purr

	A domestic cat purring. A different cat purring Different cats can sound somewhat different when purring.
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A purr is a sound made by all species of felids and is a part of cat communication. It varies between cats (for example by loudness and tone), and from species to species, but can be characterized as a tonal buzzing. Domestic cats purr in a frequency of 25 to 150 vibrations per second.

Although purring is commonly associated with felids, other animals such as raccoons purr. Other purring animals are Guinea pigs in heat, rabbits, squirrels, ring-tailed lemurs, elephants while eating, and gorillas while eating.

Purring mechanism

Despite being a universally recognized phenomenon, the mechanism by which cats purr is elusive. This is partly because the cat has no obvious anatomical feature unique to it that would be responsible. One hypothesis, backed 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^[1]. Combined with the steady inhalation and exhalation of air as the cat breathes, a purring noise is produced with strong harmonics.^[2] Purring is sometimes accompanied by other sounds, though this varies from cat to cat; the two purring examples in this article demonstrate this, as one is only purring, while the other contains low level outbursts sometimes characterized as 'lurps' or 'yowps'.

It was, until recent times, believed that only the cats of the Felis genus could purr.^[3] However, cats of the Panthera genus (Tiger, Lion, Jaguar and Leopard) also purr, but only when exhaling. Examples of a purring cheetah and a purring serval can be heard on Robert Eklund's Ingressive Speech website or on Robert Eklund's Wildlife page, see External links below.

Reasons for purring

Cats often purr when being petted, becoming relaxed,^[4][5][6] or when eating. Female cats are known to sometimes purr while giving birth.^[7][8][5] Domestic cats have been reported to purr when injured, sick, in pain or dying.^[4][8][5] Purring may have developed as a signaling mechanism between mother cats and nursing kittens. One theory is that it is not a sign of showing relaxation or content, but an attempt at "friendship" or a signal of "specific intent". For example, when a cat is nervous and cannot escape the situation (at a veterinarian perhaps), its purr may serve as an attempt to avoid being hurt.^[7][4] German ethologist and cat behaviorist Paul Leyhausen interprets it as a signal that the purring cat is communicating that it is not posing a threat.^[9]

Scientists at the University of Sussex showed in 2009 that purring, or some purring, seems to be a way for domesticated cats to signal their owners for food. According to Dr. Karen McComb and her team, purring in the "about to be fed" context has a high-frequency component not ordinarily present. Humans report feeling an urgency to investigate and satisfy the cat's needs, to wit, "feed me". However, this variety of purring seems to be found only in cats in a one-on-one relationship with their caretakers.^[10][11] This "soliciting purr" is different from a cat's normal purring.^[12]

See also

• Kneading

References

External links

• Why do Cats Purr?
• The Felid Purr: A bio-mechanical healing mechanism

Examples of a purring cheetah and a purring serval can be heard on:

• Robert Eklund's Ingressive Speech website
• Robert Eklund's Wildlife page