How many calories does a whale need? Well, it takes in a half-million with every "bite."
The largest creature ever to live, the blue whale, strains tons of crustaceans called krill from the sea in every mouthful. In each of those mouthfuls is an average of 457,000 calories. One scientist, Robert Shadwick, says they are the most efficient feeders in the animal kingdom: "When they take a gulp of water, they are filling their mouths with the amount of water equal to their own body mass, so there is nothing that comes close to doing that." This sustains an animal that may weigh over 150 tons, with a heart the size of a small car and arteries a child could crawl through. When whalers were allowed to kill blues, the first step on killing a whale was to slice it open so seawater could sluice through to cool the insides: otherwise, the latent heat of all those tons of muscle would cook the animal.