The blue whale is a marine mammal within the parvorder Mysticeti of the infraorder Cetacea. A baleen whale, this species is the largest known animal in the world as well as the heaviest, with lengths reaching 30 meters or more and weighing over 180 tons.
Blue whale taxonomy and subspecies
The scientific name for the species is Balaenoptera musculus. However, at least 4 subspecies are known: B. m. musculus, B. m. intermedia and B. m. brevicauda, with B. m. indica being considered to be a distinct subspecies. These whales are also known as rorquals, or members of the family Balaenopteridae which also includes humpback whales, sei whales, fin whales and minke whales. B. m. musculus lives in the Northern hemisphere, with its somewhat larger counterpart, B. m. intermedia, living in the Southern hemisphere. B. m. brevicauda is also known as the pygmy blue whale, and, as the name suggests, is the smallest subspecies.
General characteristics, size and weight
These whales have a somewhat narrower and thinner body than many other whales that are more compact in shape. The larger subspecies can grow to be as long as 30 meters,
with several non-scientific recordings measuring even 33 meters. Females are usually longer and heavier than males, and specimens living in the Southern hemisphere are usually larger than their Northern counterparts. The head of a blue whale is flat and shaped like a U, with a prominent ridge which runs from one of the blowhole to the corners of the mouth.
There are also between 70 and 118 grooves, which are also called ventral plates that run along the body from the throat. The mouth is large and can be extremely flexible. The mouth has around 300 baleen plates, which are comb-shaped keratin structures with the role of filtering water and retain food. Adult whales can reach 180 tons in weight.
These whales feed almost exclusively on krill, small crustaceans that make up large amounts of zooplankton. A single blue whale can eat up to 40 million krill in just one day. The Southern Hemisphere is richer in krill, and an adult whale can consume up to 3,600 kilograms of krill in one day. It is common for the whales to consume food equivalent to as much as 90 times more energy than they expend in a day and build up reserves that they will use after mating. Since krill usually descent during the day and go up during the night, whales usually feed during the day at depths lower than 100 meters and only come to the surface at night. Whales are mammals so they have to breathe air, coming up to the surface every 10 minutes and use their blowholes.
Little is known about mating habits of these whales. Females give birth every 2 or 3 years after a gestation of 10 to 12 months. Calfs measure 7 meters in length and weigh 2.5 tons at birth. Calves will drink up to 500 liters of milk each day, with each kilogram having an energy content of 18,300 kJ. It will be weaned after 6 months, and it will reach sexual maturity in 5 to 10 years. A blue whale will continue to grow in size and weight and live up to 80 years.