Mule deer (Odocoileus hemionus hemionus) at the northern limit of their continuous, high-density distribution use interior Douglas-fir (Pseudotsuga menziesii) forests as winter range. In the Cariboo Forest Region this represents 250 000 ha, or about 15%, of mapped Douglas-fir forest. The needs of mule deer and the forest industry conflict because both require large, old Douglas-fir trees. If we are to resolve this conflict, we first need a sound knowledge of mule deer habitat requirements, one of which is forage.
Sixty-one mule deer composite pellet samples were collected from seven winter ranges within the central interior of British Columbia between 1982 and 1989. Microhistological analyses found more than 87 plant species in the diet, although the bulk of the diet consisted of Douglas-fir, saskatoon (Amelanchier alnifolia), Oregon-grape (Mahonia aquifolia), red-osier dogwood (Cornus sericea), willows (Salix spp.), and soopolallie (Shepherdia canadensis). On a few winter ranges, subalpine fir (Abies lasiocarpa), snowbrush (Ceanothus velutinus), and sages (Artemisia spp.) were commonly eaten. Douglas-fir occurred in all diet samples and on average was the most abundant species (x=52%, SD=24%, N=61). The source of foliage is litterfall from large, older trees.
Diet samples collected from dry winter ranges in the Interior Douglas-fir Zone (IDF) contained more Douglas-fir than those from wetter winter ranges in the Sub-Boreal Spruce Zone (SBS). As snow depth increased over the winter, the percent Douglas-fir in the diet increased, especially on the wetter winter ranges. Faecal nitrogen (FN) and diaminopimelic acid (DAPA) correlated with the percent shrub in the diet (r=.46, P =01; and r= .52, P= .01, respectively). Both FN and DAPA are indicators of diet quality.
As important winter forage, Douglas-fir must be available to deer on winter range in managed forests. On winter ranges that can be harvested in the near future, Armleder et al. (1986) recommend low volume partial cutting, which includes maintenance of a large proportion of older trees to provide forage and shelter. Shrubs are a preferred forage and may be scarce on drier winter ranges. Harvesting may improve shrub production and there is some potential to enhance abundance of some species by planting or underburning.
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Updated May 29, 2009