Purring is synonymous with the image of a happy cat but in actual fact, they make the noise in various situations to express a range of emotions. Despite extensive research, no one is exactly sure about all of the reasons why cats purr, although it has been said that since humans are unable to hear a cat’s natural vocal range, the sound could have been developed as a way for cats to communicate with humans. Taking context into account can help us to determine how a cat is feeling and what they might be trying to tell us.
Since cats can purr from just a few days old, many think it is a verbal signal to inform the mother that they are ok and to tell her where they are. They are born deaf and blind, which supports the idea that purring is used as a method of communication. It is also believed to be a way for the mother to bond with her kittens by reassuring her young whilst they nurse, as kittens can purr and nurse simultaneously but are unable to meow and nurse at the same time. The purring then becomes a way for a kitten to communicate with their owner when they are taken to a new home.
There is no conclusive evidence that reveals exactly how the purring sound is generated, but one theory is that the opening and closing of the glottis (the vocal cords and the opening between them) creates pressure, which when built up causes the vocal folds to separate. However, what is known is that it differentiates from other cat vocalisations because the sound is made on both the inhale and exhale, and there is an instantaneous break between breaths. Studies vary widely on the range a cat can purr, although it is thought to be between 20 and 140 Hz. Interestingly, cats aren’t the only animals that can make the noise, as racoons, gorillas and some others are able to purr too.
When a cat purrs in a state of contentment, or if they are relaxed and calm, it equates to a smile. Adult cats also use the sound as a way of signalling to others that they are friendly and approachable.
Despite this, cats have been known to purr when injured, in pain or after suffering some form of trauma. Many experts are unanimous in agreeing the frequency of the sound can have restorative and healing effects. The low frequency of vibrations produced by the purring are thought to aid in healing bones, wounds, tendons and muscles, whilst also being capable of reducing pain, decreasing swelling and helping with breathing. As such, it is thought the purr could have evolved over time as a survival tactic, because the faster and more effectively the cat can heal, the greater their chance of surviving. Other more recent theories link purring to the release of endorphins, as it is thought this can soothe an ill cat.
It is believed that cats can emit different purrs depending on circumstance, and humans are able to recognise the subtle discrepancies between them. For instance, a cat’s purr is said to sound different when they are hungry compared to when they aren’t. Cats usually purr when they want something and are trying to tell their owner, which scientists have compared to the cry of a human baby, and is referred to as a solicitation purr. They tend to combine the purring with a crying or meowing sound, as it is thought humans are more likely to respond to this because of their instinct to assist someone or something in distress. Some studies also suggest cats purr when they want and receive attention.
Giving birth, being close to death and visiting the vet are other instances cats have been known to purr. Although scientists are still not really sure why they exhibit the behaviour in stressful situations, it may be a cat’s attempt to self-soothe. They also purr when nervous, and some have likened it to the human response of smiling in nervous situations when trying to comfort themselves. However, this hasn’t been confirmed as definite.
Additionally, a cat’s purr is thought to be beneficial to humans by lowering blood pressure and reducing stress, as well as cutting down the effects of dyspnoea, or breathing difficulty, in both cats and their human counterparts. The apparent healing properties a cat’s purr possesses have been thought to benefit humans in similar ways to how they benefit themselves.
If your cat begins to purr, don’t take it for granted that they are content. They may be attempting to communicate their discomfort, pain or injury to you, or trying to de-stress in the midst of a difficult situation. Ensure you take notice when your cat purrs, as it could be regarding something important.