It was rutting season, and though I’d been to Yellowstone several times before at this time of year, I’d never seen so many male bison butting heads. These two photos -- “Battle” and “Practice Battle” were taken within 24 hours of each other. Practice Battle was taken while a herd of bison passed through a hot springs area, and these two juvenile males appeared to be practicing their fighting skills, seemingly oblivious to the cauldron of boiling water that was immediately behind them. I kept listening for the mother of one of them to yell at them for playing too close to the geyser.

By contrast, these two mature males in Battle appeared to be fighting for real. They charged at each other and threw all of their weight into each blow, whereas the juvenile males had just mimicked similar actions. I never learned who they were fighting over, though it’s a safe bet given the time of year that they were fighting over a potential mate or two.