| Summary: | Beluga whales are year-round residents of the Arctic and top predators in the ecosystem. Many beluga whale populations are migratory and spend winters in polynyas and breaks in the ice to avoid entrapment. Once the ice in begins to break up and melt, beluga whale populations migrate to the same Arctic estuaries year after year. Possible uses of estuaries include feeding, aiding in skin sloughing, protection of calves from predators, and other warm water benefits. However, much is still unknown about the use of these habitats both spatially and ecologically. I investigated estuary use by Cumberland Sound beluga whales, through their distribution. Their summering area covers northern fiords of Cumberland Sound, including Clearwater Fiord where there is a large estuary. While the whales are known the frequent the fiords, the specific distribution and core areas were unknown. Using very high resolution satellite imagery, I established critical habitat within the summering region. I also provided an updated estuary abundance estimate for this small beluga whale population. Second, I explored estuary use of Hudson Bay beluga whales by investigating the primary feeding season. Migratory species often have one season where they eat the majority of their food for the year and build fat reserves, which provides energy and supports thermoregulation. This fat can be used to investigate feeding ecology of whales. Despite being the largest beluga population, fundamental ecological knowledge of Hudson Bay beluga whales, such as the primary feeding season is unknown. I used lipid content and adipocyte size throughout the blubber of Hudson Bay beluga whales to identify when they were consuming the majority of their food. I determined that there was no consistent primary feeding season, and therefore both summering and wintering areas were used for feeding. By exploring the beluga whales’ use of seasonal habitat through distribution and foraging ecology, my thesis illuminates fundamental ecological knowledge about two beluga ...
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