The question is really about overstimulating a cat when playing with him or her. Therefore the statement in the title is not entirely accurate because overstimulation during play does not necessarily mean that the cat is angry. It just means that they are overstimulated and they start to play too hard and too rough. The statement really should be, ‘how to tell if a cat has been overstimulated and/or is becoming irritated with your attentions’.
And you can tell if this has occurred in various ways but they can be quite subtle. The general demeanour of the cat can give a clue that they are going to start playing too rough and if you are using your hands you might get hurt. The experts say that a cat’s eyes become dilated, their ears turn back and their tail twitches. Or they give a warning swipe. Of these four, ears being turned back is probably my favourite. And the eyes become more prominent. This is in preparation for a fight as the ears are being folded back to protect them.
It is said that kittens learn the limitations of play – and that they should not bite too hard – during the early weeks when they play with their siblings. It seems that some cats don’t learn which means they end up learning with their owner, which in turn can lead to the owner being scratched or bitten.
I think the problem being discussed only becomes an issue if a person is using their hands to play with their cat, which is instinctive. And petting can lead to play that goes wrong. However, if you play using a cat toy such as a tease (feather on a stick), the cat will not become overstimulated provided the tease is being used in the usual way. Common sense tells us that if a person prods and pokes their cat with a cat tease they will become irritated and provoked into defensive aggression. Once again, it is about the human behaving moderately and with sensitivity towards their cat’s emotions. It’s about being alert to those emotions.
A cat playing with a tease will become disinterested after a while but not irritated. It is when a person over-pets their cat or plays rough using their hands that they can end up provoking her into aggressiveness which includes biting. This knowledge helps the cat guardian to avoid these situations by taking proactive action. This precludes the need to detect when a cat is becoming irritated.
And, if I am correct, the statement in the title would normally be irrelevant if you play with your cat using a cat tease of some sort. The best cat owners are constantly making mental notes about how to improve their relationship with their cat. They do this by understanding how their cat behaves in observing their individual traits, likes and dislikes. Armed with this understanding a good cat owner never takes their cat to the point where they are provoked into becoming angry. There is no need to distinguish between their cat playing or becoming angry.