Although blue whales should be capable of roaming the oceans freely, they are tied to certain areas. This is because there are only a few places in the world, mainly the Arctic and Antarctic oceans, where there is enough plankton to sustain them. Icy water has more oxygen and carbon dioxide than warm water which makes it rich in marine life. There is up to twenty times more plankton in the Arctic and Antarctic than in the clear blue, warmer waters of the tropics. When the polar oceans freeze up during the winter, the whales migrate to the tropics where they live mainly off their thick layer of blubber.
Prey is mainly caught by diving, up to depths of 500m. The whale can stay submerged for up to two hours, then it rushes up at the clouds of plankton with open mouth. The blue whale does not have teeth; instead it has a row of plates in its mouth, known as baleen, measuring 100 cm long by 55 cm wide. There is a ‘moustache’ of long bristles on the end of each plate to hold the tiny prey; after forcing the water out of its mouth, the whale licks the krill off with its fleshy tongue. Up to 5 tonnes of water and krill (a type of plankton) can enter this sieve with each mouthful. An adult blue water will consume about 2,032 kg (2 tonnes) of krill each day during the summer months when it is roaming the polar waters.Read More: Breeding