Thesis defense: 'Seasonal Movements, Diet Composition and Plant Nutritional Quality of Unimak Island Caribou,' May 10

Friday, May 10, 1 p.m. ConocoPhillips Integrated Science Building, Room 120

Kate Legner, graduate student in biological sciences , will defend her thesis, "Seasonal Movements, Diet Composition, and Plant Nutritional Quality of Unimak Island Caribou." The graduate committee consists of advisor Don Spalinger, Ph.D., Paddy Sullivan, Ph.D., and Matt Carlson, Ph.D.

Abstract: The Unimak Island caribou herd is in the midst of a severe population decline associated with low rates of pregnancy and calf survival. Although there are many potential causes for this decline, the productivity of any large herbivore population ultimately depends on the accessibility of nutritional resources to the individuals of a population. Legner evaluated the spatial and temporal complexity of caribou range use and diets, as well as plant availability and nutritional quality for Unimak Island caribou May-September. Legner found that Kernel Density Estimation using a bandwidth estimator hPlug-in, was most effective in delineating seasonal caribou home range boundaries, using GPS collar data from a two-year period, with few exceptions. Caribou home ranges varied in location and size within and between seasons, though home range size and overall movement were greatest in the summer and early fall respectively. A novel n-alkane long-chain fatty acid (LCOH) method of diet determination effectively resolved diet proportions to species in a two-step optimization procedure for up to 48 potential diet components. Caribou diets were complex and variable by season but contained higher proportions of forb plant species than other Alaska caribou herds across seasons. Mushrooms contained n-alkane and LCOH markers and were identified via this method to be a main component of fall caribou diets. Finally, caribou foraged on plant species selectively each season, providing a diet that was on average 14 percent higher in digestible dry matter (DDM) and 36 percent higher in nitrogen (N), than the average nutritional quality of plants available. Dietary N and DDM appeared to be well above maintenance requirements during these three seasons. Overall, Legner concluded that spring, summer and fall habitats do not appear to impose any nutritional constraints on Unimak Island caribou. Legner recommends, however, that this methodology be applied to this herds' winter habitat, which is often a limiting factor for arctic caribou herds.

May Archive