population estimates. Vehicle headlight surveys to obtain 

 estimates of lagomorph abundance were made 2-4 times each year 

 on established routes through the area and adjoining plains 

 (Trout 1978, Hamlin et al . 1984). Small mammal abundance was 

 determined from 2 permanent Sherman live-trap grids (Trout 

 1978, Hamlin et al . 1984). 



Annual forage production was estimated during 1976-1986 

 by clipping vegetation within 2 X 5 dm and 4 X 10 dm plots in 

 two stands in sagebrush-grassland and measuring current annual 

 growth of shrubs on two transects in the Douglas fir-juniper 

 type. General principles involved in establishing production 

 estimates for herbaceous forage followed Pieper (1978). 

 Estimates of production by shrubs generally followed Basile 

 and Hutchings (1966) and Lyon (1968). Modifications made and 

 more detail on techniques are discussed by Jorgensen and 

 Mackie (1976). 



Browse utilization trends were measured annually in 

 spring on transects (Cole 1958, 1959) established throughout 

 the study area during 1959-1961. Relative changes in 

 abundance of shrub species through the years were determined 

 by monitoring tagged plants on browse transects, measurement 

 of tree-shrub coverage on line-intercept transects established 

 in 1963 (Mackie 1970), and measurement of shrub density and 

 plant size on point-center-quarter transects established in 

 1971 (Martin 1972) . 



Food habits of mule deer were determined by examination 

 of feeding sites and rumen analysis during 1960-1964 (Mackie 

 1970) and rumen analysis during 1976-1987. 



Data from the Roy 8NE weather station were not detailed 

 enough to calculate several established winter severity 

 indexes prior to 1967. To have an index of winter severity 

 for all years of study, we constructed our own index. This 

 constructed index gave values relative to the mildest recorded 

 winters on the area and was calculated as follows: 



WSI = (Tw - Tc) + (Sc_^_Sl) 



is winter severity index 

 is warmest recorded mean winter 

 (Nov-Mar) temperature in degrees F 

 is current mean winter temperature 

 is total snowfall for the current 

 winter in inches 

 SI is lowest recorded total winter 

 snowfall in inches 



29 



