Rough Collie Behavioral Issue
I need some advice. I had collies as a kid and have owned five collies in the past 20 years. I currently have two males, 5 and 4 years old. Our collies have always been wonderful, gentle, loving companions. We got the younger one as a puppy from a local breeder - and she urged us to get him at 6 wks old. He is what I call a farm collie - stockier and plumper than my other collies but still beautiful. He is rambunctious but is a sweetie. He lives for approval and love. When he gets excited or wants to play - he's a bit rough with the older one which we try to stop. His face is so expressive - mostly just the face of someone who wants to know he's a good boy. He can be quite stubborn. Now to the problem...
About a month or two ago - he was getting a bit rowdy inside and I just swatted his butt (not hard at all and he's got very thick fur on his back side). But he did not like it. He turned, jumped up and pushed my chest barking and nipped my chest. It was intense and aggressive. I used my authority voice and used my body with my hands behind me to push him back and calm him down. It's happened twice since then - once when I tried to get the empty box he had gotten from the trash and was eating and another time when I took him by the collar to get him to come inside. The second incident was VERY intense and frankly scared me because he lunged several times and it took him more than a few seconds to calm down. After the incidents - he seemed subdued like he knew he did something wrong and was very careful around me (as I was around him). I don't think it's a dominance/alpha thing - looking back I just think it was more a matter of me interfering with something that really mattered to him. I adjusted the way I deal with him - less raising of my voice, more approval-based, careful with my hands so he doesn't associate them with something bad. Things seem to have improved. It's important to note that the "triggering events" have occurred many many many times in the past four years - these aren't new issues as he loves to sneak paper towels out of the trash and I sometimes have to guide him inside to get him to come. It's always been just more of a game to him that I would eventually win but he liked making me chase him a little.
Today, however, we were sitting on the patio and they started barking at something. Usually they stop quickly when I tell them to - but sometimes they get fixated and just keep barking - like today. It's the older one that does the most barking so I stood up and calmly tried to get him to stop. I must've jumped or something and it spooked the older dog and he stepped back frightened. The younger one lunged up at me snarling and nipped my chest. I didn't react - just turned away. It only lasted a second and I walked back inside. The younger one followed me trying to get me to pet him - I guess sensing we had had another disagreement. I just ignored him, sat down, and he came up to me and laid his head in the crook of my arm giving me the "I need approval" look. He was back to normal.
I've never had this happen with a dog of mine. I absolutely never hit, kick, or beat my dogs. I yell when things get too crazy - which I'm working on - but 95% of the time is loving and calm times. I don't know why the younger male is doing this. He only does this to me - not my spouse. But he is so loving all the rest of the time - he's my bud. I'm worried. Ideas?