Huggable: Knut at three months Knut has been hand-raised by Doerflein and other zoo staff after his mother rejected him and another cub that died Welcome to the bear pit: Knut cuddles up to a brave Thomas Doerflein The cub that became Berlin Zoo's star attraction after being rejected by his mother is growing up fast. Keeper Thomas Doerflein, who has been hand-rearing Knut, believes the carefree days of tumbling around with him in his den could soon be over. At a hefty 92lb, Knut is simply too powerful to play with. "He now sometimes has temper tantrums when he's hungry or when he wants something and doesn't get it," Mr Doerflein said. "Then he gives me a really good bite. He is, after all, a predator." Knut became a household name in Germany after animal rights campaigners claimed he would be better off killed than raised by humans. Pictures of the adorable ball of Arctic fuzz melted hearts the world over. A million visitors have flocked to the zoo to see him, making him its most popular attraction.