DAMAGE TO RANGE GRASSES BY THE ZUNI PRAIRIE DOG 3 



could be held under total protection from cattle as well as prairie 

 dogs; and then, by means of permanent meter vegetation quadrats, 

 and in other ways, to obtain quantitative information as to the vege- 

 tation actually destroyed under grazing (1) by prairie dogs alone 

 and (2) by cattle alone (or cattle and prairie dogs together) in com- 

 parison with (3) the amounts produced under total protection. This 

 was accomplished by actually measuring the grasses under total 

 protection, under grazing by prairie dogs, and under grazing by 

 cattle ; by mapping the areas on the quadrats occupied by the grasses; 

 and by fall clipping and weighing all vegetation from certain quad- 

 rats in the areas under the different conditions. 



ORGANIZATION AND AUSPICES. 



The project has been cooperative from the beginning. Dr. Frederic 

 E. Clements, of the Carnegie Institution of Washington, has given 

 valuable assistance and advice relative to the organization and prose- 

 cution of the experiment and has made provision for the charting 

 of the vegetation. Former supervisors Ira T. Yarnall and James A. 

 Scott, of the Tusayan National Forest, extended many courtesies in 

 connection with the work; and the present supervisor, George W. 

 Kimball, has continued quarterly inspection of the areas and assisted 

 in other ways. Dr. Chas. T. Vorhies, of the University of Arizona, 

 charted the quadrats in the spring of 1919; and D. A. Gilchrist, 

 Biological Survey rodent-pest director for Arizona, assisted by Ben 

 E. Foster, supervised the fencing of the areas, made check-counts 

 of the prairie dogs in the inclosures at different times, inspected the 

 areas at intervals, arranged for the capture and reintroduction of 

 prairie dogs, and provided for necessary eradication. The writers 

 have participated in the organization and conduct of the experi- 

 ment from its inception and have inspected the areas at least once 

 each year, checking up on the rodent relations, measuring the grasses, 

 charting the vegetation quadrats, and clipping, weighing, and pho- 

 tographing the grasses from the clip quadrats. 



VEGETATION AFFECTED. 



The region in which prairie dogs are chiefly found is in the west- 

 ern part of the Great Plains formation, called by Clements (1920) 

 the mixed prairie. This consists of two components, a tall grass and 

 a short grass. Over the greater part of the area occupied by this 

 formation the two occur mixed, but toward its' eastern border the 

 short grasses become of minor significance, while on the western they 

 are of major importance. The " tall grass " is characterized by the 

 presence of wheat grass (Agropyron) and porcupine grass (Stipa; 

 usually the neeclle-and-thread grass Stipa comata), and the "short 

 grass" by blue grama (Bouteloua gracilis). There are several ad- 

 ditional associates of both components, but only those occurring in 

 northern Arizona are of particular interest here. 



The areas covered by this investigation are in the extreme south- 

 western extension of the Great Plains formation already mentioned. 

 r The vegetation through most of this section is of the short-grass 

 type and consists of blue grama associated with ring grass (Muhlen- 

 bergia gracillima) and black or woolly-foot grama (Bouteloua erio- 



