by Brian Kenner
The more I watch them, the more I appreciate them. As I learn bison behavior---how they interact with other herd members, how they interact with their environment---I begin to understand just how much they belong to the prairie. Like other species native to the Great Plains---the rattlesnake winding its way through prairie grass, the meadowlark sitting on eggs in a nest built on the ground, the swift fox raising its young in a burrow--bison are of the prairie.
I like to watch their nomadic grazing, the herd moving along slowly in one direction as they feed on the prairie grasses and sedges, their movement ensuring no single area is grazed too heavily. As they move, they leave dung and urine that spreads seeds and returns nutrients and nitrogen to the soil, even as their hooves loosen the topsoil to help rain reach thirsty roots. One day I can see 500 bison on the prairie dog town along a gravel road; the next day they are nowhere to be seen. Their casual but purposeful movement can easily take them three or four miles in a day.
In spring, I like to watch the new calves’ early reactions to their world. Owing to evolutionary influences of predators, they can stand within minutes of birth and easily walk and run within hours. For the first several days they stay close by their mother’s side, but as spring moves toward summer they begin to spend time in groups of calves, where they learn the social skills necessary for life in the herd. They chase each other, run and kick, butt heads and lounge together. Each year, 70 to 80 percent of adult cows produce calves, ensuring a constant influx of new life to the herd.
When summer brings on breeding season, I like to watch the massive bulls fighting for the right to mate. A mature bull can weigh more than a ton, and despite their bulk, bison are amazingly quick and agile. Their small rump allows them to spin quickly on front legs, a great defense to dangerous side attacks from rivals. Thick skulls allow bison to endure the head-to-head collisions that determine who is more fit to pass on their genes. These animals can jump over a 6-foot-high fence, run as fast as a horse and keep going for miles. When bison run, their long tongues roll in and out, forcing great amounts of air through a huge trachea to their lungs. What appears to be a sign of total exhaustion actually provides remarkable endurance. Once bison stop running, their breathing quickly returns to normal, and you realize they were hardly stressed.
Bison seem immune to the harsh weather that often visits the Great Plains, whether it’s the relentless, extreme heat of August, severe thunderstorms that pound torrential rain into the prairie, or winter blizzards that blow sub-zero winds and heavy snows. Regardless of the conditions, bison don’t seek cover in woody draws or behind buttes. They simply continue grazing, or lie down and chew their cud out in the open, often on exposed hills. The thick, curly hair covering the front half of their body insulates them from both heat and cold. It enables them to face into the weather rather than turning away from it or seeking protection. This is why bison are often described as “facing the storm."
The bison here at Badlands National Park are what we call a “conservation herd,” which means we try to preserve them as they evolved, and as we hope they will continue to evolve---a wild species shaped by their environment. We want this herd to have a natural age and sex structure, feed on native plants, breed as they see fit and move across the landscape much like they did before incomprehensible cruelty and avarice nearly wiped them out. We seek to preserve their genetic diversity and purity. Simply stated, our mission is to “keep bison, bison.” They are wildlife held in trust for the American people, and my job is to ensure their proper stewardship “for the benefit of future generations” as the law provides. This is made more complex by the lack of predators that once kept the herd strong, and the limits of a park that must be fenced to keep bison from roaming onto neighboring cattle ranches. And yet, as I watch these animals, and enjoy them, and learn from them, I am reminded that we need to do everything we can to ensure a future for wild bison—and the Great Plains—in the modern world.
Brian Kenner works for the National Park Service. He is the Chief of Science and Natural Resources for Badlands National Park.