Yellowstone National Park is warning visitors to leave the park animals alone after a video of a man petting a bison went viral. 

The video shows a man approaching a bison from behind a fence and petting the animal. At one point, the bison quickly steps back, startling the man. No one was hurt in the incident. 

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Park officials are investigating the incident. Yellowstone rules require visitors to stay 25 yards from most large animals and 100 yards away from any bears or wolves at all times. 

"The individual who recently was captured on video touching a wild bison along a park boardwalk showed an incredible lack of judgement and common sense," Yellowstone National Park Superintendent Cam Sholly said in a statement. "Not only did he put himself and others at risk, he violated regulations designed to keep these animals wild. We expect better from our visitors." 

Last month, a bison injured a 9-year-old girl at Yellowstone National Park when it tossed her into the air. 

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