Why Do Cats Purr and How Do They Do It?

If you have a cat you will be well aware that they purr when they are happy and content, but you may not know that cats also purr for a number of other reasons, these include:

  • To communicate with their kittens – Kittens are blind and deaf at birth but can find their way to their mothers milk through her purring vibrations.
  • To self sooth – The rhythmic vibrations help to sooth a cat after they have experienced something which may have caused them stress.
  • To help them heal – The low frequency of a cats purr occurs within a range that is known to promote healing of muscles and bones!

When do Cats Start Purring?

Purring is a natural reflex for cats and is something which they will start doing as early as 2 days old. It is very important that kittens start purring at this stage because at this stage they can’t yet meow so purring is the only way they can communicate.

a small black and white kitten sat on a wooden piece of furniture

Surprisingly in the wild this is an advantage because high pitched meows will easily be picked up on by predatory animals, the low vibration of a purr will go u unnoticed meaning the defenseless kittens are far less likely to draw attention to themselves.

At birth kittens are also both deaf and blind so they can neither hear nor see their mother, yet they can feel her vibrations as she purrs and can use these vibrations to find their way to their first drink of milk from their mother.

Why Do Cats Often Purr and Then Bite You?

If you own a cat you have probably ‘enjoyed’ the experience of absentmindedly stroking your cat while listening to them happily purr away before suddenly and without warning being attacked by their sharp claws and teeth.

There are a number of reasons why this seemingly irrational behavior may be occurring:

  • Over-stimulation. It is common for cats to become overstimulated after a certain amount of stroking, they often reach a point where they no longer want any more stroking so if you miss the warnings signs you will suddenly find yourself on the end of an unprovoked attack. Signs to watch out for that indicate that your cat may have had enough of being stroked are: Flattened ears, pupil dilation or staring intently at your hands (seconds before she attacks it!).
  • Territorial Aggression. Cats are very territorial creatures so when someone (either a new animal or human) new comes into their environment it can stress them out. They may purr to help calm themselves down however they may also response to the stress may by suddenly giving this new person or animal a swift bite.
  • Status Induced Aggression. This happens when a cat believes that he or she is equal to you, as a result they often become territorial over areas or pieces of furniture in your home. So if you are stroking them in their favourite chair they may suddenly decide that they don’t want you there anymore and bite you.

Why Do Cats Purr and Knead Things?

Kneading is something which cats learn as young kittens when they knead their mother to help with the release of milk. At this age kittens cannot meow and can only communicate through purrs. So it is likely that cats associate kneading with purring even when they are fully grown (read our article on why cats knead here for more information on this).

Consequently you will often find that a happy and contented cat will purr and knead at the same time.

Purring and Pain, Sickness and Fear

Cats purr at a frequency somewhere between 20-140Hz. This frequency is know to be medically beneficial in the treatment of numerous illnesses. In fact vibrations within the the 25-50Hz frequency range help promote the growth and repair of broken and fractured bones!

In fact the frequencies at which cats purr are also useful for helping with muscle and ligament damage too.

It is no surprise then that if your cat ever experiences any sort of injury they purr with enthusiasm!

a black and white cat sat on a blanket with it's eyes closed

Purring is Also Good For Humans Too

Purring doesn’t just benefit cats it is also proven to be beneficial to humans too!

In fact a purring cat is a great way of lowering your blood pressure; a ten year study conducted by the university of Minnesota found that owning a cat can reduce the risk of heart attacks by up to 40% so this could be the perfect excuse for anyone looking to get a cat (as if an excuse were needed!).

This is believed to be related to the fact that an excess of stress and anxiety correlate directly with high risk of a cardiovascular problem most notably heart attacks. Owning a pet is a proven way of helping reduce stress in your life hence the positive correlation between cat ownership and reduced heart attack risk.

How Do Cats Purr?

Purring is something which only some cats can do, cats that purr include domestic cats as well as bobcats, cheetahs, lynxes, pumas and wildcats. In fact some animals which ar enot even related to cats can also purr too, these include Hyenas, Guinea Pigs and Mongooses.

It is interesting to note that if a cat has the ability to roar then it cannot purr. This is because the muscular structure or around a cat’s larynx is more loose in cats that roar and simply isn’t tight enough to allow purring to happen.

The purr is a unique sound because it occurs continuously when your cat is inhaling and exhaling.

The cats brain send a signal to their laryngeal muscles causing them to vibrate. This then causes the globus (the space between the vocal chords) to act like a valve by opening and closing, thus allowing air to pass by the cat’s voice-box and create the distinctive purring sound.

Not one is certain exactly how purring is initiated, however there are two main theories on how cats initiate purring:

  • It is a voluntary act which the cat initiates via their nervous system.
  • It is an involuntary action which is stimulated by the release of endorphins when your cat experiences pleasure or pain.

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