Prairie Dogs: A Tight-Knit Society
A 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 flood of light and sound, coolness, wind, a world of shape, motion, and perspective, whose staggering brightness extends forever beyond their own rim of familiar scent. Huddled together and shivering in the wind, they are at first loath to accept this world of sight and sun, so different from the soundless wrappings of dark, warm soil. But soon, as with all young animals, curiosity leads them to investigation and then to boldness.
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 breathtakingly short. As the days pass, the dominant males that patrol their territories rapidly lose patience with neighboring pups. Those that stray outside the invisible boundaries of their clan’s living-space are now met with annoyance. Soon the displeasure turns to snarls and bites. More and more, their own mothers refuse them milk. Nipples bleeding from the constant pesterings of their young, the mothers finally move out altogether, to establish new burrows of their own.
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 endurance is to the pronghorn: its chief means of protection. Yet it is more than just a hole in the ground, a temporary refuge from the threat of danger. More than half of a prairie dog’s life is spent below ground, so the burrow must accommodate a wide range of needs (See pages [56]-57.).
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]