Animals and Environments 2: The Land and the Bison

Imagine standing on a broad tableland, knee-high grass extending as far as you can see in all directions. The sun has just risen, well on its way north with the shift from spring into summer, and already the southwest wind ruffles the grass and hisses its hot way past. The day will be a warm one. You begin walking north. As you do, you start to see variations in the billiard table surface. Rainwater lakes, the famous playas, form broad, shallow depressions surrounded by taller grasses. Some of the largest playas have sedges, amaranth, arrow leaf, and western wheat grass in their shallows and on the shores. And you discover a faint blue line in the distance, almost like hills, or very, very far away mountains.

As you trudge closer, the land becomes a touch rolly and streams begin cutting little swales. The swales grow deeper and rougher, cutting into the grassy ground. And at once the land drops away ahead of you, revealing a broad, rough valley with a thread of water six hundred feet below the plains. You’ve reached the Canadian River Breaks, the river valley. To the north, the Dry Cimarron and Wolf Creek have similar, smaller valleys.

As you descend into the Breaks, your eyes light on what looks like a trail. You follow it past a natural spring and a beaver pond and dam down to the inner valley. Here wild plums and grape vines sprawl among hackberry, cottonwood, oak, and a few other trees. Thick stands of tule reeds mark marshes and wetlands where more arrowhead and other water-loving plants thrive. The trail continues down, and you reach a ford, one of the few places with relatively easy access to a (slightly) firmer bit of riverbed. Cross with care: the Canadian is flashy, prone to surprise floods and well-supplied with quicksand.

Who made the trail? The same creature that made the grasslands above: buffalo. The North American bison, the supremely weedy herbivore that dominated the High and Great Plains from about 12,000 years ago until 1879.  A weedy species is one that spreads quickly and adapts well when it finds a niche, and the bison did that to a T. They did not quite cover the grasslands in a solid brown-black hairy blanket, but it wasn’t for lack of effort on their part. Bison, through their grazing and other habits, shaped the High Plains and its river valleys in a number of ways.

First, a word about the Breaks. Water caused them, but not like you’d expect. Under the soil of the Llano Estacado’s caliche layer you find thousands of feet of salt, gypsum and other evaporites, the remnants of tropical seas that covered the area in the time of the dinosaurs (The Interior Cretaceous Seaway). Over time, groundwater dissolved the salts from below while rain worked from above. The Canadian Breaks are, in a way, a very long sink-hole across the Llano. OK, back to bison.

Bison graze like sheep, clipping close to the ground. They will eat a large variety of grasses and forbs, and tend to eat a plant down, then move to the next plant, and the next. Bison can go for several days without water if they have to. Because of the size of the bison herds, they could clean out an area, grazing everything down to the ground before moving on. Those plants that survived developed ways to resist grazing, usually by developing enormous root systems to store lots of nutrients (big bluestem and Indian grass on the tall-grass prairies) or tillered. By tillering, sending out side shoots low to the ground instead of trying to produce seeds, buffalo grass could reproduce even after intense, heavy grazing. And because bison did not favor one species, all the grasses suffered equally. In contrast, domestic cattle will focus on one kind of grass, eat it out, then move to their second choice, and so on. Cattle also use their tongues to pull grass rather than clipping it with their teeth.

Although they look ungainly, bison can run very fast and are quite aggressive when bothered. You do not want to p.o. a bunch of bison (or roller-skate through a herd, either. But everyone knows that song.) Cows will fight when they and their calves are threatened. 1200 pounds of angry, sharp-horned animal charging head-on at 45 m.p.h. was a most impressive sight, and one most people only saw once, and that briefly.  The only real enemies of bison were wolves, humans, and floods. Floods? Oh, yes, especially on the Northern Plains (Missouri, Platte, other rivers) they’d drown in spring floods and form bison-jams, piles of bodies across the river. Bison have excellent senses of smell, OK sight, and good hearing.

Bison tended to form sex-segregated herds for most of the year, males in bachelor herds and females with calves in another. During the mating season the herds joined, raising dust, bellowing and carrying on. When the pioneer ranchers Charles and Molly Ann Goodnight first arrived in the Texas Panhandle, Molly Ann (Mrs.) Goodnight was kept awake by the sound of a mating herd doing their thing in Palo Duro Canyon, not far from their camp (but a few hundred feet below it). Her husband seemed unbothered by the commotion. Their conversation the next morning has not been recorded, but one can imagine the gist of it.

Where cows have dish-like hoofs, bison have split hoofs. As a result, they don’t compress the soil as much as cattle do, nor do they cut cow-paths down to streams and lakes. However, when you get a herd of several hundred, or several thousand, two-ton animals going anywhere together, they will leave a mark on the landscape. There are still places in far western KS and eastern CO where, when the light is right, you can see the remnants of the trails the herds made as they migrated north and south along the ladder of rivers across the plains.

Bison also do not shade up like cattle. Cattle deal with heat by finding shady places and laying down or standing for hours and chewing their cud. Instead, bison stayed on the grasslands in summer unless drought dried the grasses and playas too much. Even then, the bison often went east, to the wetter Great Plains and Low Rolling Plains, or west to the mountains, leaving the area completely. Cattle seek shade, flattening the grass and eating out the river and stream banks and lake shores. When this happens during the end of the growing season, the plants don’t come back as well the next spring. Bison preferred the lowlands in winter, while the plants remained dormant. Grazing didn’t do as much damage, and over the ten thousand years of bison on the plains, the plants adapted to them. And vice versa.

Bison also acted as nutrient transporters. What went in also came out, and they spread nitrogen, urea, moisture, and minerals across the plains as they grazed and excreted. You did not want to drink downstream of a buffalo herd. When they died, their remains decomposed back into the soil or served as food for wolves, buzzards, insects and other scavengers.

When the Spanish and US explorers arrived on the High Plains, the land they saw was a land with bison, shaped and fitted to the great herds of shaggy bovines, and vice versa. The semi-arid environment of the Llano favored short grasses and big grazers, a buffalo steppe. Bison were one of the keystone species of the High Plains, one upon which many other species depended or had adapted to.

[Comments remain closed until September 23.]