Elk near the North Entrance of Yellowstone National Park/NPS, Diane Renkin

Yellowstone National Park elk are so conditioned to their winter and summer ranges that the park's wolves don't force them to go elsewhere, according to a new study.

"They will move about within their home range to avoid disturbance, whether it’s humans or predators, but they’re reluctant to relocate their winter range," Dr. Dan MacNulty, an associate professor of wildland resources at Utah State University, said Wednesday.

"In 1988, after those fires and the severe winter, we did actually have very good evidence from radio-collared animals of them abandoning their winter ranges and moving downstream, where conditions were more favorable," he added. "So they are flexible, but their preference is to remain in a familiar area. But if there is absolutely no option of surviving in that areas, then they will move because they don’t have a choice."

The results of the study open another portal into the dynamics of the wild kingdom that inhabits Yellowstone National Park's northern range. The elk population has had its ups and downs through the years, and one of those downs was attributed by some to the wolves that were brought to the park beginning in 1995 to reestablish the predators.

Early in the winter of 2010-11 the population survey of the elk herd produced a count of just 4,635, down roughly a quarter from the 6,070 tallied a year earlier and far from the peak of 19,045 elk in 1994. That 4,635 tally prompted an outcry from hunters, who blamed wolves for the downfall, and worried there would be fewer elk in the hunting areas in Montana to the north of Yellowstone.

MacNulty, however, said Wednesday during an interview that the decline in elk numbers started before wolves were resettled in the park in 1995. It started, he said, after that peak count made in January 1994. By December that year the number was down to about 17,000, the professor said.

"The elk population started decreasing even before the first wolves were let out of their pens. People need to know that," MacNulty said. “What that helps set up is the fact that this elk population has decreased independently of wolves."

While wolves have played a role in elk numbers in the park, so has hunting, particulary in areas in Montana just outside the park. In hunting district 313 just north of the park state officials seek to keep the numbers of elk wintering there between 3,000 and 5,000 to maintain winter range conditions, he explained. 

"They were trying to prevent over-grazing on the winter range. And so in order to meet that cap, they were increasing the annual number of permits allowed," the professor said. "And so, the number of elk being removed by hunters was increasing annually at the time that wolves that were brought down (from Canada) and released. From 1995 we had almost 2,500 elk removed by hunters. In 1997, it was over 3,000."

Even after wolves were settled in the park in a number of packs they really didn't have a great impact on the elk population, the professor said. In 2001 the number of elk taken from the northern herd by wolves was around 2 percent, said MacNulty. It peaked in 2007, at 9 percent. Hunters, meanwhile, harvested nearly 19 percent of the elk herd in 1996, he said. By around 2002 the harvest fell as Montana officials were reining in the number of licenses issued in that district.

The background ties into the latest study, led by MacNulty and Michel Kohl, also at USU, that supports other research that elk distribution and vegetation conditions in northern Yellowstone since wolf reintroduction in the mid-1990s are not caused by wolves altering elk movement behavior.

The researchers used global positioning system radio-collars to track the movements of 34 adult elk cows and wolves across four winters, between 2012 and 2016. 

"We compared recorded elk movements with those from a simulation that described how elk would move if they completely ignored wolves and risky areas" said MacNulty, who has studied wolf-elk interactions in northern Yellowstone since 1995. "In 90 percent of cases, there was no difference between real and simulated elk movements, indicating that our sample of real elk mostly ignored the risk of wolf predation."

Hunting pressure also will cause elk to move to a certain degree, the professor said.

“It’s not clear that it will cause them to abandon their winter ranges, but there is evidence, particularly from the northern Yellowstone herd, that heavy hunting pressure will bump elk, will move elk. The question is how permanent those adjustments are," he said.