PRAIRIE DOG. A Western American ground-squirra two species of which (Cynonlys ('olumbiaaus, west of the Rockies, and Cynonlys Ludoricianus, east of these mountains) are lo cally common from the Canadian to beyond the Mexican boundary of the United States. The prairie (log is about a foot long and of robust form, with strong limbs and claws, well cal culated for digging. Its home is the dry upland plains, where it dwells in colonies, whose per manent 'towns' or burrows, each marked by a hillock of earth about the entrance, spread densely over ninny acres under the natural pre historic conditions, but now sometimes cover hundreds of square miles. The burrows are deep and extensive, and at first go down at a very steep slope to a depth of 12 to 15 feet, when they suddenly turn and run in a horizontal direction, and here and there branch into cham bers. some of which are elevated and form family rooms, while in others fodder is stored, or refuse and dung are deposited. The mound about the hole is packed hard, not only by the tramping of the animals, but by crowding it down with their noses; this hillock prevents water from running into the burrows when the plain is flooded by heavy rains, and also serves as a tower of observation. The prairie dogs feed upon grass and herbage, which is soon exhausted near the burrows, compelling the animals to go far ther and farther away for food. This they dis like to do. as it exposes them to attack from enemies: and after a time they prefer to dig a new burrow nearer a supply of food. Thus a 'town' is always spreading and contains ninny empty burrows. Like other animals habituated to desert regions, they do not drink at all, and the early belief that subterranean pits were dug by them, down to a water supply, has been proved erroneous. Artesian wells within dog towns have failed to strike water as often as elsewhere. The animals are diurnal and most active morning and evening. They come out daily during the winter, except when it is very stormy; but this practice varies with the latitude and climate.
They are prolific, especially in the southern half of their territory, and would multiply with excessive rapidity were it not for numerous enemies, especially rattlesnakes and other ser pents. These are courageously resisted by the prairie dogs, which sound the alarm the moment a snake enters a hole, gather, and proceed to fill the entrance with earth, packing it down, thereby sometimes entombing the snake forever. Prob ably few snakes go down the passages, which are so steep they could with difficulty climb out, hut depend upon lying hidden in the grass and strik ing down the young squirrels when out at play or in search of food. This is the method of the
coyote, kit-fox, wildcat, hawks, and owls, who find the dog-towns a profitable hunting ground. Badgers, however, can, if they will, easily dig up a burrow and devour the helpless family. The worst enemy is the black-footed ferret, a weasel of the plains, which easily penetrates the bur rows, and against whose ferocity and skill the squirrels can make little defense. Every prairie dog town is also tenanted by many little bur rowing owls (q.v.).
All these conditions together served in the natural state of things to hold the prairie dogs in check, hut the changes brought about by civilization have been so favorable to these little animals, by the reduction of their enemies on the one hand, and the augmentation on the other hand of their food-supplies by the farmers' plantations of meadow-grass, alfalfa, and grain, that they have increased into a very serious pest. Dr. Merriam stated in the Yearbook of the United States Department of Agriculture for 1901 that colonies 20 to 30 miles in length were then not rare; and one in Texas was known to cover an area of 2500 square miles, with a probable average of 25 holes to an acre and of one animal to each hole. At this rate the prairie-dog population of this district would be 40.000.000; and on the carefully studied estimate of students that 250 squirrels will devour an nually the same amount of grass as a cow, the pa.turage consumed by this great colony would support about 160,000 cattle. When such a colony spreads over a district devoted to farming the loss is increased, for the space occupied by their mounds is a waste of valuable land; the animals are likely to cut irrigation canals, drain ing off the water, and they devour the planted crops, especially of alfalfa. Both the Federal Government and local authorities have tried various methods for relief, but are almost help less in view of the large spaces between cul tivated districts, where the pest can only he over come by public and united effort, and also by co3peration among the ranchmen. The squirrels may be killed by poison in various ways: but best by the use of bisulphide of carbon. A tea spoonful of thus cheap liquid is placed upon sonic absorbent substance (a nodule of dry horse-dung or half a corn-cob will serve the purpose well) and dropped down the hole; which should then be stopped with earth. The fumes are heavy. sink into the depths of the burrow, and kill the in habitants. Bisulphide of carbon is not only poisonous, but inflammable and explosive; it should be kept in cans or bottles, tightly corked, and never opened near fire. See Plate of GOPHERS, LEMMINGS, AND MARMOTS.