So our newest dog, Jack, that we just got over the past weekend gets along pretty well with our one dog Benji (the one I thought would have problems with him) and is getting increasingly more aggressive with our other dog Reddington. Today, he keeps putting his head over Reddington's neck and lowly growling at him and then sometimes trying to hump him or it turns out into an all out snarling match that freaks me out. He could very easily hurt Reddington and I'm getting more worried about leaving them alone at the house without one of us present. We may have to see if my husband's sister will take him if we can't get this solved quickly and we don't have tons of money to spend on someone to come in and help. I don't know what it is about Reddington that seems to be upsetting him. At first I thought he was being possessive because the first time a fight happened was over a bone, the second time was when he was on the bed with me and Reddington jumped up for attention. This past time we were just in the kitchen and I was trying to open something when it all happened so there was no obvious trigger other than Jack doing his weird head over the neck thing to Reddington.