Q: Why do my cat’s teeth ‘chatter’ when he looks out of the window?

Answer: Cats who are near to prey but unable to catch it (e.g. birds out of reach on a branch or seen through a window) often shown ‘teeth chattering’. The corners of the mouth are pulled back and the jaws come together with a rhythmic smacking noise. The same behavior can be seen in cats chasing frustratingly elusive substitute prey objects, such as soap bubbles or rays of sunlight. It should be interpreted as a sigh of frustration.