Yellowstone Country Wild Bison (Buffalo) 2019 Calendar Wild Bison 2016 combines superb photographs, artwork, facts, poems, and writings about this magnificent North American mammal. Each month offers a seasonal look at bison, bison-related artwork, and highlights of their natural history. This calendar is compiled, produced, and distributed by Buffalo Field Campaign, the only organization with a continuous presence in and around Yellowstone, monitoring and documenting the plight of wild bison in the field for the last 17 years.