| Summary: | Several populations of migratory species are actually declining. Climate changes affect the habitat of migratory species and the phenology of natural processes, and impact the migration, a critical period for migratory species. Thus, it is crucial to understand how environmental and climatic variables affect the timing and the patterns of migration. This thesis assesses the impact of climate, food resources and competition on the spring and fall migrations of migratory caribou, Rangifer tarandus, from the Rivière-George (RGH) and Rivière-aux-Feuilles (RFH) herds, in Northern Québec and Labrador. The first part of my thesis presents an objective approach, based on the detection of changes in the structure of seasonal movements, to assess the departure and the arrival dates of the migrations. The approach was validated on simulated paths, and was then applied on the spring and fall migrations of female caribou. The second part focuses on the impact of environmental conditions on the phenology of the spring and fall migrations. It revealed that migration is mainly affected by the climatic conditions encountered during migration, snow conditions partly determining the cost of movements. In the spring, caribou suffer from adverse conditions when the snowmelt is early. In the fall, caribou adjust their movements and migrate faster when snowfall occurs early to limit the cost of moving through deep snow. The third part of my thesis focuses on fall migration patterns and revealed that migration patterns are mainly affected by intra- and inter-herds competition for the winter ranges. Caribou from RGH migrate preferentially toward the furthest winter ranges in response to increased competition, linked with a high population size, limiting the competition on the closest winter ranges. The use of the winter ranges by caribou from RFH is constrained by the abundance of RGH. This constraint decreased as RGH declined and abandoned the migrations toward the winter ranges commonly used by both herds. My thesis increases our ...
|
|---|