How your cat is feeling can be most evident in their tail behavior. Looking to your cat's tail, as well as their facial expression, and overall environment will help you better understand what they want or need in a particular moment. Here are some commonly observed tail "expressions", and what they could mean for your feline friend.
Tail straight up
According to anthrozoologist John Bradshaw, the straight-up tail is a key signal in feline communication. "In cat colonies, when two cats are working out whether to approach each other, one usually raises it's tail vertically; if thee other is happy to reciprocate, it usually raises its tail also, and the two will walk up to each other," Bradshaw writes in his 2013 book Cat Sense. Bradshaw continues that the tail-up signal has evolved since domestication, noting that kittens raise their tails to greet their mothers. In human-cat relationships, the tail-up.
When your cat's tail is straight up towards you, it likely means that they are feeling friendly and greeting you. If the tail twitches near the tip while straight up, it could mean they're extra excited to see you.
A puffed tail can mean many things, and is a perfect example of why we shouldn't zero in on one aspect of a cat's body language, but rather zoom out and look at the situation as a whole.
A puffed tail, either straight up or down, paired with an arched back might resemble a Halloween decoration, and yes: this behavior means they're spooked. A cat with this expression is trying to make themselves look bigger to ward off whatever startled them. However, a puffed tail paired with hissing and flat ears means your cat is probably ready to attack. They feel threatened, and instead of flight, their fight response is kicking in.
We see examples of this type of behavior both from cats to humans, but also when cat's communicate with each other, especially in multi-cat households.
Puffed up tails aren't always a sign of fear or anger though. Sometimes if a cat is feeling extra playful, their tail will puff up, while their ears and whiskers are forward, to show they're engaged and not stressed.
If your cat's tail is curled like a question mark, it means they're asking you to play. Will you accept the invitation? A curled tail could mean that they're feeling playful and active, and would probably enjoy catching a toy and nibbling on a treat.
More often than not, your cat's tail is probably moving—flicking, twitching, swishing. A tail that's swishing slowly back and forth likely means that your cat is focused on something, perhaps a bird outside, or the toy in your hand. If your cat's tail is whipping though, with speed and force, your feline friend wants their space.