Montana livestock officials have finished hazing several hundred bison back into Yellowstone National Park to keep the wild animals from transmitting disease to cattle. Many of the park's bison carry brucellosis, which can cause pregnant livestock to miscarry.
The drive took several weeks.
Christian Mackay with the Department of Livestock says the effort was slowed by a federal court order banning the use of a helicopter to haze the animals.
Mackay say workers on the ground could not drive the bison as far as the helicopter. That allowed some animals to repeatedly return to Montana.
Environmentalists said the helicopter had been scaring federally-protected grizzly bears. The Alliance for the Wild Rockies sued to stop the practice.
Wildlife advocates say hazing would not be needed if bison could linger in Montana.