26 CIRCULAR 884, U. S. DEPARTMENT OF AGRICULTURE 



Even though range condition improved gradually from 1940 to 1948, 

 the vegetation on meadow A was still only in a grass-weed stage, fair 

 range condition, at the end of the study. The adverse effect of reintro- 

 ducing pocket gophers into meadow A when it was in fair range con- 

 dition was not so noticeable as the effect of their presence for 9 earlier 

 years on meadow B, but still it was very real. On meadow A they con- 

 tributed to the continued presence of annual weeds and to serious 

 decreases, in some instances elimination, of Lemmon needlegrass, 

 agoseris, and common dandelion, all species of moderate to high forage 

 value for sheep on Oregon mountain meadows. 



On the other hand, the control of pocket gophers on meadow B, be- 

 ginning in 1940 when parts of it were in poor and very poor condition, 

 enabled the range both under grazing and without to improve in con- 

 dition. Agoseris, which was eliminated on gopher-infested meadow A 

 increased markedly on this gopher-free meadow, and there was a greater 

 increase in Kentucky bluegrass, considering that it started with much 

 lower density in 1940. Annual weeds were drastically reduced. 



INFLUENCE OF POCKET GOPHERS 

 ON VALUES OF MEADOW FOR LIVESTOCK GRAZING 



Pocket gophers utilize forage all through the year. Sheep, on the other 

 hand, graze mountain meadows for 3 or 4 months in the summer. A 

 typical grazing season for sheep on mountain meadows in Oregon is 

 July 1 to September 30. However, a band of sheep might graze a meadow 

 only once during the summer for about a week. It is apparent therefore 

 that pocket gophers graze mountain meadows over a much longer period 

 than domestic livestock; their consequence as a foraging animal, there- 

 fore, is greater than would be expected from their small size. They are 

 also of more consequence than other foraging rodents, for example the 

 Oregon ground squirrel that remains dormant in its burrow about 8 

 months each year. 



The adverse effect of pocket gopher activity on grazing values is 

 shown by comparing the estimated grazing capacities in sheep months 

 per acre for the grazed and ungrazed plots on meadows A and B: 



Grazing capacity per acre in sheep months 



Grazed plot: Meadow A Meadow B 



1940 .. 2.59 1.31 



1943 .. 1.70 2.86 



1945 . . 2.77 4.50 



1946 . . 2.70 4.49 



19471 2.41 3.28 



19482 5.25 7.41 



Ungrazed plot: 



1940 3.50 .59 



1943 2.95 .97 



1945 3.76 2.65 



1946 4.18 2.85 



19471 4.62 2.53 



19482 8.25 6.56 



1 Driest spring during study; year of poor vegetation growth. 



2 Exceptionally moist year; year of good vegetative growth. 



