Why do cats purr?

Purring isn’t just a sign of happiness — cats also purr when they’re anxious, injured, or even giving birth. Researchers believe the vibration frequency of a purr (usually between 25–150 Hz) may actually help heal bones and reduce pain, functioning almost like a built-in recovery mechanism. So a purring cat might be content, or it might be self-soothing through something stressful.