The biggest animal in the world
Long and slender, the blue whale's body can be various shades of bluish-grey dorsally and somewhat lighter underneath. There are at least three distinct subspecies: B. m. musculus of the North Atlantic and North Pacific, B. m. intermedia of the Southern Oceanand B. m. brevicauda (also known as the pygmy blue whale) found in the Indian Oceanand South Pacific Ocean. B. m. indica, found in the Indian Ocean, may be another subspecies. As with other baleen whales, its diet consists almost exclusively of smallcrustaceans known as krill.
Blue whales feed almost exclusively on krill, though they also take small numbers of copepods.An adult blue whale can eat up to 40 million krill in a day. The whales always feed in the areas with the highest concentration of krill, sometimes eating up to 3,600 kilograms (7,900 lb) of krill in a single day. The daily energy requirement of an adult blue whale is in the region of 1.5 million kilocalories.
The blue whale is the largest animal ever known to have lived.By comparison, one of the largest known dinosaurs of the Mesozoic Era was Argentinosaurus,which is estimated to have weighed up to 90 tonnes (99 short tons), comparable to the average of blue whale.Amphicoelias fragillimus, at an estimated 122.4 tonnes (134.9 short tons) is still lighter than the largest blue whales, despite being 190 feet (58 m) in length.
Their life history
Mating starts in late autumn and continues to the end of winter.Little is known about mating behaviour or breeding grounds. Females typically give birth once every two to three years at the start of the winter after agestation period of 10 to 12 months.The calf weighs about 2.5 tonnes (2.8 short tons) and is around 7 metres (23 ft) in length. Blue whale calves drink 380–570 litres (100–150 U.S. gallons) of milk a day. Blue whale milk has an energy content of about 18,300 kJ/kg (4,370 kcal/kg). The calf is weaned after six months, by which time it has doubled in length. Sexual maturity is typically reached at five to ten years of age.