Near our campsite a herd of bison wandered the gentle rolling hills along the river. They were overall pretty mellow, in spite of numerous calves running and playing by the moms. It was cute seeing their cinnamon color coats amid the dark brown of the adults. We even got to see some wading the river. The NPS advises a 25 yard safety zone, and you might have read the news about various tourists being gored attempting to take selfies with them. Be very afraid and respectful.