Federal officials have cited a Canadian man who told rangers at Yellowstone National Park that he loaded a bison calf into his SUV because he thought it was cold.
The calf later had to be euthanized because it couldn't be reunited with its herd.
A criminal complaint filed in federal court states that Shamash Kassam of Quebec told rangers he put the bison calf in his SUV on May 9. Kassam is set to appear June 2 at the Yellowstone Justice Center.
The citation states Kassam told a ranger that he understood what he did was wrong and wouldn't disturb wildlife again.
An attempt to reach Kassam for comment Tuesday wasn't immediately successful.
A group of Vancouver men who posted pictures and videos of their travels on social media are also in trouble with Yellowstone officials after allegedly walking out to a hot spring where people are prohibited.
Rangers filed a criminal complaint Monday against three members of the group known as High on Life SundayFundayz that accuses them of stepping onto a geothermal feature.
On Tuesday, a posting on the group's website says they were "over zealous" in their enthusiasm while visiting the natural wonder and apologized.
"In an attempt to get the perfect shot, we acted in a way that doesn't reflect our respect for the environment we were trying to capture," the posting says. "It was the wrong decision to make. We realize that now."
The apology says they "wandered off the laid out path" to take photos of the Grand Prismatic Spring, adding that they were "unaware of the ecological ramifications and safety precautions."
"For this we would like to sincerely apologize to the Yellowstone park community and the public."
The Associated Press reported that the group removed photos and video showing some of them touching the hot water at the Grand Prismatic Spring over the weekend.
The criminal complaint was filed against Charles Ryker Gamble, Alexey Andriyovych Lyakh and Justis Cooper Price-Brown.
None of the men could immediately be reached for comment via the website or through Facebook.
Witnesses and video posted on the Internet show four men going about 23 metres off a boardwalk, according to the complaint.
The posting on the website says the group has been travelling the country for 75 days and its goal is to inspire others to explore.
"This is what we stand for, this is who we are, with the purest of intentions we managed to screw up on the last day."
The park's pathways are intended to protect both tourists and sensitive hot springs.
The posting offers a $5,000 donation to the park.
The Grand Prismatic Spring is the largest in Yellowstone at about 113 metres in diameter and more than 36 metres deep.
Witnesses reported the incident to rangers and provided pictures of the large recreational vehicle the group travelled in. The vehicle, with British Columbia licence plates, is registered to Charles Gamble, according to the complaint.
Gamble also could not be reached for comment.
Yellowstone distributes literature to visitors and posts signs around geothermal features warning people not to stray off boardwalks and paths.