Why do cats purr? Humans tend to think that purring is a sign of happiness in a cat – and indeed it can be – but there are other reasons why our feline friends produce this particular vocalisation.
Purring is a habit that develops very early in a cat’s life, while suckling from its mother, so clearly it is not a sound that is directed solely at humans. Cat owners will be well aware that a cat can produce more than one kind of purr, just as they have a whole repertoire of meows, chirps, growls, spits and other sounds.
The purr that is produced during suckling, is quite different in quality to the purr that you will hear when your cat is sprawling across your lap being stroked. Analysis of the sound has shown when a cat is asking for food, whether from its mother or a human – the purr contains a high-pitched note that is similar in frequency to a cry (though not as loud). It may have something of the effect of the cry of a newborn, which affects the hormonal state of female mammals and elicits a care-giving response.
When a cat is being petted or is snuggled up to its owner on the sofa, the purr it produces is much more soporific and generally soothing, and acoustic analysis shows that the “cry” component is missing.
Adult cats will often purr when they are close to or in physical contact with another cat, engaging in grooming for example. They will also do it when they play with an inanimate object, or while eating, which can be at a time when they are alone. However, the most usual time for purring is in company, and it can be the care soliciting sound, asking to be fed or stroked, or an indication of social pleasure.
The darker side
Strangely, vets also report that cats will purr when they are in great pain or just before death. This seems to be illogical if it is a sound relating to pleasure, but in fact, it could be that the cat is asking for help.