He's probably a little leery about the size difference and I dont' blame him. You could try to treat him every time she gets near (presence of german shephard = treat) in order to try to change his overall reaction to her.
This could backfire if she is TOO close and he is possessive of his treats.
Do you do any clicker training?
If they do not get along and as she matures - she may no longer put up with his aggressiveness. That could be dangerous for him and you may have to keep them separated for his safety.
I'm thinking fence?
__________________  Mommy to Lucy, Ringo, and Matthew |