The uncertain science of purring

Cat owners will argue the incomparable joy of snuggling with a purring pet. Cat owners will argue the incomparable joy of snuggling with a purring pet.

Sharing my home with both a dog and a cat, I’d be hard-pressed to say which one I prefer to keep as company. They bring such different kinds of joy, and feel like two halves of a lovely whole. But my cat does have one clear advantage that no dog can match. She can purr. Is there anything more comforting than the gentle thrum of a contented cat atop your chest while you lie down for a midday nap? In that moment, it’s as if the universe has singled you out to be deserving of the deepest kind of peace.

We should feel lucky to enjoy this unique feline trait, because it is not universal to cats as a whole. Most of the larger cats such as lions and tigers have no ability to purr, having apparently exchanged it for the privilege of roaring instead. It just turns out that the felines that eventually came to live with humans were of the purring persuasion.

Despite several millennia of domestication, we still don’t know exactly how cats do it. They don’t appear to have any specialized anatomical equipment that we don’t. It is primarily thought that their vocal folds are induced to vibrate under direction of a central oscillator in their brain, although it seems that the diaphragm and rib muscles may play some role as well. Whatever the mechanism might be, it is capable of engaging on both inspiration and expiration, allowing cats to purr essentially nonstop for extended periods of time.

The purpose of purring seems clear at first glance, communicating that a cat is pleased with the current state of things. That can certainly be true, but doesn’t tell the whole story. Cats will likewise purr under adverse circumstances, when they are severely ill or afraid, or even near death. That may seem counterintuitive, but it makes sense when interpreted as a peace sign. A purring cat, for better or worse, is letting you know that it doesn’t intend to fight.

Under normal circumstances, you can presume purring to be a good thing. As a veterinarian, I’m generally glad to have a cat purr its way through a visit, except for one problem. That otherwise endearing rumble makes it all but impossible to hear their heart with a stethoscope. If you’ve ever seen a vet carry your cat over to a running faucet in the middle of an exam, this is the reason. The water gives them just enough of a fright to halt the purring for a few moments, allowing a proper listen. Happily, most cats get back to it once the tap is off again.

Beyond communication, there are a few bits of evidence that suggest purring may come with unexpected health perks. Contact with purring cats is known to reduce stress and blood pressure in people, and it is thought that cats might be able to soothe themselves in a similar manner. Some have even suggested that the particular frequency of feline purring is able to stimulate physical healing, although this may be more fancy than fact.

In the end, I suppose it doesn’t matter. Purring is one of the most delightful benefits of living with a cat–one that I intend to go enjoy as soon as I finish typing this sentence.

Dr. Mike Fietz is a small-animal veterinarian at Georgetown Veterinary Hospital. He received his veterinary degree from Cornell University in 2003 and has lived in Charlottesville since.

Ready to adopt from the SPCA!


Bob (top left)

Everyone needs a Bob—that guy who sticks by your side. Bob doesn’t let his one bad eye hold him back, either; he’s the first one to greet folks who come to visit him. He’s a happy cat who is most content when he has a best friend—human or feline—to hang out with.

Robin (top right)

Sweet, sleek, soft and jet black, Robin is one special girl. She loves to run and play, and sit up high where she can check out all the action. This affectionate and active gal would be happiest in a home with other feline friends or a human who is home during the day.

Uma (bottom left) 

Uma was adopted as a kitten from the CASPCA three years ago, but was returned when her family moved to a place that did not allow cats. All the activity at the shelter has been a little overwhelming for this mellow girl, but she quickly warms up to friendly new people.

Buffy (black-and-white male) and Buster (gray-and-white male) 

Buffy is the small, agile, outgoing one, while Buster is a bit more cautious. These disparate bros are a bonded pair and need to go to a home together, where they could potentially be the stars of their own buddy-cat YouTube series.

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