Wildlife poses the greatest threat in the Hills. Keep your distance.
Bison
roam free in the region, and herds frequently cross and block highways. They are temperamental and unpredictable; if you get stuck in a line of cars backed up by a herd, stay in the car, roll your eyes, and wait for them to cross. Do not leave the car to approach the animals. A docile-looking bison can turn into over a ton of enraged, fast-moving muscle and horns before you know it and with no obvious provocation.In the rare event you encounter a mountain lion, walk away backwards very carefully and slowly. Never show the back of your neck to a lion. Mountain lion sightings are becoming more prevalent.
Rattlesnakes
are not aggressive unless they are messed with. Be very careful not to surprise one when climbing. Encounters between hikers and rattlers are uncommon but not unknown, and the way to deal with an encounter varies according to circumstances. If you actually see the snake, back away from it a short distance 8-10 feet at most; rattlers can only strike about half their body length, so there's no need to go running in terror. If you don't see it but only hear it, best is to stop in your tracks until you know where it is, then back away. If you're hiking in a group, make sure your fellow hikers know the snake is there say "Snake", but there's nothing to get hysterical about. Pay extra attention when hiking at dawn or dusk, when the snakes are hunting mice, not you.The best reminder for people is that wildlife is just that - wild. Even the more innocent looking animals of the Black Hills like the Prairie Dogs are not pets, and tourists should avoid trying to touch these animals or crowding their holes. Rabies is common.
fees/permits
Aside from camping fees and hunting permits, the national forest is free for all to enjoy.