356 NATURE-STUDY REVIEW 



Prairie dogs are found exclusively in the interior of North 

 America, not only on the treeless western plains and valleys from 

 North Dakota and Montana to Texas but also extending west 

 across the Rocky Mountains to Utah and Arizona and southward 

 into Mexico. Their vertical range is from 2000 feet on the plains 

 to above 10,000 feet in the mountainous parts of Colorado and 

 Arizona. 



Their gregarious instinct is very strong and their "towns" 

 may be found scattered all over the districts named. These 

 "towns" are of every size, containing from a few individuals to 

 millions in one "town" or colony, which ntimber into the htmdreds 

 of millions. Towns twenty to thirty miles long are not rare. 

 Probably the largest colony of all is in Texas and covers 2500 

 square miles. 



These little animals are early risers, and the well-beaten tracks 

 like lanes and streets thru the towns, are frequently used in 

 making early morning calls on their neighbors. There is little 

 grass or vegetation in the "towns." This is probably for pro- 

 tection but is exceedingly injurious to cattle ranges. When 

 the town becomes over-crowded the citizens wander many miles 

 away to start a new colony. 



They are very easy to introduce but hard to exterminate. The 

 only way to keep them within bounds in zoological parks is to 

 build walls of solid masonry down to bed rock. 



Their burrows are from four to five inches in diameter and are 

 located on fiat or gently sloping ground. They descend abruptly 

 from eight to sixteen feet and then turn at a sharp angle and 

 extend horizontally from ten to twenty-five feet. There are 

 several branches from the main channel which usually end in 

 rounded nests, family rooms, or storage chambers for fodder 

 or refuse, altho they sometimes return to the main passageway 

 or form a second entrance at some distance from the first. A 

 little niche about five feet below the surface and at one side 

 of the entrance tube provides a convenient resting place when 

 they are forced to flee from danger. Here they stop and bark 

 until notified that the danger is past or are warned to retreat 

 further in to their burrows. 



The black tailed prairie dogs, which are more numerous on 

 the plains, pack the soil which they have dug from their burrows 



