I think I've turned my Mastiff into a kitten! A GIANT kitten. I bought her a ball that you put treats inside. She has to roll it around, and every so often one will fall out. She is batting the thing around like a maniac...it's pretty funny to watch. She has 3 strategies: bat it around, slam it to the ground, try to chew through it (and it's hard plastic, so not likely).