Why cats can bite

Our four-year-old female neutered cat was sitting on my mother-in-law's lap being stroked. After a few minutes, without warning, the cat bit her and jumped off. The cat has never done this with me. Do you know why?

- With DAVID GRANT

This is a relatively common behaviour and there are two main areas to investigate. As with all apparent behavioural problems, a useful starting point is to rule out any sources of pain. This could be dental, arthritic, on skin, or an abdominal problem, for example.