Far bigger than any dinosaur, the blue whale is the largest known animal to have ever lived.
An adult blue whale can grow to a massive 30m long and weigh more than 180,000kg - that’s about the same as 40 elephants, 30 Tyrannosaurus Rex or 2,670 average-sized men. But this giant among giants started as something far smaller.
Like all whales, the blue whale (Balaenoptera musculus) evolved from a four-legged mammal that lived on land some 48 million years ago. This ancient ancestor, Pakicetus, was only 1.8m long. It foraged in streams and some of its descendants became adapted to living in water. This eventually led to a completely aquatic creature called Dorudon ("Spear-Tooth"), which lived 37 million years ago and grew 4.5m long.
Blue whales reach these mind-boggling dimensions on a diet composed nearly exclusively of tiny shrimplike animals called krill. During certain times of the year, a single adult blue whale consumes about 4 tons of krill a day.
Blue whales are baleen whales, which means they have fringed plates of fingernail-like material, called baleen, attached to their upper jaws. The giant animals feed by first gulping an enormous mouthful of water, expanding the pleated skin on their throat and belly to take it in. Then the whale's massive tongue forces the water out through the thin, overlapping baleen plates. Thousands of krill are left behind—and then swallowed.
Calves enter the world already ranking among the planet's largest creatures. After about a year inside its mother's womb, a baby blue whale emerges weighing up to 3 tons and stretching to 25 feet. It gorges on nothing but mother's milk and gains about 200 pounds every day for its first year.
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