tame is impossible to answer. Even after stopping at one of the park’s entrance stations and being handed a flyer warning them of the unpredictable nature of bison and how they like their space—move closer than twenty-five yards to these animals and you could be ticketed by a ranger—visitors pull over and park on the road’s shoulder, get out with their cameras and, with each successive shutter click, take a step or two closer to the bison that seems so small in the viewfinder. Or they’ll remain in their vehicles, slowly inching forward in the “bison jam,” and roll down their windows to snap a close-up of the bison alongside their rig. Rangers try to stop these behaviors, knowing full well how unpredictable, cantankerous, and dangerous bison can be.
There are times when the bison come to you, as was the case with my experience camping near Lone Star Geyser. I’ve also shared a campground with them in Theodore Roosevelt National Park in North Dakota. Crawling out of my tent one morning, I found about a half-dozen bison milling about the Cottonwood Campground. Some were munching the green grass for breakfast, while a big bull was using a tree as a backscratcher. Later in the day, while hiking toward Wind Canyon, I watched as a herd spilled through a mountain pass and rumbled down into the canyon. Standing on the trail, I knew that this scene had been repeated across the Plains for thousands of years. Bison close-ups also abound in Wind Cave National Park, and there’s little that compares with watching small bands moving freely across the prairie, or grazing the flats above the Snake River in Wyoming as the morning sun’s rays paint the Tetons.
You don’t easily confuse bison with cattle. Bison are taller at the shoulder and greater in girth, woollier, and not often swayed or intimidated by human onlookers. In Yellowstone’s expansive Hayden Valley, herds of bison loll about at midday, chewing their cud, swatting flies with their tails, gazing about. And of a sudden, they’ll take up en masse and move in late afternoon, browsing slowly as they go. As the tourist traffic slows on the Grand Loop Road and then stops, often in the middle of the road, cameras snapping and rolling, bison keep moving. Driving by these shaggy animals, they do look tame, and even willing to let you reach out your vehicle’s windows to scratch behind their ears. It can take a concerted effort to spook the big bulls and cows, who seem to consider us with disdain, an inferior species. An Oregon man discovered this in August 2018 when, emboldened very possibly by a fermented beverage or three, he got out of his vehicle and pranced and preened and hooped and hollered, taunting a bison that was slowly moving across the park road. When the bison finally half-heartedly charged him, the man somehow managed to avoid the animal. He was not lucky enough, however, to evade law enforcement rangers, who arrested him two days later at the Many Glacier Hotel in Glacier National Park where, rangers said, he again was taunting, but this time with other human visitors. A few weeks later Raymond Reinke, fifty-five, of Pendleton, pleaded guilty to four charges, including one for having an open container of an alcoholic beverage in his vehicle and another for disturbing wildlife. He was handed a 130-day jail sentence, a bargain compared to what he might have encountered on the end of the bison’s horns.
Most people who view bison do it sensibly, from a distance. It’s usually a subconscious, or even conscious, matter of self-preservation. Even though the modern-day bison are smaller than their Pleistocene ancestors, they still are imposing at more than six feet tall at the shoulder, ten or more feet long from nose to rump, and weighing as much as two thousand pounds as adult bulls. Females are roughly half as large, which is still too large for you to mock within striking range.
Why add more bison to the landscape? Because they belong there. They once were an integral part of the landscape. They evolved with it, tilled it, manipulated it, engineered it. They were then, and remain today, ecological engineers. They mow the land differently than domestic livestock, often in a healthier fashion if they are left alone. Bison don’t graze as hard as cattle; instead, appearing finicky, they browse and move frequently. The grass always is greener over there. Grazers such as cattle and sheep nip the vegetation off at or near ground level, while browsers like bison eat green stems and leaves. As a result, they leave behind grasses of varying heights, while the grazers often settle in for their meals and leave stubble in their wake. Bison also tend to pass over forbs, a choosiness that increases plant diversity. They spend less time than cattle around water sources, and so don’t trample riparian areas or graze the surrounding vegetation down to the ground. All things being equal, cattle will spend hours around water; bison take a drink and move on.
These big animals don’t require dietary supplements to remain healthy or to pack on weight for market.23 They’ll move with the seasons across their habitat. Some herds historically moved as much as two hundred miles to retreat to lower elevation winter habitat with lower snowfall, and so less work for a meal. That big hump on their backs? It is a mass of muscle that evolved as bison plowed their heads through the snows of winter to reach summer’s leftover meals. When driven by hunger, these animals can shovel through eighteen inches of snow with their heads.24 Hunger can be a powerful motivator, as bison generally require a daily diet of thirty pounds or so of grasses, sedges, willow, and even the occasional wildflower, such as a bouquet of scarlet globemallow.25
Their size, and tendency to group together against threats, makes it hard for wolves to take healthy bison down. Elk and deer are much easier prey. Still, some wolves in Yellowstone’s interior have figured out how to survive on bison. The Mollies pack, whose territory is deep in the park’s Pelican Valley, is the only pack that regularly preys on bison. That choice was in part due to the fact that while elk leave the park’s interior for lower-elevation wintering grounds, these wolves stay behind to endure the winter along with the bison that stay put. The wolves have figured out how to take down bison, usually without getting injured or killed in the process. But it’s still not easy. While the predators can kill an elk in roughly four minutes, it can take fourteen hours for fifteen wolves to kill a bison.26 Elk run, hoping to outdistance wolves. That leaves them defenseless to predators looking to hamstring their prey. Bison, however, stand their ground and rely on their horns and hooves for defense. The resulting need for more muscles, and the protein-rich diet of bison, has produced wolves in the Mollies pack that are 5 to 10 percent larger than wolves that concentrate on elk down along the Lamar River. One male measured by researchers weighed nearly 150 pounds.
Wolves might be the consummate killing machines in the wild kingdom, but bison are the apex creatures. Everything about them affects all other life-forms on the Plains. Their habit of rolling on the ground to shed fur, crush biting flies, and, for males, embed their scent in the dirt, creates “wallows,” small craters in the earth. These wallows are no small depressions, and at times bison might seem fastidious in creating them. Some bulls will seek ground softened, perhaps thanks to a seep or rain puddle, and then thrust a horn into the dirt like a pick. With growing vigor the animal then drops to the ground and uses both horns as well as the hump on his back to grind his desired indentation into the earth.27 Repeated use by any number of bison can grow some wallows to about nine hundred square feet—roughly the size of half a volleyball court.28 And because wallows are returned to again and again by bison that squirm about on their backs, grating their spines, humps, and flanks into the ground, the dirt is compacted. The result, when rains come, is that these depressions can turn into ephemeral water holes. These oversized puddles are used by the Plains spadefoot toads as nurseries, they nourish wetland plants, and they can even influence runoff. Botanists for the National Park Service have found that wallows can aid prairie plants that grow in moist settings and that, overall, they contribute to prairie biological diversity since their size, shape, and water-retention capabilities attract different grasses and forbs. Miniature wetland gardens, if you will. National Park Service researchers calculated that at the pinnacle of the bison population there might have been more than 1.5 billion wallows. Some of these relic depressions can be seen from the air today.29 In some areas, once you know what to look for, you can find yourself surrounded by them. You won’t find them in cattle pastures. Cows don’t wallow.
Bison are not averse to showing wolves a thing or two about dominance. In 2002, researchers in Yellowstone watched bison drive wolves away from recent kills the wolves had made, and saw a herd of nearly forty bison chase off eleven members of the Druid Peak pack
