Why Do Cats Wag Their Tails: Reasons & Expert Tips [+ FAQs] Why does my cat shake her tail like this? : r cats What does it mean when a cat's tail vibrates? Understanding Your Cat's Rattlesnake Tail Behavior 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 Understanding Your Cat's Vibrating Tail Behavior