a tree falls in the woods, and there's no one there to hear it, does it make a sound?" Or - "Does the light burn inside a closed refrigerator?" Yet, by far, I think the question about cats purring is the much more fascinating of the three. Truthfully, I don't know if cats purr when they are alone. It seems likely that they do, if one understands a little about why cats 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.

Answer 4

Emotion. Cats can purr when they are happy.. sad or mad. Some cats purr even when they they are hurt. It is an involunary reaction that happens when there emotion levels are high.


When your cat purrs when you are petting it, it is VERY happy. You should feel honored!

Answer 5

Because they can. Purring is produced by a cat's breathing which causes a special membrane to start vibrating, producing the purring sound you hear. Cats do this when they are relaxed and/or enjoying themselves and feeling pleasure.

Answer 6

This should answer your question well.
http://www.peteducation.com/article.cfm?cls=1&cat=1313&articleid=1151

Answer 7

they are letting you know they are happy..Probably the most affectionate way a cat can let its owner know it loves them

Answer 8

Yep because they love you. I love cats. They rule!!!!

Answer 9

... And its their way saying they are content.

>^.^<

Answer 10

JUST TELLING YOU THAT THEY LOVE YOU