My dog has always been submissive. He's never aggressive toward anyone or anything. He doesn't bark or growl. This is a great trait in him, and I love it. However, its becoming an increasing problem at the dog park. He is constantly getting mounted. I know that dogs do this to show dominance, and its normally not a big deal. Lately, some dogs have taken to following him around and every time he stops moving, they mount him. My dog is a good 50lbs. Some dogs are so little, its merely an annoyance. Some dogs are so large, I feel bad. All my dog wants to do is escape, but he never fights them off. Is there anything I can do to encourage him to be less submissive? Is this even something you can change in dog behavior? Any advice would be appreciated! Thank you!