Learn About Ecology
Data And Science
World Biomes
Marine Mammals
Classroom Projects

blue whale

The Blue Whale is the largest living animal in the world! 

Blue whales (scientific name: Balaenoptera musculus) can be found in all oceans of the world. They are most commonly seen along continental shelves and ice fronts, but sightings have been reported in the deep ocean and in shallow inshore regions. The largest populations occur in the Southern Hemisphere, the North Pacific, and the North Atlantic.

In the North Pacific, blue whales can be seen from California up to the Gulf of Alaska and the Aleutian Islands. Wintering grounds are off the coast of southern California, Baja California, Taiwan, Japan and Korea.

Blue whales migrate often, which means they move from place to place many times throughout their lives. They like to spend the winters in temperate and subtropical regions, migrating to the polar regions in the spring and summer. The whales in the North Atlantic migrate to the Arctic during the summer and spring seasons. In the southern hemisphere, blue whales can be found migrating throughout Antarctica, although not much is known about the migration routes from the feeding grounds to the breeding grounds. In the southern hemisphere blue whales have been reported as far north as Madagascar and Angola in Africa and Rio de Janeiro, Brazil, Ecuador and Peru in South America.

Back to the top

Physical Appearance

Blue whales have long and streamlined bodies with the head making up a fourth of its body length. The head region is broad and U-shaped. Blue whales do not have teeth. Instead, they have 270 - 395 plates of baleen on either side of their jaw. Baleen look like long thin teeth placed very close to one another. They are used to catch small animals swimming in the water, which the whale eats.

Color: Blue whales are blue-gray in color with white patches covering their body. The undersides of the flippers are lighter in color, and sometimes white, while the underside of the tail is dark. In Antarctica, the North Pacific, and the North Atlantic, smaller organisms called diatoms attach themselves to blue whales' undersides. These organisms give these whales' bellies a yellowish-green tint.

Length and Weight: The average length of a blue whale is 75 - 80 feet (23 - 24 meters) and these long marine mammals can weigh up to 200,000 pounds (90,000 kg). Whales in the southern hemisphere are generally larger than those in the northern hemisphere. One whale captured in the southern hemisphere measured 110 feet (33 meters) in length. Females are usually larger than males of the same age.

Fins: A small triangular-shaped dorsal fin is located on the blue whale's back. This fin measures only one foot in height. The shape and size of the dorsal fin can be very different for each whale. The whale's flippers are short and the tail is broad and triangular in shape.

Back to the top


Blue whales can usually be seen traveling alone or in groups made up of 2 to 4 individuals. Off the coast of California, groups of up to 60 whales can be seen swimming together. These whales swim at speeds of approximately 14 miles (22.5 km) per hour but they can get up to 30 miles (48 km) per hour during a quick burst or sprint. Blue whales can dive to depths of 1,640 feet (500 meters), but they usually feed around depths of less than 330 feet (100 meters). A blue whale's dive will generally last about 10 to 20 minutes.

Back to the top

Breeding and Reproduction

Sexual maturity is reached at the age of 5 to 10 years in the blue whale. A female gives birth to a calf every two to three years and is pregnant for 10 to 12 months before giving birth. Young are born in warm, low latitude waters in the winter months. A baby blue whale averages 23 feet (7 meters) long and 4,400 pounds (1,990 kg) when born. It is fed by its mother's milk for 7 to 8 months. The life span of a blue whale has been estimated to be as high as 110 years.

Back to the top


Blue whales mainly feed on krill, which are small shrimp-like organisms. They can eat up to 7,715 pounds (3,500 kg) of krill a day!

Fun Facts

  • The main arteries of a blue whale are so large that a small person could crawl through them! 
  • Blue whales eat approximately 40,000,000 krill a day!
  • A blue whale vocalizes by means low-frequency moans, pulses, buzzes, rasps, and ultrasonic clicks.

audioLots More: Sounds, Videos, Etcetera on Marine Mammals