There have been many, many theories as to how cats purr but I don't think anyone really knows completely. Did you know that the cat family is divided scientifically by that purr...into cats that do purr and cats that don't.
Cats will not only purr when content and happy but when in great pain or scared just to calm themselves. Kind of like a baby sucking it's thumb.
What I find amazing is how a cat's purr can calm people too! Contagious calmness through purring! >^--^<
Jenny(and George and Sam and CallyCat)
The Following User Says Thank You to jennybyc For This Useful Post: sjb (06-18-2012)
One theory I found very interesting was that cats purr as an aid to health, in particular, bone density. As cats lead relative sedentary lifestyles with brief bursts of activity, their bone density should be quite poor. However, their bones appear to be just fine. It is believed the constant vibration of purring acts upon the bones to make up the apparent shortfall. Like these new vibration fitness plates that perform a similar function in human bone density. I imagine that this is just part of the many reasons why cats purr.
The Following User Says Thank You to LP123 For This Useful Post: kripos (06-20-2012)
That said, cats do pur when they are kittens and they are nursing. I believe I read somewhere once that their pur is often a signal to both them and their mother that they are doing well.
I know my cat only purrs when she is happy and content. She may have purred when scared before but if she did, I do not recall it. However, a Siamese cat that my family used to have would sometimes purr when in distress. I believe that when he was hit by a car in the driveway where we lived, he cracked his hip. Well, I am pretty sure he was purring then. Of course, we did get him to a veterinarian immediately and he was okay for a while. Unfortunately, I believe he was hit by another car shortly after that and killed. I miss him very much.
Last edited by wwwgirl; 11-25-2010 at 03:28 AM.
The Following User Says Thank You to wwwgirl For This Useful Post: HisGirl1991 (04-07-2012)
I have two cats.
One of them can purr like a little motorboat.
The other one sounds like a stalling engine - all of his purrs come in spurts as if his purr function is an engine and he can't quite get it to turn over.
cats purr by moving air over a section of their tracea and it is a sign of affection. all cats except for lions and tigers can purr. mountain lions sound like a motor boat. remember cats that purr can not roar and vice versa
My cat usually jumps onto my bed, kneads and makes herself comfortable and stays there for hours until I give her the boot and need to go to sleep myself.
Often times she'll come up to me and lay on her back with her belly stretched out, asking for a rub down. She purrs a lot. I've never seen or heard her purr when scared or intimidated, she ONLY purrs when shes very comfortable.
I have two cats.
One of them can purr like a little motorboat.
The other one sounds like a stalling engine - all of his purrs come in spurts as if his purr function is an engine and he can't quite get it to turn over.
My cat purrs like crazy when she is happy. But I also read that cats purr when hurt or scared. I guess it comforts them??
I think when a cat is really relaxed instead of saying aaaaaah that feels good, they puuuuurrrrrrrrr because they cant take any other sound except for meowing.
How do cats purr? 
