You can recognize Kalluk by the big dark patch on his back that looks like a tatoo, Kinderchick; other than that, he is huge compared to his two companions. You sure can see the difference in strength, too, when he play-fights with his sister. He tries to not use too much force, and to crouch down to her level so he is not overpowering her, but sometimes this doesn't work. When he is too much for her, and he hits her too hard, she leaves the scene, so now I think they are at the point where she doesn't really want to play with him anymore. So, the keepers have to find things for Kalluk to do to keep him busy and use up his energy. In the wild, of course, he would not have this problem. Just an additional note, if you didn't already read this, all three bears were orphaned at a very young age.