YELLOWSTONE NATIONAL PARK, Wyo. - For the bison here in the world's oldest national park, roundups and slaughterhouses are nothing new.


At times, park managers tried to foster the bison herds. At other times, they killed them by the hundreds.


Until the early 1950s, most of the park's bison were treated like cattle: turned loose in the summer, rounded up and fed hay in the winter.


Bull calves were castrated, and salt was spread out for the animals. When their numbers grew, rangers ran them into corrals much like the ones drawing so much controversy on the park's borders today. Then they were killed and processed in the Park Service's slaughterhouse in the Lamar Valley.


In later years, bison were shot in the field in the park interior or herded by helicopter into traps. Then they were trucked to a packing plant in Livingston, Mont., one of the same slaughterhouses where they go today.


While the Park Service was reducing herds in some parts of the park, it cultivated herds in other parts.


Bison were loaded into trucks and transplanted to areas of the park where they hadn't been seen in years, only to be shot later when park managers decided they had overpopulated the range.


Bison "reductions' - along with much bigger and more widely known elk reductions - came to a halt in 1966 when, under intense pressure from hunting groups and others who didn't like the practice, the park began managing in ways that left the bison mostly to their own devices.


At that time there were an estimated 366 bison in the park, down from a high of 1,450 reached in 1954. Bison numbers grew fivefold, to about 2,000 animals, between 1966 and 1981 - the only time in park history when the bison were left alone. Prior to this winter's killing season, there were an estimated 3,000 to 3,500 bison in the park.


"Natural regulation" is still nominally in effect, even though bison in the mid-1980s began leaving the park in large numbers and more than 3,000 have been killed outside the park since then.


By 1981, bison had discovered snowmobile trails. Hard-packed winter trails mean higher winter survival rates, which mean more babies in the spring, causing unnatural distribution, according to Mary Meagher, a federal biologist who is the world's top authority on Yellowstone bison.


Meagher says the outflow of bison could be stemmed by cutting back on winter use of the park, or at least halting the grooming of park roads.


That is a controversial issue. The gateway community of West Yellowstone, for example, bills itself as "the snowmobile capital of the world." Thus, Superintendent Mike Finley finds himself on the horns of a dilemma: Which powerful industry does he risk alienating, livestock or tourism?


On Jan. 27, the Fund for Animals and the Boulder, Colo.-based Biodiversity Legal Foundation may have saved Finley the trouble of a decision. It threatened to sue the Park Service on the grounds that by promoting winter tourism, it is violating its statutes to protect the park. And heeding Meagher's observation, a Humane Society spokesman says the group will work to halt trail grooming in the park.


Add up the nurturing, the killing, the transplants and the snowmobile trails, and you find almost a century of manipulation of Yellowstone's bison, a story that continues today at the park's borders.


* Scott McMillion





Todd Wilkinson contributed to this report.