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Gregory W. Thiemann

Gregory W. Thiemann

Picture of Gregory W. Thiemann
Gregory W. Thiemann
Associate Professor

Eligible to Supervise

Biology Graduate Program

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 Indigenous 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.


Foraging ecology, behavioural ecology, wildlife conservation

Representative Publications

Google Scholar

*York graduate students

Ross, T.R.*, G.W. Thiemann, B.G. Young, S.H. Ferguson. 2022. Complementary diet analyses reveal intraspecific and temporal variation in ringed seal (Pusa hispida) foraging in the Canadian High Arctic. Polar Biology 45: 465–480.

Thiemann, G.W., K.D. Rode, J.A. Erlenbach, S.M. Budge, C.T. Robbins. 2022. Fatty acid profiles of feeding and fasting bears: Estimating calibration coefficients, timeframe of diet estimates, and selective mobilization during hibernation. Journal of Comparative Physiology B 192: 379-395.

Galicia, M.P.*, G.W. Thiemann, M.G. Dyck, and S.H. Ferguson. 2021. Polar bear diet composition reveals spatiotemporal distribution of Arctic marine mammals across Nunavut, Canada. Ecological Indicators 132: 108245.

Galicia, M.P.*, G.W. Thiemann, M.G. Dyck and S.H. Ferguson. 2021. Are tissue samples obtained via remote biopsy useful for fatty acid-based diet analyses in a free-ranging carnivore? Journal of Mammalogy 102: 1067-1078.

Florko, K.*, G.W. Thiemann, J.F. Bromaghin, and E S. Richardson. 2021. Polar bear (Ursus maritimus) diet composition and body condition in relation to sea ice habitat in the Canadian High Arctic. Polar Biology 44: 1445–1456.

Galicia, M.P.*, G.W. Thiemann, M.G. Dyck, S.H. Ferguson, and I. Stirling. 2021. Prey selection of polar bears in Foxe Basin, Nunavut, Canada: evidence of dietary flexibility in a specialized predator. Oxford Open Climate Change 1(1): kgab002.

Florko, K.*, G.W. Thiemann and J.F. Bromaghin. 2020. Drivers and consequences of apex predator diet composition in the Canadian Beaufort Sea. Oecologia 194: 51-63., OA:

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.

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.

Brown, T.A., M.P. Galicia*, G.W. Thiemann, S.T. Belt, D.J. Yurkowski and 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 and G.W. Thiemann. 2018. Traditional Ecological Knowledge of polar bears in the northern Eeyou Marine Region, Québec, Canada. Arctic 71: 40-58.

Sciullo, L.*, G.W. Thiemann, N.J. Lunn and 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.

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.

Research Areas

Ecology and Evolutionary Biology