Personality 180--my boy is now mean
I had my dog, Mack (australian shepherd) for a year or so when I decided to get a second. I chose another aussie, this time female to avoid fights, and she entered our family in February. Almost instantaneously, Mack became viscious to other dogs down at the park that we had visited almost every day since he was a puppy. He attacked dogs he had known almost his whole life; just a radical 180. He is/was very well socialized and was a very sweet boy before getting the second dog, now I can't even bring him to the park because I dont want him to hurt someone's dog.
I was just wondering whether anyone has any suggestions as to what to do, or has gone through this before with success. I know he can get along with other dogs again, because it seems like thats instinctive, but I just need to figure out how to get him to realize that he doesn't need to. He is NOT dominant over me, but is the dominant dog in the house. I make sure to have him follow me through doors and work for what he gets, and he listens very well.
After this problem started I got some bad advise from someone who is not dog saavy (rather harse punishment for picking fights) but I could not bring myself to punish the dog in those ways, the most I did was to grab his muzzle while sort of pinning him down and saying no. After reading tons of books I now realize that this action most likely made the problem worse! I'm all for positive reinforcement for good behavior, but do not really know where to start. Its weird because when I'm not around, he does find with other dogs. He has been with other dogs before, but when I entered the area he came up to my side and attacked the first dog that walked near me. So it has to do with some sort of protection thing. You're probably thinking "protecting his pack members" but I think it is more "Protecting the leader."
In any case, I miss going to the park, and I'm sure he does too because he gets excited when he hears "go to the park." Does anyone have any suggestions???
Thanks so much!