Humpback whales are large baleen whales found in oceans across the globe. Characterized by their long pectoral fins and distinctive body shape, they can reach up to 60 feet in length. As rorquals, they are filter feeders that must consume enormous quantities of small organisms to fuel their bodies and maintain seasonal migrations. Their specialized feeding strategies focus on exploiting dense, concentrated patches of prey to maximize energy intake.
Primary Prey Sources
The humpback whale diet consists primarily of two categories of small organisms: zooplankton and schooling fish. Zooplankton, particularly krill, often forms the foundation of the humpback’s nutritional intake in many feeding grounds. Krill are highly energy-dense due to their high fat and protein content.
In the Northern Hemisphere, small schooling fish become a more significant part of the diet. Common prey items include capelin, herring, Atlantic mackerel, and sand lance. Humpbacks are generalist predators, demonstrating the ability to switch prey and target whatever small organisms are locally abundant and offer the highest energetic value.
The whale’s massive size dictates a huge caloric requirement, necessitating the consumption of large volumes of food daily. An adult whale may consume at least one ton of prey each day during the feeding season. This need for bulk consumption means whales must locate and exploit extremely dense aggregations of prey to make the energy expenditure of hunting worthwhile.
Specialized Feeding Techniques
Humpback whales employ highly dynamic and specialized behaviors to capture their concentrated prey. The most basic technique is gulp feeding, or lunge feeding. This involves the whale accelerating rapidly into a dense patch of prey with its mouth wide open, engulfing a tremendous volume of water and organisms. Pleated throat grooves, which run from the chin to the belly, allow the mouth to expand dramatically to accommodate the large mouthful.
After engulfing the prey and water, the whale closes its mouth and uses its large tongue to push the water outward through the baleen plates. These keratinous plates hang like fringes from the upper jaw, acting as a sieve to trap the small fish or krill inside. The retained food is then swallowed, providing a substantial, energy-rich meal.
The most complex hunting behavior is bubble-net feeding, which can be performed alone or cooperatively. This method exploits the prey’s natural avoidance response to physical barriers by using air bubbles to corral them. The whale swims in an upward spiral beneath a school of fish or krill while slowly releasing a continuous stream of air from its blowhole.
The rising column of bubbles forms a curtain or “net” that concentrates the prey into a tight, dense ball near the surface. Once the prey is contained, the whale lunges vertically through the center of the bubble net with its mouth agape to engulf the entire aggregation in one gulp. In cooperative hunts, whales may use specific vocalizations to coordinate the timing of the bubble release and the final lunge.
The Seasonal Feeding Cycle
The humpback whale life cycle is defined by an annual cycle of intense feeding followed by a prolonged period of fasting. They undertake one of the longest migrations of any mammal, traveling between high-latitude feeding grounds and low-latitude breeding grounds. The feeding season occurs during the summer and late spring in polar and subpolar regions, such as the Antarctic or the Gulf of Alaska.
These cold, nutrient-rich waters support vast blooms of krill and fish. During this brief, productive season, the whales engage in hyperphagia, maximizing their food intake to accumulate a thick layer of blubber. These blubber reserves fuel the non-feeding phases of their year. Whales often exhibit the highest feeding rates immediately upon arriving at the feeding grounds to capitalize on the earliest, most abundant prey.
As the seasons change, the whales migrate toward tropical or subtropical waters for the winter breeding and calving season. During this migration and subsequent stay in warmer waters, humpbacks largely cease feeding, relying almost entirely on their stored fat reserves. This fasting period is energetically demanding, with whales estimated to lose between 25 and 50 percent of their body mass over the course of the migration and winter.