Wild animals are called that for a reason, and South Dakota residents all know at least one story of a person being attacked because they ignored repeated warnings about getting too close. While centered mostly around the southwest part of the state, Bison are best viewed from the car or from a distance — do not approach them. They look slow, but they can cover a good distance in short time.
Prairie dogs may be cute and fun to watch, but don't let your kids try to pet them. They will bite.
Also, mosquitoes in South Dakota are simply out of control. They bite through clothes and mark their territory on skin, a few inches of diameter at a time. Mosquito bites acquired in South Dakota remain red and swollen for a few days. It is crucial, although practically impossible, that you refrain from scratching them. If you feel you absolutely must do so, however, opt for alcohol on a piece of cotton applied to your war wounds before giving in to temptation, as doing so might alleviate the agitation and leave you with a somewhat cool sensation on your skin. Do not take a walk in the park without having sprayed some kind of mosquito repellent, or you will regret it as much as you'd regret feeding your cat red jelly-beans on its third day straight of diarrhea.