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
without interrupting the purring sound. (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, elephants (while eating) & gorillas (while eating) are also known to 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
, causing air vibrations 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 (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.
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.
Reasons for purring
Whatever the purpose of purring by cats, it is obviously not to have an effect on humans. It is likely that purring is used for communications between cats, not to 'talk' to humans. Nonetheless, humans have persisted in offering explanations such as these.
Because cats often purr when being petted, or when relaxed, 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. Also, domestic cats have been often reported to purr when injured, sick, in pain or dying. Purring may also be a signaling mechanism between mother cats and nursing kittens.
- 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.