Baleen whales, such as blue whales, dive in search of krill swarms. When they find them, they open their great jaws, allowing their pleated throats to fill up like sails.
A blue whale’s throat extends from its chin to its navel, and is made of a stretchy tissue that can expand to four times its original width. Incredibly, they can fill their throats with a volume of water greater than the volume of their entire body. Once its mouth is full of water and krill, a baleen whale will force the water our through the sieve-like baleen that it has in place of teeth, pushing the water out and leaving tens or hundreds of kilograms of krill behind in its mouth.
Baleen is the comb-like material found hanging from the upper jaws of krill-eating whales. Baleen is made from keratin, the same protein that makes up your hair and fingernails. Sometimes called "whalebone", baleen was once used as a strong, flexible material in applications like umbrellas and corsets.
Krill are small, free-swimming, shrimp-like crustaceans. Most krill are between 1 and 2 centimetres long. Krill consume plankton and form the basis of the marine food chain for a diverse group of larger organisms.
Blue whales are found in both the northern and southern oceans. To find all the krill they need to eat, blue whales need to travel far in the nutrient-rich temperate oceans. This can make them very widely distrubuted and diffucult to estimate total population numbers and changes in population.
