Bad Day at the Dog Park

Sunday, we brought Walter to the dog park.  We've gone before and never had any problems.  Well, Walter was in a mood.  He growled five times and looked like he wanted to get into fights with the other dogs.  He even tried to mount a Bull Mastiff that weighed 160 pounds!  He growled at a dog when he went to the drinking fountain.  We thought he would be so happy to get to run with the big dogs at the park.  In the truck on the way home with him, he wouldn't tell why he was so ornery....