February 27 is International Polar Bear Day and in celebration of the event, we feature Gregory Thiemann whose research focuses on the ecology of polar bears and other Arctic carnivores, as well as the effects of climate change on food web dynamics.
With a Killam/NSERC postdoctoral fellowship and a PhD in Biology from Dalhousie University, Thiemann primarily studied polar bear diets and Arctic marine food webs. His research focuses on the foraging ecology and conservation of large predators, particularly polar bears.
“By understanding where, when, and how predators forage, we can better act to protect not only the predators themselves, but the entire ecosystems of which they are a part,” Thiemann states. “Further, by examining the trophic relationships between predators and their prey, the food web structure can be defined and changes in ecosystems can be monitored over time,” he adds.
Much of Thiemann's research has involved the use of fatty acid signature analysis to examine the diets of marine and terrestrial carnivores. Accordingly, this technique is a valuable ecological tool for effectively examining predator diets and foraging ecology with the goal of conserving Arctic wildlife. The fatty acid profile of the predator will reflect the fatty acid composition of its prey and combined with other diagnostic tools such as stomach content measurements or stable isotope analyses, they can help define trophic linkages, and hence food web structure, in many ecosystems. What’s more, the same tissue samples that provide information diet composition also reveal details on body condition and the overall nutritional health of the animal.
Supervising his students on their research and publications, Thiemann has co-authored articles with them as part of his training and mentoring. In a study on “Measuring seasonal fluctuations in the body condition of polar bears,” the research team looked at the fluctuations in body condition experienced by polar bears in five Canadian subpopulations: Baffin Bay, Davis Strait, Foxe Basin, Gulf of Boothia, and Lancaster Sound and their responses to climatic change. Notably, polar bears are losing fat from early fall (September/October) through to spring (April/May) and begin to accumulate fat May/June suggesting that spring feeding is the time when prey species are most vulnerable to predation and the critical period for bears to accumulate enough fat reserves to rely on for much of the rest of the year.
Thiemann’s research examines a range of topics on the ecology and conservation of Arctic wildlife. His students have published research on diet composition of female polar bears, apex predator diet composition in the Canadian Beaufort Sea, polar bear diet composition in Nunavut, methods of assessing polar bear body condition, potential ecological effects of killer whales in Arctic waters, and Traditional Ecological Knowledge of polar bears in the northern Eeyou Marine Region in Quebec, Canada. These studies demonstrate how quickly Arctic ecosystems are changing in response to global warming and how science and Indigenous Knowledge can contribute to wildlife conservation in the context of a rapidly changing Arctic environment.