To purr, for a cat, is to express sarcasm.

"Oooh, you're rubbing my back... am I supposed to enjoy that? Do you really believe this is a source of pleasure for me? Here, why don't I push up against your hand so you can rub harder. Oh, NOW you're scratching my ears. Of course, I could never reach there, only being one of the most flexible of all mammals, and of course my claws are hopelessly inefficient scratching implements. I could never do as good a job as you are.”

“Oh, now you’ve decided to feed me. This stuff is sooooo delicious. What is this made of, anonymous horse fragments and meat syrup? Mmm, I’ll just scarf this down so that I may experience a wonderful episode of spastic vomiting later. That would just make me the happiest cat in the world. You dumb sap.”

Purring is feline sarcasm. That’s why they shred your hand so often right after, and why it sounds so much like growling.

My girlfriend has done this on a few occassions. Generally means I'm doing something very right.

Backrubs and scalp massages are your best bet.

Indicates extreme contentedness and peace with the world. At least the world as it stands, which is a world with someone massaging your scalp. She's usually at least a little embarrassed by it, and will stop herself if she notices it. I don't pretend to understand that. Sometimes though, she doesn't notice. That means you're doing something extremely right, and you can only stop at your own risk.

Studies done by scientists, at the Fauna Communications Research Institute in North Carolina, indicate that one of the reasons cats purr could be because it helps their bones and organs and grow stronger. They found that frequencies between 27 and 44 hertz were the dominant purring frequency for a house cat, and 20-50Hz for the puma, ocelot, serval, cheetah and caracal. Almost all cats purr, including lions and cheetahs, though not tigers.

Dr Elizabeth von Muggenthaler, the president of the institute, said: "Old wives' tales usually have a grain of truth behind them and cats do heal very quickly." Sound waves created at a particular frequency trigger the healing process in feline bones. Purring is believed to have a similar effect to ultrasound treatment on humans.

Dr von Muggenthaler also said that purring had to be advantageous to a cat to survive natural selection, but there seemed to be no obvious advantage for a cat merely to display contentment. A natural capacity for increasing bone growth and strength and reducing healing time was, however, "clearly advantageous".

As Milen's excellent write-up stated, purring is not only designed to express contentment, but the full gamut of emotion. Purring is also useful for practical purposes in the feline world, too.

When a kitten is very young and and hasn't opened its eyes yet, the mother cat purrs as a homing device for her babies. The kitten can feel his/her way to the vibrations and food, and they in turn purr while drinking, to let the mother know he/she is getting the milk. It's a commonly held but erroneous idea that the kitten is purring because it is content, as it is just telling the mother that everything is cool, please continue producing the goods. Mmm, milk.

Cats purr when they're unhappy and sick as well as relaxed and happy. Generally, the only time cats don't purr is when they're asleep; if you can hear your feline friend starting their little motor when they've got their eyes closed, curled up on your lap, they're just faking sleep and are napping. Cats have been known to purr while giving birth ("Oh yeah, I just love it when I go through this intense pain. Labour is the most rewarding, content feeling ever! ) or immediately after a car accident. One of our dear departed cats, Tiger, purred as he died; at the time I thought he was happy, now I know that cats purr when they're in terrible pain. Sometimes it's best not to know.

Cats also purr to show their dominance amongst other cats. The alpha cat can purr when approaching inferior cats, or, seemingly contradictorily, a sick or lower-level cat can purr when getting near superior or healthy cats to show their inability and unwillingness to fight.

277 Secrets Your Cat Wants You to Know claims there is a tape available which "guides relaxation by combining the sounds of human and cat purring with a new age musical background". According to the distributors, purring with your cat creates a closer bond, and makes you as content and happy as your feline pal. The tape costs US$10; put it on and see how long your cat stands in front of you, watching, before he turns away in disdain. Then he'll purr because he's quite obviously the superior being, you numbskull.

How do cats purr? Strange but true, the actual mechanism remains a mystery.

Intuitively it would seem that that the sound is caused by air moving over the vocal cords, kind of like humming. But while most theories link purring to breathing, there is some disagreement about what is actually causing the vibration. Some say that the moving air vibrates the false vocal cords, which are 2 folds of membrane behind the real vocal cords. Another theory is that muscles attatched to the larynx contract, which causes a sort of fluttering of the glottis. As the cat breathes, the air gets pushed past the glottis, causing the sound. Or the sound might be produced in the hyoid apparatus, which is a series of small bones attached to the larynx and the tongue. Or the vibration is in a ligament connecting the clavicle bone to the throat.

Another, less popular theory is that purring is related to blood flow. Again, how this actually manifests itself is unclear. It could be increased blood flow or constriction of blood vessels in the throat or the soft palate in the mouth, causing vibrations which resonate in the throat. Or it could begin in the vena cava, which is the main vein going into the heart. This vein is constricted where it passes the liver and diaphragm, and sometimes the blood gets backed up, causing a vibration as it forces its way through. The vibration resonates in the cat's body, up to the throat and sinuses, causing the purring sound.

Almost all species of cat can purr. The exception seems to be the ones that can roar: lions, tigers, leopards, and jaguars. The vocalization apparatus is different in these species. There is discussion of this, with pictures and sounds at http://www.lam.mus.ca.us/cats/P14/alt.htm. If we are going with the "purring by air vibration" theory, apparently when large cats (e.g. mountain lions) do purr, they can only purr on the exhale, unlike domestic cats who can purr inhaling and exhaling. Some scientists believe that purring is linked to the central nervous system and is a completely voluntary action. That is, the purring mechanism is going all the time, but cats can adjust the volume as they want to. Several articles, including the writeup above, say that domestic cats purr at 27-44 hertz. Several other sites say that they purr at about 26 hertz, roughly the same frequency as a diesel engine. I have no idea which is true.

Purr (?), v. i. & t.

To murmur as a cat. See Pur.

 

© Webster 1913.


Purr, n.

The low murmuring sound made by a cat; pur. See Pur.

 

© Webster 1913.

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