Alternative life-history and thermoregulation strategies in the Svalbard reindeer and the implications for population dynamics

With the Arctic warming nearly four times faster than the rest of the globe (Rantanen et al., 2022), resilience of Arctic ecosystems and population dynamics of Arctic species are raising concern among scientists. Svalbard reindeer (Rangifer tarandus platyrhynchus) is an ideal species to study these quite complex topics. Recently, analysis from Loe et al. (unpublished data) have suggested that two different thermoregulatory phenotypes may exist among individuals in the Svalbard reindeer population. These phenotypes appear to differ in late winter body mass, reproductive success, diet and microbiome. This suggests there could be a Pace-of-Life Syndrom (POLs; Careau & Garland, 2012) and that several POL strategies may exist simultaneously within this population. Since POL is directly linked to vital rates, and the phenotypic composition of the population may change with ongoing environmental changes, it is crucial to better understand individual heterogeneity in POL if we want to obtain more robust predictions of this population’s dynamic, as well as its interaction with the Svalbard ecosystem in the future. My thesis aims to evaluate the impacts of climate change on the phenotypic composition and dynamics of a population of Svalbard reindeer, and the feedback on other trophic levels. To achieve this goal, I have three specific objectives. Therefore, the first specific objective of my thesis is to characterize the phenotypic structure of the Svalbard reindeer population. As one phenotype could be better adapted to cope with climate change and because this might have implications for future population dynamics, the second specific objective is to estimate how the relative abundance and the fitness of the different phenotypes change with environmental fluctuations. Then, the third objective is to model the impacts of climate change on the population dynamics in the next 100 years, depending on climatic scenarios, and to determine the outcome for other trophic levels.