Yep, I 100%-ed it. If it's any consolation the 3* opossum was the most tedious thing to find for me. Spent days hunting for it, just wouldn't spawn. Of course when I finally got one they started popping up all over the place. If you're in a location where you know they spawn try shooting a bird and watch it's carcass from a distance. Egrets, herons and spoonbills were also tedious but I was so close to the 100% I refused to give up.