The Yellowstone bison herd is a bison herd in Greater Yellowstone Ecosystem. It is probably the oldest and largest public bison herd in the United States, estimated in 2020 to comprise 4,800 bison. The bison are American bison of the Plains bison subspecies. Yellowstone National Park may be the only location in the United States where free-ranging bison were never extirpated, since they continued to exist in the wild and were not reintroduced.
Name
Bison are distantly related to the two "true buffalo", the Asian water buffalo and the African buffalo. "Bison" is a Greek word meaning ox-like animal, while "buffalo" originated with the French fur trappers who called these massive beasts , meaning ox or bullock. The name "Bison" is considered to be scientifically correct, as a result of standard usage the name "buffalo" is listed in many dictionaries as an acceptable name for American Buffalo or bison. The term "buffalo", dates to 1635 in North American usage when the term was first recorded for the American mammal. It has a much longer history than the term "bison", which was first recorded in 1774.
Ecology
Yellowstone National Park has large areas of alpine meadows and grass prairie and this provides a nearly optimum environment for American bison who live in river valleys, and on prairies and plains. Their typical habitat is open or semi-open grasslands, as well as sagebrush grasslands, semi-arid lands, and scrublands. Some lightly wooded areas are also known historically to have supported bison. Bison will also graze in hilly or mountainous areas where the slopes are not steep. Though bison are not particularly known as high altitude animals, members of the Yellowstone bison herd are frequently found at elevations above 8,000 feet (2,400 m) and a herd started with founder animals from Yellowstone, the Henry Mountains bison herd, is found on the plains around the Henry Mountains, Utah, as well as in mountain valleys of the Henry Mountains to an altitude of 10,000 feet (3,000 m).
Gray wolves, and grizzly bears are apex predators of bison, but bison meat is not a major component of their diet. Competitive pressure from the other large grazing mammals in Yellowstone may also help limit the number of bison in the herd, but this is not considered to have had a significant effect on bison numbers. Disease, including various viruses, parasites and brucellosis, have a greater effect on bison population.
The Yellowstone bison herd is divided into two sub-herds that are somewhat isolated from each other. The northern range herd which numbers approximately 2,300 individuals ranges from the north entrance near Gardiner, Montana through the Blacktail Plateau and into the Lamar Valley. The central interior herd, which numbers approximately 1400 individuals, ranges from the Madison River valley into the Hayden Valley and Upper and Lower Geyser Basins.
The Buffalo Field Campaign and Western Watersheds Project filed a petition in 2014 that contends that these herds are two separate groups and are genetically distinct. They asked that the bison be declared endangered or threatened under the Endangered Species Act with a separate population limit for each of the two herds. They claim hunting, trapping, hazing, capture and slaughter of the bison disproportionately impacted the central interior herd, reducing the size of the herd dramatically during the last two decades. The Fish and Wildlife Service rejected the listing in 2015 and 2019, arguing that the herds are not genetically distinct. A judge ruled that the agency applied the wrong standard and failed to address a significant aspect of the question.
Management
American Bison once numbered in the millions, perhaps between 25 million and 60 million by some estimates, and they were possibly the most numerous large land animal on earth. However, by the late 1880s, they had been hunted to near extinction throughout North America. The Yellowstone bison herd was the last free-ranging bison herd in the United States being the only place where bison were not extirpated. The Yellowstone bison herd is descended from a remnant population of 23 individual bison that survived the mass slaughter of the 19th century in the Pelican Valley of Yellowstone Park. To assist in the species' revival, in 1896 the United States government obtained one bull and seven cows from the Lincoln Park Zoo bison herd for Yellowstone. In 1902, a captive herd of 21 Goodnight plains bison was introduced to the park and then moved to the Lamar Valley and managed as livestock until the 1960s, when a policy of natural regulation was adopted by the park.