• An Important Lichen of Southeastern Montana Rangelands

      MacCracken, J. G.; Alexander, L. E.; Uresk, D. W. (Society for Range Management, 1983-01-01)
      The lichen (Parmelia chlorochroa) was most abundant in sagebrush and grassland vegetation associations, less so in the pine, and absent in riparian types. It was significantly associated with drier sites and bare ground. Lichens appear to have value in reducing erosion, as indicators of intensive grazing, and in contributing to the nutrient quality of soils.
    • Diets of Domestic Sheep and Other Large Herbivores in Southcentral Colorado

      MacCracken, J. G.; Hansen, R. M. (Society for Range Management, 1981-05-01)
      The botanical composition of herbage consumed by domestic sheep, mule deer, domestic cattle and elk from critical big game winter ranges in southcentral Colorado was studied using the fecal analysis technique. The food habits of domestic sheep grazed during the late spring overlapped those of mule deer by 15%, elk 46%, and domestic cattle by 53%. Mule deer diets were 10% similar to cattle and 30% to elk. Elk and cattle diets averaged 39% identical on the study area. The low similarity in diet between domestic stock and mule elk suggests that livestock grazing in the study area could be made compatible with the winter range needs of mule deer, but the potential competition between elk and domestic stock needs additional study.
    • Mass-diameter regressions for moose browse on the Copper River Delta, Alaska

      MacCracken, J. G.; Van Ballenberghe, V. (Society for Range Management, 1993-07-01)
      Regression equations were developed to predict 3 mass components of 7 browse species important to moose (Alces gigas) on the Copper River Delta in southcentral Alaska. The accuracy of model predictions was the criterion for model selection. Model accuracy was evaluated using data splitting or jackknife procedures. Annual production of twigs and leaves and available twig mass on a stem were most accurately predicted from stem basal diameter with zero intercept models, zero intercept log-linear models, or log-log models. Twig mass eaten by moose was most accurately predicted from the diameter at the point of browsing of a twig with zero intercept or full linear models. Heteroskedasticity was significant (P < 0.05) in most of the data sets and could not be significantly reduced with log transformations or use of weighted least squares models. Heteroskedasticity appeared to have a relatively minor effect on model predictions. Most of the models gave mean predictions within +/- 20% of the actual values, particularly for the most ubiquitous species that were also the most important to moose. For each species, there were few differences (P < 0.05) in model coefficients between years and among habitat types. Differences in coefficient estimates appeared to be related to differences in stem morphology that were related to both site conditions and past browsing by moose.
    • Seasonal Foods of Blacktail Jackrabbits and Nuttall Cottontails in Southeastern Idaho

      MacCracken, J. G.; Hansen, R. M. (Society for Range Management, 1984-05-01)
      The diets of blacktail jackrabbits (Lepus californicus) and nuttall cottontails (Sylvilagus nuttalli) were estimated by examination of fecal pellet botanical composition. The deficiencies of fecal analysis are noted, but dietary trends and relative importance of forage plants are accurate. Cluster analysis combined leporid pellets into 2 distinct groups based on botanical composition, representing feeding during spring-summer and fall-winter periods. Seven variables (plant species) accounted for significant differences (P<0.05) within and among the leporids studied in seasonal food selection. Generally, grasses and forbs were most abundant in blacktail jackrabbit and nuttall cottontail pellets during the spring-summer period, whereas shrubs were most abundant during the fall-winter period. Diet similarity was greatest between blacktail jackrabbits and nuttall cottontails during the same season. Diversity of forage consumed was greatest for both leporids during spring-summer periods. Habitat segregation minimizes competition for forage between the leporids studied. Livestock grazing appears to limit leporid population density rather than alter leporid food habits.