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Blue whale

Blue whale
Blue whale feeding on krill Blue whale breaching

Found in Monterey Bay

Animal Facts

  • Scientific Name

    Balaenoptera musculus

  • Animal Type

    Marine Mammals

  • Diet


  • Size

    average maximum length 88 feet (27 m), the largest ever measured 110 feet (33.5 m)

  • Relatives

    other baleen whales

Natural History

Blue whales are the largest animals on Earth. They have astounding body parts—tongues that weigh two tons, a heart as large as a small car and skin-folds that extend from beneath the tips of their lower jaws to their navels. When expanded, these folds increase the interior of a blue whale's mouth to the size of a train's box car. Blue whales can grow to 100 feet (30 m) in length and weigh as much as 150 tons—the weight of 30 elephants.

Instead of teeth, blue whales have 300 to 400 fringed baleen plates that hang from their upper jaws and strain their food. Blue whales strain and eat krill, a tiny, shrimplike invertebrate. A whale gulps a mouthful of water and krill, closes its mouth, pushes out the water with its tongue and then swallows its catch of krill. 

In Monterey Bay

Blue whales visit Monterey Bay during the summer and fall. They come to eat, gulping tons of shrimplike krill. Finicky eaters, they eat only krill and can travel up to 30 miles a day in search of this prized food. In winter, blue whales return to the warmer waters off Central America to give birth and mate. Since krill is scarce or nonexistent in warm waters, the whales live off reserves of body fat until they can feed again.

Scientists estimate the present population worldwide to be 15,000 whales, with 2,000 of these living in California coastal waters, including Monterey Bay. This is the largest concentration of blue whales in the world. In the summer, whale watchers often see blue whales near the canyon that crosses Monterey Bay.


Whalers began hunting blue whales in earnest after the invention of harpoon guns. The pre-whaling population of blue whales quickly fell from an estimated 350,000 to 1,000 in the mid-1920s. Blue whales became so scarce that in 1966 the International Whaling Commission belatedly declared blue whales a protected species worldwide. The Endangered Species Act also protects blue whales.

Cool Facts

  • Calves nurse for seven to eight months, drinking 100 gallons of milk daily. They can gain nine pounds (4 kg) each hour and grow 1.5 inches (3.8 cm) each day.
  • A blue whale's esophagus is only four inches (10 cm) in diameter—so swallowing large fishes isn't possible.
  • In Arctic or Antarctic waters, yellow diatoms (microscopic algae) often stick to blue whales' underbodies, giving them a nickname of "sulfur bottom."
  • The Navy's Ocean Acoustic Observatory at Point Sur was built in 1958 during the Cold War and operated until 1986, when it was available for scientists studying whales. In 2001 a cable failure rendered much of the network unusable.  However, scientists continue to study blue whale vocalizations with a variety of other tools. 

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