Why do cats purr?
Short answer
A cat’s purr is produced by tissues in the larynx vibrating as air moves through it. Cats use purring in interactions with other cats and people, but the sound does not always express the same feeling.
How is the sound made?
As a cat breathes in and out, tissues in the larynx, including the vocal folds, vibrate and produce a low, repeated sound. A purr can continue during both inhalation and exhalation.
In a 2023 experiment, researchers passed air through larynges removed from domestic cats and produced low vibrations in the purring range without neural signals. The finding adds a new question to the explanation that purring depends only on the brain repeatedly activating laryngeal muscles. It does not, by itself, explain how a living cat starts and controls a purr; that mechanism is still being studied.
When do cats purr?
Cats purr in several situations, including while relaxing near familiar people, greeting other cats, and nursing. Research has also found that a food-request purr can include a higher-pitched sound that people hear as more urgent than an ordinary purr.
Does purring always mean a cat is happy?
No. Cats may also purr when they are in pain. The sound alone cannot tell us that a cat feels safe or is healthy. Its posture, ears, tail, appetite, and behavior compared with its usual pattern all help provide context.
Purring is thought to serve more than one role, including maintaining contact with other cats or people. Researchers have not established one explanation that applies to every cat and every situation.