Blue Whales: The Giants That Shape Our Oceans

The largest animal known to have lived feeds on some of the smallest — and helps fertilize the sea it lives in.

By Biosphere Editorial Team · 2026-09-26

The blue whale, Balaenoptera musculus, is the largest animal known to have ever lived — larger than any dinosaur discovered so far. It lives in every ocean except the Arctic, yet for most people it remains almost impossible to imagine.

A giant built on krill

Blue whales feed almost entirely on krill, small shrimp-like crustaceans. In a single lunge a whale engulfs an enormous volume of water, then pushes it out through the baleen plates that hang from its upper jaw, keeping the krill inside. During the feeding season an adult can eat several tonnes of krill a day.

More than a big animal

Whales often feed at depth and release nutrient-rich faecal plumes near the surface. Those plumes carry nitrogen and iron back to sunlit water, where they feed phytoplankton — the microscopic algae at the base of the ocean food web. Researchers call this the “whale pump”.

The largest animals in the ocean help feed some of the smallest.

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A voice that crosses ocean basins

Blue whale calls are among the loudest sounds made by any animal. They are very low in frequency — mostly below what humans can hear — and low frequencies travel long distances underwater, potentially hundreds of kilometres.

From whaling to recovery

Industrial whaling in the 20th century killed hundreds of thousands of blue whales, most of them in the Southern Ocean. The species has been protected from commercial whaling since 1966, and some populations are slowly increasing, but it is still listed as Endangered on the IUCN Red List.

• Collisions with ships
• Entanglement in fishing gear
• Ocean noise that masks their calls
• Climate change affecting krill

Blue Whale