Two bison (Bison bison) bulls facing off, Yellowstone National Park, Wyoming, United States of America, North America

Two bison (Bison bison) calves, Yellowstone National Park, UNESCO World Heritage Site, Wyoming, United States of America, North America

Two Bison (Bison bison) bulls sparring, Yellowstone National Park, Wyoming, United States of America, North America

Two Bison (Bison bison) bulls sparring, Yellowstone National Park, Wyoming, United States of America, North America

America Bison (Bison bison) in Yellowstone National Park, USA

America Bison (Bison bison) in Yellowstone National Park, USA

Sepia image of Plains Bison (Bison bison bison) jousting at Elk Island National Park; Alberta, Canada

Pair of American Bison bulls (Bison bison) walking through the 'Bobby Socks' trees in the Firehole River Valley of Yellowstone National Park; Wyoming, United States of America

Two Male Bisons (Buffalo) Fighting At Yellowstone National Park, Wyoming, Usa

American Bison (Bison bison) in snow in winter, Yellowstone National park, USA