Bella will growl at me (and/or Ripley) when we play Tug-O-War with her. Every dog I have ever owned has growled while playing Tug-O-War. I guess they are trying to scare me into giving up. Ripley will growl back at her when they are playing Tug-O-War and it sounds like they are both ferocious! Come to think of it, I don't think Ripley has ever growled at me, even in playing.