Blue Whale (Balaenoptera musculus)

Marine MammalBaleen WhaleLargest Animal

Overview

The blue whale (Balaenoptera musculus) is the largest animal known to have existed — larger than any dinosaur described from the fossil record. It is a baleen whale of the rorqual family, slender in build, mottled blue-grey, with a small dorsal fin set far back along the body.

Blue whales feed almost entirely on krill, small shrimp-like crustaceans, which they take by lunge feeding: accelerating into a swarm with the mouth open, engulfing an enormous volume of water, then forcing it out through baleen plates and swallowing what remains.

Conservation note: blue whales were reduced drastically by twentieth-century industrial whaling and remain far below historic numbers. Recovery is uneven between populations. Verify current status at the IUCN Red List and NOAA Fisheries.

Habitat & Range

Blue whales occur in all major oceans, generally in deep offshore water, and different populations follow different patterns — many move between higher-latitude feeding areas and lower-latitude breeding areas, though not all migrate in a simple way. Feeding is concentrated where oceanographic conditions concentrate krill, such as upwellings and shelf edges.

Diet

Krill, overwhelmingly. A blue whale's pleated throat expands enormously during a feeding lunge, allowing it to take in a volume of water greater than its own body, which is then filtered through baleen. Feeding is highly seasonal and concentrated in productive waters, with the animal building reserves that carry it through less productive periods.

Behavior

Blue whales are usually seen alone or in small groups, though many may gather where food is abundant. They produce extremely loud, very low-frequency calls that travel long distances underwater and are among the loudest sounds made by any animal; these are thought to function in communication over great range. The blow is tall and columnar, and the animal typically shows its small dorsal fin long after the blow.

Human Interaction & Conservation

Blue whales were a principal target of industrial whaling once explosive harpoons and factory ships made them catchable, and populations collapsed before protection came into force. Present-day risks include ship strikes, entanglement in fishing gear, underwater noise, and changes in krill distribution driven by ocean conditions. Verify current status and population trends at the IUCN Red List and NOAA Fisheries.