The blue whale is the largest animal ever to have existed on earth — longer than a basketball court and heavier than the largest known dinosaur. Adults reach up to 33 metres in length and weigh up to 200 tonnes. Its tongue alone can weigh as much as an elephant. Its heart is the size of a Volkswagen Beetle. Despite this immense size, it feeds almost entirely on krill — tiny shrimp-like crustaceans — consuming up to 4 tonnes per day during feeding season.
Blue whales were hunted to the brink of extinction in the 20th century — reduced from an estimated 200,000-300,000 individuals to perhaps 5,000 by the time of the 1966 International Whaling Commission ban. They have been protected globally since 1966 and have recovered to perhaps 10,000-25,000 individuals today — still a small fraction of historical numbers.
The species is divided into distinct populations across the world's oceans, each with its own migration patterns between productive cold-water feeding grounds and warmer breeding grounds. The Antarctic blue whale population — the largest subspecies — is recovering from perhaps just 0.1% of its original abundance, a stark reminder of the scale of industrial whaling's impact.
Blue whales communicate using extremely low-frequency sounds that can travel thousands of kilometres through ocean water — the loudest sounds made by any animal on earth. Scientists are still working to understand the function and meaning of these sounds in blue whale social communication.