The Blue Whale Is the Largest Animal That Has Ever Lived

The largest animal alive today is remarkable. The largest animal that has ever lived on Earth — larger than any dinosaur, larger than any creature that has ever walked, swum, or flown — is the blue whale. And somewhere in the world's oceans right now, one of them is breathing.

A fully grown blue whale can reach 30 metres in length — roughly the size of three double-decker buses lined up end to end. It can weigh up to 200 tonnes, making it heavier than 30 African elephants combined. Its heart alone weighs around 180 kilograms and is approximately the size of a small car. The blood vessels running through its body are wide enough for a human to crawl through.

Its tongue weighs as much as an entire elephant. When it opens its mouth to feed, the volume of water it can take in at once rivals that of a small swimming pool. Everything about the blue whale operates at a scale that strains the imagination.

Despite its extraordinary size, the blue whale feeds almost exclusively on krill — tiny shrimp-like crustaceans that are rarely more than a few centimetres long. A blue whale feeds by lunging forward with its mouth open, engulfing enormous volumes of water packed with dense clouds of krill. It then pushes the water back out through baleen plates — long, comb-like structures that hang from its upper jaw and act as a filter, trapping the krill inside.

During feeding season, a blue whale may consume up to four tonnes of krill in a single day. This enormous intake is necessary to fuel a body of this size and to build up the fat reserves needed to survive long migrations and the fasting periods that follow.

Blue whales were once found across every ocean on Earth. Then commercial whaling began in earnest. In the twentieth century alone, more than 360,000 blue whales were killed. By the time international hunting was banned in 1966, the global population had collapsed to perhaps just a few hundred individuals — down from an estimated 350,000 before industrial whaling began.

Since the ban, populations have slowly recovered. Today, the global population is estimated at between 10,000 and 25,000. That may sound significant, but it represents only a small fraction of the pre-whaling population. Blue whales remain classified as endangered, and new threats — ship strikes, noise pollution, and climate change affecting krill populations — continue to slow the recovery.

Blue whales communicate through deep, low-frequency calls that can travel thousands of kilometres through the ocean. Their vocalisations are among the loudest sounds produced by any animal, reaching up to 188 decibels — louder than a jet engine. These calls are too low in frequency for humans to hear without specialised equipment, but they allow blue whales to stay in contact with one another across the vast distances of the open ocean.

Exactly what the whales are communicating remains only partially understood. But the fact that their calls carry across thousands of kilometres tells us something important: even in an ocean this vast, these extraordinary creatures are still reaching out to one another — and we are only just beginning to listen.