Yellowstone Bison Calf Euthanized After Visitors Reportedly Tried to Rescue It Because It Looked Cold The visitors reportedly thought it looked cold, witnesses said.

 -- The story behind a viral photograph of a baby bison in the back of an SUV at Yellowstone National Park ended tragically, with the National Park Service saying today that it euthanized the animal after its herd refused to accept it back.

In its announcement, the park service issued a stern warning to its visitors. "In recent weeks, visitors in the park have been engaging in inappropriate, dangerous and illegal behavior with wildlife," the park service said today in a statement posted on its website. "Approaching wild animals can drastically affect their well-being and, in this case, their survival ... The safety of these animals, as well as human safety, depends on everyone using good judgment."

On May 9, the same day that President Barack Obama declared the bison the official U.S. mammal, visitors encountered a bison calf and put it in their SUV. They then drove it to a park facility because, according to witnesses, they thought the calf was cold.

According to the park service, regulations require that visitors maintain a distance of least 25 yards from all wildlife — including bison, elk and deer — and at least 100 yards from bears and wolves.

The National Park Service said moving the calf was "a dangerous activity" because adult animals are very protective of their young and act aggressively to defend them. It said interference could also cause the mother to reject her offspring.

Rangers tried to reunite the calf with its mother, according to the park service, but it was ostracized by its herd. Because the calf was found wandering among visitors' cars, making it a danger to itself and others, the park service decided to euthanize it.

"It was abandoned and causing a dangerous situation by continually approaching people and cars along the roadway," the park service said.

According to The Associated Press, the visitors were cited for touching wildlife and fined. The visitors were not identified.