How and why do cats purr

01:00 Mon 05th Mar 2001 |

How and why do cats purr, asked Cardiac

Thanks to DrPig for this answer.

The AnswerBank investigates further.

Q. How do cats produce a purring noise

A. Experiments have shown that purring is a reflex, originating from the central system, and not a voluntary act. It is caused by rapid, rhythmic pressure changes in the windpipe, which are superimposed on normal breathing.

The stimulation of muscles in the larynx and diaphragm that control the widening and narrowing of the opening between the vocal cords causes the change in pressure. As air passes through the rapidly opening and closing valve it creates a purring sound and vibrating chest.

The muscles work both during inhalation and exhalation, creating the impression that cats purr continuously

Q. Why do cats purr

A. Most people assume that cats purr because they're content, but this is only partially true. Purring also occurs when cats are in labour, frightened and ill. A veterinarian sometimes sees cats that purr when they are near death.

Although not completely understood, explanations for why both contented and distressed cats purr range from the desire to communicate with others to a way of reassuring themselves.

Q. Why do kittens and their mothers purr

A. A popular theory is that a purring mother can communicate with newborn kittens that are deaf or blind. Kittens learn to purr soon after birth and so their mother can feel them against her body without having to move around looking for them.

From an evolutionary point of view, communicating through the vibrations of purring, instead of louder meowing may have stopped predators finding the den of new born kittens and their nursing mother.

Q. Why do frightened and ill cats purr

A. As to why frightened or ill cats purr, behaviourists claim that it may have a reassuring affect, similar to when some humans sing or hum to reassure themselves.

Another possible explanation is that frightened cats purr to communicate submissiveness. Wild cats are known to purr when threatened, maybe because they're signalling that they're not about the attack.

Q. Why do cats purr with humans

A. Other than the obvious contentment theory, it may indicate that they regard us as their mother, or as we're a different and larger species, that they're submitting to us.

Q. Is it just pet cats that purr

A. No, some wild cats like pumas and mountain lions and even raccoons are all able to purr.

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by Lisa Cardy

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