The night-time speed in that stretch is either 55moh or 60mph, it changes sometimes depending on how the state is dealing with the bison each year and it's wooded on either side of the road though there's at least 50ft of clearing between the road and the trees.
The Bison will lay down on the road, often, in groups. Hitting one is bad enough, I can't imagine there's much left to the undercarriage of the front half of that semi. One year, a local woman, who was speeding, hit eight of them in a small car, don't know how she survived it but she wasn't hurt.
They also are grazing the grassy stuff that is not buried in snow, even at night. Like mentioned in many comments, you cannot see them in the dark. I lived there for a very long time and you cannot see most of the big animals in your headlights, period. This is also a very dark at night place, no light pollution, most people don't know how different it is when you can't even see your other body parts, headlights are not as great as you might think in that setting. You have the side markers along the roadside so you know where you are. If you can't manage with that, maybe let somebody else drive or wait until daylight.
In a place like that, Mother Nature rules.