My chicken house and tractors at night are out of the perimeters of my dog. I have him with my goats, since they are at risk in their night time fenced in area.. During the day the goats are out browsing with the chickens and guineas. He has total access to all during the day. My chickens are all closed in at night. Nothing can reach in to them - have 1/4" wire fencing on all enclosures. My husband makes all the houses and enclosures to my specifications.Possum can and do prey on chickens here in the states. My dad killed one HUGE possum one year that he caught in the act of eating the breast off a roosting chicken.....she was still on the roost as he was eating her alive.
I can't imagine a GP that would let a possum live in their territory. My dogs kill possum immediately, just as they do coons.