Why Cats Purr and How They Do It

purring kitten

Is there a better sound than a cat purring? For cat lovers, there surely isn't. Cats purr when they feel happy and this good feeling is spread to their owner. But did you know that cats also purr when injured or stressed? Read on to find out why cats purr and how they make this continuous, deep humming sound.

Purring is like smiling

A smile shows happiness and well-being. It encourages social interaction by generating an open and trusting atmosphere and creates warmth and a good mood for both the smiler and the receiver. Purring works in a very similar way. Our beloved feline friends purr when they are stroked, when they snooze in their owner’s bed with them, when they are fed by their mother, when they get their food, when they meet another cat and when they clean themselves. In short, cats purr when they are content. That said, purring is much more than just an indication of happiness. At times, purring can also express feelings of fear, stress, pain and hunger. So, what is the aim of this humming noise in these situations?

Cats have good reason for purring

Purring has a calming effect, not just for humans but also for the cat itself. Cats are capable of soothing themselves in a way that no other animal can. Mother cats purr while giving birth to regulate the pain and when the kittens are born, still blind and deaf, they find their way to their mother’s teat purring, which also brings them comfort. Dominant cats purr to show an inferior cat that is tense that it can calm down and some wild cats purr when frightened by a threat to help calm and control themselves. In addition to purring pleasantly for comfort, there is also purring for easing pain, reassurance and self-control. Cats also use purring as a means of communication. Kittens ask each other to play by purring to each other and domestic cats ask their owner to be stroked, for attention or for food by purring. The reasons why cats purr in a certain situation can differ:

  • To express comfort
  • To regulate stress
  • To calm themselves or others
  • To relieve pain
  • To communicate with one another or with humans
cat cuddles with ginger cat

Purring aids relaxation and promotes good health

However different the situation may be, the aim of relaxation and comfort remains the same. Purring is able to fulfil this aim thanks to a biological process. This deep, continuous hum releases serotonin in the cat’s body. Serotonin, also known as the happy hormone, is an important neurotransmitter which has a positive impact on various neurological processes, such as emotions, the reward system, moods, consciousness and feeling pain. As vets, researchers and behavioural scientists have discovered, this isn’t the only positive effect that purring has on a cat’s health. Recent studies have shown that purring has further medical benefits when a cat is injured, ill or in pain.

Whole body vibration for healing

Purring causes the cat’s whole body to vibrate. These vibrations stimulate the muscles and so support bone growth, as discovered by Prof. Dr. Leo Brunnberg from the Clinic for Small Animals at the Free University of Berlin during his research into the morphology of cats. This startling result revealing this self-healing mechanism also explains why cats break bones relatively rarely and when it does happen, they tend to heal very quickly.

In principle, purring works just like whole body vibration exercise which doctors and physiotherapists have been prescribing for a few years to athletes or patients with muscle or bone problems. Vibrations with a frequency of between 15 and 60 Hertz are sent through the body with the aim of strengthening the skeleton and the muscles around it. Many doctors also consider this kind of vibration therapy meaningful and useful for patients with osteoporosis because, as purring cats know, the continuous mechanic vibrations that are produced by purring improve the stability and thickness of the bones.

The positive effects for cat owners

We can learn a lot from the self-healing effect of purring and benefit from it ourselves. That doesn’t only go for those with muscle tension or bone or joint problems. What’s more, the soothing purring sound releases happy hormones in our bodies and has the same calming and relaxing effect on us humans as it does for our feline friends. Having a purring cat on your lap or in your bed doesn’t only help you feel happier, it also simultaneously lowers blood pressure, reduces symptoms of stress and is a remedy for insomnia.

How do cats make that purring sound?

The effect of purring is undoubtedly noteworthy, but how do cats actually produce this continuous hum? How do they make their whole body vibrate without straining or audibly drawing breath? Many scientists have pondered this question but to this day the mystery hasn’t fully been solved. Many researchers believe that the sound comes from the laryngeal muscles which open and close the glottis, while others believe that the hard, inflexible tongue bone which connects the tongue to the cranial bone is principally responsible for this steady humming. Others still suspect that flaps of skin near the vocal cords (false vocal cords) or even the main artery play a role in making this noise. At least the latter seems to have been disproved nowadays. According to current research, purring involves a resonance effect which probably occurs when the vocal cords are struck.

Why cats purr

Only cats can really purr

In fact, cats can purr while breathing in and out and this differentiates them in a certain way from most mammals who, like humans, can only produce sounds when breathing out. Purring is reserved only for cats. Besides domestic cats, lynxes, ocelots, pumas and cheetahs can all purr, whereas large cats like tigers, leopards or lions sometimes make short purring sounds when breathing out but they can’t do so continuously.

In any case, accurate tests have shown that the steady purring that cats do while simultaneously breathing in differs a little to that produced whilst breathing out. When breathing in, the purring sound has a frequency of 27-40 Hertz, so it is shorter and louder, while purring while breathing out has a frequency of 16-28 Hertz and is somewhat quieter and longer. That said, these subtle nuances are undetectable to the human ear. We hear our cats’ purrs as a long, constant hum which these creatures can effortlessly hold for several minutes.

Purring must be learned

Although it may sound easy, purring actually requires lots of physical effort. Even though kittens who are only a few hours old can purr while searching for their mother's milk, it takes a while for the babies to sound just like mum and dad. It is worth the effort for the growing kittens because purring is ultimately extremely beneficial for the mind, as well as for the muscles and the bones. In contrast to meowing, which cats use exclusively to communicate with us humans, cats purr whether they are around humans or not. A lynx on its own purrs just the same as a domestic family cat.

Has your cat already purred today?

How nice it is that we humans can benefit from our cats’ purring despite our mental and physical inability to produce such a sound ourselves that has this relaxing effect. The calming effect of purring is contagious for us humans as well as for other cats. Having a purring cat next to us on the sofa lowers our blood pressure, we become calmer and more relaxed and leave all daily stress behind us for a moment.

So, what are you waiting for? Go and get your cat, put it on your lap and start stroking! You will sense the purring conjuring a smile to your lips as the stresses of the day fall away.

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