Influence of disturbance and potential predator effects on the persistence of boreal woodland caribou (Rangifer tarandus caribou) in Manitoba
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Date
2018
Authors
Schindler, Douglas
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Abstract
The Western Canadian population of boreal caribou (Rangifer tarandus caribou) is of special concern and is listed as “threatened” under the Canadian Species at Risk Act (SARA). In Canada, a non-disturbance threshold of 65% of a given range is required. The thesis objective was to assess the influence of natural and anthropogenic disturbance on calf recruitment and adult female survival and to assess habitat use of caribou in relation to a possible predatory species, grey wolf (Canis lupus). Lambda rates (λ) were estimated and compared to disturbance regimes on 5 boreal caribou evaluation ranges in northwestern Manitoba. Fine scale disturbance was also investigated using fuzzy classification on collared females to determine the gradient of disturbance across core, peripheral and overlapping fuzzy ranges. Resource selection was undertaken on caribou and wolves to determine habitat utilization during spring and summer calving and calf rearing season. Regression of λ against percentage of landscape disturbance for natural and anthropogenic sources were found to be not significant, however, high rates of calf mortality were observed during the first weeks of life. Analysis of disturbance in fuzzy ranges indicated higher levels of disturbance in overlap areas and core areas less disturbed. Resource selection showed that caribou and wolves are not selecting similar habitat during the calving and calf rearing period. High calf mortality could not be explained by wolf predation. The research suggests that disturbance levels alone may not be appropriate for assessing population persistence, and assessment of black bear predation on calves is identified as a research need.
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Keywords
Caribou, Predator-prey, Disturbance, Range fragmentation, Wolves, Resource selection, Lambda rates, Black bear, Habitat mapping