The history of bison and their management in Yellowstone National Park could be described as cycles of endless bounty followed by scarcity. Most people know that vast herds of bison, or buffalo as they are more commonly called, once filled the North American continent. Estimates suggest that as many as 65 million bison roamed North America in the early 1800s. With such seemingly unlimited numbers, their destiny appeared certain, but, instead, their fate nearly followed that of the passenger pigeon. Market hunting and poaching all but eliminated this species from North America; by 1890 fewer than 1,000 bison remained.

Yellowstone National Park was not immune to the slaughter. In the 1870s poachers and meat hunters continued to kill bison within the newly created park. It was not until the arrival of the U.S. Army in 1886, sent to protect all of Yellowstone's resources, that poaching and hunting were brought under control. Later, in 1894, Congress passed the Lacey Act, which imposed a $1,000 fine on anyone convicted of shooting bison, and the preservation of this American species was assured.

In 1902, only 23 free-ranging bison were counted in Yellowstone's Pelican Valley, and National Park Service (NPS) officials doubted that this native herd would survive. Consequently, 21 bison from private ranches in Texas and Montana were brought to Yellowstone and placed in pens at Mammoth Hot Springs and managed like cattle. These bison were moved to the "Buffalo Ranch" in the Lamar Valley in 1907 and were intensively managed there until the late-1930s. In 1936, bison were trucked from the Lamar herd to the Firehole and Hayden valleys. Bison were now allowed to range freely in the park and mix with the native herd. With protection from poaching and hunting, the native and transplanted bison populations increased. In 1954, the park's entire population of bison numbered 1,477. By this time the bison in Yellowstone wintered in three fairly distinct herds, although there is some overlap between the herds at various times of the year. These herds are called the Northern (Lamar Valley) herd, the Mary Mountain (Hayden Valley-Firehole River) herd, and the Pelican Valley herd.

A large bull bison can measure six feet tall at the shoulder and weigh a ton. Bison have massive heads and a high hump on the shoulders. In winter bison use their head as a snowplow, swinging it back and forth through the snow to find the vegetation below. Female bison look like the males, although they are smaller and have more slender horns that point forward. Bison are gregarious and congregate in large herds. Although adult bison are dark brown with long shaggy hair on their shoulders and front legs, calves are reddish brown without shaggy hair when born in April and May. Many spring visitors to Yellowstone go to the Lamar Valley or the Firehole area to view these new calves. Bison mate in July and early August, and areas like Hayden Valley ring with their bellows and are filled with dust from the battles between rival bulls.

Management of bison in the park has changed over time. As mentioned earlier, bison were managed intensively (ranched) for many years in order to increase their numbers and preserve them as a natural species in the park. In the 1930s, National Park Service policy began to shift from artificial manipulation of wildlife to the preservation of species in a more natural state. However, bison were still managed, albeit sporadically, by way of removals (including live transplants to many areas around the nation to develop new bison herds) until the mid-1960s. In 1968, manipulative management of bison ceased, and the bison population was allowed to increase or decrease in response to environmental conditions, particularly winter weather. A parkwide count at this time placed bison numbers at 397. Throughout the late 1970s and 1980s a series of cool, wet summers produced bountiful grasses for bison to feed on. Concurrently, a series of mild winters and winter recreational activities (snowmobiles were first allowed on groomed roads in Yellowstone in the early 1970s; groomed roads cut down on the energy a bison uses to travel compared to when the bison moves through deep snow) have allowed more bison to survive the winter. By the winter of 1996-1997, an early winter count placed the park's bison population at 3,500.

Although the three states surrounding Yellowstone (Wyoming, Montana, and Idaho) had had "Boundary Control Agreements" with the NPS since the early 1970s to assure that any bison moving out of the park would be killed, it was not until 1982 that Montana instituted a public hunt to control bison moving beyond Yellowstone's boundaries. Due to public controversy, the Montana legislature halted the public bison hunt in 1989. In 1990, Montana and the NPS developed an interim management plan in which state and federal personnel shot bison in Montana to protect private property, provide for human safety, and protect Montana's brucellosis class-free status. Brucellosis is a disease that can cause abortions in domestic cattle. Some bison as well as elk carry the bacterium that causes the disease. Although there are no documented cases of wild, free-ranging bison transmitting brucellosis to cattle in the wild, the possibility of transmitting the disease exists if cattle would come in contact with infected birthing material or a new-born calf from an infected animal.

In 1995, as part of a court-approved settlement agreement resulting from a lawsuit filed by the state of Montana, a new interim bison management plan was developed. Bison entering Montana along the park's northern boundary would either be captured and shipped to slaughter or shot. Bison entering Montana along the park's western boundary would be captured and tested; bison testing positive for brucellosis would be shipped to slaughter. Due to the management removals and winter-kill, the Yellowstone bison population in March 1997 is estimated to be between 1,200 and 1,500 animals.

A long-range bison management plan and environmental impact statement is being jointly prepared by the NPS, the U.S. Forest Service, and the state of Montana with the cooperation of the Animal Plant Health Inspection Service (an agency in the U.S. Department of Agriculture). This plan will evaluate several strategies for managing the periodic movement of bison outside the park while ensuring opportunities to view free-ranging bison and maintaining a self-supporting population in Yellowstone National Park. The plan and the draft Environmental Impact Statement are scheduled for public review on July 31, 1997.

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