Beholding bison: A day in Yellowstone

When someone asks me what my role as communications associate entails, days like today leap to the front of my mind. Much of my job revolves around a laptop and Word documents and working with my colleagues behind the scenes to write stories about the wild creatures, lands, and rivers here in Greater Yellowstone. But sometimes those documents start with days like today – days I get to spend exploring Greater Yellowstone.  

London in the park – camera, binoculars, and bear spray in tow – overlooking the Gallatin Range. (Photo GYC/London Bernier) 

It’s a beautiful May day, and the early morning air is already warm and hinting at summer days ahead. Binoculars, bear spray, and camera packed, I start my journey to Yellowstone in hopes of encountering one of the landscape’s most iconic species – bison. By 8:30 a.m., I’m heading south down Highway 89 through Montana’s Paradise Valley, watching the jagged peaks of the Absaroka Range and muddy, blown-out Yellowstone River pass by under a bluebird sky. 

Yellowstone is the only place in the United States where bison have lived continuously since prehistoric times, and the bison that roam the park are widely considered the last truly wild herd of American plains bison in existence. Their lives are still shaped by natural forces such as predation, harsh winters, a vast and varied landscape, and complex herd dynamics. Witnessing bison simply exist in Yellowstone is miraculous – and always a reminder of why I do the work I do. 

Cows and calves rest alongside a park road, the Absaroka Range on the horizon. (Photo GYC/London Bernier) 

The last time I traveled this road on my way to the park it was the dead of winter. Yellowstone and the surrounding ecosystem saw one of its snowiest winters in a long time. Deep snow is typically no barrier for bison in their search for food. Sweeping their broad head side to side, aided by the powerful neck and shoulder muscles that compose the distinct hump on their back, bison can shift snow up to four feet deep in search of grass. 

But the snow this year accumulated on a foundation of ice that made it hard for bison and other wildlife to reach the vegetation they need to survive the winter. The harsh winter, combined with bison’s migratory instincts, resulted in more than 1,400 bison leaving the high elevation interior of Yellowstone and traveling beyond the park’s borders in search of food. Some bison migrate out of the park every winter, but this winter’s migration far surpassed any in the last decade. 

Looking out over the now lush Gardiner Basin, I remember seeing hundreds of bison dotting the landscape on that winter day and realizing I was witnessing something remarkable. I was getting both a glimpse into the past, a time when bison roamed freely across North America, and maybe a glimpse into the future, a future where bison can roam far beyond the park boundaries like the migratory wildlife they are. Today, bison were absent from the Gardiner Basin, having followed the spring "green up” back into the high elevation plateaus of their summer range within the park. 

Herds of bison dot the landscape along the mighty Lamar River. (Photo GYC/London Bernier) 

“Surfing the green wave” or following the “green up” is an annual spring phenomenon in Greater Yellowstone. Ungulates – hooved animals like elk, mule deer, and bison – time their spring migration back to summer habitat by closely following the simultaneously receding snowline and growing grass. But bison don’t just surf the green wave, they help shape it.  

As ecosystem engineers they manipulate the environment around them; studies have shown that grasses grazed by herds of hungry bison grew back stronger and more nutritious. In fact, their impact has been seen from space – NASA satellites detected that plant green-up is different between those areas grazed by bison and those not grazed by bison. Bison enhance their own food sources, and in turn the many wildlife they live alongside benefit.  

Today I followed the bison to the Lamar Valley, renowned for outstanding views and once-in-a-lifetime wildlife encounters. This time of year in the Lamar is particularly special when it comes to bison; starting in mid-April, bison calving season begins and baby bison – called “red dogs” – make their debut on the landscape. 

Red dogs frolic while their mothers graze. (Photo GYC/London Bernier) 

A red dog nurses. (Photo GYC/London Bernier)

The nickname “red dog” comes from their reddish-orange coloring that lasts until the end of summer, distinct from their dark brown mamas. Red dogs are born at only 30 to 70 pounds – watching them zoom around and play, it’s hard to imagine these small babies becoming 1,000-to-2,000-pound adult cows and bulls. Watching this particular herd wander and graze, I noticed it was composed of cows, calves, and juvenile bulls. Adult bulls tend to separate from the herd and form their own small groups outside of mating season, called the rut. At this point in the year, the babies are still little enough to be nursing; yet I witnessed them already learning and practicing instinctual behaviors like wallowing. 

Cows wallow and kick up dust while calves observe. (Photo GYC/London Bernier) 

A calf practices wallowing alongside its mother. (Photo GYC/London Bernier) 

If you have ever seen a bison rolling around in the dirt, kicking up clouds of dust, you’ve witnessed a behavior called wallowing. Wallowing provides many benefits to bison, like preventing insect bites or shedding winter coats, and is another way bison impact the broader health of the land as ecosystem engineers. The behavior creates wallows, circular depressions of disturbed and compacted dirt, that are the site of a little bit of ecological magic. 

Bison and the wallows they form create unique microhabitats for all sorts of plant and animal life, making the landscapes bison occupy more diverse. The depressions naturally fill with water after rainstorms, forming temporary habitats for insects and frogs and creating moist habitats for plant species that don’t typically thrive in dry prairie grasslands. The bare ground is also prime real estate for “pioneer” plant species— species that establish first after an area has been disturbed. Bison’s presence on the landscape creates a healthier, more diverse, and resilient Yellowstone for species from native bees to grizzly bears. 

A grizzly grazes alongside bison and the Lamar River. (Photo GYC/London Bernier)

Bison are not the only wildlife you'll likely encounter if you visit the Lamar Valley. Today I was treated to my first grizzly bear sighting. Alongside other excited park visitors, I watched a small brown lump wander along the banks of the Lamar River. We guessed it was a male grizzly grazing on grasses, unbothered by the bison also foraging around him. Despite their carnivorous reputation, a major part of a grizzly’s summer diet is grass.  

Giddy, and excitedly swapping wildlife-watching stories with the other folks pulled over watching this grizzly forage, I heard one gentleman’s account of 12 grizzly bear, four black bear, and four wolf sightings just that day – and it was barely 11 a.m. A few hours later, quite ecstatic about my two-bear and bison-filled day, I started my journey back to Bozeman; this day in Yellowstone is one I won’t soon forget. 

—London Bernier, Communications Associate