The blue whale (Balaenoptera musculus) is the largest animal to have ever lived on Earth, reaching lengths of up to 98 feet and weighing as much as 190 tons. Despite its immense stature, the blue whale sustains itself by feeding almost exclusively on the ocean’s smallest organisms. This specialized feeding strategy requires a unique hunting technique and massive amounts of food to fuel its enormous body.
The Primary Food Source
The diet of the blue whale is nearly monospecific, consisting overwhelmingly of krill, a tiny, shrimp-like crustacean. Krill form dense swarms in cold, nutrient-rich waters. The specific species consumed depends on the whale’s location; for instance, Southern Ocean whales target Antarctic krill (Euphausia superba), and North Pacific populations target Euphausia pacifica. Blue whales may occasionally consume other small crustaceans, such as copepods, if they are incidentally caught. Foraging is only worthwhile when the concentration of krill is extremely high, which dictates where and when the whales feed.
Lunge Feeding Mechanics
The method blue whales use to capture prey is known as lunge feeding, a high-speed engulfment technique unique to rorqual whales. The process begins with the whale accelerating rapidly toward a dense patch of krill, opening its massive mouth just before impact. This rapid movement forces water and prey into the oral cavity. The lower jaw dislocates, allowing the mouth to gape open nearly 90 degrees. This expansion is facilitated by the ventral groove blubber, a series of pleats that stretch enormously, allowing the buccal cavity to engulf a volume of water that can exceed the whale’s body weight.
Once the water and krill have been engulfed, the whale slows down abruptly and its mouth closes. The next phase is filtration, where the whale’s massive tongue pushes the water out through thousands of baleen plates that hang from the upper jaw. These plates, made of keratin, act as a fine-toothed sieve, trapping the krill inside while the water is expelled. The captured krill is then swallowed, completing one feeding lunge.
Daily Consumption and Energy Requirements
The blue whale’s enormous size necessitates a staggering amount of food to meet its metabolic demands. During peak feeding season, a single whale can consume between 4 and 16 tons of krill per day, translating to an intake of up to 40 million individual krill. A lunge is only profitable if the targeted krill density is above a minimum threshold, often estimated at over 100 krill per cubic meter of water. The feeding strategy is highly seasonal, concentrating efforts during the summer months in productive polar waters, where a whale may ingest up to 83% of its annual caloric needs over just 90 to 120 days. The excess energy is stored as blubber, which sustains the whale through long migrations to warmer breeding grounds where little feeding occurs.