Burrowing Out a Home
Viewed in a cross-section, a typical prairie dog burrow system reveals a network of tunnels and compartments. The slightly oval entrance, 10 to 15 centimeters (4 to 6 inches) in diameter, leads the prairie dog rapidly downward. This plunge hole soon tapers off into a more gentle slope that may descend another 4.5 meters (15 feet). The burrow then turns upward and approaches the surface about 9 meters (30 feet) from the entrance hole. In an emergency this safety hatch can be quickly opened and the prairie dog can escape entrapment. Every burrow contains several rooms to accommodate various needs. The first room the prairie dog encounters as it travels down the plunge hole is known as the antechamber. which is large enough for two animals. It functions as a turn-around, permitting entering and exiting animals to pass one another. But primarily it is used as a listening post. Before venturing out in the morning, a prairie dog pauses here, on the alert for possible danger. From this room it can monitor the situation by listening to alarm calls of neighbors still above ground. The nesting chamber may be found most anywhere in the burrow, but usually it is associated with the main passageway above the lowest point, to protect it from flooding. Lined with grasses and other soft plant fibers, the nest affords a degree of comfort and insulation against cold and dampness. Perhaps because of accumulating litter or parasites, such as lice and fleas, the location of the nest chamber is often changed.
Safety hatch Plunge hole Listening post and turning bay Nesting chamber
Blacktail prairie dogs build hard-packed ridges around their burrow openings as watchtowers and as dikes against downpours. A prairie dog uses various skills in this work, including, above, scraping dirt with its powerful hind legs.
Mound-building also calls for bulldozing earth with the prairie dog’s hard, blunt nose. Both excavated subsoil and topsoil are pushed around to build up the mound. Whitetails tend to merely leave an unworked pile of subsoil around the entrance.
After tamping the freshly loosened earth with its nose, above, and at other times in the whole process, the prairie dog takes a break and cleans its long claws, [page 56], and its nose.
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; the role generally falls to the males, however, possibly because of their slightly larger size or because they have more time to observe and patrol, not being tied to the demands of the young.
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.
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