results at the end of 7 years : Grass production in- 

 creased the fii-st 3 years after spraying but re- 

 turned to its original level by the sixth year; pe- 

 rennial forbs, a favorite food of gophers, declined 

 the first year after spraying, but were two-tliirds 

 as productive as originally by the sixth year; 

 gophers were scarce tlie first two years following 

 spraying, but increased until, at the end of the 

 sixth year, they were more abundant on sprayed 

 plots than on adjoining unsprayed lands. These 

 results show that some degi'ee of pocket-gopher 

 control can be expected for about 5 years after 2,4- 

 D spraying on bunch-grass-type rangelands, but 

 that the effects are largely neutralized a year or 

 two later. 



In an attempt to develop more effective control 

 of gophers with spraying techniques. Bureau re- 

 searchers at the Denver Center joined with the Bu- 

 reau of Land Management in 1960 in a cooperative 

 5-year investigation. The basic design for the 

 work involves paired acre plots in wliich tlie rela- 

 tive effectiveness of gopher control through poi- 

 soning, herbicide spraying, and grazing regula- 



tions are appraised as range- restoration practices. 



The successful and widely accepted burrow- 

 builder as a gopher control is described on page 

 5. 



Forest animal damage control. — Several chemi- 

 cals, all selected products of the Denver Center 

 screening program, are being evaluated at the 

 Olympia field station to detennine their effective- 

 ness in preventing animal damage to reforestation. 

 Tliese evaluations are carried out fir.st in outdoor 

 holding pens against deer, porcupines, mountain 

 beaver, hares, and field mice, the mammals most 

 often involved in conflicts with reforestation activ- 

 ities. Chemicals wliicli sliow up well in the en- 

 closure tests are tlien tried in tlie field. 



A vast amount of initial screening is necessary 

 to identify materials for preliminary field testing. 

 During 19fi2, tlie forest animal damage screening 

 laboratory at Denver received 438 chemicals from 

 chemical companies. Subsequently, 690 bio- 

 assays were conducted to determine the toxic and 

 repellent characteristics of these chemicals. Ac- 

 tive compounds then were subjected to more than 



?#" 



View of a pilot model of a boom which provides a "curtain of spray" through which roosting blackbirds are driven. 

 The chemical drips from arms of the boom, is retrieved in the catch-basin, and re-used. (Photo by Jerome F. 

 Besser) 



42 



