Mule deer (Odocoileus hemionus hemionus) are a regionally important species in the Cariboo Forest Region. Management plans are required for mule deer winter ranges to ensure that deer populations are sustained while providing for resource extraction. Integrating the needs of mule deer with the forest industry depends on an understanding of the habitats required during winter. During winter, deer experience a net negative energy balance and require habitats that reduce their rate of energy loss. Deep snow significantly increases the cost of travel for deer. Past research in the Cariboo Forest Region has focused on the Interior Douglas-Fir Biogeoclimatic Zone (IDF) where the characteristics of good winter range have been described as including south facing slopes and stands of old-growth Douglas-fir. These habitats generally have shallower snow and more available forage. Research on the winter diet, habitats and movements of mule deer in the Canim North Mule Deer Winter Range is essential in developing management plans for winter ranges. This study used winter track transects to measure relative habitat use and found a shift in the use of habitat variables with increasing snow depth. Deer showed a preference for warm aspects with moderate slopes, which amplified as snow depth increased. Deer activity was concentrated in stands with 1-19% and 60-79% Douglas-fir in the overstory and the use of this habitat was greater than expected and increased with greater snow depth. Stands with 20-59% and greater than 79% Douglas-fir were used less than expected. In contrast, this study indicates that stands with a low proportion of tall Douglas-fir (1-19 trees/ha) were used significantly more than stands with greater densities of trees. There was no significant relationship between deer use and crown closure based on sample period snow depth category. The greatest deer use was found in habitats with 36-55% crown closure in deep to very deep sample period snow depth categories. In general, deer are likely to utilize habitats that provide the greatest overall benefit, optimizing forage, thermal and security requirements relative to energy expenditure for locomotion. This study has shown an increasing preference for habitats with a warm aspect and moderate slope with increasing snow depth. Crown closure is also typically lower on steep, dry slopes, which allows for increased light penetration, reducing snow depths and favouring more drought-tolerant shrubs. These results are based on two years of comparable data and must be considered preliminary. Sampling must be conducted over a period of years before any reliable trends or conclusions can be made. By collecting information over a number of years, an understanding of mule deer habitat use patterns may be determined such that effective management plans can be developed for this winter range.
Triton Environmental Consultants Ltd.