Why do cats wag their tails?

Definition: wagging a tail means moving it from left to right horizontally. Cats do this when they are unsure of what to do. It is an indicator of uncertainty which may lead to irritation. Some say tail wagging indicates annoyance. I disagree, unless the irritation leads to annoyance.

Tail wagging in cats reflects an uncertain state of mind. Picture: MikeB

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Tail wagging mirrors the tail's function as a balancing tool. It moves from right to left horizontally when a cat - wild or domestic - needs to correct balance usually when climbing.

The word 'balance' is important because a state of uncertainty is a mentally balanced state. A position between two outcomes. 

So, the tail reflects a state of mind which is between two decisions. When the decision is made the tail stops wagging. Tail up is a friendly greeting. 

You will find that some websites state that when a cat wags her tail, she is annoyed. In short, it is a symptom of annoyance. I think this is probably incorrect but "annoyance" is very close to "uncertainty". I'm arguing that a cat wags her tail when she is uncertain about what to do next as a kind of visual balancing act between making one decision and another. Uncertainty creates a little bit of irritation and irritation is quite close to annoyance and therefore I see an overlap here.

The thing is that dogs wag their tail as a clear signal of happiness and excitement and perhaps a bit of nervousness. This knowledge may misguide us in interpreting domestic cat body language and behaviour.

I am following, and I agree with, the best expert on the planet in respect of domestic cat behaviour. His name is Dr. Desmond Morris. He wrote the world-renowned book CATWATCHING. And he starts off his page about cat tail wagging by stating, "Most people imagine that if a cat wags its tail it must be angry, but this is only a partial truth."

He then goes on to say that "the real answer is that the cat is in a state of conflict". The cat wants to do two things at once and each desire blocks the other. You might see this when your cat wants to go outside but it is raining. His tail may start to wag as he sits behind the cat flap trying to decide to go out. 

He may go out but becomes wet and therefore more uncertain about his decision and so his tail may wag more furiously. He decides to come in again. At that point he's made his mind up and his tail stops wagging. This is because he had resolved his conflict. The mood is not one of anger but of frustration and irritation.

This balancing act between two decisions occurs under a wide range of circumstances. That said, I do not see my cat wagging his tail very often. If he does, it'll be because he is on the lawn behind an object waiting to stalk a pigeon feeding on birdseed. 

He will have to traverse the lawn in his final rush to capture the pigeon. He is uncertain as to whether he can be successful or not. Can he make it to the pigeon before the pigeon flies off? Should he hold back? His mind is in mental conflict and as a consequence he wags his tail by being brushed across the lawn from left to right.