[Illustration: 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 [Illustration: 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.] [Illustration: 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.] [Illustration: 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.]