Gregory W. Thiemann

PhD (Dalhousie) thiemann
Assistant Professor
E–mail: thiemann@yorku.ca
Research Areas: Foraging ecology, behavioural ecology, wildlife conservation

Research Focus

My research focuses on the foraging ecology and conservation of Arctic carnivores. By examining the trophic relationships between top predators and their prey, we can define the structure of food webs and monitor changes in ecosystems over time. By understanding where, when, and how predators hunt for food, we can better act to protect wildlife populations and entire ecosystems.

Much of my research has involved the use of fatty acid signature analysis to examine the diets of marine and terrestrial carnivores. This technique is based on the knowledge that ingested dietary fatty acids (such as “omega-3’s”) are predictably incorporated into a predator’s fat stores. Therefore, the fatty acid profile of an animal can be used to make inferences about its foraging habits.

Long-term climate warming is having rapid and widespread effects on northern ecosystems. This in turn is altering the relationships between northern aboriginal communities and the wildlife populations they utilize. Accurate information on the current structure and functioning of food webs will help us predict how wildlife populations will respond to ongoing environmental change in the North.

Representative  Publications:

Bromaghin, J.F., S.M. Budge, G.W. Thiemann and K.D. Rode. 2015. Assessing the robustness of quantitative fatty acid signature analysis to assumption violations. Methods in Ecology and Evolution. Early view. doi: 10.1111/2041-210X.12456

Galicia, M.P., G.W. Thiemann, M.G. Dyck, and S.H. Ferguson. 2015. Characterization of polar bear (Ursus maritimus) diets in the Canadian High Arctic. Polar Biology. Online Early. doi: 10.1007/s00300-015-1757-1.

Marcoux, M., V. Lesage, G.W. Thiemann, S.J. Iverson and S.H. Ferguson. 2015. Age estimation of belugas Delphinapterus leucas using fatty acid composition: a promising method. Marine Mammal Science 31: 944-962

Duerksen, S.W., G.W. Thiemann, S.M. Budge, M. Poulin, A. Niemi, C. Michel. 2014. Large, omega-3 rich, pelagic diatoms under Arctic sea ice: sources and implications for food webs. PLoS ONE 9(12): e114070.

Rode, K.D., E.V. Regehr, D. Douglas, G. Durner, A.E. Derocher, G.W. Thiemann, S. Budge. 2014. Variation in the response of an Arctic top predator experiencing habitat loss: nutritional and reproductive ecology of two polar bear populations. Global Change Biology 20: 76-88.

Derocher, A.E., J. Aars, S.C. Amstrup, A. Cutting, N.J. Lunn, P.K. Molnár, M.E. Obbard, I. Stirling, G.W. Thiemann, D. Vongraven, Ø. Wiig, and G. York. 2013. Rapid ecosystem change and polar bear conservation. Conservation Letters 6: 368-375.

Thiemann, G.W., A.E. Derocher, S.G. Cherry, N.J. Lunn, E. Peacock, and V. Sahanatien. 2013. Effects of chemical immobilization on the movement rates of free-ranging polar bears. Journal of Mammalogy 94: 386-397.

Cherry, S.G., A.E. Derocher, G.W. Thiemann, and N.J. Lunn. 2013. Migration phenology and seasonal fidelity of an Arctic marine predator in relation to sea ice dynamics. Journal of Animal Ecology 82: 912-921.

Thiemann, G.W., S.J. Iverson, I. Stirling, and M.E. Obbard. 2011. Individual patterns of prey selection and dietary specialization in an Arctic marine carnivore. Oikos 120: 1469-1478.

Molnár, P.K., A.E. Derocher, G.W. Thiemann, and M.A. Lewis. 2010. Predicting survival, reproduction and abundance of polar bears under climate change. Biological Conservation 143: 1612-1622.