Bubble-net feeding is a specialized and visually dramatic hunting technique used by some of the ocean’s largest marine mammals. The strategy involves intentionally manipulating the environment by using air as a physical and psychological barrier. This concentrates small prey into a dense, easily consumable mass. This method highlights the complex intelligence and social learning capabilities present in these massive ocean dwellers, often requiring coordinated effort and precision.
Defining Bubble-Net Feeding
Bubble-net feeding is a foraging strategy where whales release streams of air bubbles underwater to create a temporary, cylindrical barrier around their food source. The primary purpose is to corral schools of small prey, such as herring, salmon, or krill, into a tight cluster known as a “bait ball.” The whales dive beneath the prey aggregation, then swim upward in a spiral while exhaling, forming a rising curtain of bubbles that acts like a physical net. This use of air as a manufactured barrier has led some scientists to describe the behavior as a form of tool use. The process is a learned behavior, not an instinct, and it varies in technique across different populations.
The creation of the bubble net serves two main functions to achieve this concentration of food. First, the visual effect of the white, shimmering bubbles rising through the dark water disorients and confuses the schooling fish. Second, the prey organisms, for reasons not completely understood, show a strong reluctance to swim through the bubble wall, effectively trapping them inside the shrinking cylinder. By concentrating thousands of small organisms into a single, dense mass, the whales transform a widely dispersed food source into a single, high-caloric target. This efficiency is paramount for animals that must consume tons of food during their brief summer feeding seasons.
The Mechanics of the Bubble Net
The precise execution of the bubble net begins with the whale or group of whales diving deep beneath the targeted school of fish. One whale, often designated as the “net blower” or leader, initiates the process by releasing a steady stream of air from its blowhole(s). The whale swims in a tightly controlled, upward spiral pattern, which shapes the rising bubbles into a cylindrical or conical wall that can range from 10 to nearly 100 feet in diameter. The whale’s large pectoral flippers provide the necessary maneuverability to execute the tight turns required for effective net construction.
As the bubbles ascend and expand, they form a solid-looking curtain that drives the prey inward and upward toward the surface. In coordinated group feeding, other whales often participate in the herding process, sometimes using their large flippers to further constrict the school. Whales can precisely control the spacing, speed, and number of bubble rings to maximize the density of the bait ball. This level of control allows the whales to catch up to seven times the prey in a single gulp compared to unassisted feeding dives, conserving the energy needed for repeated feeding attempts.
The process is often accompanied by an acoustic element, as one whale will emit a specific, loud “feeding call” or “pitch-up” sound just before the final lunge. This sound may serve as a coordinated signal for the group to attack simultaneously, but it may also contribute to the prey’s confusion. Once the fish are densely packed near the surface within the bubble cylinder, all participating whales simultaneously swim upward. They lunge through the concentrated prey with their mouths wide open, engulfing the entire bait ball and the surrounding water, which is then filtered out through their baleen plates before the meal is swallowed.
Species That Utilize This Strategy
The most frequent practitioners of bubble-net feeding are humpback whales (Megaptera novaeangliae). Humpbacks are known for their behavioral flexibility and high social intelligence, which are necessary for mastering this complex hunting method. The technique is not universal among all humpback populations, suggesting it is a culturally transmitted and learned tradition. While humpbacks are the primary species observed using this method, Bryde’s whales have also been documented engaging in a similar feeding behavior.
The social structure of humpbacks allows for significant variation in how the bubble net is deployed. While some individuals are capable of performing the entire maneuver alone, the most effective examples involve highly coordinated group feeding. These coordinated efforts can involve anywhere from two to over twenty individuals, with each whale potentially taking on a specialized role, such as the designated bubble blower or the caller. The cooperative nature of the feeding suggests that working together reduces the effort required for each individual whale to secure a meal.
Bubble-net feeding is most commonly observed in the summer feeding grounds where prey is abundant, such as the cooler waters off Southeast Alaska and the Antarctic Peninsula. For instance, in areas around Juneau, Alaska, the feeding activity is a regular seasonal event as the whales attempt to build up fat reserves for their annual migrations. Regional variations in technique, such as the “lobtail feeding” observed in New England, further illustrate the social learning and adaptation inherent in this sophisticated hunting.