Which is the largest animal that has ever lived?

A blue whale reaches about thirty metres and something like 150 tonnes, which makes it larger than any dinosaur we have ever dug up - the biggest sauropods are estimated at perhaps 70 tonnes, and estimating them is largely guesswork from a few bones. Water is what makes it possible. On land a body that size would be crushed by its own weight; floating, it is not.

The numbers stop being comprehensible quite quickly. The heart weighs about as much as a small car. The tongue weighs about as much as an elephant. A calf drinks enough milk to put on ninety kilograms a day, which is a newborn gaining the weight of an adult human every twenty-four hours.

It eats almost the smallest thing in the ocean. Blue whales live on krill, shrimp a few centimetres long, taken by lunging into a swarm with the mouth open and straining perhaps four tonnes a day through plates of baleen. Twentieth-century whaling killed around 380,000 of them in the Southern Ocean alone and left a few hundred alive. They are still here, and slowly increasing, which is closer to a good outcome than the century deserved.