Last July we adopted "Moose", a 4 year/9 month old, 80 lb. lab/shepard mix dog, from a shelter. We were looking for a an older dog who was calm and and non-aggressive, in contrast to our previous dog who attacked nearly everyone, including us sometimes, and this one seemed to fill the bill. A real charmer. Everyone, adults and children, liked Moose and Moose seemed to like everyone. For many months he was exactly what I wanted. I finally had a dog I could take everywhere without fear he'd attack or bite! That was then. Since then Moose has become very much my dog. Too much my dog - he's become extremely protective of me and our home and has gotten aggressive towards strangers on his walks and anyone who enters our house, even those he knows. It's not just exuberance. He means to attack (you can tell). He's a big, strong, quick dog and it's inevitable that he'll bite someone. I cannot keep a dog with that potential. The shelter we adopted him from didn't know much about Moose when they took him in. As a reason for surrender, the former owners said he had a tendency to run (he doesn't), but that is all they said. He had been an outdoor dog but we made him into an indoor dog. Moose seemed to make a successful transition - he didn't even need to be housebroken. We noted one odd thing - he wouldn't play. Won't chase a ball or stick, won't roughhouse, won't anything. I have a theory that his former owners simply kept him in his kennel from a pup and never socialized him and rarely interacted with him at all. Anyway, anyone have any suggestions about curing Moose of this aggessiveness he's developed? I don't know what I've done wrong. We've never hit or been mean to him in any way, rarely yell at him, pet, scratch and talk to him all the time, given him treats and rawhides to chew every day, etc. Treated him like a member of the family. But if I can't change his behavior pretty quickly, I'm going to have to give Moose up to the shelter.