We have a 4.5 year old Golden Retriever and an about 16-17 month old German Wire Haired Pointer. The GWP was found wandering around the high school where I work when he was approximately 12 weeks old, based on his teeth. My husband and I fostered him for the local SPCA, and finally ended up adopting him last April. He has played at the dog park since he was 6 months old. He runs until he drops and had no issues until recently.
In the last two months he has started being aggressive towards other dogs, some of whom he has known most of his life. The trouble seems to be with bully breeds such as boxers and bulldogs. Sometimes it starts off as play then turns nasty. Today there was a mob of dogs waiting as we entered the dog park. It started almost immediately. I don't know if it was the boxer who started it, or my GWP, but we were finally able to separate them, and we left.
He has issues with walking on lead, chewing pillows, and jumping up when greeting people. He is fine with our golden, but does not get along with my son's lab, who nipped him when he had just come to us.
He has been through basic training. He comes, sits, leaves it, lays down (but the stay is still rough). If we are outside, he goes into the house on command. He'll go to the car on command. When in the car, he is so excited he whines.
We need to solve the aggression thing. Any ideas?