In the last 2 days we rescued an 11 month un-neutered male German Shepherd named Teddy from a family who could no longer care for him. That family advised that he was just too big and too hyper for their home and that he was living outside and they didn't believe that was fair. We already have a 7 year old un-neutered male Male German Shepherd named Solomon who is great with other dogs of all sizes.
Before we agreed to take Teddy we introduced the two dogs and let them spend a lot of time together on Teddys home turf. There was of course some posturing (especially from the younger dog) and a lot of yipping and barking and what not, but all in all, they got along really well. No fights on or off leash and very relaxed body posture. When we got the two dogs home, they spent the rest of the day (about 4 hours) in our backyard and also got along really well. Lots of playing with tails wagging, tongues lolling, relaxed ears and body posture etc.
However, when we brought them in the house, Teddy changed and was suddenly very antagonistic toward Solomon. Solomon tries to ignore him by just sitting there and staring at him calmly or by walking away from him but Teddy will not allow it and will follow and snarl and bark aggressively (altho body posture isn't always aggressive). Finally Solomon gets frustrated enough and a fight begins. Its only been 2 days, but Teddy's behavior isn't showing any signs of stopping and it is now continued in the outdoors but only IF a member of the household is out there. Alone they are fine.
Another weird thing with Teddy is that he seems to be nervous about doors. When going outside, he will go out to about his shoulders, then turn around and run back in and then try to go out again. He does this several times. When Solomon is going out with him, Teddy will become aggressive at the door as well and must be the first one out.
Although he was living outside, I know in his old home they were definitely paying attention to him and loving him as his temperament is very sweet, he thinks hes a lapdog, and he knows his basic commands (sit, down, off, and come - not that he listens often). He was never before socialized with other dogs though and hes still very young.
I'm worried that we may have made a mistake by adopting him. However he is a member of our household now so I am looking for things I can do to work with him (and Solomon) to get him past this. Oh, we are also going to be getting him neutered. I just haven't called the vet yet.
Any and all help is welcome.