Thursday, December 16, 2010
December 16, 2010 : Blue Whale
The Blue whale (Balaenoptera musculus) is a marine mammal belonging to the suborder of baleen whales (called Mysticeti). At over 33 metres (108 ft) in length and 180 metric tons (200 short tons) or more in weight, it is the largest animal ever known to have existed.
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 Ocean and B. m. brevicauda (also known as the pygmy blue whale) found in the Indian Ocean and 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 small crustaceans known as krill.
Blue whales were abundant in nearly all the oceans on Earth until the beginning of the twentieth century. For over 40 years, they were hunted almost to extinction by whalers until protected by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 blue whales worldwide, located in at least five groups. More recent research into the Pygmy subspecies suggests this may be an underestimate. Before whaling, the largest population was in the Antarctic, numbering approximately 239,000 (range 202,000 to 311,000). There remain only much smaller (around 2,000) concentrations in each of the North-East Pacific, Antarctic, and Indian Ocean groups. There are two more groups in the North Atlantic, and at least two in the Southern Hemisphere.
The blue whale is the largest animal ever known to have lived. The largest known dinosaur of the Mesozoic Era was the Argentinosaurus, which is estimated to have weighed up to 90 metric tons (99 short tons), though a controversial vertebra of Amphicoelias fragillimus Furthermore, there are weight estimates for the very poorly known may indicate an animal of up to 122 metric tons (134 short tons) and 40–60 metres (130–200 ft).Bruhathkayosaurus ranging from 140–220 metric tons (150–240 short tons), besides length estimates up to about 45 metres (148 ft). The extinct fish Leedsichthys may have approached its size. However, complete fossils are difficult to come by, making size comparisons difficult. All these animals are considered to be smaller than the blue whale.