Yellowstone National Park officials euthanized a bison calf after tourists put the newborn in their car and caused the animal to be rejected by its herd, the park said Monday.
Criminal charges against the tourists, who the park did not identify, are pending.
Rangers repeatedly tried to reunite the calf with its herd, according to a statement released by the park. The efforts failed, and the calf was later euthanized because it was abandoned and approaching people and cars along the road.
Human interference can cause mothers to reject their offspring, the park said.
Yellowstone released a statement Monday after receiving criticism for euthanizing the calf. In order for the calf to leave the park, it would have had to spend months in quarantine to be monitored for brucellosis. No approved quarantine facilities exist, and the park said it doesn't have the capacity to care for a calf that's too young to forage on its own.
"Nor is it the mission of the National Park Service to rescue animals: our goal is to maintain the ecological processes of Yellowstone," the statement said. "Even though humans were involved in this case, it is not uncommon for bison, especially young mothers, to lose or abandon their calves. Those animals typically die of starvation or predation."
The tourists were cited for taking of wildlife after they put the calf in their car and took it to a park facility because of a “misplaced concern for the animal’s welfare,” the release said.
Morgan Warthin, a spokeswoman for the park, said the investigation is ongoing and she did not know what the criminal charges would be. Warthin called the visitors international but said she did not know what country they came from.
She said the situation is unprecedented, and she is not aware of another instance in which tourists put a bison in their car.
When asked to respond to critics of Yellowstone’s decision to euthanize the calf, Warthin said park officials are professionals and should be trusted to “make the very best decision they can based on the information they have at the time.”
Warthin said the park would like visitors to respect wildlife and to know and follow the safety regulations.
The visitors put themselves in danger because adult animals are protective of their young and will act aggressively to defend them, the park said. Last year, five visitors were seriously injured when they approached bison. Bison harm more visitors to Yellowstone than any other animal.
Park regulations require visitors to stay at least 25 yards from all wildlife and at least 100 yards from bears and wolves.
“Disregarding these regulations can result in fines, injury and even death,” the release said. “The safety of these animals, as well as human safety, depends on everyone using good judgment and following these simple rules.”