Why do cats purr?
Cats purr by rapidly twitching the muscles of their voice box as they breathe in and out. They purr when content, but also when stressed, hurt or giving birth.
The purr comes from the larynx. Signals from the brain make the muscles around the vocal cords twitch about 25 to 150 times a second. The vocal cords open and close quickly as air passes through, creating the steady vibration we hear on both the in-breath and the out-breath.
Kittens can purr when they are just a few days old, which helps them communicate with their mother while nursing. Adult cats purr when relaxed or being stroked, but many also purr at the vet, when injured or when giving birth. Scientists think purring can be a way to calm themselves or ask for care.
Can purring help healing?
Some researchers have suggested that the low frequencies of purring might help bones and tissues heal, but this has not been proven. Big cats differ: lions and tigers can roar but cannot purr continuously, while cheetahs, pumas and other smaller wild cats can purr but cannot roar.
Did You Know?
Some cats have a special solicitation purr, which mixes a high-pitched cry into the normal purr. Studies suggest owners find this sound hard to ignore, much like a baby's cry, which helps cats get fed in the morning.