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The blue whale is the largest mammal

 
Blue whale is the largest animal that ever lived. The blue whale reaches up to 100 feet (30 meters) long and can weigh over 150 short tons (135 metric tons). It has speckled blue-gray and white skin, relatively small, thin flippers, and a large, strong tail.

The blue whale strains food from the water using 260 to 400 thin, fringed plates called baleen, hanging from each side of its mouth. The whale eats primarily krill, a shrimplike animal. It lunges through masses of krill, taking in tons of water and food. It then closes its mouth and squirts the water out through the baleen, trapping the krill inside.

Blue whales usually dive no deeper than about 300 feet (90 meters) because krill tend to live at shallow depths. The whales surface to breathe three to six times in rapid succession, then dive for several minutes. When surfacing, they exhale sharply through their blowholes (nostrils), producing a loud sound.

Blue whales live in all the oceans. They feed in waters in or near the polar regions. They generally travel in groups of two or more. Two whales often work together while feeding, apparently using each other's bodies as walls to help trap prey. Blue whales migrate to waters closer to the equator to breed. They make loud, low moans that can travel great distances through the water. Scientists think the moans allow whales to communicate within an area of at least 100 square miles (260 square kilometers).

During the early and mid-1900's, blue whales were hunted nearly to extinction. But their numbers have steadily increased since the 1960's, when many countries agreed to stop or severely limit the hunting of blue whales. In the early 1990's, an estimated 10,000 to 15,000 blue whales survived.

The blue whale belongs to the suborder Mysticeti, order Cetacea. Its scientific name is Balaenoptera musculus.