Blue whales, the largest animals on Earth, require substantial energy to sustain their bodies. Their dietary habits are uniquely adapted to meet these considerable energetic demands, primarily focusing on highly abundant, small marine organisms.
The Dominance of Krill
Krill forms the overwhelming majority of a blue whale’s diet. These small, shrimp-like crustaceans are incredibly abundant in the polar and temperate waters where blue whales feed. Krill’s high caloric density makes it an efficient food source for an animal requiring massive energy.
A single blue whale can consume a tremendous volume of krill daily during peak feeding seasons. Estimates suggest an average-sized blue whale can eat around 4 tons of krill per day, with some studies indicating up to 16 tons daily. This consumption rate is essential for building fat reserves, utilized during migration and breeding when food is scarce.
Beyond Krill: Other Dietary Components
While krill constitutes the vast majority of a blue whale’s food intake, they consume other organisms, especially when krill populations are less dense or in certain areas. Other types of zooplankton, such as copepods, supplement their diet. These tiny crustaceans are often incidentally ingested along with krill due to filter feeding.
Regional variations in diet exist; for instance, the Northern Indian Ocean subspecies of blue whale feeds predominantly on sergestid shrimp. Occasionally, small fish or other small invertebrates might be consumed, though this is not typical. The blue whale’s feeding mechanism is specialized for filtering small, abundant invertebrates, making larger prey less suitable.
Feeding Behavior and Consumption
Blue whales are baleen whales, possessing baleen plates instead of teeth, central to their filter-feeding strategy. These plates, made of keratin (the same protein found in human hair and nails), hang from their upper jaw and act like a sieve. The whale feeds by lunge feeding, accelerating and opening its mouth to engulf a large volume of water and prey.
During a lunge, the blue whale’s pleated throat expands like an accordion, allowing it to take in a volume of water and prey that can exceed its own body weight. The whale then uses its tongue to push water out through the baleen plates, trapping small organisms inside. This energetically demanding process is efficient, enabling the blue whale to capture dense patches of food to sustain its enormous size.