My new dog is a total sweetheart around people, and he loves the dog park. He's been getting more and more aggressive lately, and I think that he's just becoming more and more possessive as he's getting more comfortable with his new (ish) home.A couple days ago he drew blood because a dog got near me. How do I stop this kind of behavior? I'm getting a muzzle so that he won't hurt anyone else, but I don't want him attacking dogs just because they get somewhat near me. He may be part chow, but I haven't done the DNA test on him yet.