Look, we’re not wildlife experts by any stretch of the imagination, but there is one very easy way to avoid injury by head-butting or other aggression from our large animal friends: Don’t get too close, even if it means the difference between an amazing selfie and one that is only great.

The National Park Service is reminding people to steer clear of park animals after two visitors were injured by a bison in Yellowstone National Park on Wednesday.

The married couple was taking photographs on a boardwalk at Mud Volcano when a bison lumbered over. It butted the woman, who then fell into her husband, sending them both to the ground.

Park rangers immediately evacuated the couple from the trail and transported them to a clinic. The husband had minor injuries, while his wife was flown to a hospital in Idaho, where she was reported to be in stable condition.

The visitors were not cited, but park officials are stressing the importance of taking “safe selfies,” and staying at least 25 yards away from all large animals — bison, elk, bighorn sheep, deer, moose, and coyotes — and at least 100 yards away from bears and wolves when they show up near trails, boardwalks, parking lots, or in developed areas.

This is the first confirmed incident of a bison-inflicted injury this year, while five people were hurt by approaching bison last year.

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