  By Greg Beaumont The Belle Fourche River meanders through northeastern Wyoming, exposing red banks of clay. It crosses the southeastern corner of Devils Tower National Monument near the entrance road. A Day at Devils TowerPouring a mug of boiled coffee, I wait for the sun to make its appearance. The cup steams in the damp, cool morning air. Shivering, I press both hands to the heat the thick porcelain holds. The sky begins to purple, and stars dim perceptibly. Through the campground cottonwoods, the immense, shadow-black bulk of the Tower materializes against the sky. It is possible now to discern the flight of bats overhead. But, in an instant, their swirling, night-long ballet vanishes with the darkness. From my campsite along the Belle Fourche—this narrow, meandering river the French fur trappers named “the beautiful branch”—I listen to the first sounds of the day. Across the river a great horned owl protests the morning’s swift advance. Coming through the veil of river fog, its haunting, pervasive hoo-hoo-hoooo is enough to freeze the blood of cottontails. Even before the first hint of light, robins had begun to sing softly. In these unhurried morning songs they prove themselves thrushes. With the increasing light, the growing blend of wren, vireo, and thrasher music intensifies. These soft phrasings soon quicken into proclamations of territory, and meadowlarks, mourning doves, and yellowthroats compete across thicket, river, and meadow, their singing seemingly sharpened for distance and authority. Nearby, a cottontail grazes on the dew-bent grass. It pauses occasionally, pointing its ears and working its nostrils in my direction. Three whitetail deer continue their cautious single-file approach, heading from the river bottom toward the higher ground of the prairie dog town. Crossing the campground, they repeatedly stop to inspect their surroundings. A log snaps and whistles in my fire, bringing their heads about in immediate, almost mechanical unison. Deliberately the lead animal lifts its tail to expose its white, silent signal of danger, and all three step smartly away as if in time to a fast metronome. Direct sunlight spotlights the Tower. As though to challenge the sudden appearance of a gigantic, equally yellow competitor, a meadowlark takes wing, singing its loud, clear claim over the prairie dog town. Dawn is announced, the day begun. The level rays of the sun accentuate the Tower’s vertical polygonal columns. The stark contrast of light and shadow imparted by the graceful taperings Sipping the strong coffee, I wonder at the long procession of vanished Indian societies that camped and hunted here periodically through the centuries. These ancient peoples devised various stories to explain such an unusual landmark. And yet what science now says about the creation of Devils Tower would have seemed to those tribes as fantastic as their legends of a gargantuan bear gouging the rock seem to us today. Minor uncertainties remain, but geologists have pieced together a rough picture of the Tower’s probable origin. Some 60 million years ago, great Earth stresses began to deform the crust of the continent, resulting in the uplifting of the Rocky Mountains and Great Plains region. As the surface rock layers began to crumple and fault, magma from deep inside the Earth welled up into many of the resulting gaps and fissures. In many places on the continent, spectacular volcanoes formed, erupting with explosive force. As the Rockies were being created, the climate of the continent’s interior began to change. The long reign of the dinosaurs that had presided over a stable, tropical landscape was coming to an end. The climate was gradually becoming cooler and drier. Doubtless the immense volumes of volcanic ash ejected into the atmosphere prevented a percentage of solar heat from reaching the Earth. Certainly the rise of the Rocky Mountains to the west influenced the old weather patterns. As the mountain blocks rose higher, they intercepted the warm, moist winds that blew inland from the Pacific. With the air masses rising ever higher, more and more of the moisture that had watered the extensive inland Cretaceous forests and swamplands was prevented from reaching what we know today as the Great Plains. Steadily the forests retreated eastward as the “rain shadow” cast by the mountains extended eastward, shutting off the moist, warm Pacific winds. No longer moderated by these winds, the mid-continent was increasingly opened to seasonal invasions of northern arctic air. Newer ecosystems, such as deserts and grasslands, slowly evolved to replace the lush forests and swamps that had for so long sustained the dinosaurs. Both the Kiowa and Cheyenne Indians held similar legends on the origin of the Tower. The story goes that tribal members were surprised by a gigantic bear, and their incantations caused a low, flat rock to rise, lifting them above the reach of the bear. The massive beast then gouged huge vertical marks into the rock as it attempted to reach the people. Finally, the Indians were able to kill the bear. But not all the magma that welled upward during this restless period reached the Earth’s surface. Extensive masses were trapped far below the surface, where they gradually cooled and congealed. The Missouri Buttes and Devils Tower, however, are believed to be necks of extinct volcanoes. Geologic evidence indicates the Missouri Buttes formed first in two separate eruptions. The magma hardened, plugging the plumbing underneath. A third eruption to the southeast resulted in Devils Tower. During the ensuing tens of millions of years, the gradual erosion of the overlying rock strata revealed these intruded plugs of volcanic rock. Since this dense, hard igneous rock resists erosion much better than the surrounding sedimentary rock, these formations will continue to stand out as features. That ancient land of sedimentary rock through which the molten mass of Devils Tower penetrated may at one time have been as high as the golden eagle I now see drifting high above the Tower. Circling slowly in its morning hunt, the eagle spirals upward on the currents of warm air rising off the sun-heated rock. Perhaps it now soars at the elevation of the land long ago when the heavy, ringing-hard rock of Devils Tower oozed like paste far below the surface. Today the top of the Tower is 386 meters (1,267 feet) above the Belle Fourche River. If that warm, Cretaceous landscape rested 600 meters (2,000 feet) above the present summit of the Tower, then more than 900 vertical meters (3,000 feet) of sedimentary rock has been pared away in the last 60 million years. The relentless physical agents of erosion—running water, wind, and frost action—together with chemical breakdown of rock particles, continue to alter the landform. Given enough time, even the very hard rock of the Tower itself will waste away. Sixty million years ago, when dinosaurs Triceratops and Tyrannosaurus Rex duelled beside the lush river banks of the predecessor of the Belle Fourche, the ancestor of the golden eagle was flying overhead. Millions of years hence, a descendant of the eagle might soar above this same Wyoming landscape. Missing will be the unique shaft of fluted rock we call Devils Tower. And what of the men, who for a mere eyeblink of time, hunted in its shadow or came to wonder at its somber countenance in the morning sun? The Tower’s Geological Story
A thwack of an ax against wood puts an end to my daydreaming. My companion the cottontail hops for cover. The pair of magpies that have been feeding on the remains of a road-killed ground squirrel flash upward to safety. The gradual awakening of campground life inspires woodpeckers to hammer in the cottonwoods, and a yellow-breasted chat adds its odd jibber to the collected noise. Gathering up knapsack and camera. I start my hike to the Tower. Already the sash of river fog has lifted and the air warmed to shirtsleeve comfort. From somewhere on the red cliffs that gown the Tower’s base, the faint singing of a rock wren beckons. Ahead lie 13 kilometers (8 miles) of trail, looping through a mosaic of sights, sounds, and smells of grassland, pine forest, woodland, and river. From Dog Town to Ant ColonyLeaving the campground, I follow the trail that leads through the prairie dog town. The prairie dogs stand upright as I approach. The ones nearest the path begin their warning call, a monotonous “churk-churk-churk-churk.” The closer an intruder comes, the lower the animals sink into their holes, and the faster and shriller the chant becomes. Finally, with a last flick of its nervously twitching tail, each disappears into the safety of its burrow. Prairie dogs, like the bison that once shared their vast range, are now reduced to remnant populations. Two hundred years ago, there were billions of prairie dogs on the shortgrass plains; these large ground squirrels had successfully adapted themselves to the harsh conditions. Perfect digging machines, they escape most predators and the extremes of the weather by spending more than half their lives underground. The prairie dogs near the road do not even bother to sound a warning as I approach. They seem to be different creatures from the wild, suspicious animals farther from the road. Laconic and fat from handouts, more curious than cautious, they approach rather than retreat. These animals are easier targets for the redtail hawk that is screaming above the river Across the road, the trail leaves the grassland of the prairie dogs and climbs steeply among ponderosa pines. Already the sun grows hot. At the edge of the forest, I stop to rest and survey the landscape before me. Spread out below, and now shimmering with sundance heat, the buff-colored dog town stands out in stark contrast with its darker, greener surroundings. Although I sit only 30 meters (100 feet) or so above the dog town, I am struck by what my vantage point reveals: a clear patchwork of life communities. The loop of the Belle Fourche and the June-bright leaves of the deciduous trees lining its course provide a bright counterpart to the somber, pine-scattered ridge beyond. Just a short distance away the ponderosas appear more black than green. It was just such a quality that gave the distant, pine-covered mountain range to the east the name Black Hills. From where I sit, the lobe of the level bench of land that juts into the river looks as if it were graded and maintained by man, for its close-cropped vegetation contrasts greatly with the rugged ridge beyond. But this old floodplain was graded level by the river, and prairie dogs, not machines, clip the vegetation. This small area of grassland, sandwiched between the base of the Tower and the encircling river, supports a surprising amount of life. Yet from all appearances, it would seem as if the multitude of prairie dogs would soon denude their patch of land and die of starvation. In contrast to the surrounding territory, the vegetation of the dog town appears exhausted. Indeed, today’s empty plains give few hints of what a crowded stage the shortgrass plains once was. Before the coming of the white man, the grasslands teemed with bison, pronghorn, wapiti—named buffalo, antelope, and elk respectively by European settlers—and sprawling towns of prairie dogs. Astounded early observers, accustomed to the lush flora of the eastern woodlands, could not imagine how so many animals could survive in such a parched-looking land. The secret is the grass itself. Whether tinder dry in midsummer or dead in winter, the grass blades remain highly nutritious. Grass plants can withstand repeated grazing and fires since new growth progresses from the stem joints rather than from the tips. continues on page 32 A Glimpse of Life on the Top
In addition, most plains animals contend with the semi-arid conditions of their environment by making efficient use of available moisture. Pronghorn, prairie dogs, and kangaroo rats, for example, need never take a drink since they obtain necessary water from the plants they eat. Such plant and animal adaptations explain why the shortgrass plains can sustain such a vast panorama of life. From a tall pine upslope, a red squirrel chatters with indignation at discovering my intrusion into its domain. The bell-like song of a rock wren answers from an outcrop nearby. The small gray bird appears atop a boulder, motionless but for an instant, then hops down to resume its search for insects among the bright, arid cliffs it claims for its own. I realize that I am seeing more than scenery here. All around me are boundaries—conspicuous where defined by plants, but invisible where respected by animals. No prairie dog has ever traveled across this slope, and no red squirrel has ever scurried into the treeless expanse of the prairie dog town. On no occasion would a rock wren enter the deep pine forest. Should its food supply somehow vanish, it would perish among the bare earth and gully washes of its own habitat rather than hunt the dog town or forest floor. Each animal species is adapted to the conditions of its preferred environment. The prairie dog and red squirrel have similar roles in their respective habitats, as do the meadowlark in the grassland, the house wren in the deciduous woodlands, the rock wren on barren slopes, and the brilliant western tanager of the pine forests that is calling “pit-ik, pit-ik, pit-ik” from a branch overhead. Whether herbivore, carnivore, scavenger, or decomposer, all of the countless, magnificently varied life-forms of each community share in the endless flow of chemical energy that originates with the touch of sun on chlorophyll. Eagle, prairie dog, bacterium, man—we all owe our lives, directly or indirectly, to the green leaf’s unique ability to convert light energy into chemical energy. So does this colony of black ants foraging near my feet. Back and forth the living lines run, each individual obeying its ancient, perfected legacy of instinct. One carries aloft the bright green corpse of a lacewing. With a little last-minute help from fellow Having tipped its load over the rim of the funnel, the ant disengages itself and attempts to crawl up the incline and get to the other side of the spider to pull it out again. But the loose soil particles offer little traction and the ant begins to slip. Frantic, it works its legs faster, making it slide downward more quickly. Alerted now by vibrations from the struggling insect, a hidden antlion waits its moment to strike. When the ant touches bottom, the hooked jaws appear, snapping once, twice, and finally closing shut about the thorax of its prey. In a moment, all is over, the ant dragged beneath the soil at the bottom of the crater. The corpse of the spider, part way down the incline, is occasionally investigated by other passing ants. But the ants at the lip of the trap seem to sense the danger and leave the stranded prize alone. Other antlions, at the bottom of their expertly engineered traps, lie hidden from the passing parade of life above. Obeying their own instinct messages, they need only wait to survive. A disturbance in the dog town starts the animals to barking and scurrying in every direction toward their burrows. Two figures from the campground have appeared up the incline. Their determined stride and the coils of rope at their shoulders suggest that the Tower’s summit may well be explored again today. Already tall cumulus clouds, the beginnings of thunderheads, are building along the eastern horizon. A gust of hot air from the sun-baked ground below rushes into the pines, making the branches whizz into motion. A pine cone bounds against rock, setting the red squirrel to chattering again. I head for the Tower Trail, leaving behind the ant colony’s ordered turbulence and the view of the deserted dog town dancing in the sun. Eye of the FalconAt the juncture with the Red Beds Trail, I decide to follow the longer circuit of the Tower. The higher, shorter Tower Trail, which bracelets the rock-strewn base, can be picked up at the Visitor Center, where this trail ends. Folding the map, I hear the climbers approach. “Good morning.” The girl’s smile does not soften the concentrated expression all climbers wear before ascent. “Which way are you going?” I ask, trying to conceal my lack of knowledge about any of the routes and knowing full well I would never venture what they are about to do. “Left arm of the south face this time,” says the man. He obviously does not desire the delay of conversation but does volunteer that he had made several climbs the summer he worked here. I hold them with another question: is there anything interesting on top? “Terrific view. Grass on the summit; lots of chipmunks; once a rattlesnake was sighted. Well, we better get moving.” “Good luck,” I call after them. The expression seems a lame wish for rock climbers. Soon they are brightly clad specks weaving through the trees. Looking up at the summit that towers above them, I wonder how a chipmunk or snake could have possibly gotten there—perhaps only by escaping the talons of an eagle or hawk. But could that happen? More than 1,000 ascents of Devils Tower are now made each year. The almost casual manner in which experienced climbers regard the structure—often scaling it to keep in shape for “difficult” climbs—would have astounded early explorers, who regarded it as unscalable. Shrill, rapid cries of a prairie falcon echo from the Tower wall. Although hidden from my view by the pines, its circling flight is revealed by its bursts of screams. It scolds the climbers who are now pressing upward and perhaps invading the security of its nest site. But the commotion soon dies away, indicating that the sharp-eyed falcon is more annoyed than threatened. Should the climbers inadvertently come close to the nest, however, the protective bird would repeatedly dive at the intruders in an attempt to drive them away, a distraction I would not relish. I continue down the trail, which gradually drops toward the river. The pines yield to communities of deciduous vegetation interspersed with grassy meadows. A whitetail deer stands at the far edge of the narrow meadow the trail is about to enter. Not yet aware of my presence, it continues to browse the succulent new growth of a chokecherry. Were it not for the meadows and wooded ravines that surround the higher reaches of the pine forest, the Monument could not support as many deer as it does. Deer like a mix of woodland and meadow. The dense cover of shrub thickets, canopied by closely spaced elm, chokecherry, hawthorn, and other trees, offers sanctuary and browse. The nearby meadows provide essential diet supplements of grasses and herbs. As I move on, the deer dashes away. A cottontail bounds across the trail and overhead, on a long, twisted branch of a burr oak, a fox squirrel scurries upward to safety. A brown thrasher scolds momentarily but soon resumes its complex song. Its music is as various in shading and structure as the many leaf shapes that can be discovered in its habitat. Before abruptly reversing itself, the trail makes a long swing northward. Leaving the pines, it crosses the maroon sediments that give the Red Beds Trail its name. The exposed formation has been cut into steep cliffs by the river. Deposited some 180 million years ago during the Jurassic Period, when the land surface was low and adjacent to a sea, this mixture of siltstone and sandstone is poorly cemented together. As a result, it weathers easily, forming a striking, ravine-cut outcrop wherever the stratum is exposed. Few plants colonize this handsome formation, making it stand out against the dull, igneous-gray Tower and its dark wreath of ponderosa. As the sun approaches zenith, I am nearing the end of the trail circuit. Coming back closer to the Tower, the trail re-enters the pine forest. I welcome the perceptibly cooler air and dimmer surroundings beneath these big, yellow-barked trees. Here, where lichen and moss cap boulders and fallen logs, is a good spot for lunch. I sit with my back to the trunk of an ancient, fallen giant whose length has collapsed and defines the contours of the ground. Its exposed, rotten heartwood nourishes miniature fungi-gardens. Compared to the sharp shadows and glare of the Comparatively few life-forms inhabit the pine forest. Fewer kinds of plants grow beneath the pines than grow in the deciduous woodland. And fewer plant types mean a more limited diet for herbivores such as insects, mice, cottontails, and deer. The scarcity of insects also reduces the number of bird species that will find the habitat attractive. The relative absence of life on the forest floor begins in the soil. Pines create acid soil conditions which do not promote bacterial growth. Decay, therefore, carried on primarily by fungi, takes place very slowly. The result is the thick accumulation of discarded needles and branches, the resinous, sweet-smelling “duff.” Not far upslope from the trail a porcupine scuttles toward a stand of young pines. It moves slowly and silently, its quills making it look prehistoric. Again I am struck by the apparent changelessness of the pine forest. But looking around, I find everywhere signs that indicate change and struggle. At the bases of the giant pines—some of which may be more than 200 years old—are fire scars. Most of the mature trees survived the frequent fires that once raced through here. Their bark was thick and fire-resistant, and they had few lower branches to pass the flames up into the vulnerable upper branches. But that was before the white man interrupted the long reign of wildfire. Ironically, fire had actually helped to maintain the health of the forest. Grass fires, sweeping into the pines, burned off the accumulations of litter and killed many of the crowded younger trees. Tinder was thus removed before it could build to dangerous levels. continues on page 40 A Home for Wildlife
Now, after 80 years of fire-prevention management, the forest is ripe for fire. Should it come now, however, the effects might be devastating. Fed by an abundance of ground fuel, a cool-burning, fast-moving grass fire could quickly become “hot.” Lifted up into the upper branches of the old pines via the closely spaced younger trees, the ground fire would quickly develop into a crown fire. Few, if any, trees would survive such a conflagration. The role of natural fire has only recently been appreciated. However, in the small area of Devils Tower, where the scenic qualities of the pine forest are paramount to visitor enjoyment of the Monument, fire cannot be permitted without virtual destruction of the surrounding forest. Thus, for esthetic reasons, fire is regarded as unacceptable here. After lunch I walk on beneath the trees. The openness of the mature pine forest soon gives way to dense groves of younger ponderosa. Deprived of the separation they require to develop naturally, these “doghair” stands strain upward together their trunks toothpick thin—to reach the light. Many exhibit long, yellow wounds, from which sap bleeds. This is the work of porcupines. Gnawing through the thin bark of young trees with sharp, chisel-shaped teeth, they strip away the tender, living tissue of the tree. Most wounds are not severe, but should the trunk be girdled, the moisture and nutrient transport system of the tree will be severed and the pine will die. Thus, even though fire no longer occurs here regularly, other agents of control, such as porcupine damage and insect infestation, continue to work. The trail emerges from the deep north-slope forest, runs parallel to the visitor center access road for a short distance, and ends at the parking lot. The glare of afternoon light and shimmering heat waves is a sharp contrast to the cool, dim surroundings of the deeper forest. Before continuing on around the circuit of Tower Trail, I stop at the visitor center for water. Beside the fountain sits an old man, leaning his chin and hands on a cane and staring upward at the broad west face of the Tower. An immense mushroom of a towering cumulus cloud billows up behind it. “Quite a sight,” I say. He seems to deliberate, then finally answers: “I can remember seeing a picture of this in my school I don’t know what to say. One does not make idle conversation with a man who has made a pilgrimage. We watch a pair of rock doves, outlined against the white brilliance of the boiling cloud, ride an updraft near the summit. Wings set and almost touching, they dip and recover, their resonant calls clear despite the distance. Nothing more to be said, I set out toward the trail. Not once did the man take his eyes off the Tower. With the first dull report of thunder, I hear the chiding call of the falcon again. Its sharp voice momentarily silences the mellow cooings of rock doves that filter down from the high crannies and ledges. The trail steeply ascends a slope of broken, fallen columns, weaving among the immense rock slabs like a mouse-run in a boulder field. I am surprised to see a grove of aspens. Their crooked trunks bend in the freshening wind, their leaves dancing and blinking on and off the dusty silver of their undersides. What a contrast to the rigid stature of the surrounding pines that barely acknowledge the approaching storm. The presence of aspen probably means that a fire once swept across this dry western shoulder. Quick to invade new territory after a fire, aspens play an important role as a pioneer species of the western and northern American coniferous forests. Like the ponderosa, they can grow on dry, rocky sites. Since they often reproduce vegetatively—a grove of aspens is often produced by sprouting from the roots of a single tree—aspens are well suited to unstable or fire-swept sites. Although readily consumed by fire, aspen groves regenerate quickly from their undamaged root systems. Without periodic fire, in fact, aspens are eventually excluded from the forest composition, shaded out by the taller growing conifers. The growing turbulence spurs me onward. Hugging the steep upper slopes of the Tower’s circular base, the trail allows a speedy orbit. The falcon continues to scream. Now along the southeastern face, I can hear the climbers shout to one another. The belly of the cloud is overhead and angry-black. Lightning flashes are now immediately followed by loud reports, sharp as splitting wood. I should turn back In a rock crevice where the trail passes along a cliff face, an untidy ring of trash reveals the nest site of a wood rat. Called “pack rats” because of their habit of carrying off unguarded items, these big rodents adorn their nest entrances with anything from bottle caps to sunglasses. This one has amassed a fine collection of discarded gum and candy wrappers. As the first large raindrops thud down into the trail’s soft earth, I envy the animal’s protective retreat. In ten minutes I am back at the spur that leads to the Visitor Center. If the old man is still there, perhaps I will wait out the storm with him beneath the porch roof. But I cannot see him, so I continue on to the campground. I am already soaked through anyway, so the lashing rain is no longer a threat. I retrace the section of trail I had walked an hour before. Ten minutes more and I leave the pines and enter the deserted, puddled prairie dog town. Nearing the road, I see a car approaching slowly. As it passes I notice the old man. Leaning forward, he cranes his neck to catch a last glimpse of the Tower he had waited so long to see. Voice of the KingfisherBy late afternoon the storm has passed, and with the return of sunlight a rainbow arches the Belle Fourche. Taking advantage of the softened earth, the prairie dogs busily reshape their mounds, scratching dirt loose, bulldozing it up the slopes of entrance mounds, and tamping it. All but the young wear black noses. At the return of the climbers the town suspends its work, rises to alert, and chirps warning. A meadowlark sings from a fence post near the river. Against the purple southern sky, its black and yellow vestments seem unnaturally bright, and its call in the rain-cleared air seems sharply amplified. It glides into the glistening grass. Soon the female, wearing a duller version of its mate’s tuxedo, flies up and disappears across the narrow river. When she returns, her bill is crammed with insects for her demanding A red-headed woodpecker, which has been shuttling between a certain cottonwood and other trees, also reveals its nest site. High up in the tree it has excavated a perfectly round hole. Leaning back on stiff tail feathers, it jerkily climbs up and around the trunk, pauses at the hole, then leans in to deliver the white grub to its squealing young. So insatiable are nestling birds, their demands exert a significant control on insect populations. A pair of adult house wrens may log more than 1,100 daily trips to feed their young. That so many varieties of birds can co-exist in the same area is possible because different species generally do not compete with one another for the same food source. Each gleans its food in a slightly different manner and locale. Each species vigorously defends its territory from others of its kind but will tolerate neighbors that occupy a different niche in the community. A single plum thicket may contain the nests of a pair of catbirds, mourning doves, robins, and vireos. Because each bird hunts its food in a slightly different manner and place, they do not directly compete. The cliff-nesting swifts and swallows have reappeared above the river, a twittering confusion of swirling, darting shapes that manage to survive by capturing insects on the wing. Higher up, the booming of nighthawks announces that insects are active in the upper air also. After supper I walk along the river. Now that shadows fill the river bed, there might be an opportunity to see a beaver working or a mink hunting along the shore. Passing close to where the meadowlarks have their nest, I cause a panic of concern. Both birds, invisible a second ago, lift off the ground, scolding and threatening, to distract my attention from the location of the nest. The outcry brings a killdeer up from the shore of the river. Uttering its plaintive, reedy cry, it circles about, lands, runs rapidly along the bank, then crouches down to display a “broken” wing. It is joined by a mate and both birds take up the act, leading me away from their own eggs or helpless young hiding motionless on the ground. So adept are the killdeer at this diversion, it seems incredible that instinct and not intelligence is responsible for their highly specialized behavior. continues on page 46 Among those birds living in the forest at the base of the Tower is the white-breasted nuthatch, which commonly makes its fur- and bark-lined nest in the cavity of a tree. Many a woodland hiker has paused for several minutes to watch this inquisitive, sparrow-sized bird creep head first down the trunk of a tree, stopping now and then to look out at a 90 degree angle. The red-breasted nuthatch also inhabits the park. The intense sky-blue of the male mountain bluebird catches the eye of the most casual of birdwatchers. Its blue breast distinguishes it from the western bluebird. Like the white-breasted nuthatch, this bird nests in a tree cavity, usually a deserted woodpecker hole. It often hovers low over the ground, then darts down to catch insects. Though small in area, Devils Tower National Monument provides a sanctuary for an extensive variety of birds. Because the mountains and the plains converge here, species common to both can be found. More than 90 species have been counted. Several large birds may be seen flying around or near the Tower itself, occasionally swooping down to prey upon life in the open grasslands. These include Cooper’s and red-tailed hawks; American kestrel; golden and bald eagles; prairie falcon, and turkey vulture. Only the prairie falcon and the rock dove, or pigeon, live on the Tower. (See pages Standing still or in flight, the black-billed magpie is distinguished by its white shoulders and belly, by white patches under its wings, and by its long tail. The nighthawk nests in the open grasslands here. This robin-sized bird was mistaken for a hawk by the pioneers because of its long wings and swift flight. The red-headed woodpecker spends most of its time in the open deciduous woods. Its entirely red head and a large white patch on its wings distinguish it from other species. The meadow across the river is a solid yellow of blooming spurge. In contrast, the ground on the Monument side of the river presents only a few isolated plants, and they are limp and pale from the effects of herbicide. Because spurge is an exotic plant that invades grasslands and displaces native flora, it is exterminated, through selective application of herbicide, within the Monument boundaries. The rattle of a kingfisher precedes its sudden appearance around the sharp bend in the river. Skimming low across the water, the blue and white bird darts upward to perch on a cottonwood snag that overhangs the river. Its large crest and straight bill make the kingfisher look more caricature than real. Intently studying the river below, it need not wait long before plummeting from its observation post straight into the water. Reappearing a second later, it quickly regains its perch, the silver glint of a small fish caught in the parted scissors of its black bill. After swallowing the fish with a toss of its head, it shakes the water from its feathers and resumes its patient inspection. Like a giant, soundless mosquito, a cranefly rises upward from the river bank. Another hovers low across the surface of the water, frequently dipping its abdomen below the surface to deposit its eggs. The first quickly disappears with the banking flight of a nighthawk; the second with the darting intercept of a dragonfly. Like countless other species of insects that divide their lives between the water and land, the craneflies are a living link in the food chain that helps bind the aquatic and terrestrial life communities together. The many thousands of insect species requiring an underwater environment for their larval stage help sustain many species of terrestrial predators when the insects emerge from the water as adults. The kingfisher that nests here and the occasional great blue heron that stops during migration also enjoy the fruits of the water community, taking fish and frogs. But the process is not a one-way street. Nutrients leached from the land help fertilize the aquatic food chain. And the grasshopper that inadvertently hops into the river, only to disappear quickly into the gullet of a fish, represents another of the ongoing exchanges between land and water. As I round the sharp bend that sends the river Growing dusk fills the river valley. In the failing sunlight vanquished to a thin, vertical display on the Tower face, it is almost possible to imagine what this splendid landscape must have been like as wilderness. Bison, not cattle, would have grazed nearby. Instead of the howling dog that has escaped the campground and races into the prairie dog town, a wolf might be pressing home its attack on an injured pronghorn. Grizzlies and cougars knew this valley, and the river was tamed not by a nearby reservoir but by a latticework of beaver dams. There are no prairie dogs left above ground now to challenge my trespass as I head back toward the welcome firelights of the campground. The deer have left their daybeds to graze in the open, and the great horned owl again asserts its dominance in the river timber. With a long rattle, briefly echoed from a cliff, the kingfisher quits the day. Beneath the expanding population of stars, I return to the comfort of hot coffee and the confines of my own world. For now, I am content with the memory of eagle and falcon. In my mind they will continue to soar, inspecting the splendid terrain my memory today acquired. Prairie Dogs: A Tight-Knit SocietyA prairie dog family gathers at the entrance to their burrow, watching the activity in the town and keeping an eye out for intruders. When the long grip of winter’s crusted snow relaxes, pasqueflowers burst forth in ravines, unplowed pastures, and abandoned cemeteries. Their delicate silvery purple contrasts with the bleak stubble of last year’s ruined grasses. Before plows ever broke the grassland sod, pasqueflowers were so profuse the distant ground seemed veiled in haze. The pioneers called it “prairie smoke.” With the appearance of the pasqueflowers, spring begins to renew the sun-warmed ground. Gone are the long days of waiting. Perhaps, the few prairie-dog sentinels that had stood motionless in the March wind wished that the spring would come. The sharp wind divides the dense fur of their winter coats while they survey the snow-skiffed ground of their silent town. They almost appear to regard the sun wistfully, wishing it strong, the snow gone, and the grass resurgent once again. But at last the meadowlarks lose their winter-long quiet, and the horned larks now lift up with extravagance, unhuddling from their long ordeal. Below ground, in the deep, secure warmth of their nursery chambers, a new generation of prairie dogs is developing, part of the ancient ritual of replenishment that spring brings to the Great Plains. The breeding season of the prairie dog is determined by geographic location and weather conditions. On the southern plains of Texas it may be as early as January; on the Canadian plains as late as March. For four or five weeks there is much kissing, grooming, and investigation. Males become aggressive and squabble over territory. Besides the older females, perhaps half of the yearling females will mate. After a month’s gestation, the litters are born. In the dark quiet of specially prepared nesting chambers, the babies appear, hairless, sightless, uncoordinated, weighing but 14 grams (0.5 ounce). They live in grass-lined nests for seven or eight weeks, attended almost constantly by the females as they develop. Growth is rapid. At 28 days they are crawling, and by 32 days the finely furred pups can walk and bark. Soon their eyes open and they fully resemble the adults. Until now the pups have known only darkness, blind passageways, and a single adult. One day soon they will be led upward. That first moment above ground marks for them another birth. Now their senses experience a sudden The range of the prairie dog extends from Canada to Mexico and at its widest point from eastern Kansas to western Utah, with the blacktail’s range a bit more extensive than that of the whitetail. The range of the rare black-footed ferret, a predator, is nearly identical. The prairie dogs protected at Devils Tower are blacktails. Each day the young spend more time above ground. Nearby, the mother remains alert for danger and solicitous, accepting the maulings of her playful and increasingly independent pups. Although ranging farther and farther afield, they remain obedient to their mother, and scamper back to their burrow when commanded. The first few weeks above ground is a time of weaning, learning, and conditioning. During their first few days in society, pups have the run of the town. Boundaries that adults respect do not exist for them, as they wander about, inspecting every feature of their new world. The young have an insatiable need for body contact and much time is spent at play, and in grooming and kissing, activities that seem to reinforce the social nature of the prairie dogs. Adult males tolerate the young for a time during this period of general acquaintance. At first the pups attempt to nurse from any adult they encounter, and these misguided attempts are not rebuked, even by the males; they are turned into grooming sessions. Life on this greening land seems too good to be true. Entertainment is everywhere. Grasshopper nymphs, which the adult prairie dogs occasionally capture and consume unceremoniously, provide them with hours of chase and stalk. Food is everywhere and easy to obtain. Imitating their elders, the pups sample the wide array of grasses and forbs surrounding every burrow. Like the young of all the other animals they see, the pups have no way of realizing that their debut coincides with the season most favorable to their survival. So they scamper about in witless abandon, uncautious and innocent, ignorant as yet of the harsher outlines of their world. For a time, their place in the community is as idyllic as the soft-winded afternoons of spring. But on the Great Plains, spring is at best an uncertain season, its lifespan often To survive predatory perils, the new generation of prairie dogs, like countless previous ones, must master a two-pronged defense system evolved over millions of years. First, the pups must learn to engineer a burrow system with alternate escape routes. Second, they must learn to live in a highly organized social order, heeding its signals and respecting its boundaries. Prairie dogs are divided into two general classes, the blacktailed and the whitetailed. Blacktails inhabit the semi-arid regions of the Great Plains; whitetails live in the higher elevations of mountain parks and foothills. But it’s difficult to generalize, for Devils Tower and Wind Cave National Park, in South Dakota, are in the Black Hills and the prairie dogs at both are blacktails. The dog town at Devils Tower occupies a level grassland bench between the Tower’s base and the nearby meandering Belle Fourche River. Blacktails are protected in their more typical arid topography at two other National Park System areas: Badlands National Park in South Dakota and Theodore Roosevelt National Park in North Dakota. Generally, as a result of dissimilar habitats, the two species exhibit slightly different patterns of behavior. Unlike the blacktails, which emerge to forage on sunny winter days, whitetails are confined to their burrows by deep mountain snows. Those at high elevations must hibernate to survive the long winter. The whitetail community is a much less highly developed social structure than the blacktail community. The animals are unable to enjoy the luxury of long summers. In the short season they must spend a great amount of time feeding to store up body fat for winter. They have little time for social rituals—grooming, greeting, or play. Time does not allow them to establish and maintain territories. The burrow is to the prairie dog what speed and Often old burrow systems are abandoned and new tunnels excavated. The debris from the new tunnel system is dumped into the old burrows. These plugged burrows, called cores, may, in time, be more extensive than active tunnels in a long-occupied town. Whether knowingly or unknowingly, the prairie dog, by plugging unused passages, is practicing sound engineering; if all excavated material were brought to the surface, the weakened sub-surface, riddled with tunnels, would begin to settle and the burrows would eventually collapse. As with the beaver—the only North American mammal whose engineering feats surpass the prairie dog’s—it is often difficult to distinguish instinctive behavior from actual problem solving. Burrow systems vary from individual to individual and with local topography. However, as early attempts to “drown out” prairie dogs soon proved, the overall design of their burrow networks minimizes the dangers of flooding. While the lower angle of the tunnel may fill with water, the portion of the burrow that culminates in the sealed escape hole serves as an air bell, preventing a further rise of water and protecting the animal from being flooded out of its sanctuary during periods of heavy rain. Not realizing that prairie dogs can live without water—as can many other plains mammals that manufacture metabolic water from foods they eat—instigators of attempts to drown out the animals concluded that the animals dug down to ground water. The myth of the “town well” persisted until well diggers discovered that the water table in most townsites was hundreds of meters down. More than once their burrows have saved them from talon and teeth, and they take care to maintain the mounds surrounding the entrances to their tunnels. These structures serve not only as watch-towers, but also as dikes against downpours that may temporarily turn a town into a lake. But even instinctive digging habits and well engineered burrows, by themselves, would not have permitted prairie dogs to achieve their once staggering population levels—estimated to have been about 25 billion individuals. Only through the additional benefits of some form of social organization and an effective means of communication could such success have been attained. continues on page 58 Togetherness—Prairie Dog Style
Burrowing Out a Home
Gregariousness is a common trait of many plains animals. In a land where movement is necessary and concealment difficult to achieve, it provides a definite survival advantage. Bison calves find protection in the herd, where their defense is the concern of all adults. Pronghorns take turns as sentries, allowing the other members of the group to rest and feed. Coyotes are more effective when hunting in pairs. The success of the wolf in bringing down large prey and even evicting grizzlies from their kills was largely due to their family group or pack organization. But lacking physical adaptations for speed and mobility, prairie dogs are forced to rely on their burrows for refuge. The need to remain close to their burrows imposes on the animals a serious problem: how to maintain an adequate food supply? Although a dog town might appear to be one big collection of affectionate family members, all coming and going at will, the impression is false. Instead, each town is divided up into small groups of related animals. These family groups, called coteries, are the basic social unit, much as human families are in our own society. As the prairie dog pups soon learn, each coterie defends its own territory from intrusion by others, thus preserving for itself necessary living space and an adequate food supply close to the safety of its own burrows. Only in times of dire emergency, when the scramble to safety supersedes all territorial claims, will prairie dogs allow other coterie members the use of their burrows. So strong is an offending animal’s sense of trespass, it will often brave the hazard of dashing back to its own burrow rather than staying long in a neighbor’s territory. The typical coterie consists of about seven to eight animals, arranged in a hierarchical order. Each usually has a dominant male that protects the coterie’s territory from invasion by other males and oversees the activities of the females and young. If the coterie is a large one, more than one individual may enjoy dominant status and share the duties of leadership. In some cases, females may be dominant in rank; Not only their social organization, but also their social behavior makes prairie dogs unique among rodents. The function of coterie hierarchy is cooperative, rather than oppressive, resulting in a remarkable absence of conflict and social stress. Aggressiveness is generally limited to inter-coterie contacts along the invisible boundaries. In an established town, infractions are usually accidental and seldom precipitate lasting disputes. The end result of intra-coterie cooperation and inter-coterie respect is a stable and harmonious town. Energies and attention that would otherwise be squandered in conflict can thus be focused on mutual defense. For brief periods during spring and fall, the strict laws of territoriality are relaxed. In spring, the period coincides with the appearance of pups. Not only does this prevent undue strife in the community over the wanderings of the socially ignorant pups; it also allows those females seeking new territories to cross established ones. In the fall, the period is also necessary, accommodating the dispersal of overcrowded family groups. During autumn, the urge to emigrate is strong, and many animals move out into the “suburbs” of the town. Thus the town maintains a degree of flexibility and avoids permanent pockets of overpopulation. Coterie members maintain mutual recognition through an often-repeated ritual involving mouth contact. Prairie dogs that appear to be “kissing” or “talking” are simply establishing identities. Generally the most dominant member will initiate mouth contact, approaching the second animal with head tilted back and presenting its open mouth, to which the other responds in like manner. Often the recognition ceremony is accompanied by tail wagging and frequently leads to another form of social reinforcement, the process of grooming. Generally, the prairie dog that initiates the mouth contact does the grooming, nibbling, and combing the fur in an effort to dislodge dirt and parasites. The act is more significant for its symbolic value, however, for the animal of lower rank will often completely roll over on its back during the process; by exposing its vulnerable undersides, it is submitting, canine fashion, to the dominance of its fellow. Pups that annoy adult males with their attentions are often rather roughly groomed. No doubt the procedure communicates authority as well as affection. continues on page 62 Dog Town Predators and Fellow Inhabitants
Should the individual invited to mouth contact not reciprocate, an immediate challenge is made. Apparently, mouth contact is the only positive means of identification available to prairie dogs, and any animal refusing it is immediately deemed a trespasser and aggressively evicted. The wild chase that ensues, accompanied by indignant calling and fierce chattering of teeth, sometimes leads the righteous landowner deep inside its neighbor’s territory. The roles abruptly reverse and, after a moment of mutual realization, the pursuer suddenly becomes the pursued. In the glare of the early evening sun it is difficult to distinguish the individual prairie dogs as they go about their various activities. A single warning call, however, and the town instantly sprouts battalions of erect postures. For a moment, each motionless, backlit figure shines its sun-haloed position. All the disparate activities of the scattered animals become instantaneously fused to a single purpose: identifying the danger. Vocalizations distinguish the prairie dog from all other rodents. At least ten different calls have been identified in the blacktail class of prairie dogs. Most of the calls—such as the challenge bark, defense bark, disputing “churr,” fighting snarl, fear scream, muffled bark, and tooth chattering—do not involve the entire community. Except for the fear scream, which is immediately noted by all members, these vocal signals are largely ignored by neighboring animals since they usually denote a local disturbance among the prairie dogs themselves. There are three warning calls, however, that are intended for the entire community; these constitute the bond that unites all the separate coteries of the town into a single social unit. At the sound of the warning bark, usually uttered by many animals at once and quickly relayed through the entire town, each prairie dog immediately rises to alert in an attempt to define the immediate danger. If the wave of alarms is particularly intense, the animals usually rush to burrow mounds, where they will await further developments. Usually only the Another, more urgent, signal is the hawk warning call. The high-pitched, musical twin notes of this cry prompt an immediate dash for cover. Unlike the typical reaction to the warning bark, response to the hawk warning call is unhesitating. When this cry is given, seconds count, and visual confirmation of danger is not required to prompt a rush to safety. After danger has passed, the all-clear is sounded. Known as the song bark, this melodic whistle is always associated with a particular body posture. Rising up on its haunches, the prairie dog points its nose to the sky, gives the whistle, and promptly falls back on all fours. When learning to execute this call, pups usually topple over backwards. Once uttered, the call is repeated sporadically throughout the town. Communication is as important to the survival of the prairie dog society as is adequate food and shelter. Towns decimated by disease or poisoning soon vanish if the survivors are too few or scattered to communicate effectively. Deprived of an efficient warning system (and perhaps of the psychological need of social contact, as well), individual animals make easy targets for predators. Certainly they are too large and conspicuous to blend in well with their sparse surroundings. Unlike their small, well-camouflaged cousins, the thirteen-lined ground squirrels, prairie dogs cannot survive as individuals. After the females leave their weaned pups to establish new burrows for themselves, the young will remain together for a while until they, too, begin to split up. No longer do they resemble the playful, romping pups of spring, annoying their elders with their ceaseless games, demands for attention, and disregard for territorial boundaries. Now full-fledged members of their clans, they capture grasshoppers in a business-like fashion. Like the season, they have matured. With the company of their elders they now share a suspicion of the sky and every uninspected plot of ground. Lessons a Long Time LearningIn the early days of the cattle range, before sound land management of the plains was understood, cattlemen were perplexed to witness mushrooming populations of prairie dogs. Formerly lush grassland often became a dog town “wasteland” following the introduction of cattle. Believing that the prairie dog, and not the cattle, was responsible for this sudden transformation, ranchers rapidly came to despise prairie dogs. A massive war of extermination began against these “varmits” that “ate the grass down to nothing.” In reality, the appearance of prairie dogs merely indicated that the land was being overgrazed. As the bison had done before them, cattle now began to open up to the prairie dogs new territories that they could not otherwise colonize. Prairie dogs were never found on the eastern prairies simply because they could not contend with the taller growth of the more humid grasslands. On their own, prairie dogs cannot easily invade unbroken areas of established grassland. The grass cover simply rejuvenates faster than the animals can work. But if the land has been disturbed by overgrazing, prairie dogs can quickly spread. Once established in an area, the animals wage a constant struggle against the vegetation. Since tall-growing plants offer concealment to a predator, the plants are routinely clipped off even if they are not to be eaten. The feeding, clearing, and burrowing activities of the dog town tend to retard the grasses while encouraging the persistence of forbs—the broadleaf plants that quickly invade disturbed ground but are eventually crowded out by the returning grasses. By arresting the normal process of plant succession, an active dog town delays the return of the site to its climax vegetation of grasses. In so doing, it inadvertently perpetuates a wider variety of plants than would otherwise be found on the site. Selective feeders, prairie dogs put pressure on a particular plant species when it becomes most abundant, then ignore it almost entirely in favor of another, and so on. This cyclic feeding allows each species to recover, preventing it from being eliminated. Dry years help the prairie dog maintain control over the vegetation, and thus favor town expansion, while wet years speed recovery of the grasses and In some cases, the clearing activities of prairie dogs may actually speed plant succession. As a direct result of overgrazing by domestic stock, much of the grassland of the semi-arid West was invaded by sagebrush, a tough, drought-resistant plant that tends to perpetuate itself indefinitely once introduced. By cutting down the sage, prairie dogs eliminate it from the plant community and open the land to grasses. In its struggle for control of territory, the prairie dog was aided by the bison. The vast herds that moved across the landscape like a black plague of giant locusts left choice tracts of the grasslands devastated in their wake. The effects of such a physical force are difficult for us to comprehend today. Migrating northward in huge columns that sometimes measured 80 kilometers (50 miles) across, the bison cropped and trampled the greening spring grasses. Surely when the bison and the prairie dog were finally replaced by cattle, the grasslands, free at last from such punishment, would flourish. But no, instead the grasses languished. How could this be so? Nature is always more complex than our perception of it. For countless centuries the Great Plains had survived its many moods of drought, dust storm, and wildfire, its scattered plagues of bison and grasshopper. Nature knows no “varmits,” and change is not catastrophe, but opportunity. But to the settler who shot hawks, owls, and eagles to protect his calves, poultry, and children, the lesson was a long time dawning. Ironically, the grasslands needed the periodic despoilment of bison and burrow. When the bison herd moved on, it left behind tons of fertilizer, key to the area’s future rejuvenation. But the millions of hoofs also left the ground compacted. Were it not for the ceaseless activities of countless burrowing animals, including the industrious prairie dogs, loosening the soil and undoing the damage, the bison would have eventually destroyed much of their range. For an animal so successfully adapted to life on the unrelieved expanses of the open plains, it is ironic that today prairie dogs survive in isolated colonies at the very margins of its desirable habitat. |
|
