DALLES POCKET GOPHER 27 



The grazing capacities are based on the sum of the products of density 

 and the relative grazing value (5) of the individual species growing on 

 the meadows each year. Although only indicative, these values reflect 

 differences in value of the vegetation as sheep forage in 1940 after 9 

 years of gopher control on meadow A and continued infestation on 

 meadow B. They also reflect changes in value following the introduction 

 of pocket gophers on meadow A and the removal of the gophers from 

 meadow B in 1940. 



The estimated grazing capacities in 1940 give some idea of the serious- 

 ness of permitting pocket gophers to remain on a mountain meadow in 

 poor condition. The grazed plot of meadow A, after 9 years cf protec- 

 tion from pocket gophers, had a grazing capacity of 2.59 sheep months 

 per acre, about twice the 1.31 sheep months for the grazed plot of 

 gopher-infested meadow B. This represents the difference in grazing 

 capacity that would result in a period of 9 years from gopher-control 

 measures on a properly grazed meadow in poor condition. 



On the ungrazed plots the spread in estimated grazing capacity was 

 even greater. The grazing capacity for gopher-free meadow A was 3.50 

 sheep months per acre, six times the 0.59 sheep months for gopher- 

 infested meadow B. This greater spread was due to the better vegetation 

 on meadow A in the absence of both gophers and grazing and the poorer 

 conditions on meadow B where gophers occurred on ungrazed areas. 



Another striking example of increased grazing capacity resulting from 

 pocket gopher control is obtained by comparing the 1940 grazing capac- 

 ities of meadow B with those of the unfavorable growing year 1947 and 

 the favorable growing year 1948 after gophers were removed in 1940. 

 The grazing capacities for sheep on this meadow in 1947 were 3.28 sheep 

 months per acre on the grazed plot and 2.53 sheep months on the un- 

 grazed plot. This represents grazing-capacity increases of 2.5 times on 

 the grazed plot and 4.3 times on the ungrazed plot during the 7-year 

 period. 



The spread between the grazing capacities for 1940 and those for 

 1948 was much greater, the estimated grazing capacity in 1948 being 

 7.41 sheep months per acre on the grazed plot and 6.56 sheep months on 

 the ungrazed plot. Thus, the elimination of Dalles pocket gophers in 

 1940 from a grazed range in poor condition, with a grazing capacity of 

 only 1.31 sheep months, increased the grazing capacity almost 5.7 times. 

 And elimination of gophers from the plot of ungrazed range in very 

 poor condition and capable of supporting only 0.59 sheep per acre per 

 month in 1940 increased its grazing capacity 11 times. 



Grazing capacity increases on meadow B began rather soon after 

 pocket gophers were controlled. The increases were brought about by an 

 increase in species of relatively high value as forage for sheep and a 

 decrease in relatively low-value species. Species that ordinarily would 

 have 40 percent or more of their herbage removed, when properly 

 grazed by sheep, had more than doubled in density on the grazed plot 

 by 1943 and increased nearly 4 times by 1945 (table 5). Species that 

 ordinarily would have from 20 to 39 percent of their herbage used 

 showed essentially no change, and those that would be used less than 

 20 percent or remain ungrazed were greatly reduced. 



The increases in value on meadow B were by succulent species that 

 tend to mature and dry up early. Although they are of high grazing 



