The blue whale which have the botanical name "Balaenoptera musculus" is a marine mammal belonging to the baleen whale suborder Mysticeti. It's also called sulfur-bottom whale, the most massive animal ever to have lived, a species of baleen whale that weighs approximately 150 tons and may attain a length of more than 30 metres (98 feet).
A blue whale's age is most reliably measured using ear plugs. Blue whales secrete earwax (cerumen) throughout their lives, forming long, multilayered plugs. Each deposited light and dark layer (lamina) indicates a switch between fasting during migration and feeding. As one set is laid down per year, the number of layers is an indicator of age. The maximum age of a pygmy blue whale determined this way is 73 years. Before the ear plug aging method, layers in baleen plates were used, however, these wear down and are not as reliable. The blue whale's ovaries form a permanent record of the number of ovulations (or perhaps pregnancies), in the form of corpora albicantia—fibrous masses that are permanent scars and were once used as an indication of age. In a female pygmy blue whale, one corpus albicans is formed on average every 2.6 years.
The blue whale's diet consists almost exclusively of euphausiids (krill). Blue whales feed on krill at the surface and depths greater than 100 meters (328 ft.), following their prey's diel (24 hour) vertical migration through the water column.
Blue whales capture krill through lunge feeding, a bulk filter-feeding strategy that involves accelerating toward a prey patch at high speeds. A single adult blue whale may consume as much as eight tons of krill per day.
In the winter blue whales move toward the Equator to breed. After a gestation of about 12 months, one calf about 8 meters (about 26 feet) long is born in temperate waters. While nursing, calves gain up to 90 kg (about 198 pounds) per day on the rich milk of their mothers. Young are weaned after seven to eight months, when they have reached a length of about 15 meters (about 49 feet).
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