Creatures Great and Small

When we think of large animals, elephants come to mind. Considerably larger, however, are the whales. The orca, for example, weighs some 8 tons, and a blue whale might tip the scales at 120 tons.

A huge supply of food is needed daily for the survival of these monsters, but they feed in quite different ways. The orca (also called the "killer" whale) is a fierce predator on seals and penguins, while the blue whale is a plankton-feeder. It strains ocean water through its mouth to catch small plants and animals, especially the shrimp-like animals called krill.  A single whale might consume some 4 tons of krill (40 million animals) each day!

That the larger predator eats such tiny prey may seem to be a paradox. After examining the food pyramid, however, we can readily understand why the blue whale feeds on plankton.