Study On Wolf Pack Size And Elk Survival Spotlights Strong Cougar Impact

A longterm study of wapiti and wolves in Idaho turned up some pretty interesting results.

Mountain lions appear to kill more cows and calves and could also be having a larger impact on the elk herds, but wildlife managers can also increase the ungulates’ survival during snowy winters by downsizing large wolf packs preying on them.


The study also tied calf survival to predation by either toothsome species by how robust the young elk were going into their first winter, which in turn is linked to the quality of their habitat.

“There’s kind of something for everyone in there, and that’s OK, because it’s reflecting the real complexity of the system” Jon Horne, an Idaho Department of Fish and Game researcher, told David Frey of The Wildlife Society for a story entitled “JWM: Wolves reduce elk survival — but they’re not alone.”

JWM is the organization’s Journal of Wildlife Management, in which Horne and IDFG colleagues Mark Hurley, Jon Rachael and Craig White recently published “Effects of wolf pack size and winter conditions on elk mortality.”

For it, they paid close attention to 1,266 cows and 806 calves (captured at half a year old) in 29 herds from across Idaho between 2004 and 2016 to come up with a model that could predict the risk of death for the elk, according to the paper’s abstract.


They found that outside of hunting harvest, 9 percent of cows and 40 percent of calves died annually.

Mountain lions accounted for 45 percent of calf deaths, 35 percent of cows. They’re an ambush predator, better in rougher, denser terrain.

Wolves were responsible for 32 percent of cow mortalities, 28 percent of calves. They’re a coarser, more effective in open country.

“Wolves preferentially selected smaller calves and older adult females, whereas mountain lions showed little preference for calf size or age class of adult females,” the researchers state.

They were able to best predict whether a calf would die based on its chest girth — a measure of how healthy it was — the average number of wolves running in nearby packs, and how deep winter snows were, in that order.

For cows, it was age, average number of wolves, and snow depth, again in that order.


It all led to some conclusions for hunters, biologists, managers and policy makers to mull:

“Although our study was prompted by management questions related to wolves, mountain lions killed more elk than wolves and differences in selection of individual elk indicate mountain lions may have comparably more of an effect on elk population dynamics,” the researchers’ abstract states.


“Our study indicates managers can increase elk survival by reducing wolf pack sizes on surrounding winter ranges, especially in areas where, or during years when, snow is deep,” they write.


“Additionally, managers interested in improving over?winter calf survival can implement actions to increase the size of calves entering winter by increasing the nutritional quality of summer and early fall forage resources.”

While the results were not uniform, varying by region, that last point has been repeated a billion times, and here I’ll make it a billion and one — habitat is the key.

Elk country really needs to continue to be improved with the ungulates in mind to make them stronger, more fit and able to evade predators.

As for improving survival, in winter 2013-14 a professional hunter sent by IDFG into the Frank Church-River of No Return Wilderness to kill wolves to improve elk survival ended up taking out two entire packs before he was yanked out of the woods.

That’s unlikely to happen in Washington, but the state wolf management plan does say that if “at-risk” big game herds are found to fall 25 percent below population benchmarks for two straight years or see their harvests decline by a quarter compared to the 10-year average for two consecutive seasons, it could trigger consideration of reducing local wolf numbers if the wolf recovery zone that the deer, elk, moose, etc., herd occupies has four or more breeding pairs.

“Under this form of management, wolves would be controlled by moving them to other areas, through lethal control, and/or with other control techniques. While wolves are recovering, non-lethal solutions will be prioritized to be used first,” WDFW’s plan states.

It’s probably not the final word, but the IDFG biologists’ study is sure to kick up more sparks in the blazing fire that is the debate about the impact wolves are having on our region’s elk herds.

But two things are for sure: It appears that a whole ‘nother species — cougars — are playing an even bigger role in things than we’ve suspected, and this latest insight helps flesh out how complicated it all is.

“What we’re realizing now is that to really understand these systems, we have to treat them as multiple-predator, multiple-prey systems,” Horne told The Wildlife Society’s Frey.

In the coming years, details more specific to Washington should begin to come out through WDFW’s big predator-prey study in the Eastside’s northern tier. It’s looking at deer and elk, and wolves, cougars, coyotes and bobcats.

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