YELLOWSTONE NATIONAL PARK, Wyo. (AP) — Two brothers accused of riding motorcycles off-road and harassing bison in Yellowstone National Park have pleaded not guilty.

Dallin McAllister, 25, of Provo, Utah, and Tyler McAllister, 36, of Gilbert, Arizona, entered the pleas Monday before U.S. Magistrate Judge Mark Carman in Yellowstone. Each was charged with operating a motor vehicle in prohibited areas and feeding, touching, teasing, frightening or intentionally disturbing wildlife.

The two drove off-road near Fountain Flats Drive in western Yellowstone Friday evening, park spokeswoman Ashton Hooker said.

Video posted online showed motorcyclists riding off-road within several feet (2 meters) of a group of running bison, including some calves, the Bozeman Daily Chronicle reported.

Tyler McAllister didn't immediately return a phone message Tuesday at his solar power business. Dallin McAllister didn't immediately respond to a request for comment Tuesday through Facebook.

Visitors in Yellowstone are required to stay 25 yards (23 meters) from bison and at least 100 yards (91 meters) from bears and wolves. Visitors may not go off road on vehicles or bicycles.

Yellowstone visitors had at least two other run-ins with bison this year. A bison knocked a woman down near Old Faithful in May.

A bison gored a woman after she approached it to take a photo near Yellowstone Lake's Bridge Bay in June. She was flown by helicopter to a hospital.

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