Even their inner organs are weighty. The heart of a blue whale can weigh up to 1,300 pounds, while its tongue can weigh 5,400 pounds, which is the average weight of an adult female elephant.

The blue whale is a filter-feeder. Its throat has an expandable, pleated structure to engulf a volume of water and prey that is greater than the animal's own body weight. The water it takes in at the ...