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A Spatial and Phenological Perspective of Forage Minerals for Arctic Caribou
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The central question of this thesis is to assess whether concentrations of mineral nutrients in Alaskan tundra vegetation have the potential to influence patterns of movement and productivity of arctic caribou (Rangifer tarandus). Chapter II proposes a method for the estimation of mineral requirements of wild ungulates using caribou as an example. This method incorporates observed rates of food intake, mass change, antlergenesis, lactation and milk mineral composition of Rangifer over the summer season, which were then applied to relationships for maintenance and growth requirements of domestic animals. For each mineral, we averaged the requirements from domestic species projections to arrive at a consensus of caribou mineral requirements. Chapter III describes the spatial and phenological trends of 9 mineral nutrients in known caribou forages with interpretations of those trends in relation to the requirements derived in Chapter II. Requirements of Ca, P, Mg, Na and K declined from parturition as dietary intake increased over the summer. Conversely, requirements of Fe, Mn, Cu, and Zn increased over the summer season due to their greater association to lean mass gain. From Chapter III, Caribou are unlikely to be affected by spatial to temporal trends of Mg, Fe or Mn. Na was the most limiting nutrient on the landscape for caribou which was exacerbated by high concentrations of K in emergent vegetation. Soil pH was heavily influenced by concentrations of Ca in soils in the range of the Central Arctic caribou herd, which in turn limited availability of P in caribou forages and resulted in higher Ca:P ratios on that transect. Copper alone was not limiting to arctic caribou in our study. However, increasing concentrations of Zn in forages over the summer are likely to limit the availability of marginal Cu concentrations as the summer progresses. Overall, this work shows that arctic caribou are extremely limited in the availability of Na on the landscape, and have short windows of opportunity to gain adequate concentrations of P and Cu to survive the long arctic winter. These limitations have the potential to influence movement patterns and productivity of arctic caribou in Alaska.
Oster, Keith Westley (2017). A Spatial and Phenological Perspective of Forage Minerals for Arctic Caribou. Master's thesis, Texas A & M University. Available electronically from