Blue whales are also probably the biggest creatures that have ever lived. It has a blue-grey body, with spots along its back and a pale pleated throat. The blue whale may weigh more than 161 US t (146 te). Its body is streamlined and, despite its enormous bulk, it is graceful in the water. It has 64 to 94 grooves on its throat. These gigantic whales feed entirely on small planktonic crustaceans and, unlike many baleen whales, are highly selective, taking only a few species. Blue whales feed during the summer months, which they spend in nutrient-rich polar waters. These cetaceans have huge appetites. An individual may consume as much as 3.6 tonnes (4 tons) of krill daily, representing some 40 million of these tiny shrimp-like creatures. Their pleated throats distend to four times their normal size as the whales take in mouthfuls of krill-laden water.
Blue whales live in small groups, comprising two or three individuals, and swim at speeds of about 19 kph (12 mph), although they can travel up to 48 kph (30 mph). The populations of the northern and southern hemispheres never meet. In autumn, when ice starts to cover their feeding grounds, the blue whales migrate toward the Equator but eat virtually nothing while in the warmer water. They mate during this period and, after a gestation of 11 or 12 months, the calves are born in warm waters the following year. Whaling nearly led to the extinction of these giants, and although they have been protected since 1966, their population is still relatively small, and it is in danger of extinction.
Distribution: Ranges widely through the world’s oceans, but has distinct populations in the North Atlantic, in the North Pacific and in the vicinity of Antarctica.
Habitat: Open ocean.
Weight: Up to 133.3 tonnes (147 tons); females are much heavier.
Length: At least 30 m (100 ft).
Maturity: 6 - 10 years.
Gestation Period: About 365 days; females give birth once every 3 - 5 years.
Breeding: 1; weaning occurs at 8 - 12 months.
Diet: Use their baleen plates to filter zooplankton; krill forms the major part of their food intake.
Lifespan: Up to 110 years.
Flat, broad and thick, the tail moves up and down as the whale swims.
Greyish-blue on the upperparts, with paler spots.
This is yellowish, because of marine algae growing on the skin here.
The mouth of blue whale is huge and cavernous, with the baleen plates evident in the upper jaws.
These act as sieves, retaining the krill in the mouth while the water is expelled as the whale closes its jaws.