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Dietary niche relationships among cervids relative to winter snowpack in northwestern Montana

    • Authors: K. J. Jenkins, and R. G. Wright

      Date: 1987

      Journal: Canadian Journal of Zoology

      Volume: 65

      Number: 6

      Pages: 1397-1401

      Summary of Methods: Winter diets of elk, white-tailed deer and moose in Glacier National Park (48⁰47’ N, 114⁰ 16’ W) were measured to determine the effect of snow depth on dietary overlap and nutritional quality. Fecal samples from each species were collected in February for two years. Over the same time, samples of consumed forage species were collected to determine nutrient content. Each winter’s severity was rated.

      Article Summary / Main Points: The first year’s winter was considered to be harsh and the following year was classified as a mild winter. Dietary overlap increased with increased snow depth. Deer and elk diets showed annual differences coinciding with the amount of snow depth and the resulting forage availability. Both species were able to dig through the snow to preferred forage (e.g., grasses and low shrubs) when snow levels were low, but during the harsh winter both species foraged on more deciduous and coniferous browse above the snow. Moose diets did not differ between winters due to their natural diet of foraging on deciduous and coniferous browse. Nutrient content of selected forages varied little over both winters.

      Vegetation Types: Grazed Forest

      MLRA Ecoregions: 43B Central Rocky Mountains

      Agrovoc Control Words: Ungulates Foraging Dietary overlap

      Article Review Type: Refereed

      Article Type: Experimental Research

      Keywords: odocoileus virginianus ochrourus, cervus elaphus nelsoni, alces alces shirasi, dietary overlap, opportunistic foraging, specialized foraging

      Annotation: This replicated study was conducted over two years; its coinciding results are applicable to northern Rocky Mountain rangelands. As is true for all grazing research, the results are most directly applicable to areas with similar landscapes, type of ungulates, weather conditions and season of use. Quantification of various snow depths was not provided, and would improve understanding of when forage is available vs. unattainable. Additionally, Jenkins and Wright (1988, J. Applied Ecology 25:11-24) studied resource partitioning and competition between cervids during winter months in Glacier National Park, also summarized in the RSIS website. Together these articles describe resource selection and competition among ungulates sharing winter rangeland.

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