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Aspects of the winter ecology of black-tailed deer Odocoileus hemionus columbianus Richardson on Northern Vancouver Island Jones, Gregory William

Abstract

Black-tailed deer Odocoileus hemionus columbianus Richardson) were studied in the Nimpkish Valley on northern Vancouver Island to determine the effects of clearcut logging upon the ecology of the deer in winter. Because Provincial government biologists suspected that logging was decreasing the amount of winter range, and therefore the number of deer, on Vancouver Island, most emphasis was placed upon the interrelationships between logging, snow depth, habitat selection by deer, and nutritional condition of deer. The study was done during during the winters of 1971 - 72 and 1972 - 73 . The first winter was severe and had heavy snowfall, and the second winter was mild and had light snowfall. If deer sink deeper in snow than their chest height, they have a hard time moving. In the Nimpkish Valley, fawns had chest heights of about 17 inches, and adults about 22 to 23 inches. During the first winter, snow in the logged habitats averaged 4 ft deep, but snow in the mature timber habitats averaged less than 2 ft deep. There was more snow at high elevations than at low elevations. Snow was less deep than deer chest height only in mature timber habitats at low elevations. Snow was also shallowest in mature timber habitats having a high crown closure. During the severe winter, only mature timber habitats at low elevations with crown closures greater than 65% were used heavily by deer. The most important aspect of snow is not simple snow depth, but how deeply deer sink in it. When a hard crust formed on deep snow in the regenerated logging slashes, deer were able to move freely on top of the crust, and made heavy use of these areas for feeding. Deer also used mature timber habitats heavily during the mild winter. Deer made more use of timber habitats having a shrub understory than these having a conifer understory, probably because there was more food available in the timber having a shrub understory. Many deer remained as high up the mountains as snow conditions and food availability permitted. Generally, deer made light use of the logged habitats during both winters, but they used these habitats heavily in the spring. Deer were collected to measure their food habits and physical condition. Deer were not able to eat as many plant species in the severe winter as in the mild winter, and were in worse physical condition in the severe winter than in the mild winter. In the Nimpkish Valley, deer made heavy use of nature timber habitats during winter. In many other areas of western North America, black-tailed deer use logged habitats for winter range. However, the Nimpkish Valley is much more mountainous and has more snowfall than many other areas in which deer ecology has been studied. The habitat selection patterns of deer in the Nimpkish Valley probably occur only in areas having similar topography, vegetation, and climate. Most other studies of black-tailed deer have concluded that logging is beneficial to deer. However, continued clearcut logging in the regions of Vancouver Island having high snowfall will eliminate deer winter range and reduce deer populations. It is recommended that legging companies leave strips of mature timber, going from the subalpine to the valley bottom, and including winter range habitats, in all those areas where deer populations are desired.

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