I've recently taken on 2 wheaton terriers to exercise and socialize with my dog pack. One is fantastic - she's a little shy, but very good natured and obedient. She sticks close to my leg and leans against me in a chummy way. The other is ok as long as the conditions are correct, but certain things trigger extremely aggressive behaviour. One trigger is possessiveness, he will see a dog playing with a ball, stand over the ball and fixate on it, then attack the dog with a very loud screaming/roaring noise. He will continue to attack even if the other dog is on its back yelping in pain and fear. He's injured other dogs before (before I took him on), causing bleeding and torn ears. Needless to say this is disgusting and abnormal for a dog, and I'd really like to eliminate this behaviour so he can lead a happy and well balanced life. It would also make my life a lot easier, since I have to take him out every day and his aggressive crap really messes with the dynamics and mood of the pack. It's not fair to the other dogs that there is a crazy one who brings tension and unpleasantness to their daily walk.
I'm dealing with the aggression as it happens, and keeping him on lead most of the time, but I'd like to be able to eventually let him run with the well balanced dogs. When he attacks another dog I make a pincer shape with my hand and "bite" his neck hard, forcing him to lie on the ground until he calms down. My reflexes are good so I am always able to do it instantly. When I do this he becomes hysterical and kicks up a huge fuss, tries to bite me and screams at the top of his lungs, before eventually winding down and lying still when I say "No! Bad!" and "Hey! Calm down!".
The weird thing is, their owner seems like a sensible person who seemingly does all the right things and apparently disciplines them both reasonably well. Could this be some kind of mental illness caused by bad breeding or a neurological disorder? Like I said, his female friend is fine, a very gentle soul and I've never had any problems with her at all.
I give him treats and praise when he is friendly, and when he does not act aggressively in situations where he normally would. Does anyone know any other strategies to deal with this kind of thing? Is it fixable or will he be like this forever? I've dealt with this kind of thing before but not with this level of sheer insanity.