Yellowstone National Park officials made "heroic efforts" before deciding to euthanize a newborn bison that well-meaning tourists put into the trunk of their SUV, a spokeswoman said.

The death of the bison calf, announced Monday, followed repeated failed attempts to reunite it with its herd, Charissa Reid, a Yellowstone spokeswoman, told The Huffington Post. She said the euthanasia decision was "not made lightly" and followed "heroic efforts."

In the end, Reid said, Yellowstone's resources and mission focus on protecting the natural process, not rescuing animals.

"This is what they had to do," Reid said.

On its Facebook page, Yellowstone explains: "In order to ship the calf out of the park, it would have had to go through months of quarantine to be monitored for brucellosis. No approved quarantine facilities exist at this time, and we don't have the capacity to care for a calf that's too young to forage on its own."

The baby bison's heartbreaking death, if nothing else, shines a spotlight on a pervasive issue facing America's national parks: Some visitors are completely ignorant to the fact that wildlife is -- get this -- wild.

"Really, all you need to do is go online and look at" social media, Reid said, when asked how often visitors ignore warnings not to get too close.

"It's not safe for the people or the animals," she said.