Been to both Yellowstone National Park as well as Antelope Island in Utah, Bison are huge animals to say the least; so anyone who things they're 'smart' enough to get too close & provoke these is only asking for trouble & themselves there own worst enemy! In both places we saw people getting what we believed to be way too close, don't know if they were 'locals' or not but the American folks that we were with were calling them back in no uncertain terms - luckily none were charged!