They've said it before and it looks like they'll have to say it again - don't get too close to the animals.
Shocking video footage shows the moment a female tourist at Yellowstone National Park in the US got too close while photographing an elk -which then charges directly towards her, leaving her lying on the ground.
The footage was taken by a visitor from a nearby vehicle and ranger Jody Tibbitts can be heard in the background advising the woman to keep her distance.
The woman can be seen attempting to photograph or video the animal in the woods.
Tibbetts, who shared the clip on Facebook and has worked at the park since 1991, warns the woman by asking "ma'am, ma'am could you please . . .".
But his words came too late and the elk appears from behind the trees and charges at the woman.
While the camera misses what exactly happened during the encounter, as it pans back, the woman can be seen on the ground.
"I was just going to tell you you're too close to that elk, and that's why," Tibbetts says.
She then says "it won't happen again" and Tibbitts replies, "I'm sure it won't.
The ranger told EastIdahoNews that the woman tripped before she could be butted by the elk.
"Literally on a daily basis I'm having to tell people they're way too close to animals," he said.
"I've even seen folks chase bears into the woods for a picture."
On its website, Yellowstone warns visitor to "stay at least 100 yards [90m] away from bears and wolves and at least 25 yards [22m] away from all other large animals - bison, elk, bighorn sheep, deer, moose, and coyotes".
The incident follows the death of a baby bison in the national park. The animal had to be euthanised after tourists worried that it was cold and put it in their car to drive to a ranger station.
A New Zealand man was also recently accused of walking through no-go areas of the United States' biggest hot spring in Yellowstone National Park, to take photos and videos to put online as part of the social media group High on Life Sunday Fundayz.