| Summary: | Specialization: Conservation Biology Degree: Master of Science Abstract: Understanding the distribution of forage is important in predicting the distribution, habitat use (behaviour), movements, and fitness-related traits of large, grazing ungulates. Although this bottom-up perspective provides a foundation for understanding habitat supply and thus nutrition, foraging decisions are also affected by among other things trade-offs with energy expenditure and predation risk. This includes energy expenditures associate with thermal stress, deep snow, and predation from biting flies and larger carnivores. The objectives of this study were to quantify trade-offs between summer forage availability for wood bison with that of biting fly abundance representing a form of predation, and soil firmness which affects movement and thus energy budgets and carnivore predation risk. Specifically, trade-offs were assessed for three habitat types and one landscape feature at nine replicate sites (n = 36 sites) utilized by bison in the Ronald Lake area of northeast Alberta, Canada in the summer of 2016. At each site dung counts (summer vs. winter) were quantified in belt transects to measure bison use, forage measured in quadrats as dry biomass of graminoids, soil firmness quantified along transects with a penetrometer, and biting flies trapped and netted throughout the summer. Structural equation models were used to relate summer and winter use of habitats by bison as dung counts with that of forage, footing, and biting flies. Graminoid availability was not related to summer wood bison use, but was related positively to winter use when biting insects were absent and footing was firm (frozen). Although summer bison use was not related to graminoid biomass, it was negatively related to biting fly abundance and positively related to sites with more firm footing. These results were consistent with diet and habitat selection studies of wood bison with summer diets generally more diverse than that of winter diets. Studies of bison habitat ...
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