I'm curious... Do your dogs mark? If yes, do they mark over other dogs? If yes, do they mark over all other dogs or only some? Do they mark over pack mates? This came to mind as I have noticed something interesting. Summit has always been a marker. That is what he spends 90% of his time doing when we go hiking or walking. If we go to the dog park and he sees another dog mark something he will inevitably trot over and mark over top of it. We hike regularly with my good friend and her dog, a young intact lab who has just started to mark. Summit and Cole obsessively mark over top of one another. If my landlord comes over with their GSD, the next time I let Summit out he goes around the backyard marking over every spot where Diesel peed. There's a guy who rents the basement of our house, and he has a little female mutt. Summit will mark over her as well in the backyard. But he NEVER marks over Kili. Ever. Mind you, she doesn't really mark. She just pees all in one spot. But still, Summit never marks over top of a spot where she has gone. I just thought it was interesting that the "pack" or family unit is very well defined. Even though we share territory with another dog, he still knows she is not a part of our unit. Even thou we walk almost weekly with my friend's dog and spend a lot of time at each other's houses... Cole is also not a member of this pack.