A cat's tail is a powerful form of communication that reveals its emotions and intentions. When the tail is erect and twitching, the cat is usually excited or happy, while a straight up What Does It Mean When A Cat's Tail Vibrates? Why Do Cats Vibrate Their Tails? Reading Your Cat's Body Language Kinship Cat tail signs: What your cat's tail tells you Does your Siamese cat's tail vibrate when excited? Why Do Cats Vibrate Their Tail? This Is What They Might Be Signalling With It We Love Catz