The Seasonal Migration Cycle
The beluga whale, Delphinapterus leucas, is a highly mobile species with a circumpolar distribution across Arctic and sub-Arctic seas. Adults are recognizable by their pure white coloration, earning them the nickname “white whale.” They possess a prominent dorsal ridge instead of a fin, allowing them to navigate easily beneath sea ice. Their flexible neck permits them to turn their heads, and a thick layer of blubber insulates them in the frigid environment.
Beluga migration is synchronized with seasonal changes in their northern habitat. In the spring, as the Arctic sea ice thaws, belugas follow the retreating ice edge toward their traditional summering areas. This movement is generally northward or toward coastal regions as open water becomes available. The onset of autumn and the formation of new sea ice cue the whales to begin their southward or offshore migration to wintering grounds.
Movements are driven by the need to access food, find open water, and locate suitable environments for biological processes. Spring migration allows belugas to exploit abundant food resources in newly ice-free areas. Warmer, shallow water provides a safer environment for newborn calves, which lack the necessary blubber layer for deep, cold water survival. The warmer, less saline water of summer estuaries also facilitates the annual molting process, where the whales shed their outer layer of skin.
Key Summering Grounds
Belugas congregate in predictable, shallow coastal areas during the summer months, typically between June and September. These summering grounds are characterized by river estuaries and bays, where the influx of freshwater creates warmer, turbid conditions. The Mackenzie River Delta in the Canadian Arctic is a significant concentration point for the Eastern Beaufort Sea population. The shallow estuary serves as a core area before the whales disperse into the Amundsen Gulf.
The largest known population, estimated at 55,000 to 60,000 individuals, returns every summer to the western Hudson Bay. Within this bay, the whales concentrate intensely in the estuaries of the Churchill, Nelson, and Seal Rivers. These areas are selected for warmer water and because river plumes carry suspended sediments associated with increased prey availability.
The St. Lawrence River Estuary represents the southernmost permanent population, remaining year-round rather than migrating north. Similarly, the Cook Inlet population in Alaska is non-migratory and stays within the inlet throughout the year. The preference for these shallow, nutrient-rich coastal zones maximizes feeding opportunities and provides protection from predators.
Deep Water Wintering Habits
As coastal waters freeze in autumn, most beluga populations move offshore into the deep, ice-covered Arctic Ocean. They spend months near the edge of the pack ice, often in dense ice cover. For instance, belugas from the Beaufort and Chukchi Seas migrate south to the northern Bering Sea for the winter.
Survival in these ice-dominated environments relies on specialized adaptations and knowledge of ice dynamics. Belugas can dive 800 to 1,000 meters for up to 25 minutes to forage for fish and invertebrates near the ocean floor. To breathe, they utilize natural openings in the ice cover, such as polynyas—areas of open water surrounded by sea ice—or cracks and leads.
The heavy ice cover offers security from their main predator, the Killer Whale, which generally avoids dense ice fields. Hazards remain, including the risk of becoming trapped if a breathing hole closes unexpectedly. Some eastern Canadian Arctic populations, such as those from Baffin Bay, overwinter in large, recurrent polynyas like the North Water, while others continue along the West Greenland coast.
Mapping the Movement
Beluga movements across the Arctic seascape are tracked using advanced scientific methods. Scientists rely heavily on satellite telemetry, attaching small, satellite-linked transmitters to the whales’ dorsal ridge. These tags record location, dive depth, and duration, transmitting information to a satellite when the animal surfaces to breathe.
Tracking data reveals that migration is not uniform but organized into distinct populations, or stocks, each following unique routes. For example, the Beaufort Sea and Chukchi Sea populations use different corridors and timing for autumn migrations, even if they share summer feeding areas. These specific migratory paths are culturally transmitted, passed down from mother to calf across generations.