Distribution, movements and habitat use of mule deer associated with the Bracket Creek winter range, Bridger Mountains, Montana

A study was conducted from March 1978 to April 1979 in the Bridger Mountains, Montana.Objectives were to determine the distribution, movements, habitat use, food habits and population characteristics of mule deer associated with the Brackett Creek winter range.A total of 114 mule deer were marked, 18 with radio collars.Mule deer generally occupied two seasonal ranges: winter-spring and summer-fall.Movements between these ranges were usually abrupt and direct and did not involve the use of holding areas.Mule deer were distributed throughout the winter range in early winter.From mid-January to mid-February most were concentrated on a primary use area comprising about 37 percent of of the total winter range.In winter, the movements of all but one of the deer centered on a series of subseasonal ranges.Polygon home ranges, standard diameters and average activity radii of 8 radio-collared mule deer averaged 12.9 km2, 3.3 km and 1.4 km, respectively, and differed significantly with those of mule deer on other Bridger Mountain winter ranges.During summer, mule deer were distributed thoughout the study area.Average polygon home ranges, standard diameters and average activity radii of 9 radio-collared mule deer were 2.9 km2, 1.5 km and 0.6 km, respectively and appeared to be larger than those reported on other Bridger Mountain ranges.During winter, sagebrush, grassland and agricultural cover types received 37, 43 and 14 percent of all recorded use.Mule deer selected the Douglas fir type during the early, severe portion of the winter.The sagebrush, agricultural and Douglas fir cover types were most important during summer, receiving 27, 23 and 18 percent, respectively, of recorded use by mule deer.Browse, forbs, and grasses received, respectively, 48, 33 and 19 percent of total utilization at winter mule deer feeding sites and accounted for 56, 9 and 35 percent by volume of the contents of 38 rumen samples, During summer, browse received 69 percent of recorded use and forbs and grasses 24 and 7 percent, respectively, at 5 mule deer feeding sites.Lincoln Index population estimates of 2352 and 1642 were calculated for early and late winter, respectively.The mid-summer population was estimated as at least 2866 animals.Densities of mule deer were calculated to be 12/km2, 23/km2 and 16/km2 during summer, early winter and late winter, respectively.On the primary winter range, the density of mule deer approached 62/km2.An initial fawn:doe ratio of 150 fawns:100 does was noted for 8 radio-collared does though fawn production for the entire herd was less.Overwinter mortality totaled about 10 percent of all adults and 58 percent of all fawns present in early winter or about 30 percent of the entire herd.The Brackett Creek population was dominated by young and middle-prime aged deer.Maximum ages of deer handled during the study were 10 1/2 for females and 8% for males.Examination of reproductive tracts indicated production below that observed in 1978 and below the long term average for mule deer in the Bridget Mountains.