A healthy pasture on the Northern mixed-grass prairie is not just a homogeneous expanse of grass. In our country, a healthy pasture is not smooth, flat or small. It is not cultivated or inter-seeded with invasive, hybrid or genetically modified plants. It is home to 2,095 species of amphibians, reptiles, mammals, butterflies, birds, grasses, sedges and wildflowers. It is not sprayed with fertilizer, herbicides or insecticides. There are herbivores grazing these healthy pastures of the Northern Great Plains. For many reasons, a healthy pasture is nothing like a golf course. It is much more complicated.
Grasses 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 these estimated 2,095 species. Each plant waits to bloom and pushes 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 wondering. 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 specie 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 is 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, leadplant, needle and thread grass, pasque flowers, smart weed, prairie drop seed, 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 critical, 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. It is all part of a healthy pasture. It is all more elegant than simply arranging for an animal to stand on green grass.