One of my mom's snowshoes - who's named Harley, by the way! - sucks the tip of his tail. She had another kitty who's at the rainbow bridge now who used to nurse on her old pink bathrobe! All of my mom's cats are rescues, so who knows their backgrounds, but my vet says some cats just have the "habit", it probably doesn't have anything to do with how and when they were weaned.