Cutie! Aw, poor Scout - he's probably just feeling verrry insecure; I know my Wylie felt very insecure and needy when I got Marcel - and I felt just terrible about it! So, I'd take Wylie in my arms, and, in front of Marcel - I'd give Wylie alllll this important good lovin' - so that Wylie felt all puffed up and alpha-like and first-born.
Also, it's very important to let the dogs interact (well, within safe limits of course) so that Scout can indeed confirm that he remains alpha - that he is *safe* (lol) in his supreme position. He shouldn't need to get so aggressive about it - and it seems he might still be feeling that way - but he should calm down a bit. If he doesn't, you may want to go buy some D.A.P. - a calming pheromone for dogs that is proving to be quite wonderful.
