Prairie

by Candace Savage

  The Nuttall’s cottontail lives in brushy ravines and rocky breaks across the western plains. In spring, the female rears her young in a cozy, underground nest, often appropriating a burrow dug by a prairie dog or badger.

  So, despite everything we’ve heard to the contrary, the presence of earthworms in the soil is not always a mark of good health. Across much of the Great Plains, it is a prime indicator of disturbance. In arid regions, the work of digesting organic matter is assigned by nature not to tender worms but to the invincible legions of drought-hardy microorganisms. Meanwhile, an unlikely consortium of animals has taken on some of the earthworm’s other tasks. For instance, the job of turning the soil—digging in dead vegetation from the surface and bringing up clay from below (a service that is provided by earthworms where they are plentiful)—is here performed by burrowing mammals, including ground squirrels, pocket gophers, prairie dogs, and badgers, and most notably by ants. Given their impact on prairie soil, it could almost be said that ants are the earthworms of the Great Plains grasslands.

  There are dozens of different species of ants on the prairies (eighty-three, for example, in North Dakota alone), and while they differ in many particulars—size, color, diet, habitat—they tend to have one characteristic in common. Unlike ant species elsewhere that may take shelter in rotten logs or inside rolled-up leaves, most of the ants on the grasslands nest in the soil. An anthill is merely the visible extension of a complex of tunnels that extends down through the topsoil and into the subsoil beneath, often to a depth of 3 to 6 feet (1 to 2 meters). The labor of excavating these underground runways and lugging the soil up, grain by grain, can occupy a colony of several thousand ants for the better part of a decade.

  Formica inserta

  But this Herculean effort is justified by the benefits that accrue to the ants. Like all insects, ants are ectothermic, or cold-blooded. In other words, they assume the temperature of their surroundings and regulate their body heat by seeking shade or sunlight, as required. By constructing their complex, multilevel dwellings, ants alter their environment to create a range of microhabitats, each with its own particular microclimate. In winter, for example, they may retreat to their deepest chambers (below the reach of the frost), where they shuffle groggily through the coldest months. In summer, some species make sophisticated use of their anthills, which are carefully angled to soak up rays from the sun. As heat builds up in the hill, crews of workers lug their larval brood from place to place inside, striving to keep both themselves and their charges at just the right temperature.

  As ants manipulate their surroundings to meet their own needs, they inadvertently replenish the soil. The particles of clay that they carry up from their basements are rich in the minerals needed by plants and thus help to maintain the fertility of the upper layers. One estimate suggests that the top 2 feet (60 centimeters) of prairie soil is turned over every hundred years through the infinite efforts of ants and other soil creatures. And all this is achieved without any attention from us, beyond the farthest horizons of our senses.

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  > DUNG BEETLES

  Death by desiccation is a threat to many insects, particularly to the soft-bodied, unprotected larvae. One way to avoid this hazard is to take shelter underground, away from the drying effects of the wind and sun. This need for protection from the elements explains why so many fly and beetle larvae—maggots, wireworms, and grubs—are found in the soil, within wriggling reach of subsurface moisture.

  As a rule, the adult forms of these insects are not attentive parents: they simply lay their eggs in the soil and leave the larvae to look after themselves, as they grow, pupate, and eventually take wing as a new generation. Not so the members of the family Scarabaeidae, or dung beetles. Despite what may seem a lowly station in life as eaters of excrement, dung beetles are sophisticated insects that invest in parental care by providing their offspring with food, moisture, and shelter. On the Great Plains, the 100 or so species of dung beetles accomplish this task in one of four ways. First, there are the “rollers,” largish beetles (up to an inch, or 3 centimeters, in length) that cut chunks of moist dung from a bison or cow pat and use their forelegs to form it into a ball. Then, engaging their hindlegs and walking backwards, they shove the ball through the grass until they find a suitable place to bury it. In this underground nursery, the female lays an egg inside the ball of dung, which will provide sustenance and protection for the larva.

  The second group, the “tunnelers,” follow a similar strategy. But instead of struggling to transport the dung cross-country, these species (which tend to be smaller than the rollers) simply chew out chunks of dung and dig them directly down in the dirt, either under or beside the dung pat. Here again, the female lays her single egg inside the lump of dung, which will be the larva’s only source of sustenance during its two-to-three-week period of metamorphosis.

  Then there are the “dwellers”—the smallest of the lot—which take an even simpler and less laborious approach. Rather than carrying dung down into the soil, they lay their eggs right inside the pat. Because dung pats dry out quickly, these insects have a short reproductive cycle, which speeds them from eggs to adults in a few days’ time.

  Cow pat with fungus

  Candace Savage photo

  Finally, there is a unique group of pat-dwelling beetles that, over the last ten thousand years, have become adapted to eat rodent dung and to live in the cool, moist environment of rodent burrows. Some of these species are at home in open-mouthed burrows, like those made by ground squirrels and black-tailed prairie dogs, while others are found exclusively in the closed burrows of pocket gophers. On the rare occasions in spring and fall when the pocket gophers open up their dens, the air is sometimes peppered with thousands of tiny dung beetles making their escape, as they search for new burrows and fresh opportunities.

  Bite by bite, dung beetles and dung-beetle larvae process enormous amounts of organic matter and make an incalculable contribution to the fertility of the soil.

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  > AN ASTONISHMENT OF ANTS

  The fascination of ants extends far beyond their importance in building the soil. Although prairie ants represent only a tiny fraction of the 15,000 species that have been described around the world, they nonetheless exhibit a full range of weird and wonderful behaviors.

  By and large, prairie ants are carnivores with a taste for sweets. Because they hunt in groups, they are generally the most successful predators in their size range, subduing impressive numbers of spiders and smooth- and soft-bodied insects. Prey animals are generally torn into bits and carried back to the nest, where they are fed to the larvae. The worker ants’ main source of nourishment, however, is nectar from plants. This they typically obtain from one of two sources. Many plants, including native sunflowers and partridge peas, have special glands on their leaves, stems, or buds that produce ant-sized drops of nectar. Ants come to sup at these honeyed fountains—or “extrafloral nectaries,” as they are formally known—and defend them vigorously, in the process inadvertently defending their hosts against plant-eating insects.

  Ants also acquire nectar secondhand, by milking “honeydew” from the anuses of sap-eating aphids. Some ants carry on this trade in public, on the leaves of aphid-infested plants, but others prefer to milk their aphids in the privacy of the soil. Except for nuptial flights—when winged “reproductives” burst forth to mate and form new colonies—these ants spend their entire life cycle underground. Their nests feature special chambers around the roots of selected plants, where they keep their “herds” of root-feeding aphids. The ants tend their livestock constantly, tapping the aphids with their antennae to induce them to secrete sweets and slaughtering the tender young to supply their need for meat.

  Lasius neoniger

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  The Richardson’s ground squirrel, or prairie gopher, is one of a hardworking cadre of burrowing mammals that aerate and turn the soil as they tunnel through it.

  Arthur Savage p
hoto

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  HOME ON THE RANGE

  Oh, give me a home, Where the buffalo roam, And the deer and the antelope play, Where never is heard a discouraging word, And the sky is not clouded all day.

  HOMESTEADER BREWSTER HIGLEY, ON THE BANKS OF BEAVER CREEK, KANSAS, 1872

  IF I HAD to name my favorite place on the prairies, it would be the high, arid benchlands that sweep along the rim of the Frenchman Valley in southern Saskatchewan. Climb up there on a blue day in early September, out and onto the bald steppe at the top, and the wind will slam against you as if it had a grudge against anything that dared to raise its head above the grasses. This is a landscape that has held to the horizontal for thousands of years, even resisting the torrents of meltwater that once rushed down from glaciers in the Cypress Hills and gouged out the wide, flat trench of the river valley. From up on the benches, you can see the descendant of this ancient flood, a soapy, sleepy little stream that writhes through its oversized course, as if trying to make up in complexity for what it has lost in force.

  High on the benchlands, the grasses are stunted and crisp, and the ground bristles with clumps of prickly pear cactus. At one time, long before the Ice Age, this drought-stricken upland was itself the course of a great river that flowed down from the young Rocky Mountains across the northern plains, burdened with loads of gravel and debris. As stones were dropped by the river, they settled onto the riverbed, where they formed a thick layer of sediment. (As the ages passed, this pavement helped the land resist erosion by water and wind, with the result that the former valley is now a high tableland.) Millions of years later, the benches of the Frenchman Valley are still strewn with rounded, river-washed stones, most of them two or three times the size of a clenched fist, all speckled and splotched with lichens.

  The eye scans the stone-pocked surface, searching for clues. Grass, sky, rocks. Scattered rocks that suddenly swerve to follow a curve, a curve that coalesces into a circle. Two concentric circles of stones lie half-buried in the grass, tracing a circumference of about twenty paces. A few steps away, another ring and another. People have been here before us in the fairly recent past, though whether it was two hundred years ago or two thousand is more than we can tell. All we know is that a party of bison hunters once chose this bank of the valley to make their camp and that they used these rings of rounded stones to anchor their skin tents. Downslope from the tipi rings, where the benchland begins to fold toward the valley, smaller rocks and pebbles have been washed into terraced drifts, and some of them are chipped and sharpened along one edge as if they had been fashioned for working skins. They fit neatly into the hand.

  This land has never been disturbed by the plow—not even a stone has been touched—and it would be easy to think of it as wild, the last stand of the great North American grasslands. In the beat of the wind, you can almost believe you are hearing the muffled drumming of a bison herd that, any minute now, will come rolling into view over the horizon. Through bones and stones and life-forms, these lands conserve not only the memory of the past but the whole promise of a future for many grassland animals and plants. The surviving native grasslands bring us as close as we can now get to the prairie in its natural abundance. Yet when you walk toward that horizon and peer down into the valley beyond, you will not find wild herds or camps of nomadic hunters. Instead, you are very likely to see a bunch of cows. It’s still fabulous out there on the rangelands, but it ain’t exactly wild.

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  > INTO THIS WORLD OF BEAUTY

  When a Kiowa woman named Old Lady Horse looked back on the past, she recalled the not-so-distant time when all the necessities of life had been provided to her people by the bison. Hides for shelter and clothing, bones for tools, blood and meat for food. “The buffalo were the life of the Kiowa,” she said.

  When Europeans came to the plains to build railroads and raise cattle, the bison did their best to protect the Kiowa from harm. “They tore up railroad tracks and the gardens,” Old Lady Horse recollected. “They chased the cattle off the ranges. The buffalo loved their people as much as the Kiowas loved them.”

  But when the newcomers sent in soldiers and hide hunters, the buffalo admitted defeat and gathered in council to decide what to do. As it happened, the Kiowa were camped on the north side of Mount Scott, Oklahoma, at this time. Early one morning, a young Kiowa woman looked up from camp toward the mountain, through the mists over Medicine Creek, and saw the last bison herd appear like a spirit dream. As she watched, the face of the mountain opened and the bison walked inside, into a world of plum blossoms and freshness, where “the rivers ran clear, not red.” Into this world of beauty the buffalo walked, and the mountain closed behind them and they were gone.

  Old Lady Horse told this story to Alice Marriott, who included it in her book American Indian Mythology in 1968.

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  The Intercontinental Bovid Boogie

  Rangelands—expanses of native grassland that are grazed by livestock—exist only where the prairie has somehow managed to escape the plow, usually because the soil is too dry, too thin, too rocky, or too steep to be suitable for crops. The greater the agricultural potential of a region, the less native prairie is left. Because moisture and soil fertility improve from west to east and from south to north, the percentage of the land in natural cover increases in reverse, from east to west and from north to south. Out west on the short grasslands, where the rains are meager and the soil is relatively poor, something on the order of 70 percent of the landscape has survived with its natural integument of grasses and wildflowers. A little to the north and east, by contrast, in the slightly moister mixed-grass zone, the percentages drop off, and what little prairie survives is badly fragmented. (In Manitoba, to cite the most extreme example, less than 0.1 percent of the original mixed-grass landscape remains intact.) On the whole, the irresistibly fertile tall-grass zone has fared worst of all, with less than 1 percent of the entire ecoregion remaining in a more-or-less natural condition. This state of affairs earns the tall-grass prairie dubious honors as the most endangered ecoregion in North America. Today, the only large, continuous blocks of tall grasslands lie in the Flint Hills of eastern Kansas and the Osage Hills of northeastern Oklahoma, where a stony rime of crystalline quartz just beneath the surface long ago put a dent in the enthusiasm of plowmen.

  The surviving native grasslands span the complete spectrum of prairie types, from the stony benchlands of the Frenchman Valley and the rollicking dunes of the Nebraska Sand Hills to the sculpted badlands of the Palo Duro and beyond. Ecologically, they are as different from one another as big bluestem is from blue grama or as a sage grouse (a threatened bird of arid prairie) is from a prairie chicken (its threatened cousin on the humid tall grasses). Yet for the last century or so, these diverse grasslands have all answered in similar ways to one set of human demands—to produce food for large numbers of cattle and ultimately for ourselves.

  His body a blur of intensity, a male sharp-tailed grouse performs his mating dance. In spring and fall, groups of male grouse meet at leks, or dancing grounds, to compete for the attention of the females.

  In some ways, the introduction of domesticated livestock onto the Great Plains was not much of a shock to the ecosystem. Bison and cattle belong to the same evolutionary lineage, the family Bovidae, and trace their ancestry back to India and China some 2 million years ago. But whereas the ancestral bison headed north across the Bering land bridge into the Americas, cattle took a turn to the west and wandered through the Near East and into Europe. (They are thought to have been domesticated in or around what is now Turkey some 10,000 years ago.) True to their common ancestry, the two species filled much the same ecological role on their respective continents, as large mammalian herbivores that specialize in consuming grasses and, to a lesser extent, other forbs, or nonwoody plants.

  Greater prairie chicken

  Since grasses are ribbed with particles of silica (grains of glassy sand), both
bison and cattle have self-renewing teeth that grow in to compensate for the wear and tear. And since grasses and other plants are composed mostly of cellulose, which mammals cannot digest, both species have fermentation vats for stomachs—elaborate four-chamber structures in which a frothing stew of microorganisms breaks down the tough plant fibers. Halfway through this process (between stomachs 2 and 3), the animals cough up a “cud” of half-digested mush, give it a thoughtful second chew, and send it back down for another round of microbial demolition. By collaborating with these small-but-mighty microbes, large ruminants like cattle and bison free up nutrients locked inside plants and keep resources cycling through the ecosystem.

  As they convert plant tissues into cold-cuts-on-the-hoof, herbivores inadvertently provide a source of highly digestible food for the next trophic level in the system, the carnivores. The carnivores, in their turn, inadvertently assist the herbivores in avoiding predation. By removing the halt, lame, and unwary from the breeding stock, predators select for individuals that are best adapted to escape from their grasp and hence make successive generations of their prey more difficult to catch. Thanks to this rigorous breeding program, bison and cattle have both acquired large eyes and excellent vision, the better to help them detect predators. They have become strong and sure-footed, able to sprint away from danger or to travel long distances to seek safety. Most important of all, both species have become overwhelmingly sociable. Like many other animals that live on the plains, bison and cattle find comfort in the company of others of their species. Not only can they benefit from the combined vigilance of the group—all eyes peeled for a possible threat—but they can also attempt to use their neighbors as “bovine shields.” The more potential victims that are available to a predator, the less chance there is that any given individual will end up as a sacrifice to trophic exchange.