The us government culls bison from the Yellowstone herd every year, to discourage them from leaving them park and competing with cattle grazing on public lands.
Bison are managed completely differently than other wildlife in the area like moose and elk, because they compete with cattle. They’re forced to stay inside the higher elevation park boundaries, even when the snow is too high for them to forage effectively. They get hazed by helicopters, chased by DOL agents and rangers on horseback, and forced to run miles through snow to cross that invisible line back in Yellowstone. I’ve seen newborn bison calves with broken legs from getting hazed back into the park.
If they were allowed to migrate seasonally and breed normally, they would have a much larger range and population.
Source: I used to live on the park boundary and was part of a group documenting bison management.