Purr

A purr is a sound made by all species of felids 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 (help·info) to a domestic cat purring)

Although purring is most commonly associated with felids, other animals, such as raccoons, also purr. Guinea pigs (while in heat), rabbits, squirrels, ring-tailed lemurs, elephants (while eating), and gorillas (while eating) are also known to purr.^[1]

[edit] Purring mechanism

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, causing air vibrations during inhalation and exhalation^[2]. Combined with the steady inhalation and exhalation of air as the cat breathes, a purring noise is produced with strong harmonics.^[3]

It was once believed that only the cats of the Felis genus could purr; some older texts may still say this.^[4] In fact, all cats are able to purr, although the cats of the Panthera genus (Tiger, Lion, Jaguar and Leopard) are only able to purr when exhaling. All cats other than the Panthera, even larger ones such as the cheetah, purr.^[5]

[edit] Reasons for purring

Because cats often purr when being petted, becoming relaxed,^[6][7][8] or when eating, owners tend to assume that purring is a sign of contentment, and find it pleasant to hear. However, cats are also observed to purr in other situations. Female cats are known to sometimes purr while giving birth.^[9][10][7] Also, domestic cats have been often reported to purr when injured, sick, in pain or dying.^[6][10][7] Purring may also be a signaling mechanism between mother cats and nursing kittens.^[9][6]

[edit] References

[edit] External links

• Why and how do cats purr?
• Why do Cats Purr?
• The Felid Purr: A bio-mechanical healing mechanism