The Largest animal ever

Blue whale

The blue whale  is a marine mammal.  At up to 29.9 metres in length and with a maximum recorded weight of 173 tonnes.  it is the largest animal known to have ever existed.

There are at least three distinct subspecies:

1.  B. m. musculus of the North Atlantic and North Pacific
2. B. m. intermedia of the Southern Ocean 
3. 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 

Nature of blue whale

                Blue whales can reach speeds of 50 kilometres per hour. Blue whales typically swim at a depth of about 13 meters. The deepest confirmed dive is 506 meters. 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. They do not form the large, close-knit groups seen in other baleen species.

Feeding

Blue whales feed almost exclusively on krill, though they also take small numbers of copepods. The species of this zooplankton eaten by blue whales varies from ocean to ocean. An adult blue whale can eat up to 40 million krill in a day.The daily energy requirement of an adult blue whale is in the region of 1.5 million kilocalories (6.3 GJ).