unprovoked aggression towards only certain breeds

Question
I have an intact male Standard Schnauzer, named Rebbie, fourteen months old. We got him from a breeder when he was four months old. He's very fit, happy, and playful. He's very sociable with other dogs and loves to go to the dog park.  When at the dog park, he plays nicely with other dogs, although, until recently, he tried to do a lot of humping. Within the last few months he's calmed down a lot as far as that is concerned.  

The only problem is that with certain dogs, mainly boxers, male or female, he shows unprovoked aggression.  He doesn't bite, but he gets the boxer down, puts his teeth on their necks or near their ears and growls and snarls, often baring his teeth. The boxers don't seem to mind. In fact, when I hold him by the collar and tell him no, they often come back over to him wanting to play. Eventually, I have to remove Rebbie from the park.

This is not a major problem, but I'm mystified as to why he shows such behavior, and only with boxers (and sometimes bulldogs as well).

Thank you for your time.  

Answer
Hi Diane, An intact male will show other dogs that he is the pack leader. The behavior you are seeing is simply Rebbie's way of establishing pack dominance. He may feel threatened by brachioencepholic dogs as he is not familiar with their look and sounds. Since he is establishing his dominance without hurting them, it should not be a problem, unless the owners take offense. It is common dog behavior. If you do not plan on breeding him, get him neutered. It is your job to keep him under control. He is being a fair pack leader and it probably will not progress. If you are his established pack leader, you can give him a quiet noise (shhh, or ahhh) but if you get upset it may make him worse. Stay calm and try to talk to the other owners, so that they do not get offended. I commend you for taking him out for exercise, it is very good for him, keep up the good work. You are not only physically, but mentally exercising him. When we establish ourselves as pack leaders, we use our hands to do exactly what he is doing to the other dogs. Thank you for writing. Leave me some feedback, follow up with me to let me know how you progress with this problem. Warm Regards, Susan