American Bison (Bison bison) in Rut DDZ_0065
During mating season, an American Bison male will threaten and sometimes attack other males that try to get too close to a female he is tending. Fights between males can involve headbutting, shoving, or locking horns.
American Bison were in full rut in Yellowstone National Park during August 2008. Here, two bulls challenge each other.