If you're a cat lover, purring probably sounds pleasant, cozy and inviting. While purring might elicit a relaxed response in listeners, mystery surrounds human understanding of the vocalization. Felines generally purr when they're feeling happy and calm, although important exceptions exist.
Purring and Happy Campers
Cats frequently purr when they feel satisfied, relaxed, calm and at ease. Most felines share the action of purring, and big cats in the wild are no exception. Some older felines even purr when they wish to initiate playtime with fellow cats. Purring in that case indicates affability. If your cat purrs when you pet her, she could be expressing that she appreciates the close physical contact.
Mama Cats and Kittens
Researchers believe that mother cats rely on purring as a means to provide comfort to their young and helpless kittens and to bond with them. The little guys often return the favor, too. When kittens are merely hours old, they start purring while their mothers nurture them through nursing. When kittens purr to mom, they could be reassuring her and letting her know that they're just fine.
Purring, Stress and Fear
Cats may also purr when they're in frightening, stressful and anxiety-inducing circumstances. Caregivers report that cats make the familiar low, continuous vibrating sound when they are close to dying or suffering from illnesses or injuries. A scared feline might purr as a way of soothing herself amid uncertainty.
Other Feline Vocalizations
Purring is the most common feline vocalization. Other common feline vocalizations include meowing, hissing and growling. Cats frequently meow when they seek acknowledgement from the people in their lives for playtime, petting and treats. They frequently hiss when they're in intimidating situations. If you adopt a second cat, your original feline might hiss because she's upset that the newbie is invading "her" perceived territory.
Growling often signals that a cat is in a threatening situation and is perhaps even about to become physically aggressive with claws or teeth. The vocalization can also signify irritation.