Distribution, movements, and habitat use during spring, summer, and fall by mule deer associated with the Armstrong winter range, Bridger Mountains, Montana

A study was conducted in the Bridget Mountains of southwestern Montana from June through September 1974 and from June through December 1975.Objectives were to obtain data on summer and fall distribution, movements, habitat use and food habits, including ' nutritional relationships, of mule deer associated with the Armstrong winter range.Special emphasis was directed to use of forest habitat types by monitoring five radio-collared adult females.Fourteen habitat types and five phases associated with five major climax series were recognized and described.Deer numbers, productivity, distributions, movements, and range use characteristics were determined from 22 aerial flights and regular ground surveys.Approximately 210 deer occurred on the Armstrong Range in early winter 1975, of which only 139 survived the severe winter and dispersed onto summer ranges in the spring of 1975.Observed fawn:doe ratios declined from 26:100 in early fall 1975 to 9:100 by early winter, with most of the change occurring during a period of severe weather in late November when deer were concentrated on fall "holding" areas.Relocations of individually marked animals showed that 73 percent had summer and/or fall ranges within 6 kilometers of the winter range.The remainder migrated greater distances north and south of these areas as well as along the east slope of the Bridget Range.Most deer appeared to habitually use the same summer and winter home ranges each year.Seasonal migrations followed definite routes which included local "holding" areas where deer aggregated for variable time periods during spring and fall.Normal summer home ranges averaged 52 hectares (128 acres) for the five radio-collared females, while total home ranges averaged 107 hectares (264 acres).Heavy usage of forested habitats, especially the Pseudotsuga menziesii series, was observed during late spring, summer, and fall 1975.The DF/Caru, DF/Cage, and DF/Agsp habitat types were most important during spring and fall.The DF/Caru and Krummholz types were most important in summer.Relocations of radioed deer indicated that use of the Pseudotsuga menziesii series may have been overestimated by general observations while usage of Abies lasiocarpa and Pinus albicaulis series were underestimated.Significant shifts in use of habitat types occurred during late summer, apparently in response to shortages of succulent forage caused by dessication and killing frosts.Food habit studies showed that forbs and browse, in order of importance, were used during late spring (June); while forbs, browse, and grass and browse, forbs, and grass were orders of importance for use during summer and fall, respectively.Protein contents of important forage plants were highest at emergence in spring and declined steadily to fall dormancy.