English

Verb

purring

1. present participle of purr

A purr is a sound made by all species of felines and is a part of cat communication. 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. Domestic cats purr in a frequency range of 22.4 to 30.2 hertz. Some cats purr so strongly that their entire bodies vibrate; conversely, other cats may purr so quietly that the only indication is a vibration felt when touching the cat's throat. In addition, some are able to meow or hiss without interrupting the purring sound. (Listen to a domestic cat purring)

Although purring is most commonly associated with felines, other animals, such as raccoons, also purr.

How felines purr

Despite being a universally recognized phenomenon, the exact mechanism by which the cat purrs has been frustratingly elusive for scientists. This is partly because the cat has no obvious anatomical feature unique to it that would be responsible. One hypothesis, backed up by electromyographic studies, is that cats produce the purring noise by fast twitching of the muscles in their larynx, which rapidly dilate and constrict the glottis, thus causing vibrations in the air both during inhalation and exhalation. Combined with the steady inhalation and exhalation of air as the cat breathes, a purring noise is produced with strong harmonics.

It was once believed that only the cats of the Felis genus could purr; some older texts may still say this. In fact, all cats are able to purr, although the cats of the Panthera genus are only able to purr when exhaling. All cats other than the Panthera, even larger ones such as the cheetah, purr.

Historical theories

One hypothesis held that purring involved blood hitting the aorta. Another possibility was that another area of soft tissue or muscular tissue in the neck or torso (e.g., the diaphragm) similarly vibrates. Another held that purring might be caused by vibration of the hyoid apparatus, a series of small bones connecting the skull and the larynx that nominally serves to support the tongue. Yet another hypothesis held that cats might possess a special purring organ, though none was ever found.

Why felines Purr

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.

Purring may also be a signaling mechanism between mother cats and nursing kittens. Female cats are known to purr while giving birth.

In many instances domestic cats have been reported to purr when in pain or dying.

References

• Stogdale L, Delack JB. Feline purring. Compendium on Continuing Education for the Practicing Veterinarian 1985; 7: 551-553.

Reprinted in: Voith VL, Borchelt PL (eds). Readings in Companion Animal Behavior. Trenton: Veterinary Learning Systems, 1996; 269-270.

External links

• Why and how do cats purr?
• Why do Cats Purr?

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