8 



BULLETIN 1227, U. S. DEPARTMENT OP AGEICULTUEE 



Table 1. — Quadrat study, giving weights of grasses clipped each fall from per- 

 manent meter quadrats under the different conditions as stated, to indicate 

 the amount of forage destroyed by prairie dogs at Coconino, Ariz., 1919-1922. 



Kind of grass. 1 



Total- 

 protection 

 area. 



Rodent- 

 grazed 

 area. 



Cattle- 

 grazed 

 area. 



Quantity 



destroyed 



by rodents. 2 



Western wheat grass: 



1919 



Gravis. 

 100.0 

 117.1 

 138.8 

 161.1 



164.6 

 32.8 

 81.9 

 38.7 



Grams. 

 36.8 

 24.3 

 22.6 

 77.2 



( 3 ) 

 ( 4 ) 

 (<) 

 3.7 



Grams. 

 6.6 

 8.7 

 6.7 

 6.7 



4.6 

 ( 4 ) 

 6.4 

 6.1 



Grams. 

 63 2 



1920 



99 8 



1921 



116 2 



1922 



83 9 



Sand dropseed: 



1919. 



164 6 



1920 



32 8 



1921 



81 9 



1922 



35.0 



1 Blue grama did not occur in sufficient quantity to be taken into account. 



2 Obtained by subtracting amounts under rodent-grazed conditions from those under total protection. 

 The rodents concerned are chiefly prairie dogs; a negligible quantity of forage may have been taken by 

 others. 



s Trace. 

 4 None. 



It is to be. recalled that the figures in Table 1 were obtained under 

 controlled conditions, by actual weights, and that the amount shown 

 as destroyed by rodents is undoubtedly somewhat less than would be 

 the case had it been possible to keep a full number of prairie dogs in 

 the rodent inclosure and to exclude them completely from the total- 

 protection area. The figures indicate in very general but impressive 

 terms a potential rate of damage which may be expected where 

 rodent grazing takes place in the wheat-grass forage type under con- 

 ditions similar to those of this experiment. The following state- 

 ment (Table 2) presents some of the results obtained under these 

 conditions : 



Table 2. — Annual production of forage and its reduction per acre by prairie dogs. 





Forage. 



Produc- 

 tion in 

 pounds. 



Destroyed by prairie 

 dogs. 





Pounds. 



Per cent. 





1,153 

 709 



794 

 701 



69 





99 









Total 



1,862 



1,495 



80 







The annual forage loss on a section of land in this forage type 

 at the rate shown in Table 2 would be the impressive total of 479 

 tons. Nowhere on the range, however, is this type the continuous 

 vegetation cover, and in most of the region it occurs as comparatively 

 small islands in the surrounding types. It should be pointed out 

 also that the quantity of forage destroyed by rodent grazing does 

 not necessarily represent the quantity actually consumed. Part of 

 the loss is due to the reduction of vigor of many grasses through 

 early spring grazing, which inhibits their growth and prevents them 

 from producing the quantity of forage they otherwise would. Un- 

 fortunately, no satisfactory quantitative data are as yet available 

 which indicate the amount of this loss. Continuous clipping of the 



