Recently I got asked: “What should I do when my dog goes over to another dog, puts his head over the other dog’s shoulder and, depending on the other dog’s reaction, they will start squabbling?” So far no one got hurt. The dog is just two years old and has no previous history of aggression.
Most dogs go through a phase where they become a bit ‘stroppy’ (as we say in Australia) with other dogs in off leash situations. Anecdotal evidence suggests that male dogs may be more prone to show that kind of behavior.
A previously well socialized and easy going dog suddenly becomes a bully. His body language towards other dogs is more assertive, he might get into scraps and he does not take no for a no.
Behavior is never stable and it always changes, sometimes for the better and sometimes for the worse. The change I am talking about often happens when the owners already have a difficult time with their teenage dog.