There's an old joke about two tourists in Custer State Park who encounter an agitated bull buffalo. One of the tourists reaches into his backpack, pulls out a pair of running shoes and puts them on.
"You really think you can run faster than that bison?" his friend asks.
"I don't have to run faster than the bison," the hiker replies as he bolts off across the pasture, leaving his friend behind.
If you want to understand bison behavior, there's one very important thing to remember. If the animal is flicking its tail, it's planning to either charge, or discharge. Better hope it's the latter, because there's not much you can do about the former.
However, there's no need to be overly concerned. Bikes and bison have coexisted quite nicely in Custer State Park since the first Sturgis Rally in 1938. But it's the biker's responsibility, not the bison's, to make the relationship work. While not exactly friendly, most bison are willing to ignore people in cars and on motorcycles.