What Buffalo Eat

By Dan O'Brien
Jill O'Brien

A healthy pasture on the Northern Great Plains is not just a homogeneous expanse of grass. It isn’t smooth, flat, or small. It isn’t cultivated or seeded with invasive, hybrid, or genetically modified plants, or sprayed with fertilizer, herbicides, and insecticides.
This healthy pasture is nothing like a golf course. It is home to 2,095 species of amphibians, reptiles, mammals, butterflies, birds, grasses, sedges, and wildflowers. Bison graze here.

Grass and forbs have been growing on what is now our bison ranch since the glaciers receded. That is when the ponderous process of evolution began. The ancestors of bison followed the receding ice and the nascent vegetation for centuries as, driven by natural selection, they got to work determining how they could use each other to survive and thrive. Of course, that process is still functioning though, through human eyes, it usually seems stagnate. The species on the Northern Great Plains have evolved strategies for thriving in spite of very cold winters and hot summers –blizzards, droughts, wild fires, and merciless wind. The tenacity of these Northern Great Plains species is a scream of defiance in the face of marching industrialization.

Included in the evolutionary outcomes that this cauldron of life is brewing up for our education is a specific set of behaviors for each of the estimated 2,095 species on the Northern Great Plains. Each plant waits to bloom, and push its energy above ground level, for the perfect combination of moisture and temperature. Most birds fly south for the winter, ducks go flightless when the summer vegetation will hide them, rodents gather bison wool to line their nests, antelope gather into herds when the conditions are right, prairie dogs estivate. And the bison move.

Bison are famous for their desire to roam. I’ve made a project of watching them move and concluded that the movement of bison for miles over the prairie is not a case of random wandering. I’ve watched a herd of several hundred dozing on a hillside for a whole day before one older cow stands up, stretches, and rousts her calf to its feet. Then another stands up, followed by a half dozen more. Sometimes they begin to drift as the rest of the herd wakes up and meanders in the same direction. Other times they jump to their feet in a way that makes you wonder if they were dreaming of wolves. I’ve seen them lope for miles and suddenly come to a stop on a high mesa and lower their heads in unison as they begin to graze. When I investigate, I find that there is a preponderance of one species of grass or congregation of a certain forb on that mesa. In the spring or fall, it might be green needle or western wheat grass. In the summer it is more likely to be one of the blue stems or gramma grass. if their chosen grazing spot holds a little more water than the surrounding prairie, it could even be canary grass. In winter they might stop on the south facing slope that grows thick with yucca. The old female who led the herd to that particular place remembered it from the last time conditions were like that day. She knew that the vegetation that grows in that place would be ripe, energy rich and tasty on that particular day. It is one of the subtle but very important traits that makes her a bison.

She might lead the herd to a patch of Indian grass, big blue stem, porcupine grass, western wheatgrass, buffalo grass, milkweed, wild rye, tender shoots of one of the native sages, Indian paintbrush, June grass, lead plant, needle-and-thread grass, pasque flowers, smart weed, prairie dropseed, purple coneflower, fescue, sand reed, scarlet mallow, serviceberry, lupine, switchgrass, blue grass, or a patch of red cedar that is just right for rubbing their old fur off in the springtime. Access to all those plants and many more is the reason large pastures are critical.

The importance of bison moving freely on the landscape could not be more important, not only for the bison but also for the amphibians, reptiles, birds, mammals, pollinators, and the plants themselves. While bison were evolving to utilize all the plants on the prairie, the plants were evolving to thrive under the uniquely shaped, chopping hooves of many bison moving in unison.

All this is a healthy pasture. It is far more elegant than simply arranging for an animal to stand on green grass.

Dan O’Brien and his wife, Jill, co-founded Wild Idea Buffalo Company in 1998, now managed day-to-day by his daughter, Jilian Jones, and his son-in-law, Colton Jones. Together they raise buffalo on the Cheyenne River Ranch in South Dakota. Besides being a rancher and falconer, O’Brien is a wildlife biologist and the author of six novels and four works of nonfiction.