More than 10,000 people have commented on Yellowstone's Facebook post about euthanizing the bison calf abandoned by its herd, and placed in a tourist's SUV.
A majority of those comments, critical of the tourist's actions, also wanted to know why the calf couldn't be saved and placed with a zoo or sanctuary.
Tom Ronning, a wildlife refuge specialist at the Rocky Mountain Arsenal National Wildlife Refuge outside of Denver says just because the bison there, or in Yellowstone, are inside a fenced area and are protected doesn't make them not still wild.
Ronning says only the strong survive.
"Many times if animals can't keep up they get left behind," he said. "That's the herd mentality. An individual isn't a herd."
Ronning says Yellowstone bison often carry a disease known as Brucellosis, so the calf couldn't be moved to another location without months of quarantine.
Yellowstone says it does not have a facility that could accommodate that kind of quarantine, and isn't part of its mission to do individual animal rehabilitation.