Last year I was hunting a tree stand for the first time in an old Elm tree. Shortly after I got settled into my stand I heard something hissing real close. I'm looking all around me to see if I can make out what the heck is hissing at me, and then I look up and see a opossum with two little ones literally about 5 feet above me in the tree next to my stand just staring me down. We had a stare off for probably 10 minutes before they finally climbed down and scampered away. Those things have some serious teeth I wouldn't want to piss one off anymore than I did.