pain

It can be difficult to identify pain in cats. Yowling and meowing are not necessarily the best ways to assess pain, because, in fact, most cats experiencing pain go off their food, may be quieter or more aggressive than usual, may have disrupted sleep patterns or spend more time away from the owner. Cats are very good at masking signs of illness and pain and it can be harder to treat an illness if it is more advanced by the time it is recognised.

SOURCE: cats.org.uk