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]
Togetherness—Prairie Dog Style
A prairie dog sounds the alarm, alerting the whole town about an impending danger, such as a coyote, a ferret, or a person. The rest take up the call, and as the danger approaches each burrow the inhabitants duck underground. The others continue to stand erect and sound the warning. By listening carefully, those underground can track the location of the enemy. When two high-pitched notes are sounded, all rush for cover, for that means a hawk is overhead or nearby and there’s no time to wait and repeat the signal. After the danger has disappeared, a dog sounds a melodic whistle, and a few others repeat the all-clear before the usual activities of grooming, breeding, eating, and burrow building are resumed. Blacktails make at least seven other calls, but they mostly concern matters of interest to the coterie, or family, instead of to the whole town.
After spending a little more than a month below ground, newborn pups warily venture into the daylight, closely watched by their mother. They soon lose their timidness, venturing farther and farther from the burrow but remaining obedient to mother’s commands. Most of the first few weeks on the surface are spent mauling, kissing, or grooming each other and their parents. As the weeks go by, the adults tolerate less play and the pups learn more and more day-to-day survival responsibilities.
A prairie dog eats a blade of grass sitting on its haunches. After falling over a few times, pups soon learn this dining posture. The dogs eat various grasses and forbs, though for different periods they tend to ignore some plants in favor of others. However, they usually clip off all vegetation around their burrows even if they don’t eat it. This habitual grass-cutting apparently is defensive, for predators can conceal themselves better in tall grasses. That is why you don’t see prairie dogs in lush grasslands where there is a bountiful rainfall. They satisfy most of their needs for water with the juices of green plants and grass roots.
Prairie dogs also eat insects that inhabit their towns and sometimes prey upon the eggs or young of animals, such as the burrowing owl, that dwell in homes deserted by prairie dogs.