Rex must know that's his tail he's stalking surely? I've never understood why dogs chase their tails. He stands still looking at it, like he's lulling it into a false sense of security, then pounces and spins round and round. He doesn't catch it very often. Then again, who am I to criticise? He's confused by my behaviour every day, instead of happily grabbing the toys he offers, I come and sit and look at the weird shiny screen and tap the square things on a board and when he tries to have a go and jump onto the little square tile things to press them, I get cross.