No one knows for sure why a domestic cat purrs, but many people interpret the sound as one of contentment. Most scientists agree that the larynx (voice box), laryngeal muscles, and a neural oscillator are involved.
Kittens learn how to purr when they are a couple of days old. Veterinarians suggest that this purring tells ‘Mom’ that “I am okay” and that “I am here.” It also indicates a bonding mechanism between kitten and mother. As the kitten grows into adulthood, purring continues. Many suggest a cat purrs from contentment and pleasure. But a cat also purrs when it is injured and in pain, so it’s been suggested that the purr, with its low frequency vibrations, is a “natural healing mechanism. Purring may be linked to the strengthening and repairing of bones, relief of pain, and wound healing.
Purring is a unique vocal feature in the domestic cat. However, other feline species such as Bobcats, Cheetahs, Eurasian Lynx, Pumas, and Wild Cats also purr. Although some big cats like lions exhibit a purr-like sound, studies show that Lions, Leopards, Jaguars, Tigers, Snow Leopards, and Clouded Leopards do not exhibit true purring. What makes the purr distinctive from other cat vocalizations is that it is produced during the entire respiratory cycle (inhaling and exhaling).
There is an absence of purring in a cat with laryngeal paralysis. The laryngeal muscles are responsible for the opening and closing of the glottis (space between the vocal chords), which results in a separation of the vocal chords, and thus the purr sound.
Other vocalizations such as the “meow” are limited to the expiration of the breath.