Every cat lover, upon hearing that familiar low rumble from their pet, has probably wondered why cats purr in the first place.
Zoologists recently ran a series of studies that revealed the real reasons behind this sound we all find so soothing. AdmiGram.com rounds up the most fascinating findings.
Why Do Cats Purr: Scientific Facts
How Does a Cat Actually Make That Sound?
© Paul Hanaoka / Unsplash
The mechanism behind purring puzzled scientists for a long time, mainly because cats don’t have any special organ dedicated to producing it. According to recent research, here’s what’s actually going on.
Electrical impulses fire in the cat’s brain and travel to the muscles surrounding the vocal cords, making them contract rhythmically. This “purr center” sits between the base of the skull and the base of the tongue, near the hyoid bone — the small, delicate bone structure that supports the tongue and larynx.
As those muscles contract, the vocal cords vibrate, and the sound travels out through the cat’s nose and mouth. The vibration is strong enough to spread through the animal’s entire body — so strong that it can be difficult for a vet to hear a cat’s heart and lungs through a stethoscope while it’s purring.
Do Other Cats Purr, or Just Growl?
© Oleg Ivanov / Unsplash
All cats purr, even the wild and famously fierce ones. Purring and growling are produced by entirely different mechanisms. In a 2010 paper, researchers Robert Eklund, Gustav Peters, and Elizabeth Duthie found that cheetahs purr at a frequency of roughly 18.3 to 20.9 Hz, while domestic cats purr somewhat higher, at around 22 to 23 Hz.
A 2011 follow-up study by Eklund and phonetician Susanne Schötz confirmed those earlier findings. The domestic cats in their experiment purred at frequencies ranging from about 21 to 27 Hz, and the study also noted that purring varies noticeably between individual cats in terms of amplitude and duration, even though it stays within a similar general range.
Overall, purring frequency across cats tends to fall somewhere between 20 and 30 Hz. A 2013 paper by Eklund and Peters found that this frequency is essentially independent of age — kittens, young cats, and adults all purr in the same range.
So, Why Do Cats Purr?
© Nora Hutton / Unsplash
Research has confirmed that cats purr most often when they’re being petted and feel safe, and less often while eating. Cats also purr during labor, and kittens can start purring within their first couple of weeks of life. Purring is a form of communication that signals pleasure, or the anticipation of it — not unlike the way we might clap our hands when we’re happy.
Some researchers have found that cats also use purring more strategically — to solicit food from their owner, or simply to get attention. Depending on the context, purring can express:
- Contentment
- Boredom
- A greeting to their owner
- Anxiety
- Gratitude
Other studies suggest that purring triggers the release of endorphins, the body’s natural feel-good chemicals, which may explain its calming and even pain-relieving effects — researchers have documented injured cats purring, possibly as a way of self-soothing.
There’s also a theory, championed by bioacoustics researcher Dr. Elizabeth von Muggenthaler, that the vibration from purring — typically in the 25 to 50 Hz range — may help strengthen a cat’s bones, which take a hit from all those long naps. (Cat owners already know their pets can sleep 16 to 18 hours a day.)
That same frequency range overlaps with vibrations used in some bone-healing therapies, which is why scientists have floated the idea of using “purr-like” vibration at around 25 Hz to help astronauts counteract bone and muscle loss during long stretches in zero gravity.
image on top: Piotr Musioł / Unsplash
