In this photo from May a mother black bear with cubs runs toward a group of camera-clicking tourists as the animals cross a bridge in Yellowstone National Park. Montana Fish Wildlife and Parks spokesman Bob Gibson witnessed the encounter and said some visitors ignored or were slow to heed a park official's commands to leave the bridge.
In this photo from May a mother black bear with cubs runs toward a group of camera-clicking tourists as the animals cross a bridge in Yellowstone National Park. Montana Fish Wildlife and Parks spokesman Bob Gibson witnessed the encounter and said some visitors ignored or were slow to heed a park official's commands to leave the bridge. Bob Gibson/Montana Fish, Wildlife and Parks Associated Press
In this photo from May a mother black bear with cubs runs toward a group of camera-clicking tourists as the animals cross a bridge in Yellowstone National Park. Montana Fish Wildlife and Parks spokesman Bob Gibson witnessed the encounter and said some visitors ignored or were slow to heed a park official's commands to leave the bridge. Bob Gibson/Montana Fish, Wildlife and Parks Associated Press

Yellowstone officials now studying humans, the most problematic species of all

June 20, 2016 05:08 PM

UPDATED June 20, 2016 06:09 PM

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