The bison of Yellowstone National Park migrate up to 70 miles between their summer and winter ranges, moving the lower elevations as snow gathers and the snowpack grows. During these colder months, tourists are most likely to spot the animals in hydrothermal areas and along the Madison River, Blacktail Deer Plateau, Tower, and the Gardiner Basin.
Bison are massive animals (males weigh up to 2,000 pounds) and they’ll react aggressively if they believe they’re in danger. In fact, bison have injured more people in Yellowstone than any other animal. Human activities often appear as threatening to the large animals and might spark an attack, so people are encouraged to stay plenty far away.
Such was the case when these snowmobilers along one of Yellowstone’s snowed-in roads managed to spark a lone bison into aggression:
All animals inside Yellowstone National Park should be given a wide berth. For bison, that means at least 75 feet. If one is in the middle of a trail or road way, visitors should continue to give the animal plenty of space. Fortunately this bison didn’t make contact with any of the riders, but it certainly gave them a good scare. Read more on bison safety below:
Yellowstone National Park Bison Safety Guidelines:
Bison have injured more people in Yellowstone than any other animal. Bison are unpredictable and can run three times faster than humans. Always stay at least 25 yards (23 m) away from bison.
- Give bison space when they are near a campsite, trail, boardwalk, parking lot, or in a developed area. If need be, turn around and go the other way to avoid interacting with a wild animal in close proximity. 
- Approaching bison threatens them, and they may respond by bluff charging, head bobbing, pawing, bellowing, or snorting. These are warning signs that you are too close and that a charge is imminent.
- Do not stand your ground. Immediately walk or run away from the animal. Spray bear spray as you are moving away if the animal follows you.