My Dog is a 1yr. old/3months-Lab mix w/ some kind of husky and ridge back. He's a mutt! He is really sweet, friendly, passive, and submissive. For the past couple of weeks though he has been getting aggressive at the dog park (putting his ears back and lifting his lip and growling/snapping). He looks so mean! It's like he did it once, and it has been escalating. He is fine at first when we let him in the area: running around, playing with all the dogs... then, it seems to always be one dog that just sets him off. Like today this dog was just staring at him, and he just started walking in circles around us doing the lip/growling thing and when the dog came close he started showing his teeth. Then, when the others dogs just came to play or walked by he starting growling at everyone! Even the dogs he was fine with a second ago! I DON'T GET IT! Is it an age thing? maybe trying to become dominant? Someone help!