Why do cats purr and what causes it?
Most experienced “cat wranglers” now know that cats don’t purr only when they are content and happy. They also purr during tense or traumatic moments. When suddenly and violently injured, even at moments near death, a cat will often purr. One study determined that purring involves activation of nerves within the voice box. These nerve signals cause vibration of the vocal cords while the diaphragm serves as a piston pump, pushing air in and out of the vibrating cords, thus creating a musical hum. Veterinarian Neils C. Pederson, author of Feline Husbandry, believes that purring is initiated from within the central nervous system and is a voluntary act. In other words, cats purr only when they want to. The other theory is that the sound comes more from vibrating blood vessels than in the voicebox itself.
