Why do blue whales need to be so big when they only eat plankton?
• Blue whales need to be so big precisely because they eat tiny food, specifically krill, that feed on plankton.
Krill defend themselves against smaller predators by forming very dense shoals that confuse attackers. Blue whales get around this by swimming very fast at the shoal with their mouth wide open, often from below, and engulfing as much as they can. Their pleated throat can expand enormously to take in as much of a shoal as possible. The whales then strain out the krill by…
