The life of a Wyoming mule deer is a tough one. In order to survive, thousands of the deer undertake an arduous 150-mile migration twice a year to find food. Manmade and natural hazards abound on this two-month trek.



“It’s not just about getting from point A to B, they have to forage all along the way,” said Matt Kauffman, a University of Wyoming zoologist. “These animals are slowly starving to death all winter. If winter is long enough or they are held up, the animals will die.”

Migrating animals can wander on to highways and be flattened by trucks, or tumble through frozen lakes. Fences, mining operations and other obstacles also provide a challenge. But for the mule deer, there is no choice – they must follow what Kauffman calls the “green wave” of young, lush vegetation from the mountainous greater Yellowstone area to the brush of Wyoming’s interior as the seasons change. They either move or starve.

Facebook Twitter Pinterest Mule deer make a two-month trek twice a year to find food. Photograph: USFWS

This Red Desert to Hoback migration is the longest in the contiguous US and, despite having occurred for thousands of years, was only fully discovered by researchers in 2011. Its epic length is rivaled only by the “path of the pronghorn”, a journey that takes America’s fastest land mammal on a biannual trudge to and from Grand Teton national park in search of water.



These migration routes take the animals through a patchwork of public and private land. The importance of publicly owned national parks was recognized long ago, but these crucial wildlife corridors linking protected areas are only starting to be understood and valued.

But the nascent movement to safeguard wildlife corridors – vital for animals as diverse as wolves, bears, elk, tortoises and ground-dwelling birds – is now at risk. In recent years, congressional Republicans have pushed for federal land in the western states to be handed over for development. With Donald Trump now in the White House, these ambitions could come to fruition.

Despite occurring for thousands of years, the longest migration in the contiguous US was only discovered in 2011.

A bill put forward by Jason Chaffetz, a Utah congressman, to sell off 3.3m acres of federal land was hastily withdrawn following uproar from conservationists and the outdoor recreation industry. But with Trump voicing support for greater oil and gas drilling on public land, wildlife corridors risk being disrupted or even severed.

“When a migrating mule deer hits an energy development area, they tend to speed up or try to detour around them,” said Kauffman. “This affects their access to food and makes migrations more difficult. As these corridors become less viable, they can be lost.

“Selling off public land would risk that. We are are at the infancy of understanding wildlife corridors, but we are starting to make progress. It looks like that could all be wound back.”

The deer and pronghorn that roamed the western states before white settlers arrived may no longer be in the tens of millions, but these species are currently at little risk of extinction. Still, their abundance could be severely hit if their corridors are lost, which raises concerns for recreational hunters, as well as ecologists who study the network of life in the west.

We are are at the infancy of understanding wildlife corridors, but we are starting to make progress.

Wolves and bears require reliable access to prey species. Unlike hoofed animals that have well-worn, repeated pathways, wolves and bears disperse to adjoining lands depending on the dynamics of their groups. Young male wolves, for example, tend to leave groups in order to establish new ones elsewhere. The reintroduction of gray wolves to Yellowstone in 1995 has created a ripple effect – wolves have moved through a network of protected areas as far as Washington state.

Facebook Twitter Pinterest Large predators are less popular in states with livestock populations, where ranchers often advocate hunting to keep populations down. Photograph: Kevin Rushby/Getty Images/Minden Pictures RM

While most landowners are happy to allow deer or elk pass through their land, wolves or bears aren’t quite as welcome given their tendency to devour livestock. The population of grizzly bears in the Yellowstone region has rebounded sixfold since it was placed under federal protection in 1975. Surrounding states, pressured by landowners concerned about bears exiting the national park, have successfully persuaded the federal Fish and Wildlife Service that the species should be delisted to allow them to be hunted.

Conservationists are increasingly turning their attention to private landowners to help promote and secure wildlife corridors. In a single 20-mile search for food, a species may cross land overseen by the US Forest Service, the Bureau of Land Management and privately owned ranches.

“It’s a real mix,” said Mark Elsbree, vice-president of the Conservation Fund, which works to buy private land to avoid bottlenecks in migration routes. “Private landowners are generally interested in wildlife habitat but as the properties are sold, the generations turn over, we risk losing that connectivity. New migration routes keep coming up on our radar and we need to act upon that.”

In 2015, the Conservation Fund purchased a 364-acre property at a notorious bottleneck for the mule deer’s Red Desert-to-Hoback route, near the city of Pinedale, Wyoming. The fund then switched its attention to the greater sage grouse, known for its elaborate mating rituals and for being in the middle of a struggle between its protection and land development.

The sage grouse has been known to move up to 100 miles at a time, between its sage brush winter habitat to open meadows used to rear young. The species has lost almost half of its habitat since European settlers arrived, with 45% of its remaining domain on state and private lands.

Facebook Twitter Pinterest Male sage grouse fight for the attention of a female south-west of Rawlins, Wyoming. The ground-dwelling bird’s vast range spans 11 western states. Photograph: Jerret Raffety/AP

In February, the Conservation Fund scooped up 100,000 acres of sage grouse habitat in Idaho, Wyoming and Colorado, but risks remain. Senate Republicans are attempting to end federal involvement in sage grouse protection, which could allow the states to open up more habitat for drilling.

“The pinch points for migration typically exist on private land,” said Elsbree. “But if federal lands were to change hands, then the very platform upon which species survive will be compromised.”

Climate change provides another threat to wildlife corridors. Maps produced by the Nature Conservancy last year showed the stark implications for nearly 3,000 species in North and South America. Many are already retreating northward to cope with warming temperatures, although a pathway isn’t always evident. According to a study published last year, only 41% of US land area is currently connected enough to allow species to move to more bearable climes.

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Some will have nowhere to go, either hemmed in by human constructions or simply a lack of livable space. “The bottom line is that species will need to move or adapt, or die,” said Brad McRae, a senior landscape ecologist at the Nature Conservancy.

“More and more people are understanding that wildlife needs protection outside distinct national parks, especially with climate change,” said Elsbree. “It’s important that we look at the whole system. If lands are sold and developed, we could lose some migration routes. We need to avoid that happening.”