BOZEMAN — Montana officials have begun hazing bison back into Yellowstone National Park to make way for livestock.
The bison leave the park during winter in search of lower-elevation grazing and are forced back each spring to keep them from spreading diseases to cattle.
Officials from the Montana departments of livestock and fish, wildlife and parks already have made a few trips into the area north of the park, pushing back 100 or more bison each time.
The conservation group Alliance for the Wild Rockies said helicopter hazing of bison began Saturday. The group is suing to bar the use of helicopters, saying they harass and displace threatened grizzly bears.
The case is pending with the 9th U.S. Circuit Court of Appeals.