BUREAU OF BIOLOGICAL SURVEY, 427 



PUAIUIE DOGS AND GROUND SQUIKUELS. 



Among rodent pests, one of the most conspicuous and destructive 

 in the area which it inhabits is the prairie dog, but the various 

 species of ground squirrels occupy a vastly larger area and because 

 of their abundance and general distribution cause even heavier losses 

 to farmers and stockmen. Prairie dogs occupy more than 120,000,000 

 acres of grazing and farming land in 11 States, as follows: Texas, 

 New Mexico, Arizona, Utah, Colorado, Kansas, Nebraska, Wyoming, 

 South Dakota, North Dakota, and Montana. Ground squirrels of the 

 various species infest practically the entire country west of the 

 Mississippi River. These animals cause enormous losses by digging 

 up the planted seeds of farm crops and by cutting down the growing 

 crops throughout the season to harvest time. 



Over great areas both prairie dogs and ground squirrels reduce the 

 forage available for livestock by as much as 25 per cent or more. 

 Prairie dogs often completely denude productive lands of all grasses, 

 leaving them to make barren wastes also of new locations where food 

 is more readily available. In many places these bare areas grow up 

 to woithless weeds and require several seasons before desirable for- 

 age plants are able to become reestablished. In other cases the top 

 soil is washed away down to the bedrock or to a clay base, leaving 

 more or less permanently waste land. 



Not only do prairie dogs and ground squirrels select the more fer- 

 tile lands, but their competition with livestock is rendered increas- 

 ingly serious because they select and feed upon the same highly nutri- 

 tious grasses w^hich are most sought and fed upon by livestock. This 

 not only results in a marked decrease in the numbers of livestock that 

 can be carried on the grazing lands but it prevents complete success 

 in efforts to increase the production of forage through improved 

 range-management practices, such as deferred grazing or grazing 

 rotation. The rodents prevent the normal growth and reestablish- 

 ment of grasses during the interval that the stock are kept off such 

 ranges, while the more abundant food supply thus made available to 

 them is favorable to their more rapid multiplication, as it is found 

 that their increase is closely correlated with the abundance of food. 



In organized campaigns against prairie dogs and ground squirrels 

 13,673,079 acres of Federal and private lands were given a first treat- 

 ment with poisoned baits during the year, and follow-up work was 

 done on 12,358,315 acres. This makes a total of 11,093,884 acres of 

 Federal and 97,718,640 acres of State and private lands on Avhich 

 the heavy percentage of these pests have been poisoned since 1916 in 

 Arizona, California, Colorado, Idaho, Kansas, Montana, Nebraska, 

 Nevada, New Mexico, North Dakota, Oklahoma, Oregon, South Da- 

 kota, Utah, Washington, and Wyoming. The bureau assumes the 

 cost of operations on Federal land, although adjacent landowners 

 often contribute the labor required for distribution of the poison and 

 even the grain used as bait, in order that the limited Federal funds 

 may be used to cover the largest possible acreage. State officials pro- 

 vide for work on State lands and farmers and stockmen on their own 

 holdings. Funds contributed by State and county appropriations 

 and those expended by landowners in this cooperative undertaking 

 during the year amounted to $592,812. 



