The animals roaming Yellowstone National Park are American Bison, not true buffalo. The term “buffalo” has been used colloquially in North America for centuries, even though it is scientifically inaccurate. The Yellowstone herd is significant because it represents the only population of American Bison that has continuously existed in a free-ranging, wild state since prehistoric times. Their conservation history and management present unique ecological and administrative challenges.
Bison vs. Buffalo: Settling the Terminology
The animals in Yellowstone belong to the species Bison bison, placing them in a different genus from the two types of true buffalo: the African Cape Buffalo (Syncerus caffer) and the Asian Water Buffalo (Bubalus bubalis). These Old World buffalo are native only to Africa and Asia. The confusion began in the 17th century when early European explorers and fur trappers encountered the bison.
The French word bœuf, meaning “ox or beef,” was used to describe the large, shaggy animals, and this term eventually evolved into the American English “buffalo.” True bison are distinguishable by several physical characteristics, most notably a massive hump over their shoulders, which is absent in true buffalo. Bison also have a large head carried low, a thick shaggy coat, and a “beard,” while true buffalo have a smooth coat and long, curved horns. The bison’s hump is supported by long vertebrae and muscle, which aids them in plowing snow away to find forage during winter.
The Yellowstone Bison Population
The Yellowstone bison herd is unique due to its continuous lineage since the late 19th century. By the early 1900s, commercial hunting had decimated the American bison population, reducing the Yellowstone herd to only about 23 wild individuals. This small, surviving group became the genetic foundation for the current population through conservation efforts.
To bolster the depleted numbers, park managers introduced privately owned bison from Montana and Texas in 1902. This action helped the population recover, and today, the herd fluctuates between approximately 4,000 and 6,000 individuals. Recent genetic studies show that the bison, once considered two distinct subgroups within the park, have now interbred sufficiently to be managed as a single, large, and genetically healthy population. The population freely roams the expansive public lands of the Greater Yellowstone Ecosystem.
Management and Conservation Challenges
Managing the Yellowstone bison population involves navigating complex ecological and political challenges, primarily centered on their seasonal migration outside the park boundaries. The core issue revolves around the bacterial disease brucellosis, which is carried by a portion of the herd. Although transmission to cattle has been rare, the disease remains a major concern for the livestock industry in surrounding states.
This conflict led to the creation of the Interagency Bison Management Plan (IBMP) in 2000, a collaborative agreement between federal, state, and tribal entities. The IBMP aims to maintain a wild, free-ranging bison population while reducing the risk of brucellosis transmission to domestic cattle. To mitigate this risk, the plan includes provisions for population control, often involving the capture and slaughter of bison that migrate beyond designated tolerance zones. Recent updates prioritize working with Native American Tribes to transfer brucellosis-free bison to tribal lands, providing a culturally relevant alternative to culling.