The surprising truth about why cats purr.
A purring cat sounds like the picture of contentment – and often is. But cats also purr at the vet, when they are frightened, when they are in labour and even when they are badly injured. The purr turns out to be less a mood announcement than a built-in instrument the cat uses for several […]
A purring cat sounds like the picture of contentment – and often is. But cats also purr at the vet, when they are frightened, when they are in labour and even when they are badly injured. The purr turns out to be less a mood announcement than a built-in instrument the cat uses for several different jobs.
A sound made by muscle, not just voice
The purr is produced in the larynx. Signals from the brain drive the laryngeal muscles to twitch rapidly, moving the vocal cords apart and together as the cat breathes in and out. Because it happens on both halves of the breath, the sound can run almost continuously, at frequencies roughly between 25 and 150 hertz – low enough to feel as a vibration when a cat sits on your lap.
The first map a kitten ever gets
Kittens are born with their eyes closed and limited hearing, but they can feel vibration. A mother cat purrs during and after birth, and her kittens use that vibration as a homing signal to find her and nurse in their first days. The purr starts as a map before it is anything else.
Contentment, comfort – and a request with a cry inside it
Cats purr when relaxed, but the stress cases suggest a self-calming role too: an animal that purrs when hurt may be soothing itself. Researchers have also identified a ‘solicitation purr’ used around people at feeding time, which embeds a higher-frequency, cry-like component inside the low rumble – a sound humans find hard to ignore. And there is a long-standing hypothesis, still a hypothesis rather than a proven treatment, that the purr’s frequency range overlaps frequencies studied in connection with bone and tissue health, which is one proposed reason cats recover from falls and injuries as well as they do.
Purr or roar – not both
The anatomy splits the cat family. Cats that purr continuously, like domestic cats and cheetahs, cannot roar; the big cats that roar, like lions and tigers, have a more flexible throat structure and cannot sustain a true purr the same way. Your cat chose the rumble.
Sources
- Encyclopaedia Britannica: Why Do Cats Purr?
- Smithsonian Magazine: Why Do Cats Purr?