How do I train my new dog to not bark and growl at strangers?
At 4 I’d say he’s pretty “set” in his ways. It may be a defensive mechanism for him. You can try and expose him to new experiences in positive ways so he doesn’t feel the need to be aggressive when faced with new people and situations, but that would work far better if it was done when he was a puppy. You may need to do extensive discipline training so that even if you can’t get him to not react negatively at a situation you can get him to at least “sit” or “heel” quickly before he lunges at people. If you need to go extreme you can do something like shock-collar training, but that may just make him meaner. He may just not be able to be around unfamiliar people at this point, at least in uncontrolled situations.
