Why Big Mammals Thrive in the Greater Yellowstone Ecosystem

Its late summer and my camera shutter slows as the setting sun casts a mosaic of golden light and shadows across the Lamar Valley. My focus wanders to the sea of wildlife enthusiasts—their buzz of excitement drowning out the sound of flitting insects. 

“THERE! They just crested the hill,” shouts a man buried in his spotting scope. Dozens of other spectators scurry to catch a fleeting glimpse of one of Yellowstone’s iconic gray wolves. 

In that moment, I am reminded how close I am to wildlife, yet how far removed I am from their very wild lives. My perspective is interpreted differently by Monica Terkildsen, citizen of the Oglala Lakota Nation, and Native Nations Liaison of World Wildlife Fund’s Northern Great Plains program. She observes: 

“From high atop the hump of the Turtle’s back I can look out and see all the relatives moving across the landscape. The life sustaining foods—grasses and plants—blow and sway in the wind. I smell the freshness that the root nation brings to the air that we breathe. I feel Grandmother Earth— Unci Maka—beneath my feet. From the tiniest buzzing insect to the thunder of hooves touching the land, the world is alive with sound. I am enlightened and humbled when I recognize that I am only a small part of this wonder, a fragment of the ecosystem and the many relationships that have evolved and survived throughout the ages.” 

Terklidsen’s viewpoint illustrates the intimate entanglements shared by Indigenous peoples and the land. Of the 15 Native nations throughout the Northern Great Plains region, all share a unified vision for how best to restore and manage their ancestral lifeways. 

The Greater Yellowstone Ecosystem 

The Greater Yellowstone Ecosystem (GYE) is one of the largest nearly intact temperate-zone ecosystems on Earth. The prairie expanse is biologically integral to myriad species—providing critical habitats and migration routes. As one of the most threatened biomes on the planet, its preservation is equally significant to Tribal nations within the Northern Great Plains, who share spiritual and symbolic attachments to the landscape. 

The GYE encompasses an area between 12 and 22 million acres. The region spans portions of Wyoming, Montana, and Idaho, contains extensive climatic and elevational gradients, and intersects numerous social and political boundaries. The ecosystem is collectively managed by private individuals in addition to federal, state and Tribal governments. Though Yellowstone National Park was established in 1872, it wasn’t until the 1970s, that the contiguous geographic area beyond Yellowstone and Grand Teton national parks was defined. 2 

Researchers, John and Frank C. Craighead introduced the concept of a Greater Yellowstone while tracking grizzly bears across jurisdictional lines and into the surrounding forests. They reasoned that like grizzlies, there are other native mammals with extensive home ranges that require space beyond the amount allocated by law. To secure vital sanctuary for the animals, critical linkage habitats must be maintained and wildlife corridors connected. 

Mammal Menagerie 

The Greater Yellowstone Ecosystem is home to the largest concentration of mammals in the lower 48 states, a fact that its moniker, “North American Serengeti,” refers to. Similar to Africa’s “Big Five,” Yellowstone has its own prides of impressive predator and ungulate (hoofed herbivore) species. They include: gray wolf, bear (grizzly and black), plains bison or “buffalo” (“iinniiwa”: Blackfoot, “tatanka”: Lakota, “ivanbito”: Navajo, “kuts”: Paiute), moose and elk. The sheer diversity and distribution of species positions Yellowstone as prime territory for observing the complexities of predator-prey dynamics. 

There is something even more extraordinary about this ecosystem that is not evident anywhere else in North America. Yellowstone has served the bison population since prehistoric times, and this population represents the nation’s largest free-roaming herd on public land. Just as Yellowstone has provided habitat and nourishment for the herd, the herd provides life-sustaining benefits in turn. 

Bison 

In contrast to top-down trophic systems, bison influence natural systems from the bottom-up, which makes them a keystone species. Wolves may be Yellowstone’s top predator, but where bison lack in ferocity, they make up in size. As the largest land-dwelling mammal in North America, bison exhibit the ability to transform the landscape simply through engaging in their typical behavior each day. Comparable to how elephants engineer the African Serengeti by clearing forest cover and germinating seeds through dung droppings, bison are the eco-engineers of America’s Serengeti. 

Bison play critical roles in shaping the biodiversity of open grassland communities. They even influence how the spring season blossoms through the valleys and mountains of the Greater Yellowstone Ecosystem. Through grazing, bison keep the grasses short and nutrient-dense. Grazing may appear to be a destructive process within the environment, but it actually preserves soil moisture, increases the rate at which nutrients are recycled back into the earth, and stimulates productive plant growth. The non-uniform, yet repetitive grazing patterns of bison, and the intensity at which they graze, turns back the clock on forage green-up (progression of plants emerging), allowing for a longer and more fertile spring. And with up to eleven hours a day dedicated to foraging, it’s easy to imagine how verdant these landscapes can become. 

All of Yellowstone’s 67 mammal species have benefited from bison in one form or another. Prairie dogs, for instance, use the packed earth to dig burrows and feed on greenery that would otherwise be too tall to reach. 3 

The excess of young plants that spring up from grazing are also most advantageous to Yellowstone’s other free-ranging and migratory wildlife, which collectively consume as much as 35 million pounds of plant matter each year. 

Beyond grazing, bison also “wallow,” or roll around in the dirt, to remove insect pests. The resulting depressions in the ground alter the topography to such an extent—specialized habitats emerge for certain rare and medicinal plants. The divots also create optimal breeding and nesting grounds for birds. The long-billed curlew has even adapted its nest construction to mimic the appearance of bison droppings for an added layer of camouflage. On a larger scale, bison wallows capture and store rainfall, forming vast networks of wetlands, which function as breeding pools for amphibians and drinking sources for a host of species. 

Bison are responsible for breathing life into the heart of the American West. It is no wonder they were designated the national mammal in 2016. Led by President Obama, the U.S. House of Representatives signed the National Bison Legacy Act to celebrate the conservation success of a species previously on the brink of extinction. But Congressional recognition isn’t enough: for the bison’s resilience to endure, they require continuous advocacy, and there are no better champions for their protections than the Indigenous peoples who share their history. 

World Wildlife Fund recognizes that conserving large herds is one of the greatest challenges of our generation. That is why they partner with the following Native communities seeking to restore bison to their ancestral lands: the Fort Peck Assiniboine and Sioux Tribes, the Fort Belknap Indian Community and the Sicangu Lakota Nation. In addition, WWF supports the Buffalo Nations Grasslands Alliance, a Native-led initiative that provides technical and financial resources to sustain traditional lands and waters within the Northern Great Plains. WWF’s goal is to restore five herds of at least 1,000 bison each by 2025. 

In an unprecedented effort to preserve the valuable genes shared among Yellowstone bison, the National Park Service (NPS), the Animal and Plant Health Inspection Service (APHIS), the State of Montana and the Fort Peck Assiniboine and Sioux Tribes launched the Bison Conservation Transfer Program. Since its inception, the initiative has contributed to the largest transfer of Yellowstone bison among Native American Tribes in history. In August 2019, 55 bison were relocated to the FortPeck Indian Reservation in northeastern Montana. 

Member of Fort Peck Sioux Tribe, Lois Red Elk, recalls, “I longed for that time when Tatanka Sicun, Buffalo Spirit as ancestor, mingled with mine…then yesterday it came…it came in the form of trucks and trailers carrying sacred beings into the realm of our higher plains…” 

Saved from annual culls throughout Greater Yellowstone, this small herd has become an emblem of hope—reconnecting culture and community wherever they roam. 4 

Wolf 

Lois Red Elk’s vision of returning lost beings to their natural habitats was also present in 1995, as trailers carried wild wolves through the famous Roosevelt Arch. Over the next two years, 41 wolves from Canada and northwest Montana were released in Yellowstone in an effort to remedy a history wrought with habitat loss and government-sanctioned eradication. The wolf was once the world’s most widely distributed mammal, ranging from the Arctic tundra to Mexico. Although they are extinct across much of their former territories, Yellowstone National Park works to safeguard the species’ long-term viability in the Greater Yellowstone Ecosystem. As of January 2021, there were an estimated 123 gray wolves in the park, spread among nine packs. 

The reintroduction has revealed fascinating examples of kinship within and between the packs, as well as with other Northern Rocky Mountain populations. Wolves lead complex social lives, from the communal care of pups—to the group hunting of large prey. Genetic studies have even found evidence of coat color being a determining factor in the physical and behavioral traits of offspring. 

About half of the wolves in Yellowstone display a black coat, while the other half more closely resemble their nomenclature. The darker pigment is an outcome of gene mutation that may have originated within the last 7,000 years from the hybridization between dogs and wolves in northwest North America. Biologists have observed that the black-coated wolves are less aggressive than the gray-coated wolves, which is a survivorship advantage when territorial conflicts arise. However, the gray wolf temperament leads to greater reproductive success. Interestingly, there is superior mate choice between male and female pairs of opposite coat colors. 

Natural Habitat Adventures has a dedicated team of Expedition Leaders composed of professional naturalists and biologists who possess intimate knowledge of wildlife behavior. Their constant communication with local wolf researchers grants travelers unparalleled access to wolf locations and activity. Despite the millions of visitors who scour through sage and shrubbery each summer, WWF and Nat Hab’s Hidden Yellowstone and Grand Teton Safari ensures private experiences and close encounters with elusive wildlife. 

Bear 

In addition to wolves, Yellowstone is home to two other species of large carnivores: grizzly bears and black bears. Bears and wolves share another characteristic in common—the high probability for human-carnivore conflict. Grizzly bears roam over hundreds of square miles, and as private and commercial development encroach on bear-inhabited ecoregions, grizzly mortality rates caused by environmental degradation, vehicle collisions and hunting activities inevitably rise. 

In order to curb carnivore fatalities, WWF partnered with the American Prairie Reserve and National Geographic to create the largest nature refuge in the continental United States. Pioneering large carnivore research and restoration, is National Geographic Society Fellow and STEM diversity activist, Dr. Rae Wynn-5 

Grant. In an interview with Nat Geo, Dr. Wynn-Grant explains, “I hope to accomplish a thorough understanding of carnivore ecology at the human-wildland interface and use those scientific conclusions to make recommendations for how humans can modify their behavior to coexist with carnivores.” 

In 1975, the estimated population of grizzly bears in the Greater Yellowstone Ecosystem was 136. In 2018, grizzlies received federal protection. Under the Endangered Species Act, their population has grown to a promising 728 in Greater Yellowstone. If their population is to remain stable and thriving, continuous efforts must be made to analyze corridor and connectivity routes and identify key areas for protection. 

Elk

Among all large mammals found in Yellowstone, elk are the most abundant. The Greater Yellowstone Ecosystem shelters approximately 10,000-20,000 elk over the summer months. During that time, six to seven herds can be found dappled across the Cascade Meadows, Madison Canyon and Lamar Valley. Though elk make up the bulk of the gray wolf diet, herd size and distribution face a much graver threat—climate change. As a migratory ungulate species, elk mothers and calves are disproportionately affected by volatile conditions. There is unfortunately but one herd (Madison-Firehole) that resides in the park during both winter and summer, so research on reproduction and survival is limited. Thus far, studies have conclusively determined that environmental variability plays a role in food accessibility and nutritional content. Warmer temperatures stimulate plant growth and accelerate green-up, which in turn causes a shorter growth cycle. Consequently, there is poor synchronization of calving with peak plant nutrition—resulting in lower fat reserves and an associated high mortality of newborn elk. Moose In the park’s southwestern corner and in the Soda Butte Creek, a solitary moose may be spotted grazing on aquatic plants such as water lilies and duckweed, or making use of their impressive stature to tear off leaves and twigs high in the willow trees. An adult moose will eat as much as 50 pounds of food each day over the summer. The longer days, coupled with teeming riparian ecosystems (biome at the interface of land and water), make for a very comfortable life. That is not to say moose don’t have to contend with their own particular set of adversities, however. Fewer than 200 moose remain in Yellowstone. Their decline in population can be attributed to the loss of old growth forests beyond the borders of the park, hunting across the boundary lines, and ravenous wildfires. In the United States, summers are becoming dryer and hotter. Fire activity has therefore increased in frequency and severity, compromising forest health and resilience. Moose in the Greater Yellowstone Ecosystem rely on mature conifer forests for their wintering habitat. The more spruce and fir forests that become decimated in blazes, the less likely moose will be able to survive the West’s harsh winters.

Protect the Prairies!

Martha Kauffman, Vice President of WWF’s Northern Great Plains program, declares, “The Northern Great Plains is as important as the Amazon or Arctic, and deserves our attention.” Grasslands are responsible for sequestering and storing carbon. Destruction of these lands has an equally devastating effect as global deforestation. In 2019 alone, approximately 2.6 million acres of intact grassland were plowed and converted for row-crop production across the U.S. and Canadian Great Plains. That is an area larger than Yellowstone National Park. In the Northern Great Plains, 600,000 acres were lost to wheat, corn, and soy production. In June 2021, the United States Geological Survey (USGS) Northern Rocky Mountain center released the Greater Yellowstone Climate Assessment in collaboration with scientists, resource managers and Tribal communities from Wyoming, Montana and Idaho. The report analyzed climate trends in the Greater Yellowstone Ecosystem from 1950-2018, revealing illuminating information about how these changes could progress by 2100 based on various greenhouse gas emission scenarios. According to the data projections, if future emissions are not mitigated, Bozeman, Montana and Jackson, Wyoming will be subject to 40-60 more days per year exceeding 90℉. A repercussion for higher temperatures is less soil moisture, which would place significant stress on plant communities and impact the dietary quality of browse species. Drought conditions would also increase, magnifying the risk for wildfire outbreaks. The Greater Yellowstone Ecosystem is one of our planet’s last large landscapes and one of Earth’s “Last Wild Places.” It urgently needs protecting.

When you travel with World Wildlife Fund and Natural Habitat Adventures, you become privy to a world often unseen. Through sustainable tourism, you actively assume a role in determining how delicate ecosystems are perceived and conserved. When you explore the Greater Yellowstone Ecosystem, perhaps then you too will understand how deeply interconnected all life is here, as so eloquently expressed by Lakota Nation’s Monica Terkildsen.