The warning, which was issued on Wednesday, comes as mating season kicked off in the park.

The National Park Service warned travelers this week to stay away from bull elk in Yellowstone National Park as they enter their fall mating season.

The warning, which was issued on Wednesday, comes as mating season kicked off in Yellowstone for the most abundant large mammal found in the park. While it’s always important to stay away from wildlife, the park service noted it was especially imperative now since “bull elk are unpredictable during this time of year and people have been severely injured.”

The NPS added: “Elk run quickly and may change direction without warning.”

Park goers should stay at least 25 yards away (or about two bus lengths) from elk at all times, and if an elk approaches them, they should back away immediately. The NPS said travelers should find shelter in their vehicle or “behind a tall, sturdy barrier” if an elk charges and to run away if shelter isn’t available.

In total, there are about 10,000 to 20,000 elk from six to seven herds living in Yellowstone during the summer. During the fall mating season, the animals are typically found in the northern range, including by Mammoth Hot Springs and Madison River.

Male elk, known as bulls, can weigh about 700 pounds and stand at about five feet tall. Female elk can weigh about 500 pounds.

This isn’t the first time the NPS has warned travelers to stay away from wildlife. This summer, the park service advised visitors to be extra careful after two people were injured by wild bison at both Yellowstone and the Theodore Roosevelt National Park.

It’s also not the first time Yellowstone visitors have been cautioned to be wary of elk. This spring, the NPS told park goers to take extra care during elk calving season when the animals could become extra aggressive.

Beyond elk, Yellowstone features 67 different mammals from bison and moose to black bears, grizzly bears, mountain lions, wolverines, and more. Fall is the best time to visit Yellowstone to see bears, elk, and raptors.

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