It looks like they are vibrating. When a cat's tail shoots straight up and quivers or rattles at the tip, it is the highest form of excitement they can show. It's a Ask A Vet: Why Does My Cat Twitch His Tail? Why Do Cats Vibrate Their Tail? This Is What They Might Be Signalling With It We Love Catz Your cat's tail is talking are you listening? From flicks of frustration to swishes of overstimulation, tails can reveal so much about how your cat is feeling. #cats #catbehavior #bodylanguage Why Does My Cat Meow So Often? The Main Causes!