The beluga whale, Delapterus leucas, is a small, toothed cetacean uniquely adapted to the harsh environment of the Arctic and Subarctic regions. Often called the “canary of the sea” for its high-pitched vocalizations, this marine mammal thrives in frigid waters due to a thick layer of insulating blubber and a lack of a dorsal fin, which allows it to navigate easily beneath sea ice. Belugas are highly intelligent and social animals that function as opportunistic predators. Their feeding habits involve a wide array of marine life, making them generalist feeders who can exploit different food sources as they migrate across various regions and seasons.
The Primary Components of the Beluga Diet
Beluga whales prey on about 100 different kinds of marine organisms, which scientists categorize into three main groups: fish, crustaceans, and cephalopods.
Fish
The fish they consume are diverse, often including schooling species abundant in Arctic and Subarctic seas. Common examples are Arctic cod, saffron cod, capelin, herring, and smelt, which provide significant caloric intake. They also target bottom-dwelling species, such as flounder, sole, sculpin, and the deep-water Greenland halibut. In certain areas, like Bristol Bay, the presence of anadromous fish during spawning runs makes salmon, particularly sockeye and coho, a prevalent prey item.
Crustaceans and Cephalopods
Crustaceans form another substantial part of the diet, particularly invertebrates that inhabit the seafloor. Shrimp is the most common invertebrate consumed, with species like the northern shrimp being a frequent meal. Other smaller organisms are regularly ingested while foraging along the seabed:
- Amphipods
- Crabs
- Bristle worms (polychaetes)
Belugas also feed on cephalopods, including various species of squid and octopus. For instance, the smoothskin octopus is a known food item for belugas in the Beaufort Sea, while other squid species are common in the St. Lawrence Estuary population.
Specialized Foraging and Hunting Strategies
Belugas employ a range of sophisticated adaptations to hunt successfully in the challenging, often dark or turbid waters of their habitat. A key tool is echolocation, a biological sonar system that uses high-frequency clicks emitted from the bulbous organ on their forehead, known as the melon. The echoes allow the whale to determine the size, shape, distance, and movement of potential prey, which is essential for locating food under low-visibility conditions or beneath thick ice.
Belugas can dive to considerable depths to pursue prey that live on or near the ocean floor. While they often forage in shallower waters between 20 and 40 meters, they have been recorded diving as deep as 700 meters (2,300 feet) when necessary. Their flexible necks, unlike those of most other cetaceans, provide a wide range of motion that aids in searching for these bottom-dwelling organisms.
Belugas swallow their meals whole, using a specialized method called suction feeding. They create negative pressure with their mouths to pull small prey straight into their throats, which is highly effective for capturing small, soft-bodied organisms. Observations suggest belugas can also use a strong jet of water to dislodge prey like sandworms and clams from the sediment before sucking them up.
Hunting is often a cooperative effort. Groups, sometimes consisting of six to ten whales, work together to herd schools of fish, such as salmon or herring, into confined spaces like shallow water or river mouths. This teamwork improves their capture rate and conserves energy, which is beneficial when exploiting dense, seasonal fish migrations.
How Geography and Season Influence Diet
The beluga whale’s diet is highly dynamic, shifting significantly based on migratory patterns and the specific habitat it occupies during the year.
Seasonal Shifts
During the summer months, belugas typically migrate to warmer, shallower coastal areas, including estuaries and river deltas, for both calving and feeding. These areas offer abundant seasonal prey, such as the large runs of salmon and smelt that migrate upriver to spawn, providing a concentrated and easily accessible food source. In contrast, the winter diet involves a greater reliance on deeper-water species, as the belugas move away from the coasts and into the offshore pack ice. Under the ice, they hunt for fish like Greenland halibut and various invertebrates, including shrimp and cephalopods, which are available year-round. This shift is reflected in their body composition, as their blubber stores are thickest in late winter and early spring.
Geographical Variation
Geographical location also dictates the type of prey available, leading to distinct diets among different populations. Belugas in the Beaufort Sea, for example, primarily consume Arctic cod and shrimp. Those in the Eastern Chukchi Sea rely heavily on shrimp and echiurid worms. The St. Lawrence Estuary population consumes a varied diet of hake, redfish, and squid, demonstrating how local marine ecosystems determine the composition of the beluga’s meals. This flexibility in diet is a crucial adaptation for survival in the Arctic, allowing belugas to adjust their consumption based on the availability and distribution of prey species.
Nutritional Requirements and Energy Consumption
The beluga whale’s diet must provide a substantial and continuous source of energy to support its existence in the freezing Arctic waters. Maintaining a thick layer of blubber, which can account for up to 40% of their body weight, is necessary for insulation against the cold and serves as a vital energy reserve. This physiological demand necessitates a high caloric intake throughout the year, especially during periods of migration and reproduction.
To meet these requirements, a beluga whale must consume a considerable amount of food each day, typically eating approximately 2.5% to 3% of its total body weight. For an average adult beluga, this translates to a daily intake of about 18.2 to 27.2 kilograms (40 to 60 pounds) of fish and invertebrates. This volume of food provides the necessary fats and proteins essential for growth, blubber maintenance, and supporting the energetic cost of long-distance migrations. The fat content from their prey, such as oily fish like capelin and salmon, is important for replenishing and maintaining the insulating blubber layer.