The Blue Whale

The blue whale is the largest animal ever known to have lived. It is even bigger than the largest dinosaur that lived – the Argentinosaurus.

It is estimated that there are about 8,000-14,000 blue whales worldwide.

The IUCN Red List counts the blue whale as "endangered".  

The blue whale was too quick and powerful for the 19th century whalers to hunt, but with the arrival of harpoon cannons, they became a much sought after species for their large amounts of blubber. The killing reached a peak in 1931 when 29,649 blue whales were taken. By 1966, blues were so scarce that the International Whaling Commission declared them protected throughout the world.

Kingdom	Animalia (animals)
Phylum	Chordata (vertebrates)
Class	Mammalia (mammals)
Order	Cetacea (whales and dolphins)
Suborder	Mysticeti (baleen whales)
Family	Balaenopteridae
Species	Musculus
Subspecies	B.m. intermedia (from the southern hemisphere) B.m. musculus (from the northern hemisphere in the Atlantic and Pacific oceans) B.m. brevicauda (the pygmy blue whale; Yochem and Leatherwood 1985). The little-studied pygmy blue whale, B. m. brevicauda, is found in Indian Ocean and is the one most likely sighted off southern Sri Lanka. A fourth subspecies, B. m. indica, was identified by Blyth in 1859 in the northern Indian Ocean, but difficulties in identifying distinguishing features for this subspecies led to it being used a synonym for B. m. brevicauda, the pygmy blue whale. Records for Soviet catches seem to indicate that the female adult size is closer to that of the Pygmy Blue than B. m. musculus, although the populations of B. m. indica and B. m. brevicauda appear to be discrete, and the breeding seasons differ by almost six months.

Habitat
The blue whale is found in all major oceans of the world. It is found mostly in cold and temperate waters and prefers deeper ocean waters to coastal waters.
Blue whales most commonly live alone or with one other individual. It is not known how long traveling pairs stay together. In locations where there is a high concentration of food, as many as 50 blue whales have been seen scattered over a small area. However, they do not form the large close-knit groups seen in other baleen species.

Size
The longest whales ever recorded were two females measuring 33.6 and 33.3 metres (110 and 109 ft) respectively. Blue whales are difficult to weigh because of their size. Measurements between 150–170 metric tons were recorded of animals up to 27 metres (89 ft) in length.

Cool facts
A blue whale's tongue weighs around 2.7 metric tons and, when fully expanded, its mouth is large enough to hold up to 90 metric tons of food and water. Despite the size of its mouth, the dimensions of its throat are such that a blue whale cannot swallow an object wider than a beach ball. Its heart weighs 600 kilogrammes (1,300 lb) and is the largest known in any animal. A blue whale's aorta is about 23 centimetres (9.1 in) in diameter.
Blue whales can reach speeds of 50 kilometres per hour (31 mph) over short bursts, usually when interacting with other whales, but 20 kilometres per hour (12 mph) is a more typical traveling speed. When feeding, they slow down to 5 kilometres per hour (3.1 mph).

Calves
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 a gestation period of ten to twelve months. The calf weighs about 2.5 metric tons (2.8 short tons) and is around 7 metres (23 ft) in length.

During the first seven months of its life, a blue whale calf drinks approximately 400 litres  of milk every day. Blue whale calves gain weight quickly, as much as 90 kilograms (200 lb) every 24 hours. Even at birth, they weigh up to 2,700 kilograms (6,000 lb)—the same as a fully grown hippopotamus.

Weaning takes place for about six months, by which time the calf has doubled in length. Sexual maturity is typically reached at eight to ten years, by which time males are at least 20 metres (66 ft) long.

Females are larger still, reaching sexual maturity at around the age of five, by which they are about 21 metres (69 ft) long.

Feeding
Blue whales feed almost exclusively on krill, though they also take small numbers of copepods – a type of small crustacean. 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.

Diving
Because krill move, blue whales typically feed at depths of more than 100 metres (330 ft) during the day and only surface-feed at night. Dive times are typically 10 minutes when feeding, though dives of up to 20 minutes are common. The longest recorded dive is 36 minutes. The whale feeds by lunging forward at groups of krill, taking the animals and a large quantity of water into its mouth. The water is then squeezed out through the baleen plates by pressure from the ventral pouch and tongue. Once the mouth is clear of water, the remaining krill, unable to pass through the plates, are swallowed. The blue whale also incidentally consumes small fish, crustaceans and squid caught up with krill.

Loudest on Earth
Blue whales are also the loudest animals on Earth! Their call reaches levels up to 188 decibels. This low-frequency whistle can be heard for hundreds of miles. The blue whale is louder than a jet, which reaches only 140 decibels! Human shouting is 70 decibels; sounds over 120 decibels are painful to human ears.

Sources:
http://www.blue-whale.info/
http://en.wikipedia.org/wiki/Blue_whale

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