|MadSci Network: Zoology|
No one knows, really, how cats purr. Although you are correct, it is believed to be the vibration of blood vessels rather than something vibrating in the cat's larynx. Cats are all allegedly supposed to have the ability to purr, but I am not sure there is evidence that "big" cats have been observed "purring" (but see leopard, below). Cats also purr not only when they are allegedly content, but perhaps during any time of sensory stimulation or stress (for instance, cats purr while giving birth, something I certainly wouldn't have done the two times I gave birth!). The purring mechanism has been attributed qualities of communication (see below), "oscillatory regulation" (cats can continue to purr even when the nerves to the area are experimentally severed) and sensory interaction with the environment. According to the Britannica Encyclopedia:
'While lions and other big cats roar, domestic cats and other Felis species purr. Purring has been described as a low, continuous, rattling hum and often is interpreted as an expression of pleasure or contentment. Purring also occurs in cats that are injured and in pain, however, so that this vocalization can be seen as the cat's 'mantra'--that is, as a relaxing, self-comforting sound and a friendly mood-conveying signal...
The calls of the leopard vary and include a series of harsh coughs, throaty growls, and deep, purring sounds...'
There are also about a zillion cat links on the internet, where there are daily
chat groups with verterinarians and lay persons, wherein the lastest "purr
science breakthroughs" may be discussed. Try this link:
This link will ultimately try to sell you stuff, but part of their text reads:
'How does a Cat purr?'
No one really knows. Purring is a mystery. No one can definitively say which mechanisms in a cat create a Purr. The Purr, so familiar to Cat lovers' ears, is created, according to some feline experts, by the vibration of a Cat's vocal cords when it inhales and exhales. Yet, others who have studied felines believe Purring is a vibration caused by blood passing through a large vein in a Cat's chest.
Beyond the mystery, what attracts humans to a Purring Cat?
Initially born blind and deaf, what unites the newborn kitten with the Mother Cat is...the Inner Purr. During nursing, both kitten and Mother Purr in a symphony of physical and psychological Contentment. The Inner Purr connects a Cat to its Mother...to its owner...to the world around it...and to its own purr-fect Contentment....
They then proceed to try to sell you tapes of purring or something for self-enrichment (hey! You can get anything you want on the internet!), but from this site, you can link to several other cat sites.
'Purring' has also been attributed to other mammals, such as civets and other mustelids, but I don't think 'purr' has a legitimate scientific designation.
Right now, in other words, we don't know, but these are our best guesses!
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