The blue whales, scientifically known as Balaenoptera musculus, are marine mammals. Being a Baleen whale, they are one of the 76 octacean species and are the largest animal (including the terrestrial animals) ever known in the earth. They belong to the rorquals, a family of whales that includes fin whale, humpback whale, Bryde’s whale, sie whale and minke whale. As they are marine creatures, the weight is supported by water and there is no need of heavy bones. Before 20th century, they were found in nearly all the oceans on earth abundantly.
The body of blue whale is long, slightly tapered and streamlined. The head makes up approx. one-fourth of its total body length. The upper part of the head is very broad and flat and almost U-shaped. The blowholes are found to be contained in a large splash guard raised above the body. The blow is straight and can be measured over 6 meters high. Their flippers are measured to be 3–4 meters long. The upper sides are grey with a thin white border; the lower sides are white. Small fishes attach themselves to the edge of the fluke, the tips of the flippers and the dorsal fins; for food. There are 60 to 90 grooves (called ventral pleats), which run along the throat parallel to the body length.
In southern hemisphere blue whales reach a length of 90-100ft but in northern they smaller in length (about 75-80ft) on an average. The weight can be over 100 tonnes. Generally females are larger than males. Blue whales feed on small creatures like the euphausiids or krill, and during summer they can eat up to 4 tonnes or more each day. Their breeding occurs mostly in the winter to early spring in warm water. Gestation period is 11-12 months. The new born calf measures 25ft long weighing 6-8 tonnes. For more than 100 years they were hunted by whalers until they came to extinction, and were saved in 1966 by international community.