Why Do Cats Shake or Vibrate Their Tails? Vet Verified Reasons Explained Catster she always vibrates her tail at this exact spot very.. confused?? anyone else experienced this? : r cats 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 Decode your cat's mood instantly! Is your cat's tail a question mark, a low swish, or an excited high wag? Each position has a secret message