A Yellowstone visitor tried to help a struggling bison calf. It had to be euthanized.

Yellowstone National Park staff had to euthanize a newborn bison calf after a park visitor tried to help the struggling animal near a riverbank but caused the herd to reject it, officials said.

After being abandoned, the calf had to be put down because it posed a danger by approaching cars and people on the roadways, the National Park Service said in a statement Tuesday.

“Approaching wild animals can drastically affect their well-being and, in this case, their survival,” the Park Service said.

According to the Park Service, the calf became separated from its mother when the herd crossed the Lamar River near the confluence of Soda Butte Creek.

A park visitor “intentionally disturbed the calf” by pushing it from the river and onto the roadway, the Park Service said. The incident happened Saturday evening and is under investigation, officials said.

Visitors later observed the calf walk up to and follow cars and people, which can be hazardous both for animals and humans.

“Interference by people can cause wildlife to reject their offspring,” the Park Service said. “In this case, park rangers tried repeatedly to reunite the calf with the herd. These efforts failed.”

On Facebook, the Park Service said that the calf had to be euthanized rather than sent to a sanctuary because it is illegal to remove bison from the park unless they are being sent to a meat processing or scientific research facility. There is a quarantine facility for sick bison to be tested for brucellosis, an infectious disease, or to be used to start conservation herds elsewhere if they test negative for the disease.

“However, the use of quarantine for a newborn calf that’s abandoned and unable to care for itself is not a good candidate for quarantine,” the Park Service wrote. “Situations like this one are challenging, but they also offer a space for all of us to engage in deeper conversations about the meaning of wild places.”

According to park regulations, visitors must remain at least 25 yards away from all wildlife, including bison, elk and deer, and at least 100 yards away from bears and wolves. Violators can be fined and risk being injured or killed by the wildlife, the Park Service said.

Officials are seeking help in identifying the man who moved the calf, described as being in his 40s or 50s, wearing a blue shirt and black pants, and asked anyone who may have information to contact the park tip line at (307) 344-2132 or email [email protected].

A similar incident happened at Yellowstone in 2016, when two tourists put a baby bison in their car’s trunk because they thought it looked cold and drove it to a ranger station. The calf was deserted by its herd and had to be euthanized.

Yellowstone is the only place in the United States where bison have lived continuously since prehistoric times, according to the National Park Service. Their population ranges from 2,300 to 5,500, depending on their breeding schedules.