DAMAGE TO RANGE GRASSES BY THE ZUNT 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 
Ii. 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. 
Kamball, has continued quarter ly 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 needle-and-thread grass Stipa comata), and the “ short 
grass” by blue grama (Bouteloua gracilis). There are several ad- 
itional 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. 
- The vegetation through most of this section is of the short-grass 
type and consists of blue grama associated with ring grass (J/uhlen- 
bergia gracillima) and black or woolly-foot grama (Bouteloua erio- 
