Why Cats Purr

Your cat's purr can mean many different things. Find out what she's trying to tell you.

By Annie Stuart
WebMD Pet Health Feature

Reviewed by Drew Weigner, DVM

The purring cat. It may well be considered the epitome of contentment. But when it comes to purring, there's much more than meets the eye – or ear, in this case. Have cats figured out how to get their needs met through purring? Do cats' purrs have special healing abilities? Although we don't really know the answer to these questions, some studies are starting to shed some light on purring.

The Physiology of Purring

How do they do it? Experts have offered a number of theories over the years. Most now say that purring begins in the brain. A rhythmic, repetitive neural oscillator sends messages to the laryngeal muscles, causing them to twitch at the rate of 25 to 150 vibrations per second (Hz). This causes a sudden separation of the vocal cords, during both inhalation and exhalation – the unique feline vibrato. “Opera singing for cats,” is what animal behaviorist Karen L. Overall, VMD, PhD calls it. But the purr is usually so low-pitched that we tend to feel it as much as hear it.

Housecats Aren't the Only Ones Who Purr

Purring isn't the sole domain of domestic cats. Some wild cats and their near relatives – civets, genets, mongooses – also purr. Even hyenas, guinea pigs, and raccoons can purr. Cats that purr, such as mountain lions and bobcats, can't roar, however. And cats that roar, such as lions and tigers, can't purr. The structures surrounding their voice box (larynx) aren't stiff enough to produce a purr. But it appears these cats evolved the roar for good reason, says Benjamin L. Hart, DVM, PhD – mainly to protect their prides.

“If you're a big cat and you have to move around a lot to get prey, loud roaring plays a huge part in maintaining your territory,” says Hart, distinguished professor emeritus at the University of California, Davis School of Veterinary Medicine. But small cats are loners and don't compete with each other for meals, he says. Their communication doesn't need to be far-reaching. For them, scent marking does the territorial trick (as some unfortunate cat owners quickly learn).