Yellowstone National Park officials say two wolves from the Junction Butte Pack that were fatally hit last month had become habituated to people and roads.

The black male and female pups died from a vehicle strike on the road between Tower Junction and the Northeast Entrance. Yellowstone law enforcement officers are investigating the incident, which occurred around sunset on Nov. 19.

The Junction Butte Pack is one of the most frequently observed packs in the park. Their territory ranges between Tower Junction and Lamar Valley.

Over the summer, the pack of 11 adults attended a den of pups near a popular hiking trail in the northeastern section of the park. Wanting to keep visitors and wolves apart, Yellowstone officials closed the den and surrounding area to the public.

When the pups approached the trail and were in proximity to hikers, most people quickly moved away. However, some people violated the required 100-yard distance from wolves and approached the pups when they were on or near the trail to take a photo. Other people illegally entered the closed area to get near the wolves. Having grown accustomed to hikers, the pups then came close to visitors along a road.

Yellowstone staff hazed the pups several times over the last five months in an attempt to make them more wary of people and roads. This effort was never fully successful and the pups continued to demonstrate habituated behavior due to continued close encounters with visitors.

“Having studied these pups since birth, I believe their exposure to, and fearlessness of people and roads could have been a factor in their death,” said Yellowstone’s senior wolf biologist Doug Smith. “Visitors must protect wolves from becoming habituated to people and roads. Stay at least 100 yards from wolves, never enter a closed area, and notify a park ranger of others who are in violation of these rules.”