Why cats purr, and why it isn't always happiness

Purring is the sound most people link with a happy cat, and most of the time that is right. But a purr is not a simple 'I'm happy' switch.

How cats purr

The purr comes from muscles in the larynx twitching rapidly as the cat breathes in and out, which is why a purr can run for minutes without a break. The rumble is low, typically somewhere around 25 to 150 vibrations per second.

The contented purr

A cat curled on your lap, eyes half closed and body loose, purring as you stroke it, is content. Kittens purr while nursing, and many adult cats purr to ask for food or attention.

The worried purr

Cats also purr when they are frightened, in pain, giving birth or seriously ill; one idea is that purring helps them soothe themselves. If a cat is purring while hiding, not eating or holding itself stiffly, treat the purr as a warning sign rather than a thank you, and talk to a vet.

A quick check

Ask three questions. Is the body relaxed? Is the cat eating and using the litter box as usual? Does it come to you, or hide? If the answers point to relaxed and normal, enjoy the purr. If not, it is worth calling your vet sooner rather than later.