How did the blue whale get so big?
The blue whale is the largest animal ever, yet baleen whales only became giants in the last few million years.
โถ Start the storyThe blue whale got so big by eating one of the most abundant foods in the sea, , in giant mouthfuls, and by growing from a calf at an astonishing speed. But the surprising part is when it happened: a 2017 analysis of fossils and living species found that baleen whales only became giants within the last 3 million years, long after they had invented filter feeding.
Size is not a long, steady climb. Before 4.5 million years ago few baleen whales were longer than 10 m, and the two largest species of the were under 13 m. Then, geologically very recently, several lines of baleen whales grew huge. The blue whale reaches about 30 m and up to roughly 190 to 200 tonnes, which makes it the largest animal known to have existed.
~30 m
What changed? The likely answer is climate and food. Climate change made collect in rich patches that shifted with the seasons, and a whale that could travel far and swallow a big baitball in one go could make the long trips pay. Filter feeding alone was not the cause, because baleen and filter feeding long preceded gigantic size.
The blue whale's feeding trick is the lunge: it expands its jaw to take in a volume bigger than the whale itself, then sieves the from the water. A newborn calf, fed on rich milk, gains about 90 kg a day.
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Recap
The blue whale is a recent giant, probably the product of a changing ocean that bunched up its krill.
๐ก A trick to remember it ยท Big mouth, tiny meals: the blue whale is a krill vacuum whose giant size appeared only yesterday, in geological time.
Surprising fact ยท Few baleen whales exceeded 10 m before 4.5 million years ago.
Sources (3)
No source, no claim. Every fact in this lesson (15 claims) cites at least one of these.