with forest and range experiment station 

 personnel of the U.S. Forest Service in the 

 Pacific Northwest, Intermountain, Rocky 

 Mountain, Lake States, and Southern Re- 

 gions, 



Small mammal studies . --A 5-year study 

 of pocket gopher populations in relation to 

 grazing intensity on the Black Mesa Ex- 

 perimental Area of western Colorado was 

 inconclusive. Plant species composition 

 and ground cover conditions, which change 

 slowly on this type of range, will require 

 extension of the study to define the relation- 

 ship. In 1957 and 1958, when pocket gopher 

 populations were high on Black Mesa, 61 

 and 56 percent, respectively, of the ani- 

 mals were young of the current season; 

 when a population low occurred in 1959, 

 only 13 percent of the animals were re- 

 corded as young -of -the -year. The percent- 

 age of young increased to 40 and 57 

 percent, respectively, in 1960 and 1961. 



'Mm 

 m 



Foliage, stem, and branches of advanced subalpine 

 fir reproduction were clipped and barked by voles 

 as high as 66 inches above ground level during winter 

 with the aid of heavy snow cover on cut strips. Fool 

 Creek watershed, Oregon. 



(Photo by Jay Gashwiler.) 



On the Fool Creek Watershed, Fraser 

 Experimental Forest, Colorado, population 

 studies have been made of small nnammals 

 over a 5-year period following experimental 

 strip-cutting of lodgepole pine and spruce- 

 fir timber by the Forest Service. As mea- 

 sured by seed traps, seed production has 

 been negligible. Deer mice, chipmunks, and 

 other small mammals frequently considered 

 important in causing loss of tree seeds 

 were present, but not abundant. On the other 

 hand, red-backed and montane vole popula- 

 tions were high in 1957, 1 year after the 

 strip-cutting, when green slash provided an 

 abundance of food and cover for these 

 animals. Evidence of extensive feeding on 

 the inner bark of the slash and on advanced 

 conifer reproduction was prevalent during 

 the winter of 1956-57. As the logging 

 debris dried and deteriorated, this abundant 

 food supply was lost and the vole population 

 declined. 



In the H.J. Andrews Experimental Forest 

 of Oregon, seedling loss from time of 

 germination until winter was estimated at 

 77 percent for Douglas fir, 98 percent for 

 hemlock, and 97 percent for western red 

 cedar. Most of the hemlock and western 

 red cedar seedlings succiimbed to drought. 

 Douglas fir losses were attributed to heat, 

 drought, mice, and cutworms. Live -trap 

 sampling indicated that deer mice, Oregon 

 voles. Cooper's chipmunks, and wandering 

 and Trowbridge shrews were present on 

 both virgin timber and logged areas, red- 

 backed voles were present in timbered 

 habitat, and Douglas ground squirrels in the 



Litter of 5 deer mice about 24 hours old. In 1961 the 

 average litter size was 4.9 young per female. 



(Photo by Jay Gashwiler.) 



13 



