Blue whale

The blue whale, Balaenoptera musculus (with 'musculus' meaning either, Very strong, or Little mouse), also known as the sulphur-bottomed whale (from its yellow underside - the color coming from a coating of diatoms) or Sibbald's rorqual (after the Scottish natural historian Robert Sibbald) is, at up to 110 feet in length and sometimes nearly 200 tons in weight, the largest animal known to have ever lived.

The blue whale feeds upon plankton, particularly the euphausiid crustacean Euphausia superba, otherwise known as krill. The krill itself feeds upon microscopic phytoplankton. This relationship represents the shortest complete food chain in nature.

Blue whales were once far more numerous, but whaling has reduced the world population to about 5,000 individuals.