There's no doubt that cats are awesome, but what exactly does it mean when they purr?

I love petting a happy cat who arches under my hands. Playing flirt pole with an athletic cat who leaps, twists, and pounces on the toy is better than watching anything on TV. There are so many things I like about my cats but one on my lap purring until her bones shake certainly tops the list.

How Does a Cat Purr?

There is considerable debate as to how a cat creates her purr. At one time it was thought that the sound was blood rushing through large blood vessels. There were also theories that cats had a unique organ that makes the purring sound. Unfortunately, these and other theories were hard to prove (or disprove) because sedated cats don't purr; this made research difficult. Today, however, researchers believe that the purr is created by laryngeal muscles that vibrate the vocal cords as the cat breathes. The definition of a purr is that of a continuous sound produced as the cat breathes in and out and which goes on for several minutes. Cats of many species purr at a frequency of between 25 and 150 Hz.

Most but Not all Cats Purr

Domesticated house cats aren't the only cats who purr; many species of felines including bobcats, servals, cheetahs and even mountain lions purr. These cats have a rigid hyoid bone while African lions and tigers (which do not purr) have a flexible hyoid bone. Researchers are still trying to find out why there is a difference in the hyoid bone, but they do know it is located in the throat and provides support for the larynx. African lions and tigers can make a sound like a purr, but do so only when exhaling so their sound is not a true purr.

The Purr is Unique to Felines

Several other animals make a noise that is similar to a purr but isn't quite the same. Mongooses, hyenas, guinea pigs, and raccoons each have a noise in their vocabulary that is similar to a cat's purr but it differs in frequency, sound, and use. In addition, most make this sound only when exhaling. The purr made by felines is unique.

Is Purring Healing?

Some experts on felines believe that the frequency at which cats purr is healing for them. Since research is ongoing as to whether low intensity ultrasonic sounds can aid humans in healing broken bones (and other injuries) perhaps this has some validity. Nothing is proven yet and research is ongoing but it might be fun to be told to take an aspirin, grab your cat, go to bed and call the doctor in the morning.

Happiness and More

Although most purrs occur when the cat is happy, purrs are not limited only to happiness. Many cats will also purr when stressed. For example, many cats will purr at the veterinarian's clinic. All of the cat's body language will show stress, including a lashing tail, ears plastered to the skull, and wide open pupils; yet the cat will still be purring. If you need to judge your cat's mood, don't listen to just her purr; look at all of her body language.

Mother Cats Purr

No one knows why mother cats purr while giving birth. It might be a response to the discomfort or perhaps a means of bonding with her kittens. Purring while nursing the kittens is common and this is thought to be a means of bonding with the kittens as well as a means to calm them. Purring begins early in life; kittens begin purring when only a few days old.

Cats Use their Purr

Cat owners, like myself, enjoy it when our cats purr and cats figure this out. How many times has your cat rubbed up against you, meowed, purred and then lead you to the cat food? Cats are excellent at training their owners and their purr is a big part of the process. Now that you're thinking about your cat's purr, see if you can find different tones and sounds associated with it. Many cat owners feel their cat can mix meows and other sounds with the purr in order to gain their owner's attention. Other cat owners say their cat has different purring sounds associated with the cat's needs: one sound for going outside, one sound to request petting, and so on. Since some people find meows as too demanding, perhaps cats today are evolving to communicate with us using more purrs and less meows.