Hi, please help. I adopted a dog 2 years ago, and from the start, he has learned that I am the alpha dog through proper training and leadership which is great. When we do to the dog park, he usually meets and greets and everything is fine for a little while, big dogs, small dogs, whatever, but after a minute or two of running and getting dogs to chase him, he thinks he is "park police" and starts to charge at dogs who are playing together, and will try to mount the dog who is playing the roughest. i do not let him. he gets protective of small dogs, and he also will get into a stalking position when a new dog enters the park, but only if it is larger than him, or the same size. then he charges at them to intimidate them. also if if big dog is trying to play or challenge him playfully, he will snap, and bark in an aggressive tone, and wont engage in play. the last time i took him to the dog park, he was playing so well, and running with a great dane and a whippet running with him, and as soon as that great dane got too close, my dog was trampled and my dog immediately barked, and snapped, and took the aggression out on both dogs. well, needless to say, overprotective owners shrieked and gave me dirty looks. he never has hurt or actually bitten a dog, and i dont think that is his intention, but he seems to think that big dogs are threatening and it makes him defensive. i try to recall him before things get out of hand, which he does at the drop of a hat, but the problem is that the switch in his head has already gone off before i ever knew what happened. i really want him to be balanced, but he feeds off the other dogs energies too. he is supposed to go to a dog daycare facility next week, and his test on saturday is to meet the female boxer mascot of the facility, and if he gets along with her, he will be admitted. i was told that they teach proper social pack behavior there, so i am really hoping that he will pass his test with her. 75% of the time he loves to play with other dogs, but im worried about that 25% that is kind of a defensive/dominant behavior. please help.....thanks!