Despite your best intentions, it's probably not a good idea to put a wild animal in the back of your car - even if you're concerned it might be cold.

That's exactly what happened in Yellowstone National Park in Wyoming this week, where a father and son put a bison calf in the back of their SUV, before driving to a ranger station with it.

"They were demanding to speak with a ranger," Kate Richardson, who witnessed the incident, told "They were seriously worried that the calf was freezing and dying."

Law enforcement officers were called to the park and the tourists, who were from outside of the US, were given a ticket.


While the bison was released back into the wild close to where it was picked up, the story had a sad ending.

In a statement this morning, Yellowstone said the calf had to be euthanised as it had been rejected by its herd.

The calf was "causing a dangerous situation by continually approaching people and cars along the roadway", it said.

There had been other recent dangerous incidents involving bison at the famous park recently, including a viral video where a visitor approached within an arm's length of an adult bison in the Old Faithful area.

Five people were seriously injured by bison in the park last year and the animals caused more injuries than any other in Yellowstone.

Park regulations require visitors to stay at least 23 metres away from all wildlife, including bison, elk and deer.