Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
Some of mine do it when they are kneading on me or when I brush (groom) them or just stroke the sides of their mouth. Sometimes they drool so much that they start making this smacking sound...lol!