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Blue Whale

Balaenoptera musculus [bah lE nop' teh ruh muhs ku' luhs]; the largest animal to have ever lived


Dwarfing even the largest dinosaurs, adult blue whales average 80 to 105 feet in length and weigh up to 200 tons. The tongue is as heavy as an elephant, and the heart the size of an automobile. Females are larger than males in both length and weight.

The blue whale's head is broad, flat, and almost U-shaped, with a single ridge that extends from just forward of the blowholes to the tip of the snout. The body is long and tapered, and ends in wide, broad, triangular flukes. The dorsal fin, which is located about three-fourths of the way back on the body, is small and either triangular or curved in shape.

Although it looks truly blue underwater, the blue whale is actually more of a mottled blue-gray in color. Its underbelly often takes on a yellowish hue due to the presence of microorganisms in its skin.

blue whale

full-size blue whale skeleton

Distribution and Habitat

Blue whales can be found in all the oceans, except for the extreme polar regions. It is common for them to summer in sub-arctic and arctic waters and migrate towards equatorial waters as their food supply moves.


Blue whales feed almost exclusively on krill, a variety of shrimp that is only about an inch or two long, but can eat 4 to 8 tons of it per day. Lacking teeth, they feed by taking in enormous mouthfuls of water then forcing the water out through baleen plates that line the inside the mouth; they then use their enormous tongues to sweep the krill off the plates and down into the throat.


Mating usually occurs while the blue whales are in warmer waters, and a single calf is born about one year later, when the mother is again in warmer water. The calf is about 25 feet long at birth and can weigh as much as three tons. It also grows rapidly, gaining about 200 pounds a day in its first year, and is weaned at about eight months (or when it is about 52 feet long). The mother will not breed again until her calf is fully independent.

It takes six to ten years for a blue whale to reach sexual maturity, and it is not uncommon for a blue whale to live 80 to 90 years (or more) in the wild.

Other Habits and Behaviors

A blue whale's spray (when it exhales) is tall and straight, and can reach almost 30 feet into the air.

Blue whales are typically seen either alone or in pairs, but will on occasion come together in small groups (pods). When food is plentiful there may be as many as 50 or 60 blue whales in one group, although such groups are temporary and there is generally no relationship between most individual pod members.

Blue whales produce a variety of sounds, including pulses, groans and moans. Scientific investigation has shown that blue whales may be capable of hearing each other up to 1,000 miles away. Whether the whales are actively communicating with each other is not known, however.

A blue whale can swim at more than five miles per hour, and accelerate to more than 20 miles per hour when agitated.

Conservation Status

The blue whale is an endangered species, with only about 25,000 remaining in the wild. It is protected by treaties signed at the 1966 International Whaling Commission.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Mammalia
order Cetacea
suborder Mysticeti
family Balaenoptera
genus & species Balaenoptera musculus

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The Robinson Library >> Science >> Zoology >> Mammals >> Order Cetacea

This page was last updated on April 21, 2017.