Diet & Food

Baleen whales are the ocean's most impressive filter feeders, using specialized mouth structures to strain enormous quantities of small prey from seawater. The key to this feeding strategy is baleen, a series of flexible plates that hang from the upper jaw like a curtain. Each plate is fringed with bristles that trap prey while allowing water to flow through. Different species have evolved distinct baleen configurations suited to their preferred prey and feeding methods. Blue whales and fin whales are lunge feeders, a high-energy strategy in which the whale accelerates toward a dense patch of prey, opens its massive jaws, and engulfs a volume of water and krill that can exceed the whale's own body weight. The ventral grooves on a rorqual whale's throat expand like an accordion to accommodate this enormous intake. The whale then closes its mouth and uses its tongue to push the water out through the baleen plates, trapping the krill inside. A single lunge by a blue whale can capture up to 500 kilograms of krill and requires an enormous expenditure of energy, making it profitable only when prey is densely concentrated. Right whales and bowhead whales use a different technique called skim feeding. Instead of lunging, they swim slowly through patches of prey with their mouths open, continuously filtering water through their exceptionally long and fine baleen plates. Bowhead whales have the longest baleen of any species, with plates reaching up to 14 feet in length. This skim-feeding approach is lower in energy cost than lunge feeding but requires the whale to find sustained concentrations of small prey like copepods. Gray whales have a unique feeding method among baleen whales: they are bottom feeders. Gray whales roll on their sides on the seafloor and suck up mouthfuls of sediment, filtering out amphipods, worms, and other small invertebrates through their short, coarse baleen plates. This behavior leaves distinctive feeding pits on the ocean floor that can be observed by divers and scientists. Gray whales feed primarily in the shallow waters of the Bering and Chukchi Seas during summer, building up fat reserves for their long migration to breeding lagoons in Baja California. Humpback whales are versatile feeders that employ multiple techniques depending on prey type and conditions. They lunge feed on krill and schooling fish, but they are best known for bubble net feeding, one of the most sophisticated cooperative hunting strategies observed in any marine mammal.

Bubble net feeding is one of the most spectacular and complex feeding behaviors observed in whales. This cooperative hunting technique is primarily associated with humpback whales, though some other species have been observed using similar strategies. In bubble net feeding, a group of humpbacks works together to corral and concentrate prey, dramatically increasing the efficiency of each feeding lunge. The process begins when one or more whales dive below a school of fish or a swarm of krill and begin swimming in an upward spiral while releasing a steady stream of bubbles from their blowholes. These bubbles rise to form a cylindrical curtain, or net, that surrounds the prey. The fish or krill instinctively avoid crossing the wall of bubbles, becoming trapped in an ever-tightening column. Meanwhile, another whale may produce loud feeding calls that further frighten the prey and drive them toward the surface. Once the prey is sufficiently concentrated, the whales lunge upward through the center of the bubble net with their mouths wide open, engulfing huge quantities of fish in a single coordinated effort. Bubble net feeding involves distinct roles within the group. Some whales specialize as bubble blowers, creating the net, while others serve as callers, producing the vocalizations that herd prey. The coordination required suggests a high level of social intelligence and learned behavior. Research has shown that bubble net feeding is not instinctive but is culturally transmitted, with whales learning the technique from other group members. Some humpback populations use bubble nets extensively while others in different regions have never been observed doing so. Killer whales display an equally impressive array of cooperative hunting strategies, though their approach is predatory rather than filter-based. Different killer whale populations have developed specialized hunting techniques suited to their preferred prey. In Norway, killer whales use carousel feeding to hunt herring: the pod works together to herd a school of fish into a tight ball near the surface, then individual whales stun the fish with powerful tail slaps before feeding on them. In the Antarctic, killer whales hunt seals resting on ice floes using a technique called wave washing. Multiple orcas swim in formation toward the ice floe, creating a coordinated wave that washes the seal off the ice and into the water. Patagonian killer whales have learned to intentionally strand themselves on beaches to capture sea lion pups, one of the most daring hunting strategies in the animal kingdom. These diverse techniques illustrate how whale feeding strategies are shaped not only by anatomy but also by cultural learning and ecological circumstances. Sperm whales hunt alone during their deep dives, but they coordinate at the surface level, with pod members taking turns watching over calves while others descend to hunt. This cooperative childcare allows individual whales to make longer, deeper foraging dives, ultimately increasing the group's overall food intake.

Toothed whales are active hunters that pursue individual prey items rather than filtering small organisms from the water. Their diets are as diverse as the species themselves, ranging from tiny fish to giant squid to great white sharks, and their hunting strategies reflect the remarkable intelligence and adaptability of these marine predators. Sperm whales are the supreme deep-sea hunters among cetaceans. They feed primarily on squid, including the legendary giant squid and colossal squid that inhabit the deep ocean. Sperm whales make extraordinary dives to depths of 1,000 to 2,000 meters (3,300 to 6,600 feet), and occasionally deeper, hunting in complete darkness using their powerful echolocation clicks. A single sperm whale may consume approximately 900 kilograms (2,000 pounds) of squid per day. The sucker scars found on the skin of many sperm whales are evidence of violent encounters with large squid in the deep ocean. Killer whales have the most varied diet of any whale species, and different populations specialize on dramatically different prey. In the Pacific Northwest, resident killer whale populations feed almost exclusively on salmon, particularly Chinook salmon, and use echolocation extensively to locate their prey. Transient (Bigg's) killer whales in the same waters are marine mammal specialists, hunting harbor seals, sea lions, porpoises, and even other whale species. Some Antarctic killer whale populations specialize in hunting Weddell seals, minke whales, or penguins. This dietary specialization is culturally inherited, with calves learning their population's hunting techniques and prey preferences from their mothers. Beluga whales eat a diverse diet of fish, squid, shrimp, crabs, clams, and worms. Their flexible necks, unusual among cetaceans, allow them to orient their bodies to suction feed along the bottom, and their diverse tooth structure enables them to handle a wide variety of prey types. Belugas in different habitats adjust their diets seasonally, feeding heavily on spawning fish like salmon, eulachon, and smelt when these prey are abundant in river mouths and estuaries. Narwhals feed in the deep Arctic waters beneath sea ice, preying on Greenland halibut, Arctic cod, squid, and shrimp. Despite having only two teeth (one of which, in males, develops into the famous tusk), narwhals are efficient predators that use suction feeding to capture prey. Studies using stomach content analysis and dive data from satellite tags have revealed that narwhals feed intensively during winter months beneath the pack ice, a period when they were previously thought to fast. Pilot whales are primarily squid specialists that make deep dives, though not as extreme as sperm whales, to capture their prey. Both long-finned and short-finned pilot whales feed heavily on squid species, supplemented by various fish. Their strong social bonds and pod-based behavior may facilitate cooperative foraging, with pod members sharing information about prey locations through vocalizations.

The daily food intake of whales varies enormously by species, body size, and time of year. Many whale species follow a feast-or-famine pattern, feeding intensively during summer months in productive polar waters and then fasting or eating very little during winter migration and breeding periods. This seasonal cycle of gorging and fasting is one of the defining features of whale ecology. Blue whales, the largest animals ever to have lived, can consume up to 6 tons (12,000 pounds) of krill per day during peak feeding season in Antarctic or North Pacific waters. This staggering intake is necessary to build the thick layer of blubber that sustains the whale during the months-long fasting period of migration and breeding. During the feeding season, a blue whale may increase its body weight by 50 percent or more, storing energy as blubber that can be up to 12 inches thick. Humpback whales consume roughly 1 to 1.5 tons of food per day during the feeding season, dining on krill, herring, sand lance, and other small schooling fish. Like blue whales, humpbacks fast for much of their migration and breeding season, surviving on stored fat for several months. A nursing humpback mother may lose one-third of her body weight during the breeding season as she converts her blubber reserves into milk for her calf while eating little or nothing herself. Gray whales feed primarily during a five-month summer season in Arctic waters, consuming an estimated 1,200 kilograms (2,600 pounds) of amphipods and other bottom-dwelling invertebrates daily. They must consume enough during this relatively short window to sustain them through a 10,000 to 12,000 mile round-trip migration, one of the longest of any mammal, during which they eat very little. Sperm whales eat roughly 900 kilograms (2,000 pounds) of squid and fish daily. Unlike baleen whales, sperm whales do not follow the same extreme feast-and-fast cycle, as they continue to feed throughout the year. However, their breeding and social activities do influence feeding patterns, with males in particular reducing their food intake during the breeding season. Killer whales eat 100 to 250 kilograms (220 to 550 pounds) of food per day, depending on their size and activity level. The caloric requirements of different killer whale populations vary significantly based on their prey type: fish-eating populations must consume large numbers of salmon to meet their energy needs, while mammal-hunting populations obtain more calories per prey item but expend more energy in hunting. The enormous food requirements of whale populations have significant ecological implications. Scientists estimate that before commercial whaling reduced their numbers, the great whales of the Southern Ocean consumed over 400 million tons of krill annually, roughly twice the current total krill biomass. Ironically, the recovery of whale populations following conservation efforts may actually help krill populations by recycling iron and other nutrients through whale fecal plumes, stimulating the phytoplankton growth that krill depend on.

Whales play a far more important role in ocean ecosystems than scientists previously realized. Rather than simply consuming prey, whales actively shape the productivity and health of the marine environments they inhabit through a phenomenon scientists call the whale pump. This nutrient cycling process has profound implications for ocean food webs and even global climate. When whales feed at depth and then return to the surface to breathe and rest, they release nutrient-rich fecal plumes in the upper ocean layers where sunlight penetrates. These fecal plumes are particularly rich in iron and nitrogen, nutrients that are often in limited supply in surface waters and that are essential for phytoplankton growth. Phytoplankton are the microscopic plants at the base of the marine food web, and they are also responsible for producing roughly half of the oxygen in Earth's atmosphere and absorbing billions of tons of carbon dioxide. By fertilizing phytoplankton, whales effectively boost the productivity of the entire ocean ecosystem. Research published in the journal Nature has estimated that the great whales of the Southern Ocean historically recycled approximately 12,000 tons of iron per year through their fecal plumes. This whale-mediated iron fertilization likely supported significantly larger krill populations than exist today, creating a positive feedback loop: more whales meant more nutrient recycling, which supported more phytoplankton, which fed more krill, which in turn supported more whales. The dramatic reduction in whale populations due to commercial whaling may have disrupted this cycle, contributing to declines in overall ocean productivity. Whales also transport nutrients horizontally across ocean basins through their long migrations. Humpback whales, blue whales, and gray whales feed in nutrient-rich polar waters and migrate to nutrient-poor tropical waters for breeding, releasing nutrients in areas where they are scarce. This biological transport of nutrients, sometimes called the great whale conveyor belt, enhances productivity in tropical and subtropical ecosystems that might otherwise be nutrient deserts. When whales die, their carcasses sink to the ocean floor and create unique deep-sea ecosystems known as whale falls. A single whale carcass can sustain a complex community of scavengers, bacteria, and specialized organisms for decades, providing a massive input of organic carbon and nutrients to the deep ocean. Over 400 species have been identified on whale fall communities, including many species found nowhere else. These whale falls serve as stepping stones for deep-sea species, connecting isolated populations across the vast expanses of the ocean floor. Understanding the ecological role of whale feeding is increasingly important for conservation policy. Protecting whale populations is not just about saving individual species but about maintaining the health and productivity of entire ocean ecosystems. As whale populations recover from centuries of exploitation, scientists are documenting measurable increases in ocean productivity in areas where whales have returned, providing compelling evidence that healthy whale populations benefit the entire marine environment.