Gregory W. Thiemann

PhD (Dalhousie) thiemann
Associate 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:

Google Scholar

Yurkowski, D., E. Richardson, N. Lunn, D.C.G. Muir, A. Johnson, A.E. Derocher, A. Ehrman, M. Houde, B. Young, C. Debets, L. Sciullo, G.W. Thiemann, S.H. Ferguson. 2020.
Contrasting temporal patterns of mercury, niche dynamics, and body condition of polar bears and ringed seals in a melting icescape. Environmental Science & Technology 54: 2780-2789.

Galicia, M.P., G.W. Thiemann, and M.G. Dyck. 2020. Correlates of seasonal change in the body condition of an Arctic top predator. Global Change Biology 26: 840–850. https://doi.org/10.1111/gcb.14817

Shave, J.R., A.E. Derocher, S.G. Cherry, and G.W. Thiemann. 2019. Chronic stress and body condition of wolf-killed prey in Prince Albert National Park, Saskatchewan. Conservation Physiology 7(1): coz037. https://doi.org/10.1093/conphys/coz037

Ferguson, S.H., D.J. Yurkowski, B.G. Young, C. Willing, X. Zhu, D.C.J. Muir, A.T. Fisk. G.W. Thiemann. 2019. Do intraspecific life history patterns follow interspecific predictions? A test using latitudinal variation in ringed seals. Population Ecology 61(4): 371-382. https://doi.org/10.1002/1438-390X.12008

Brown, T.A., M.P. Galicia, G.W. Thiemann, S.T. Belt, D.J. Yurkowski, M.G. Dyck. 2018. High contributions of sea ice derived carbon in polar bear (Ursus maritimus) tissue. PLoS ONE 13(1): e0191631. doi: 10.1371/journal.pone.0191631

Laforest, B.J., J. Hebert, M.E. Obbard, G.W. Thiemann. 2018. Traditional Ecological Knowledge of polar bears in the northern Eeyou Marine Region, Québec, Canada. Arctic 71: 40-58.

Ferguson, S., X. Zhu, B. Young, D. Yurkowski, G.W. Thiemann, A. Fisk, D. Muir. 2018. Geographic variation in ringed seal growth rate and body size. Canadian Journal of Zoology: 96: 649–659. doi: 10.1139/cjz-2017-0213

Sciullo, L., G.W. Thiemann, N.J. Lunn, S.H. Ferguson. 2017. Intraspecific and temporal variability in the diet composition of female polar bears in a seasonal sea ice regime. Arctic Science 3: 672–688. doi: 10.1139/as-2017-0004.

Bromaghin, J.F., S.M. Budge, G.W. Thiemann and K.D. Rode. 2017. Simultaneous estimation of diet composition and calibration coefficients with fatty acid signature data. Ecology and Evolution 7: 6103-6113. doi: 10.1002/ece3.3179.

Regehr, E.V., K.L. Laidre, H. Resit Akçakaya, S.C. Amstrup, T.C. Atwood, N.J. Lunn, M. Obbard, H. Stern, G.W. Thiemann, and Ø. Wiig. 2016. Conservation status of polar bears (Ursus maritimus) in relation to projected sea-ice declines. Biology Letters 12: 20160556. doi: 10.1098/rsbl.2016.0556

Sciullo, L., G.W. Thiemann and N.J. Lunn. 2016. Comparative assessment of metrics for monitoring the body condition of polar bears in Western Hudson Bay. Journal of Zoology, London 300: 45-58. doi: 10.1111/jzo.12354.

Galicia, M.P., G.W. Thiemann, M.G. Dyck, S.H. Ferguson and J.W. Higdon. 2016. Dietary habits of polar bears in Foxe Basin, Canada: possible evidence of a trophic regime shift mediated by a new top predator. Ecology and Evolution 16: 6005-6018. doi:10.1002/ece3.2173.