Study: In Idaho, cougars kill slightly more elk than wolves

An expansive study of elk mortality in Idaho’s wolf country did what most good science does: challenged ideas held as gospel by wolf partisans and wolf antagonists.

Namely, wolves kill elk, but mountain lions kill more. And, food availability and winter severity are the most important factors for elk calf survival.

“Things are usually more complicated than one thing,” said Jon Horne, the lead author of the paper and a senior wildlife research biologist at the Idaho Department of Fish and Game. “But it’s sometimes really hard to show that.”

The study looked at 15 years of data collected on Idaho’s wolf and elk population. It was published earlier this year in the Journal of Wildlife Management.

In particular, the study found that wolves accounted for 32% of identified mortalities for female elk while mountain lions accounted for 35%. That disparity grew when looking at elk calf survival with wolves accounting for 28% of known-fate deaths and lions accounting for 45%.

“The one variable that mattered the most for calf survival was how big it was,” Horne said.

Which isn’t to say wolves don’t have an impact on elk survival. They certainly do, Horne said. The larger the wolf pack, the more elk were killed “by an amount that was not insignificant,” he said.

Horne and the other researchers in the study found that during deep snow years, elk mortality increased. This makes sense, he said, first because snow makes for harder, longer winters and second because wolves have an advantage in deep snow.

An important caveat: While Horne and the others were able to look at the size of a wolf pack’s impact on mortality, they were not able to do so with mountain lions.

“We didn’t have a variable like the wolf variable where we knew what the lion population size was in an area,” he said.

Horne said the study’s findings likely hold true for wolf-elk interactions in Washington, Montana and Canada.

The mortality study builds on previous work that also threw cold water on some of the hottest wolf rhetoric. In that 2018 study, also published in the Journal of Wildlife Management, Horne found that the mean pack size in Idaho didn’t change much between 2005 and 2015, despite a legal hunting season.

“On one side of the ledger you have a portion of the public that thinks that harvest is just going to send the wolves to extinction and that has not been the case,” he said of that 2018 study. “And then … there is a side that thinks wolves are taking over and they will grow without limits.”

Both studies add to the growing body of research looking at wolves, both internal pack dynamics and their impact on the ecosystem. Like other areas of research, it’s slow, nonlinear and incremental with studies occasionally coming to slightly different, or completely different, conclusions.

An example of that sort of scientific back-and-forth can be found in a 2018 study finding that Washington wolves “had little or no impact on the deer from a survival standpoint.”

But unlike other less-controversial scientific disciplines, wolf research is used strategically by proponents and opponents alike.

“From a distance, this just looks like science as usual, moving forward in its crooked line,” wrote journalist Christopher Solomon in a profile of former Washington State University researcher Rob Wielgus’ work. “But the topic here was wolves, and that weaponized everything.”