Two tourists in Yellowstone National Park allegedly placed a baby bison into their SUV and drove off with the animal.

Karen Richardson told NBC Montana that she was chaperoning a fifth-grade trip to the park when two tourists arrived at the ranger station with the animal in the back of their SUV. She said the pair had taken the calf because they were worried it was cold .

Rob Heusevelet, a father of a student on the class trip, told East Idaho News the tourists "sincerely thought they were doing a service and helping that calf ."

The unidentified pair were ticketed, and the animal was returned to where it had been found, the website reported.

A bison expert said the baby animal probably wasn't healthy and may have been abandoned by its mother, or else it wouldn't have been caught so easily.

"From about 3 days old, they can run up to 30 miles per hour," bison rancher Troy Westre told NBC Montana. "If the mother is around, she's going to kill you any chance she gets."

Although President Barack Obama recently signed the National Bison Legacy Act into law, officially making the American bison the national mammal of the United States, park officials do not want tourists approaching the animals.

Yellowstone visitors should remain at least 25 yards from bison , and signs around the park warn people to keep their distance: