Travel to the east entrance of Yellowstone National Park from Wapiti, WY. Continue towards Fishing Bridge, then to the Hayden Valley. Large herds of bison gather in the Hayden Valley in the summer for the rut, which is quite an exciting spectacle.
During the August rut, bull bison compete rather violently for breeding rights to females. This poor bison calf was minding his own business, when these two mature bulls really got into it. They continued fighting for a brief time and pushed themselves all the way towards me and my camera. I had to run to my truck to get out of their way. In my hasty retreat, I forgot about my camera, tripod and lens. Lucky for me, they went around it!