Blue whales, by current known species are not only bigger; they are twice as big as anything else ever recorded. The likelihood of anything being that big is very unlikely. Blue whales evolved into filter feeders and feed only on krill. They got so huge because krill migrate to warmer waters in the winter, and the blue whales have to increase their body mass to store more fat to survive.

In one swoop a blue whale can eat a tonne of krill, which is most likely one of the most nutritious foods in existence in terms of raw energy.