I have an almost 3 yr old Beagle/Boston terrier who is my first dog. I've had her for about 2 years, and now I have my puppy GSD who I have had for about a month and a half now. They are fine with toys, they will play tug of war with each other, and generally play good together without toys..(generally) I first noticed my older dog started becoming aggressive with her treats towards my GSD puppy when I gave them both a treat, my GSD puppy ate his, then went over to play with my older dog and she had the puppies head in her mouth tossing him around and he was squealing like someone was murdering him. I was so scared at this point, I thought she was trying to kill the puppy. So, I had separated them. Now fast forward a month, I gave them both a veggie bone to gnaw on while I clean the house, puppy isn't interested and goes to play with my older dog, and she once again has his head in her mouth and he starts screaming bloody murder again. I'm not really sure on what to do at this point other than to just completely stop treats and bones? I don't understand why they are fine with the toys and not these other things.. at this point in time, my puppy is still smaller than my older dog, so he can't really hold his own yet... but i'm afraid of when he will be able to the outcome won't be good for the both of them.. He starts obedience and puppy protection training tomorrow.. maybe I should ask the trainer for some tips?