Why Cats "Wag" Their Tails
One of your cat's most beautiful features is her tail. Long and graceful, it curls around her body softly when she sleeps or sits, or floats behind her when she walks. The tail is another marvelous part of your cat's anatomy, and she uses it in various ways.
About 10 percent of your cat's bones are in the tail – up to 20 vertebrae. These small bones are encased in muscles that allow finely graded movements, such as elevation of the tail its movement from side to side, and the lowering or curving of it around the body. Interestingly, the domestic cat is the only feline species able to hold the tail vertically while walking.
Many animals, including cats, use their tails to communicate with other animals. For example, the position of a wolf's tail can tell another wolf what mood he's in. A confident wolf holds her tail up high, whereas a frightened wolf holds her tail between her legs; a white-tailed deer shows alarm by flicking her tail; horses flatten their tails between their legs when frightened and lash them back and forth when they are irritated or annoyed.
Likewise, your cat's tail is a barometer of her feelings. A high vertical tail is a sign of happiness. If that high tail quivers from the base up, it indicates that she is really happy and excited. If that tail goes in the opposite direction and is tucked between the legs, your cat is afraid or trying to avoid a confrontation.
A cat's wagging tail means various things, each wag is slightly different. Broad wagging, even whopping, indicates annoyance. Your kitty may be curled up next to you enjoying a nice petting session when suddenly she decides that she's has enough. She will signal this to you by swishing her tail up and down or its tip from side-to-side. If you miss the signal, she may bat at you with her paw, or worse, to make her point.
If she's really agitated, she will wag her tail rapidly back and forth from the base. This is a threatening signal to warn other cats (and you) to back off. On the other hand, a tail that waves back and forth slowly and gently indicates that your cat is relaxed and happy.
Your cat may swish her tail when she's in her hunting mode. By swishing her tail, she mesmerizes her prey. Since your cat can't see her prey if it becomes still, she moves her tail to initiate the slightest movement of her target, which she can then see. Mother cats train their kittens in the fine art of hunting by twitching the tips of their tails to provoke playful attacks.
Then there's that little tail flick, which involves just a quick movement of the tail. Your kitty may be resting at the foot of the bed and you say her name and there it is - a little flick. Her eyes are closed and she appears to be sleeping, but you say her name again, and there it is again – a little flick. You know she hears you, even though she's pretending she doesn't. This is a movement of happiness and contentment. Your cat trusts you enough to remain sleeping in your presence – and in her own way, she's letting you know that she hears you and all is well.