Ever cuddled up to your cat and wondered what causes your favourite little fluff ball to purr its little heart out? Wondering why your dog doesn’t make the same adorable sound?
(This kitten may or may not be purring, but it's adorable. Source: www.pets4homes.co.uk)
The purr originates when the brain sends signals to the laryngeal (voicebox) and diaphragmatic muscles telling them to vibrate. When they vibrate, it causes the space between the vocal chords, known as the glottis, to open and close, like a valve. As the cat breathes in and out, the air hits the vibrating muscles and the glottis (the space between the vocal cords) producing bursts of noise- the purring sound. It works when cats are both inhaling and exhaling and it creates sound between 25 and 150 Hz. Scientists are sure that this is how purring works due to cats with laryngeal paralysis being unable to purr.
So, you’re probably wondering how cats initiate this familiar purring noise. Not all scientists agree on the reasons for this. Purring may be a voluntary act chosen by the cat or due to the release of endorphins when cats experience pleasure or pain. Yes, cats don’t always purr just to show happiness! However, nine times out of ten, if your cat is rolling around on its back while you are petting it, then it most likely is very happy.
Cats may also purr as a sign of them being injured, frightened, sick or even dying. Female cats may also purr when they are delivering their kittens. It has been known that frightened or injured cats may purr to send peaceful signals to other cats to warn them that they are not going to attack. If a cat was dying, it may purr to comfort itself as the purr has also been hypothesised to be a self-healing mechanism that can heal pain. Not only has purring been known to heal pain, but also to repair bones and even heal wounds.
It has been found that the frequency of a cat’s purr has the same frequency that is therapeutic for bone growth, tendon repair and fracture healing. It has been discovered that frequencies of 25 to 50Hz will promote bone growth by 20% and frequencies of 50 to 150 Hz have been known to relieve suffering of chronic and acute pain. There’s an old saying still repeated in some veterinary schools saying “if you put a cat in a room of broken bones, the bones will heal”. The cats’ purr has been compared to the smile. We smile when we are happy, nervous or just trying to be friendly and make someone feel comfortable. This is the same as the purr.
Purring isn’t just good for cats, it is also good for cat owners. Various studies have shown that cats are better at relieving stress and reducing blood pressure than other animals. This is partly because people link purring with calmness and peacefulness.
Not all cats can purr. Cats that can purr can’t roar and cats that can roar can’t purr. Very confusing! This is because the structures around the roaring cat’s larynx aren’t stiff enough to allow purring. Roaring cats actually evolved this way due to their roar being effective when protecting their prides and territory, whereas purring cats are a lot smaller and are in no competition for prey. Purring cats also don’t need to roar to protect their territory as they leave a scent to mark their territory rather than roaring.
So, next time your cat is purring, think about all the good things that both you and your feline friend are getting from it! Reduced stress, self healing and strengthened bones. It’s definitely a win-win situation so try to make your cat purr a little more often.