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UBC Theses and Dissertations

Ecology of a partially migratory elk population Woods, John G.


In this thesis I investigate the ecology of a partially migratory (<100% of the animals migrate) population of elk (Cervus elaphus) in the Canadian Rockies. I radio-tagged elk in a 330 km² area of the Bow River valley (BRV) in Banff National Park, Alberta and followed them for 36 months. Elk movements to adjacent watersheds expanded the study area to 2900 km². My goals were to describe the seasonal movements made by BRV elk and to reach some understanding of the causes of these movements. The M/R (migrant/resident) ratios for adult bulls and adult cows were 4.3 and 0.5 respectively. Classified ground counts revealed that adult bulls made up only 11% of the population and that the overall M/R ratio for the population was 0.6. Migrations did not take elk beyond the foraging range of timber wolves (Canis lupus), their principal predator. Three cows changed migration status between years and some migrants were sympatric with residents during the rutting (breeding) season. These observations are consistent with the hypothesis that migration in elk is a conditional ESS (evolutionarily stable strategy). Although 1 adult radio-tagged bull dispersed, individual annual home-ranges of the remaining elk overlapped from year-to-year. Elk were strongly philopatric to winter, summer, and rutting ranges. There were no differences detected in the relative philopatry of bulls and cows, or of migrants and residents. Bulls had average 1-way migrations of 30 km horizontally and 840 m vertically. Cows had average 1-way migrations of 36 km horizontally and 1079 m vertically. The net energy and time investments for these movements were calculated and judged to be trivial. Elk on both high and low elevation ranges ate primarily grasses and sedges during the autumn, winter, and spring, and the leaves of deciduous shrubs during the summer. Similarities outweighed differences between high and low elevation ranges. Elk population characteristics (numbers, composition, survival, recruitment, predation, parasites, animal morphology) were measured during 1985-91 and compared with similar data gathered during 1944-69. In most respects, the population has not changed over these years and little is known of density-dependent processes.

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