The blue whale (scientific name: Balaenoptera musculus) is a marine mammal belonging to the suborder Baleen Whales. *** There are four subspecies. The blue whale is considered to be the largest animal known to have survived on Earth, up to 33 meters long and weighing up to 200 tons. The blue whale has a long, lean body and a greenish-gray back, although it sometimes looks lighter in color in the water. Like other baleen whales, blue whales feed mainly on small crustaceans (such as krill) and small fish, sometimes including squid. Usually, blue whales need to feed at depths of more than 100 meters during the day, and only come to the surface at night to feed. Blue whales begin mating in late fall and continue to do so until late winter. Females usually give birth once every 2-3 years, usually in early winter after a 10-12 month gestation period. They are found in all four oceans.