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The Mackenzie Delta region, NWT, has a short growing season and highly seasonal climate, and brown bears (Ursus arctos) there face many challenges obtaining their nutritional requirements. Consumption of meat by brown bears is linked to increases in population density, fecundity, growth and body size. I examined the use of Arctic ground squirrels (Urocitellus parryii), and broad whitefish (Coregonus nasus) as meat sources by Mackenzie Delta brown bears. As a preliminary step, I built an Arctic ground squirrel habitat model, using field-surveyed ground squirrel burrow locations. Using this model, I examined bears selection for Arctic ground squirrel habitat as a population, by sex and as individuals, and linked this to results of stable isotope analysis and site investigations. Bears showed little evidence of Arctic ground squirrel use at the population and sex level, but some individual bears appeared to prey heavily on ground squirrels, particularly during hyperphagia. I also described observations of a brown bear using broad whitefish in autumn, and used telemetry locations to show that other bears may also feed heavily on broad whitefish during hyperphagia. My research provides prey-specific evidence for intrapopulation niche variation among Mackenzie Delta brown bears. / Ecology