These dog towns are most curious, and a visit to one of them well repays the traveller. Strangely enough, the prairie-dog is exceedingly inquisitive and this very quality often costs the little animal his life. Mr. Wood, in describing the prairie-dog's habits, says that this wise little Westerner, when perched on the hillocks which we have already described, is able to survey a wide extent of territory and as soon as he sees a visitor, he gives a loud yelp of alarm, and dives into his burrow, his tiny feet knocking together with a ludicrous flourish as he disappears. In every direction similar scenes are enacted. The warning cry has been heard, and immediately every dog within a hundred yards repeats the cry and leaps into his burrow. Their curiosity, however, cannot be suppressed, and no sooner have they vanished from sight than their heads are seen protruding from their burrows. Sometimes hundreds of them will be peeping from their homes at one time, their beautiful eyes sparkling as they cautiously watch the enemy's every movement.
The prairie-dog is truly a tenement dweller, and his home is occupied not only by his own kind, but by owls and rattlesnakes. Most naturalists believe that these incongruous families live in perfect harmony; but it is a well-known fact that the snake occasionally devours the young prairie-dogs, and he must be considered by them as an intruder who procured board and lodging without their consent. The owls, on the other hand, are supposed to do no harm, although it may be that they also occasionally feast on a tender young pup.
The magnificent little animals known to scientists as vizcachas, and whose homes are on the pampas of South America, are the most skilled builders of underground cities in the animal world. Their villages or cities are called "vizcacheras" and are provided with from ten to twenty mouths or subway entrances, with one entrance often serving for several holes. If the ground is soft, it is not uncommon to find twenty to thirty burrows in a vizcachera; but if the ground is rocky and hard, only four or five burrows are found. These wide-mouthed, gaping burrows are dug close together, and the entire town usually covers from one hundred to two hundred square feet.
The vizcacheras are different from other underground animal cities; some of the burrows are large, others are small. Most of them open into a subterranean main-street at from four to six feet from the entrance; from this street other streets wind and turn in all directions, like a man-made subway, and many of them extend clear into other streets or subways, thus forming a complete network of underground passageways. All the tunnelled-out dirt is brought to the surface and forms a large mound to prevent the water from entering the cities.
According to W. H. Hudson, in The Naturalist in La Plata, "in some directions a person might ride five hundred miles and never advance half a mile without seeing one or more of them. In districts where, as far as the eye can see, the plains are as level and smooth as a bowling-green, especially in winter when the grass is close-cropped, and where the rough giant-thistle has not sprung up, these mounds appear like brown or dark spots on a green surface. They are the only irregularities that occur to catch the eye, and consequently form an important feature in the scenery. In some places they are so near together that a person on horseback may count a hundred of them from one point of view."
Unlike some burrowing animals, the vizcacha does not select a spot where there is a bank or depression in the soil, or roots of trees, or even tall grass; knowing that they only attract the opossum, skunk, armadillo, and weasel, he chooses an open level plot of ground where he can watch in all directions for enemies while he works.
The great or main entrance to some of these underground cities is sometimes four to six feet in diameter. A small man stands shoulder deep in them. The going and coming of these little vizcachas would almost lead one to believe that they have a primitive city government, and are ruled according to definite laws. Their cities stand for generations, and many of the old human inhabitants tell of certain vizcacheras around them which existed when their parents were living. The founder of a new village is usually a male; and he goes only a short distance from the other villages to establish his new colony.
These cities are by no means occupied by their builders alone, but have their undesirables within their borders. The unique style of burrowing which the vizcachas employ benefits several kinds of birds, especially the Minerva, and one species of the swallows, which build their nests in the bank-like holes in the sides of the vizcacha's cities. Several insects, among which may be mentioned a large nocturnal bug, with red wings and shiny black body, also seek the same shelter; another foreign inhabitant is a night-roaming cincindela, with dark green wing-cases and pale red legs, which remind one of oriental jewels. There are also no less than six species of wingless wasps, beautifully coloured in red, black, and white. Dozens of spiders and smaller insects that live in and near the vizcacheras, which are everywhere sprinkled over the pampas, pass in and out among the streets recognising their respective friends and enemies.
The home life in these communities is most interesting. The burrowers remain indoors until late in the evening during the winter, but in summer appear before the sun sets. One of the larger males is the first to appear, as if to see if everything is safe from danger; if it is, others immediately pop up and take their places at the entrance to the burrow. The females are smaller than the males, and stand up that they may see everything that happens. Curiosity struggling within them for mastery is often the cause of their death. Tiny swallows hover over the entrances, like myriads of large moths, with never-ending low, mournful cries.
Of all the incongruous inhabitants of the vizcacheras, the fox is the most dreaded and the least welcome. To appease his growls and snarls the vizcachas are sometimes forced to let him occupy one of their rooms for a season, or even permanently. During a part of the year he appears quite unassuming and indifferent to the general affairs of the household, and he really goes quite unnoticed, even though he may be sitting on the mound in the family group. But when the vizcachas appear in the spring, the fox begins to become interested in the nursery and as soon as the older animals are away he devours the young. Occasionally, if the fox is hungry, or if he has another friend to aid him, he will hunt the vizcachera from end to end, battling with the old, and usually killing all the young. It often happens that the mother vizcacha, when her babes are large enough to follow her, will take them away to another place that is safer.