Why do cats purr?

How to read it

Purring starts in kittenhood. Cats Protection says kittens can purr almost from birth and purr mostly while suckling, to tell their mother all is well. International Cat Care describes the mother purring quietly to her kittens when she returns to the den, and the kittens suckling and purring back; it also says it isn’t exactly clear how cats make the sound. For a purr that means a happy cat, Cats Protection gives these signs: relaxed ears and whiskers, small pupils, and the tail up or curled round the body.

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The purr that asks for food

In 2009 Karen McComb and colleagues at the University of Sussex reported in Current Biology that cats embed a cry in the low purr when they are asking for food. In the study, the purrs of 10 cats were played to 50 people, not all of them cat owners. They judged the purrs recorded while the cats were seeking food as more urgent and less pleasant, and with the cry taken out, the same purrs sounded less urgent (ABC Science’s report of the study). The study found the purr used most in homes where the cat has one-to-one contact with its owner, and McComb said it works best when the cat has the owner’s undivided attention, particularly in the bedroom in the morning. Cats Protection’s behaviour guide describes this solicitation purr as more urgent than an ordinary purr and hard for owners to ignore.

Purring when stressed, unwell or in pain

International Cat Care says cats also purr when they are sick or injured, and gives two theories: that a sick cat’s purr has a different frequency and may help it heal, or that the cat is soothing itself when it feels most vulnerable. Cats Protection says the low-frequency vibration is suspected of promoting bone and tissue growth. Neither charity puts this forward as proven.

Cats Protection says cats purr in stressful situations too, such as a visit to the vet. Flat or sideways ears, wide eyes with large pupils and whiskers pointing forwards or down suggest a stressed cat rather than a content one. Its behaviour guide says a cat in pain tends to purr more rapidly than the slow, rhythmic purr of a content cat, but that the two sound very alike, so the rest of the cat’s body language and the context count for more. A cat that purrs much more than usual, or in new situations, or that suddenly stops or starts purring, may be unhappy or unwell (Cats Protection). If this is new or comes with other changes, check with your vet.

Purring while being stroked

Loud purring while a cat is stroked or played with shows that it is stimulated, often with Why do cats make biscuits? (kneading), drooling and licking, according to Cats Protection. It adds that a cat that becomes overstimulated may suddenly grab and bite: see why cats bite.

Which cats purr

Not every cat purrs. Cats Protection says some communicate in other ways, with Cat meows and sounds or body language. On the wild cats, the two charities differ. Cats Protection says small cats such as bobcats, lynxes, cheetahs and cougars purr, while lions and tigers can’t, because the hyoid bone in their throat is only partly rigid. International Cat Care says many of the larger members of the cat family can generate the vibration.