There are rattlesnakes present. Be aware, especially when in the national park or on the trails outside of town. I worked in Medora for 4 months in the summer, and spent much of the next summer in Medora as well. I never saw a rattlesnake, but they are there.
I camped overnight at Sulley's Creek. About sunset a group of local youth set up in the next camp about 50 yards away. They had a loud party until about 2AM when I yelled at them to quiet down. They were so drunk that they couldn't whisper, and I overheard their plans to "bust up" my camp and "drop a few elbows" on my head (wrassling term). I awaited them with an empty glass bottle, which I broke on the fire pit as they entered my camp and switched on my flashlight at the same time. This sent them scampering back. I went to the "park ranger", a retiree volunteer in a camper several hundred yards away, and he would not answer when I knocked on the door. I explained the situation, but he didn't want to do anything about it. He finally suggested "I suppose I could call the sherrif's office" in Medora but quickly found out that no one was answering. He suggested I go driving around and see if I happen to run into any deputies on patrol. At my insistence, the old man went into town (2 miles) to try to find the deputies. They arrived an hour later. They said "What do you want us to do about it?" "How about evict them from the campgrounds?" "Well, if it's true that they've been drinking, we don't want them driving." WHAT THE F***!!!!!!????? "Who said anything about them driving? Can't you take them?" They looked me straight in the eye and said, "We don't have a jail in Medora, the closest one is in Dickinson 60 miles away." A brand new courthouse in Medora and no jail. So Dumb and Dumber suggest that I might want at 4AM and check into a motel. My expense of course. "One last thing", I said. "The sign at the entrance to the park says 'RANGER PATROLLED'. Just how often is that?" "Uhh, well, I guess, not at all." At this point I am so full of contempt that I'm yelling. "So I guess it should really read "NEVER PATROLLED'!!!!!!" The park entrance sign also states no firearms. My advice would be to ignore that sign. Not like anybody is going to enforce the rules anyway.
Avoid trying to go up close to the many buffalo located in the park.They look very calm and appear tame but are very dangerous to approach many people have been injured trying to approach these animals.they are very interesting to see out in the wild as they are a close knit bunch and are very protective of their kind.