10 BULLETIN 1227, U. S. DEPARTMENT OF AGRICULTURE 



around on barbed wire. Above the galvanized net wire were three 

 barbed wires at 6 to 8 inch intervals. The south area (planned for 

 a total protection tract) was inclosed with 6 barbed wires and with 

 galvanized net wire, 1-inch mesh, to exclude prairie dogs. Installa- 

 tion was by the Biological Survey and the Forest Service jointly. 



It seemed to be well-nigh impossible to confine prairie dogs in 

 the inclosure successfully, even though an apron of galvanized net 

 wire was later installed inside and buried in the ground in an at- 

 tempt to prevent their escape; they either found some way to get 

 out, perished from natural causes, or became the prey of predatory 

 animals or birds. It was then poncluded to try a different plan, and 

 the north inclosure was retained as a total-protection plot instead 

 of a prairie-dog inclosure, and by removing the galvanized net wire, 

 the south plot was so arranged as to permit free grazing and coloniz- 

 ing of prairie dogs from the outside, though cattle were excluded by 

 the barbed wire as before. 



This arrangement, according to which no attempt was made to 

 confine the prairie dogs, was found much more satisfactory than 

 the previous one. Meter quadrats were installed on November 6, 

 1919, one in each of the plots, and one outside of the fences. Addi- 

 tional quadrats were measured off and typical quadrats were clipped 

 for the first time on October 18, 1922, this being the first year when 

 reliable and significant results could be obtained in this way. 



PROGRESS OF THE EXPERIMENT. 



The failure of earlier attempts to retain prairie dogs in their 

 inclosure and to stop their invasion of the total-protection area pre- 

 vented the obtaining of results of much value in regard to the effect 

 of rodents on forage until the season of 1922, when (as observed 

 during the month of October) contrasts were marked. The blue 

 grama {Bouteloua gracilis) (PI. VI) showed many seeding heads 

 in the total-protection area, though very few were noted in the 

 prairie-dog plot or outside. Many clumps of a tall grass, bottle- 

 brush squirrel-tail (Sitanion hystrix), and a few of sand dropseed 

 {Spore-bolus cryptandrus) were observed in the total-protection 

 area, while neither gras's was in evidence either in the prairie-dog 

 plot or outside the fences. 



It is obvious that these grasses were enjoying far more favorable 

 opportunities for seeding in the total-protection area than in the 

 prairie-dog plot. The prairie dogs evidentty not only destroyed an 

 appreciable quantity, by weight and bulk, of the best forage plants, 

 but also attacked them at their critical seeding period, thus having 

 a markedly detrimental effect on their reproduction. The infesta- 

 tion of prairie dogs in the plot appeared to be about the same 

 as, or in some cases much less than, the average infestation in 

 the open country round about. It is felt, therefore, that the figures 

 given are a conservative statement of actual destruction of this 

 type of forage by prairie dogs under the prevailing conditions in the 

 vicinity. 



