The migratory portion of an elk herd near Cody has hit historically low calf numbers because of drought and increased predation, according to a study released today.

Drought limits pregnancy, explained Arthur Middleton, one of the authors of the paper “Animal migration amid shifting patterns of phenology and predation: lessons from a Yellowstone elk herd,” published in the journal Ecology. The lower pregnancy levels come at a time when elk also

face increased predation from grizzly bears.

The migratory elk will likely not disappear. But their future is uncertain in part because of possible continued drought that some scientists link to climate change.

Grizzly bear numbers have increased in the greater Yellowstone ecosystem. Their diet in some areas is also shifting more toward elk calves than it did before a recent decline in cutthroat trout, Middleton said.

Much of the predation comes from grizzly bears, not from wolves as many would believe, he said. Middleton completed the research while working for the Wyoming Cooperative Fish and Wildlife Research Unit at the University of Wyoming. He is now with the Yale School of Forestry and Environmental Studies.

This study means wildlife managers need to continue limited hunting pressure on migratory animals and liberal hunting opportunities on resident elk, said Wyoming Game and Fish biologist Douglas McWhirter, who also helped with the paper.

Middleton started research on the Clark’s Fork herd when wildlife biologists in the Cody region noticed the migratory elk returning from their summer range with fewer and fewer calves. Migratory elk classically survive better than resident elk because they follow higher quality food.

The opposite seemed to be true in the Cody region. Resident elk from the same herd as the migratory elk found areas with irrigated fields to eat, few predators and more limited hunting on private land, McWhirter said.

“All of those things combined together, what a perfect place for an elk to be and thrive,” he said.

That didn’t explain why the migratory elk continued to have fewer calves.

Researchers discovered after three years of following elk with GPS collars that pregnancy rates were lower in migrating elk. About

90 percent of the resident elk became pregnant each year compared to about 70 percent of the migratory elk.

Migratory cow elk nursing calves were not becoming pregnant. They couldn’t seem to find enough nutrition to finish nursing and produce another calf, Middleton said.

Then once the calves were born, they faced increase predation, especially by grizzly bears, he said.

Bringing calf numbers back up may be more complicated than simply increasing hunting quotas on wolves or black bears, he said.

Habitat projects could help, but options are limited in the wilderness and backcountry areas frequented by migrating elk.

“This highlights how challenging it is to do wildlife management in the Yellowstone ecosystem,” Middleton said. “It’s growing in complexity and hard to manage in that context.”

Reach Open Spaces reporter Christine Peterson at 307-746-3121 or Follow her on Twitter @PetersonOutside.

(6) comments

Cody Coyote
Cody Coyote

It should be pointed out who financed Middleton's study , and why. The funding was almost entirely private, organized by the Rocky Mountain Elk Foundation whop contributed the most money. They conscripted the other big hunting clubs...Safari International, Sportsmen for Fish and Wildlife, Boone & Crockett. A number of smaller groups including the Cody Country Outfitters and Guides association pitched in. Then the study proceeded with a great deal of logistical assistance from Wyoming Game and Fish ( those helicopters and capture crews aren't cheap, at $ 1500 / hour give or take). Finally , nearly every federal and state agency was on board, as were a few private ranches.

I beleive the total dollar value of this 5-year study ( 3 years field, 2 years data crunching) was somewhere near $ 650,000 , comprised of $ 350,000 actual funds raised and $ 300,000 of In Kind contribution.

But get this. as INCLUSIVE as all this may sound at first, not a single environmental group, or non-hunting conservation organization was asked to participate. Several wanted in and were willing to contribute, but were refused. This study was by hunters for hunters. Worse yet, it was front-loaded against Wolves. It was steered from the get-go to try to generate defensible science showing that Wolves were the reason for the strange imbalances in Elk herds showing up in Sunlight-Crandall-Clarks Fork. These hunting groups were positive going in that wolves would be found guilty, but had to buy some science.

Unfortunately for them, Middleton is a man of good character and a great scientist , unsullied by politics and special interest groups He followed the science where it led him. That science led away from wolves, towards grizzlies, cougars, black bears, and the whole emporium of Climate Change effects on vegetation , snow pack, weather cycles etc etc etc. A loittle followup work by Middleton since has shown that the crash in Yellowstone Lake cutthroat trout due to the illegal introduction of predacious Lake Trout has forced some grizzlies to turn back to Elk for protein. Migratory elk. The same elk that were showing such low calf recruitment in some cases.

So if the gun hunters want someone to blame for loss of " their" trophy bull elk , go yell at the fishermen---those bucket biologists . Blame God , Exxon-Mobil, Encana , and Peabody Coal wreaking climate change upon us all.

The Enviros had nothing to do with this. Except to say " We told you so...."


Sorry, when predator numbers go up calf numbers go down, you don't have to be college educated to figure that out on your own. You cut down mountain lion number's and look how deer number's come back up on the mountain, increase predator number's and look how low moose and elk calve number's are, hunter's could also say we told you so..."


Cody You can do your fancy writing but at the end of the day places where ungulates are around saturated wolves NEVER fair well...... Now, we continue to read endless wolf science about how it is global warming that is hurting moose yet places like Colorado & Utah are doing better than just fine.... Utah matter of fact has had to cull the population a few years ago to get it in line with habitat. Numerous articles out recently in Colorado on how the moose are doing great.....

Now, here is an article pimping for more wolves in Isle Royale.....wolves die off and walla moose rebound despite "global warming"


The really funny thing about all of the trying to blame every thing except wolves is the fact, environmentalists insisted that wolves were the ONLY thing that could control elk numbers sufficiently. Now that elk herds are in real trouble, the wolves just don't have that much impact, it has to be something else.


"But their future is uncertain in part because of possible continued drought that some scientists link to climate change."
I truly hope your readers aren't so ignorant that they would believe this line of manure.. The wolves are killing the elk, and the constant pressure of being followed and chased by wolves lowers the pregnancy rate in cows. Do some research people!! They have an agenda!!


I'd say the "environmental terrorists", the Canadian Grey Wolf has for the most part been, the "climate change' referred to in this story.

Welcome to the discussion.

Keep it Clean. Please avoid obscene, vulgar, lewd, racist or sexually-oriented language.
Don't Threaten. Threats of harming another person will not be tolerated.
Be Truthful. Don't knowingly lie about anyone or anything.
Be Nice. No racism, sexism or any sort of -ism that is degrading to another person.
Be Proactive. Use the 'Report' link on each comment to let us know of abusive posts.
Share with Us. We'd love to hear eyewitness accounts, the history behind an article.