Yellowstone Migrations
Joe Riis
2017
Notes by Sam Strauss
What does home mean to you?
Think about what home means to the animals, plants, and people that we’ll talk about today
For many of these animals, “home” is movement itself
Six wild, native ungulate species- pronghorn, mule deer, elk, bison, and bighorn sheep- migrate through the GYE
They take advantage of lush high-elevation forage in the summer and escape from snow at lower elevations in the winter (i.e., they travel between low valleys and high mountains)
These animals are built with stout, muscular bodies and durable hooves so they can migrate.
Recent tracking studies show many of the herds travel annually anywhere from 25 to 150 miles
Some more than 200 miles
Natural and human-made obstacles
Their journey has natural obstacles and challenges like mountains, rivers, extreme weather, and temperatures, fires, and famine
It’s made worse by the addition of fences, roads, cars, guns, subdivisions, and huge areas of land where food and forage have been supplanted for pavement, towns, and ranch land.
Humanity’s Relationship with Ungulates
Legend Rock
Located 75 miles southeast of YNP, Legend Rock is a long wall of Native American petroglyphs, many of which depict hoofed animals like elk, deer, and pronghorn
They are made by scraping away the darker skin of the rock
Some date back 10,000 years
Native people depended on ungulates for food, tools, and shelter. They viewed them as the lifeblood of the landscape.
At Legend Rock, there are also figures of hybrid creatures- antlered humans- perhaps symbolizing the acuted dependence of native inhabitance on these animals.
Today, are we all that different?
The ungulates give us enjoyment, inspiration, sustenance, and livelihoods. Our fates may be linked as tightly as they ever were.
Tens of thousands of animals in dozens of herds sustain the park’s famous wolves, bears, and scavengers. They attract millions of tourists and many thousands of hunters annually. These visitors pay local businesses. (Outfitters, guides, hotels, restaurants). Without them, this ecosystem would slowly unravel.
Spring Migration
The young, bright, fast-growing vegetation is the most nutritious of the year. Animals try to keep pace with the spring green-up.
It’s a critical part of the year to put on fat after a lean winter and produce milk for newborn calves, fawns, or lambs.
Animals that stay behind, opting not to migrate (known as “residents” do not gain as much weight as their migratory counterparts.
For some animals, spring migration lasts as long as 8 to 10 weeks.
Some species, like elk, give birth to their young along the way. The newborn offspring make the journey with the adults
Other species, like pronghorn, wait until arriving at the summer range to give birth
Fall Migration
When the first snow falls in the high country, the animals retrace their journeys back to the lowlands
The winter storms push them, like a huge exhalation, out toward the edges of the GYE and beyond, back to the lower elevations and drier landscapes where they can escape deep snow and eat grass and shrubs that grew through the summer
Pronghorn
Weigh 90-150 pounds; they’re designed for speed
They prefer wide open spaces where they can make a big mistake (and see far and run fast). So much of their migration corridor is the wide-open sagebrush-steppe habitat
Along their migration route, they move as quickly as they can through areas where their visibility is limited, like in thick patches of willow
They’re not designed to break trails through drifts or swim in rivers swollen with spring runoff, but to migrate they must do so.
Swimming through fast-moving rivers is one of the most dangerous natural challenges that pronghorn face.
Does typically leads the way when the group crosses rivers or other dangerous places. A lead doe will punch a trail through the snow for the rest of the group to follow.
Pronghorn that summer in and near GTNP undertake a 100-mile long journey from winter range in Wyoming’s Green River Valley. This is one of the longest terrestrial migration in the lower 48.
Each spring, 300 or so pronghorn set off to reach GTNP on a long, dangerous trek, crossing cliffs, a high mountain pass, fences and ranches, subdivisions and energy fields.
They start in the desert-like Green River Basin to the south, work their way up the Green River, climb to a snow 9,000ft mountain pass in the Gros Ventre Mountains, and then reach GTNP.
They stay in GTNP in the summer to bear fawns and eat sagebrush to put on fat
Trapper’s Point and Pronghorn:
This highway crossing is the worst example of human-built infrastructure interfering with the western Wyoming pronghorn migration
Located about 6 miles west of Pinedale, its narrow strip of land is shaped like the neck of an hourglass, outlined by rivers on either side.
Migrating pronghorn, like sand falling through an hourglass, all crossing the highway in a quarter-mile wide area, at the narrowest spot.
Archeologists have unearthed 7,000-year-old bones of adult and fetal pronghorn, suggesting the prong migration has passed by this spot for thousands of years.
At this spot, drivers surge over the crest of a blind hill at 65 mph. Fences line both sides of the highway
Fences that reach down to the ground (especially woven wire sheep fences) can block pronghorn from crawling under, trapping them far from their winter range
The highway dept tried putting up signs that flashed when the animals ran onto the highway, but vehicles still collided with wildlife.
Solutions:
In 2011, a wildlife-crossing overpass was built. In the first three years, nearly 60,000 mule deer and 26,000 pronghorn crossed via this overpass. Traffic collisions with wildlife dropped more than 80%
In 2008, the Bridger Teton Nation Forest amended its forest plan to prevent future development in the northernmost 45 miles of the antelope corridor.
The JH Conservation Alliance organized volunteer days to remove unnecessary fences from the migration path.
The Green River Valley Land Trust rebuilt hundreds of miles of fence on ranches along the Green River to make it easier for pronghorn to crawl under (barbless and at least 16 inches off the ground)
In 2009, the Bureau of Land Management designated 9,500 acres surrounding Trappers Point an Area of Critical Environmental Concern, putting it off-limits to natural gas drilling and other surface disturbance.
In 2010, the Conservation Fund placed a 2,500-acre conservation easement on a ranch that overlapped the corridor along the Green River to prevent any future subdivision or development there
Ongoing Problems:
Wyoming’s gas boom brought people and money to this part of WY, and once-open agricultural land is being cut up into housing developments
Already a subdivision has blocked one-half of the hourglass neck at Trappers Point, and dogs harass pronghorn.
Mule Deer
Migrate 150 miles from southern to northern Wyoming
Their summer range is Hoback Basin
Their winter range is the Red Desert
This is the longest land migration in the lower 48, and one of the most dangerous. They must cross 5 highways, negotiate one hundred fences, and scale 11,000 ft mountains-all outside of park boundaries
Mule deer cross more highways and jump more fences than any of the other animals in the GYE
Does lead the way and bucks follow when crossing streaks along the migration route
Unlike the pronghorn, mule deer don’t enjoy the security of a national park as their summer range or a protected corridor through national forest land at one end of their migration
Their fall migration takes them through mostly private and BLM lands, places vulnerable to development, and their winter range is far beyond the GYE’s accepted boundary
While they can jump more easily than pronghorn, they’re sensitive to development that cuts off access to their best forage, especially in winter and spring when they need it most.
Appearance/ Behavior
Weighting up to 250lbs, they are more elusive than pronghorn
Dark caps on their foreheads, large forking antlers, and enormous ears nearly as big as their heads
All 4 hooves leave the ground at once as they bound, a movement that lets them navigate rugged terrain
Prefers a habitat that’s a mix of sagebrush, aspen, and forest.
Population:
Mule deer are abundant across North America, but they’re in decline range-wide
Wyoming had a high of around 578,000 in 1991. Over the following 25 years, the number dropped by more than a third to less than 375,000. Similar decreases have taken place in Colorado, Utah, Idaho, and other western states.
On their migration from the Red Desert to Hoback, they experience a 400 yard wde pinch point between the town of Pinedale and Freemont Lake
Each spring 4,000-5,000 deer travel here
It was private land, but in 2015 the Conservation Fund bought and donated the land to Wyoming Game and Fish Department and made it into a Wildlife Habitat Management Area
Recent Discoveries about Mule Deer Migrations
In 2011, a study was done to delineate the hone range of a population of mule deer that winter just north of Interstate 80. Everyone believed they were resident deer that, if they migrated at all, stayed within a 40 mile range
Biologists put collars on 40 mule deer
The collars emitted a VHF signal and recorded a satellite location every three hours. If they had known where the deer would take the collars, they would have invested in the more expensive callars that transmit data in real time. They would have to wait 2 years for the collars to drop off the animals to locate the GPS data
That first spring, the biologist hired a pilot to fly over the Red Desert to search for the radio signals. He got a text that the deer were missing- the pilot had scanned the area from the capture site to the Wind River Range and found only a couple of the deer.
The pilot went back to the airport in Pinedale, 100 miles to the north, and started detecting more collars. The deer had migrated up the western flank of the Wind River Mountains, traveling much farther than anyone had expected
In western wyoming, close to the center of the continental US, where wildlife has been studied endlessly, where avid hunters stay deer year round, where people have observed and swapped stories about them for generations, was a migration non one knew about; a 300 mile round trip mule deer journey. Longer than that of the pronghorn
Rocky Mountain Elk
Of approximately 900,000 Rocky Mountain Elk in North America, about 20,000 migrate through the GYE
Nine different hereds of elk migrate within and beyond the GYE, some of these migrations spanning a region 5x the size of the park
Many of the Yellowstone elk populations rely on private lands beyond the GYE, below the 7,000 foot contour and the national forest boundaries
Appearance:
Largest antlers of all subspecies of North American Elk
Weigh 400-1,000 pounds (4x the size of a mule deer)
Migration behavior
Along the way, they care for their young, resting to give calves a chance to nurse
They care for each other. They’ve been observed moving slowly, trying to allow a cow who had a broken leg to keep pace
Migratory elk that follow the spring wave of fresh green grass into the mountains can gain up to 15 lbs of fat than their non-migratory counterparts
Migrations of the Cody Elk Herd
The Cody elk move between huge ranches for wintering grounds, and the deepest wilderness and most remote place in the lower 48
Though it’s a shorter migration than the pronghorn and mule deer’s. It’s much more rugged
The bulk of the Cody herd’s migration takes place outside of YNP
They go up and down mountains to the high mesas of the Thorofare Plateau, one of the wildest and least accessible areas in the lower 48
They ascend snowfields almost to the 12,100 foot summit of Needle Mountain
There, thousands of years of passing elk hooves have worn grooves into the volcanic rock
This is a nearly vertical crossing over 2 foot wide, knife-edge ridge near the summit
They travel in the mountains all night, then reach the South Fork of the Shoshone River at down and plunge into its rapidly moving waters.
About 4,000-6,000 Cody elk stay on two large, private ranches that harbor wintering elk. This is in the arid sage-grasslands along the Greybull River
They graze on hayfield stubble, find shelter in creek bottoms, and enjoy relative protection from wolves and bears on these ranches
In spring, the elk leave the ranches, heading toward the lush meadows of YNP, about 40 miles away and a few thousand feet higher in elevation
The Thorofare Plateau
(Located just outside of the southwest corner of YNP)
Commonly known as “The Thorofare” because it is the main route for thousands of ungulates and other large animals who traverse it dduring their annual migrations
The headwaters of both the Snake and Yellowstone rivers are found here
It’s the most remote swath of the GYE and arguable the most remote region in the continental US
Bison
Once were up to 30 million, but were nearly wiped out by 1889
Now public lands support few that 20,000 wild bison, with roughly a quarter of those inside of Yellowstone
Bears
Grizzlies ascend the 11,000 foot high scree slope of Silvertip Basin, then make a small platform to stand or sit on and then dig for moths
Millers moths are also mid-migration, having flown from Nebraska and the Dakotas
A grizzly can eat up to 40,000 moths in a sigle day. The importance of this food source wasn’t realized until the mid 1990’s
At these elevations, snow begins to fall in late August
Rancher’s Perspective
A herd of elk (for example) that winters on neighboring ranches may eat valuable grass, draw predators to mix with cattle, and carry infectious diseases
Some have had their herds quarantine by the US Dept of Agriculture after elk passed disease to their livestock
Some struggle to make their ranches break even, much less earn a profit from year to year
Worse yet, those ranches that don’t make ends meet wometimes end off swaths of land for development
Problems:
Habitat Fragmentation and Island Effects
Continental islands (were once part of an adjacent continent when sea level was lower during the last ice age) have less species than the continents they were once a part of
Habitats lose species when they become islands and are no longer part of a larger expanse of habitat
National Parks may provide safe patches of land, but as islands of habitat, they too will lose species
Nature needs connections as well as protection
In 1979, the Greater Yellowstone Coalition was founded in recognition that Yellowstone can’t be successfully managed as an isolated entity
Development
New gas rigs and pipelines eat up the sagebrush. Private ranch land sells to developers, who chop them into subdivisions. Rural sprawl cuts off the passages that wildlife needs. Roads, highways, towns, cities, reservoirs, and fences interfere with the migration corridors and winter ranges on the flanks of the GYE
Such development compromises the wintering ungulate populaltions, and that loss echoes deep inside of Grand Teton and Yellowstone National Parks where fewer animals return to the summer ranges. Even as the system appears strong and protected, it is crumbling at the edges
Over 15 years, the development of a high-density natural gas field in the southern GYE cut in half the number of deer in one migratory herd
Other studies have shown how deer move more quickly through developed areas, skipping important stopover areas where they used to rest and feed
Another major impact of development isn’t just the conversion of open space to infrastructure, but animals’ avoidance of the remaining habitat because of new noise and truck traffic
“The Incremental Loss of Migration” Hypothesis
The benefits of migration are slowly outweighed by cumulative huan-imposed costs (a new fence, a new road, another subdivision, etc)
Populations decline and, ultimately, the animals even lose their memory of traditional routes
Solutions
Protect essential wildlife corridors by
Allowing animals to inter on land we aren’t using
Leaving gates open in winter
Removing bottom wire of our fences for pronghorn to squeeze through
In 2008, the Freedom to Roam initiative was launched to help remove or modify barriers to migratory species
Where development is inevitable, we can avoid the most important habitats
Core winter and summer ranges, stopover ares, and high use migration corridors
Employ technologies that minimze noise, traffic, and other disturbances
Install overpasses and underpasses to reduce risk and stressors along major corridors
Example: At Trapper’s Point, a highway underpasses for deer and overpasses for pronghorn- they pay for themselves in savings from averted car wrecks and wildlife death in just over a decade. In the first three years, mule deer crossed over nearly 60,000 times and pronghorn crossed over 20,000 times
Make our maps include not just houses, towns, and highways, but also migration trails, seasonal nesting and denning sites and pathways across lakes, rivers, meadows, and mountains.
Public interset and advocacy
Progress in wildlife conservation and management depends heavily on people asking decision makers for change
It was public interest in 2008 that prompted Bridger-Teton National Forest to protect 40-mile Path of the Pronghron from further development
It was public interest in 2011 that led to WYO Dept of Transportation to build highway overpasses and underpasses to give deer and pronghorn safe passage
In 2015 that nudged the WY Dept of Fish and Game to designate migration corridors as critical habitat in the context of future development plans
Science, public outreach (like photography) and public interest are necessary for future protection of migration routes
Yellowstone National Park History
At its inception in 1872, YNP was a straight-sided rectangle, roughly 50 miles by 60 miles. Those boundaries protected geysers, waterfalls, hot springs, and other geologic features. Settlement by people and wanto hunting or fishing were prohibited.
The place was meant to “provide for the preservation, from injury or spoliation, of all timber, mineral deposits, natural curiosities, or wonders within said park, and their retention in their natural conditions” according to the 1872 act that created the park.
This was a creative experiment, to outline a piece of land and set it aside to forever be protected “fro the benefit and enjoyment of the people”
Yellowstones’ linear boarders shifted over the years, today it’s eastern edge better traces the landscape’s hydrologic divides
Greater Yellowstone Ecosystem Histroy
Almost exactly a century after YNP’s creation, a scientific idea changed the way that biologists and other thought of the park- the idea of the park being part of a larger ecosystem
In the early 1970’s biologist Frank Craighead applied the term “ecosystem” to the lands surrounding the park. He described a network of national forests and wilderness areas adjacent to Yellowstone that were connected by grizzly bear movements
The idea of the “Greater Yellowstone Ecosystem” took hold, though different entities drew its edges in different places
Some traces its boundaries along those of the half doen national forests adjacent to and surrounding the park
Other biologist focus more on watershed function and vegetation more than wildlife, and described the GYE as those area within a 7,000ft elevation contour, a region much larger than what the Craighead’s grizzlies defined
Whatever its exact boundaries, what we call the GYE covers millions of acres of mostly public mountains and forests, spanning about 300 miles of central WY to Eastern Idaho and southwest Montana
Federal land-management agencies responsible for this area: NPS, USFWS, USFS, and BLM.
With the ideas of an “ecosystem” we no longer accept that the interior of YNP and GTNP are safe regardless of what happens outside their boundaries
New Paradigm Shift
50 years after the idea of ecosystem took hold, we must once again challenge and transform our understanding of this place. To grasp ther new shift, we must look to migration
Improved GPS collar tech is helping to track these migrations for the first time
We are starting to understand how the park animals rely on distant deserts, valleys, and agricultural lands for half the year.
May winter ranges are below the 7,000 foot contour, beyond the accepted edges of the GYE
YNP’s creator in 1872 couldn’t have fully realied how thees hoofed migrator link the park interior to the outside, of the barriers these animals would one day have to navigate to make their journeys
We also can’t conserve migration routes in the same way that we initially snoserved national parks- we can’t just draw another rectangle and set it aside for wildlife
We need a new model, a nw way of interacting with the landscape, a way to start knitting our own existence more closely with the other species that also rely on these lands for survival
History of Studying Migrations
1985: Before GPS Collars, researchers fitted over 300 pronghorn with colored neck bands printed with letters and numbers. They monitored their movements throughout the seasons and discovered that some migrated more than 150 miles.
1998: 35 female pronghorn in and around GTNP were fitted with VHF radio collars, which emit a frequency on a unique radio channel that carries up to a few miles. Researchers use special antennae to locate the collars from fixed-wing airplanes about once a week during the spring and fall migrations
1999: Researchers followed pronghorn racks on the ground through a portion of the migration corridor. This let tmedraw a rough map o the route from GTNP to the Green River Basin
2003: Biologists captured pronghorn in GTNP and fitted them with GPS collars. GPS collars communicate with satellites to fix locations on a given time interval and store the waypoints on a computer chip. After two migration seasons, the collars automatically dropped of the animals’ neck and researchers collected them.
Shoshone National Forest
Designated in 1891, it’s the first national forest in the US
It stretches from the Montana state line south to Lander, WY. It holds portions of the Absaroka, Wind River, and Beartooth mountains. YNP sits on its western boarder.