The Science of Purring

Science has progressed to the point that we know how cats purr. In house cats, purrs are produced by vibrations of folds in the larynx. This was difficult to determine, as cats tend to stop purring when examined by a scientist, and cats that are restrained or unconscious do not purr. Such research is much more difficult for those studying lions and tigers.
But the details of who can purr and who can’t is not so simple. In a review of purring in cats, G. Peters tabulated that 20 of 36 species of cat have been said to purr, including lions, leopards, and other big cats. (As for the other 16, Peters wrote, there is not yet enough information to know whether they purr or not.) The question is whether the noises made by the big cats within the genus Panthera are true purrs — a sound created by moving air modulated by vocal folds as in smaller cats — or are actually different noises that only vaguely sound like purrs.  The “rolling, gurgling growl” female big cats emit while in heat may be a kind of purr, or it may be something else entirely. And, Peters says, big cats might have the ability to purr but simply don’t. Somebody is going to have to make careful, close-up acoustic recordings of these purr-like sounds to better understand how they correspond to purrs of smaller cats, although I imagine finding volunteers for taping tigers in heat is a difficult task.

How much more frightening would it be to try looking down the throat of an actively purring big cat? Still, there is some research on the subject.
In 1989 anatomist M.H. Hast published a study on the larynges of big cats and found that lions, tigers, jaguars, and leopards had “a large pad of fibro-elastic tissue” near the forward portion of their paired vocal folds. (The exception was the snow leopard, a big cat that has never been heard to roar.) These expansions, in addition to the ability of these cats to lower the larynx thanks to the flexibility of the hyoid bone and its attachments, allowed lions, tigers, leopards, and jaguars to better transfer the energy required to make loud, low-frequency roars.

So it is possible that the biological differences that allows some big cats to roar has left them unable to purr. Read more about purr research at Laelaps. Link

(Image credit: Brian Switek)

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