Accumulating Migration: Report Highlights Importance of Wildlife Corridors |

Ungulates, such as these pronghorns approaching the Pinedale Anticline natural gas field in Wyoming’s upper Green River basin, increasingly encounter oil rigs and other developments energy in their habitat.

The deer, elk, and pronghorns of the western United States are able to travel long distances through rugged country each spring and fall to reach the best food available to ensure their survival.

Until the advent of GPS collars and more affordable mapping technologies, the extent of these movements was unknown. Over the past decade, however, research has “blossomed”, providing the public with a great opportunity to preserve and protect roads and therefore animals, according to Matt Skroch.

Skroch is project director for the conservation of public lands and rivers in the United States at the nonprofit organization Pew Charitable Trusts, a global “agent of change” in research and public policy. He and Leslie Duncan recently co-authored a report compiling many of the major wildlife migration studies, noting the implications of the work as a means of promoting conservation. The article is entitled: “How to conserve wildlife migrations in the West”.

“The report is a call to action, really,” Skroch said in a phone interview. “It’s a call to use the latest and greatest scientific knowledge to preserve these incredibly important wildlife populations for the future.”

Some of the barriers to migration highlighted in the report include: urban sprawl, highways, fences, mining, oil and gas exploration. “An estimated 620,000 miles of fences criss-cross the western United States, much of it in wildlife habitat far from population centers,” the report notes.

Moose crossing

Wildlife-vehicle collisions pose serious risks to motorists and ungulates, like these elk crossing US Highway 89 north of Jackson, Wyoming, during their spring migration.


Skroch said that as states like Montana continue to see population growth, problems for wildlife will increase. He cited the growth of housing in rural areas as an example of how traditional wildlife habitat is being fragmented. Montana communities experiencing population growth include Bozeman, Big Sky, and Livingston, which are located on the edge of the Greater Yellowstone Ecosystem, one of the most intact segments of wildlife habitat in the United States.

“There are more people living in Montana than in the history of the state,” Skroch said. “There are more cars on the road, more houses in the exurban interface, and greater pressure on these wildlife populations.”

Much of the research cited in the Pew report took place in studies conducted as part of the University of Wyoming’s Wyoming Migration Initiative. Program researchers have identified long migration routes used by mule deer, pronghorn and elk populations in the western third of the state. The schematic representation of the movements showed the importance of the mountainous public lands as a source of nutrition while the lowlands are essential for the wintering range.

“Conserving a given migration may involve a highway bridge, an exclusion zone for new energy development, a county land use plan that incorporates areas of wildlife movement,” Skroch advocates. and Duncan. “The science is clear and solutions exist. It only remains for the various stakeholders to adopt these solutions.

While wildlife studies may be known regionally or in biology circles, Skroch and Duncan have condensed research highlights — along with challenges and possible solutions — into a digestible package for a wider audience. Skroch hopes agency officials and lawmakers, who are in a position to make “good public policy,” will read the document.

For those affected in tax terms, the report also notes possible economic impacts.

“Detailed assessments of the modern economic impact of ungulate migrations are rare,” the report says. But an analysis of 2015 data from Wyoming found that the state’s big game species, most of which are migratory, support $224 million in retail sales, have a total economic impact of more than $303 million. dollars and supports at least 3,100 jobs, mostly guides, who welcome hunters from out of state, and hunting and outfitting provide significant economic benefits to other western states, for example, in 2014 , elk hunters spent $138 million on food, lodging, transportation and equipment in Montana.

Migratory move

It is rare to see the pronghorn in the woods or wooded areas. They are only found in places like this during migration.


After scanning the Pew report, Justin Gude said the studies were all familiar but the report’s tone of suggesting a “sense of crisis” did not apply to Montana. Gude oversees wildlife studies in the state as head of the Office of Wildlife Research and Technical Services for the Montana Department of Fisheries, Wildlife and Parks.

In Big Sky State, Gude said wildlife movements are not unnecessarily impeded. In locations where GPS-collared wildlife have identified fences blocking movement, the agency has successfully worked with nonprofits, landowners, the state, the Forest Service, and the Bureau of land management to make fences wildlife-friendly.

“We’ve been working on this together for a long time,” he said.

This is the final year of a three-year pronghorn tracking project in eastern Montana. About 700 pronghorn antelope have been collared across eight study areas, 400 of which are still transmitting data, Gude said. So far, the collars have revealed that most animals in eastern Montana move around a lot in search of the best food but don’t migrate.

Meanwhile, in western Montana, a herd of pronghorn annually migrates through the Big Hole Valley to reach their wintering grounds south of the Pioneer Mountains. The animals summer near Anaconda and the Mount Haggin Wildlife Management Area, Gude said.

Several hundred moose also have collars. A bull walked from the Broadus area to the Black Hills of South Dakota and stayed. An elk cow from the Ashland area almost walked to Ekalaka but returned to its homeland, Gude said.

As Skroch noted, there’s something about the idea of ​​wildlife migrations that piques people’s interest.

mule deer

A recent study, conducted over 14 years, found that mule deer blocked their migrations in Wyoming when confronted with drilling rigs.

mule deer

In south-central Montana, FWP wildlife biologist Shawn Stewart tracked about 60 mule deer that were collared at three wintering grounds near Belfry’s sagebrush lands. The idea was to examine possible transmission routes for the chronic wasting disease, which was first detected in a mule deer shot in the area.

So far, the study has shown that most deer are moving northwest toward Red Lodge Creek and Cooney Reservoir, not up the mountains or south into Wyoming as Stewart thought.

“I would never have predicted this, ever,” Stewart said.

Monitoring has highlighted the importance of the sagebrush drylands at the foot of the Beartooth Mountains for wintering mule deer, he added. It also emphasizes the chronic wasting disease’s ability to move around the region, although so far it has not been detected in deer further north.

Whether it’s disease, drought or habitat loss, mule deer populations have been in slow decline across Beartooth Face, Stewart said. When he last surveyed, mule deer numbers along the Stillwater and Clark’s Fork of the Yellowstone Rivers were at their lowest levels in the 40 years he’s been conducting counts.

“Upper Stillwater has always been our breadbasket for mule deer,” he said.

As deer numbers have plummeted and public access has been restricted, use of the area by hunters has also declined, Stewart noted. Meanwhile, elk populations continue to rise in Hunting Districts 575 and 502, around 2,600 animals – the highest on record.

Moose migrations

Elk choose their path along a mountain in the Greater Yellowstone ecosystem. Nine herds that use the area migrate 30 to 100 miles from the valley lowlands to the high grasslands in the summer in search of green fodder.


The Pew report also noted that climate change and increasing recreational use of public lands pose threats to wildlife.

“One of the main ways that climate change can affect migratory ungulates is by shortening growing seasons and increasing the frequency and intensity of droughts, which can reduce the forage the animals access along their ranges. migratory routes.These effects may diminish the foraging benefits of migration to the point that animals will experience increased mortality and lower reproduction or choose to reside year-round rather than migrate,” the report states.

Recreational use of public lands covers a wide range of activities.

“Mountain biking; use of e-bikes, all-terrain vehicles, and motorcycles; backcountry skiing and snowmobiling; mountain climbing; scattered camping; and other activities are gaining popularity,” the authors noted. Existing trail networks are increasingly being used, and new trail networks are expanding rapidly into areas that historically had low levels of human use.And the potential impacts on migrating animals of these increasing recreational demands on public lands, including possible displacements, increased energy expenditure and reduced reproductive rates, are not yet well understood.

The lengthy report, highlighted by footnotes to the numerous wildlife studies, outlining imminent threats as well as possible solutions, can be viewed online at:

“We have the science and the data to inform the correct response to these threats,” Skroch said.

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