Bison are being pushed back into Yellowstone National Park this week, but livestock managers won't be using any helicopters in the round-up.
The Associated Press reports that the annual effort to nudge bison back into Yellowstone is designed to keep the animals away from the region's cattle.
Wildlife managers will be riding horseback and ATV's during this week's drive, pushing approximately 300 bison nearly 7 miles until they're back in Yellowstone's confines. Previous year's efforts included the use of a helicopter but that triggered lawsuits from some environmental groups.
The AP reports that bison make their way to lower elevations of southwestern Montana each winter, but an agreement between state and federal agencies requires that the bison return to within Yellowstone's borders in the spring, yielding the lower elevations of southwestern Montana to grazing cattle.