When a cat wants to express contentment or pleasure, it purrs. Purring of a contented cat results in a low vibrating noise. It is a kind of low, continuous rattling hum and has nothing to do with a cat’s real voice. A mother cat purrs when it wants to call her kittens for feeding. At birth the kittens cannot see, hear or smell. So in the initial stages after birth, it is the purring of their mother that helps them to communicate with her. Once the kittens start feeding themselves, the mother stops purring. It implies that purring began as a kind of homing device.
Now the question arises how a cat produces the purr?
Purr is caused by the vibrations in a cat’s vocal cords. When a cat takes air into its lungs, the air passes through the voice-box that contains the vocal cords. If the cat then wants to express its satisfaction about something, it will allow the vocal cords to vibrate as the air passes in and out of the lungs during breathing. When it chooses not to purr, the passing air does not affect the vocal cords and thus doesn’t produce any such sound.
Although there are many other members of the cat family such as lion, tiger, leopard, cougar, jaguar, ocelot and lynx, their throat structure is quite different from a cat and hence they cannot purr. However, they can make other kinds of sound.