A group of mule deer cross Highway 352 north of Cora on the world's longest mule deer migration. Wyoming Game and Fish has recommended two more major migration corridor designations.

As Wyoming’s big game herds huddle together on high, windswept plains, scrounging for whatever food they can find, the Wyoming Game and Fish Department is preparing to recommend designation of two more major migration corridors.

The first route, from Jackson to north of Rock Springs, would recognize 180 miles of antelope migration route including the renowned Path of the Pronghorn. The other, from southeast of Alpine to north of Evanston would recognize about 150 miles of mule deer paths.

Game and Fish and other state and federal officials gathered Monday night in Casper to explain the importance of migration as well as how development is planned and, at times, avoided, within the migration routes. The talk kicked off a series of public meetings across the western half of the state intended to answer questions about the corridors and what a designation means. But as the Bureau of Land Management continues to place thousands of acres up for oil and gas leases in and around those corridors, some advocacy groups wonder if more could and should be done.


Up until 2016, most wildlife officials and land managers focused on trying to limit development on big game winter ranges. The winter is the harshest time of the year, when animals are at their weakest and most vulnerable. Compared to summer ranges in the mountains, winter ranges are also often the areas most disturbed by humans and energy development.

But a flood of new information by researchers gathered using tracking collars on mule deer and antelope began to formalize the exact movements of migrating wildlife.

The information shows that mule deer, for example, will follow roughly the same path over 150 or even 250 miles every year, taking advantage of what Matt Kauffman, leader of the Wyoming Cooperative Fish and Wildlife Unit, calls the green wave.

“As plants grow they start out low in fiber and high in protein and this is what animals seek out to make a living,” Kauffman said. “If a deer is occupying a habitat exactly when it’s at peak forage… then they’re surfing.”

While winter and summer ranges are critically important, big game spend up to four months of each year migrating.

The growing body of information led the Wyoming Game and Fish Commission to become the first state in the country to create a migration route designation, allowing agency officials to consider where animals migrate when offering recommendations for drilling and other development.

Another piece of research from UW in 2018 articulated the importance of those routes: Once knowledge from a migration corridor is lost in a herd, it can take a century or more to find it again.

Following the commission’s designation, and a 2017 Department of Interior Secretarial Order focused on migrations, Game and Fish officials have begun analyzing BLM and state of Wyoming energy lease sales as they overlap with migration routes.


As habitat protection supervisor, it’s Angi Bruce’s job with Game and Fish to identify what leases pose the greatest risk to migration corridors. Generally speaking, if more than 90 percent of the lease parcel is within a migration route, the department asks BLM or the state to defer the lease. Similarly, if the lease is within a stopover point – the areas where big game spend days at a time foraging and resting along their journeys – they recommend the lease for deferral. But if there is less than 90 percent of the lease in the corridor, and it seems possible for development to occur adjacent to but outside of the designated corridor, Game and Fish recommends it be a special lease notice.

That’s a sticking point for some groups who worry the special lease notice – basically a heads-up from the BLM that a portion of the lease is in a migration corridor – doesn’t carry enough weight.

“We are looking for assurance the corridor won’t be interrupted,” said Kristen Gunther, conservation advocate with the Wyoming Outdoor Council. “We are concerned especially with mule deer because all research shows they have high fidelity to routes. If 99 percent is protected and 1 percent isn’t, it’s like putting road blocks on I-80.”

She is also critical of the sheer pace of leases offered by BLM right now – which included sales that increased each quarter of 2018, for example.

While Bruce said in an ideal world Game and Fish would recommend formal stipulations — basically condition of uses — to leases, she believes the department’s plan is sufficient. The special lease notice states that the producer, BLM and Game and Fish must all come to an agreement about where infrastructure such as wells can be placed before drilling begins. If they can’t agree, the producer must complete an environmental impact statement.

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“But long term we are planning for a stipulation that will take the place of the deferrals and special lease notice,” Bruce said. “This is an interim strategy.”

In the last three BLM lease sales, which have nominated hundreds of thousands of acres for potential leasing statewide, the BLM has deferred all of the leases requested by Game and Fish because of migration corridors, Bruce said.

Joshua Coursey, president and CEO of the Muley Fanatics Foundation, a growing sportsman’s group based in southwest Wyoming, said the Department of the Interior is looking at states like Wyoming to take the lead on what should and shouldn’t be developed.

“I think that it’s clear by the amount of studying being done, migration corridor protection is a legitimate concern that groups have,” Coursey said. “And I believe Game and Fish needs to be more engaged and proactive in making their opinion known.”


How many migration routes might traipse across the state, no one quite knows right now, said Doug Brimeyer, Game and Fish’s deputy chief of wildlife.

Game and Fish has established three so far for mule deer – the Sublette corridor, known as the famous 150-mile Red Desert to Hoback migration, and the Platte Valley and Baggs corridors.

The next two corridors being proposed face different challenges. Development, while still an issue, doesn’t likely encompass quite as much of their routes. Researchers are also not sure if pronghorn are impacted as much as mule deer by oil and gas development.

But they do face roads, fences, possible bottlenecks, habitat issues like food quality, invasive species and, in some places, potential leases.

“In those migrations, in the seasonal movements those animals make, exist all the knowledge they have accumulated over generations and generations of how to make a great living and prosper and produce herds on Wyoming’s landscape,” said Kauffman.

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