About Blue Whales

Blue whales are the biggest animals that have ever lived on earth — longer than the longest known dinosaur, and much more massive.

They inhabit every ocean on the planet, and travel from frigid polar waters, where they feed, to warm tropical waters, where they give birth to their calves. In spite of their great size and range, there is still much we don’t know about these gentle giants.


Blue whales are the largest animals that have ever lived on earth. Whaling records from the early 20th century document blue whales as long as 33 m (108 feet). Females are, on average, 3 m (10 feet) longer than males. Animals this size are difficult to imagine. To put it in perspective, they are longer than two Vancouver trolley buses parked one behind the other (each is 40 ft long). Their hearts are the size of a car and the arteries connected to the car-sized heart are large enough that a human baby could crawl through them. The blue whale’s scientific name is Balaenoptera musculus. The genus name Balaenoptera means ‘winged whale’, and the specific epithet, musculus, can be translated from the Latin as either ‘muscular’ or ‘mouse’, which was probably a little joke on the part of Linnaeus, who named the whale.

The Belly of the Beast

Blue whales, the biggest animal that has ever lived on earth, feed exclusively on one of the smallest: krill. Cold, deep ocean waters are home to superabundant populations of these small shrimplike creatures. Individual krill are approximately 2 cm long, but swarms of these tiny crustaceans can take up hundreds of square kilometers of ocean.

Blue whales dive as deep as 300 m in search of krill swarms, and when they find them, they open their great jaws, allowing their pleated throats to fill up like sails. A blue whale’s throat extends from its chin to its navel, and is made of a stretchy tissue that can expand to four times its original width. Incredibly, they can fill their throats with a volume of water greater than the volume of their entire body, according to Jeremy Goldbogen, a PhD student at UBC who studies whale feeding. Once its mouth is full of water and krill, a blue whale will force the water out through the sieve-like baleen that it has in place of teeth, pushing the water out and leaving tens or hundreds of kilograms of krill behind in its mouth.

A mature blue whale can eat as much as 4-6 tonnes of krill per day, and must feed for upwards of four hours a day. At approximately 25 m long, these giants are 1250 times larger than their food (krill are ~2 cm long). If we humans ate food so much smaller than we are, we would eat nothing larger than a grain of sand, ~ 1mm across. No wonder blue whales must eat 40 million krill per day!

Baby Blue

Blue whales mature at the age of 5 or 6 years. After reaching maturity, the females give birth to a calf every 2 or 3 years. Gestation takes 11 months, and the newborn calves are 8 m long and weigh about 4 tonnes. In size and weight, they are approximately as big as 2 minivans.

For the first 6 months of their lives, the calves drink mothers’ milk (they are mammals). Drinking 50 gallons of milk per day, baby blue whales gain 8 pounds an hour (about 200 pounds a day) and grow about 4 cm per day.

When they are 6 months old, and have roughly doubled in length (they are now approximately half as big as they will be when they reach maturity, so they are about as long as a Vancouver trolley bus) – they start to eat krill, and to travel the oceans alone.


Blue whales are not just the biggest of animals, they are the loudest, too. A blue whale’s call is 190 decibels, louder than a jet at 140 decibels, much louder than a human can shout (70 decibels). They sing at a very low frequency, and this, combined with the loudness of their voices, allows their songs to travel thousands of km. These far-ranging calls may allow the mostly solitary blue whales to communicate with others of their kind in distant parts of the ocean. The whales may also be using echolocation to map the ocean floor, allowing them to plan routes around seamounts and other large underwater features.

Listen to blue whale sounds from the National Oceanic and Atmospheric Administration. A subwoofer will help you appreciate the full range of this call, which will shake your bones with its low frequency.

Night in the Ocean

At night, blue whales rest near the surface (~20 m deep), where they are neutrally buoyant and sing or sleep. As mammals, they need to come to the surface to take a breath of air approximately every 20 minutes, so they can’t sleep for hours like landlubbers do. Instead, they put half of their brain to sleep at a time, and rest… until they are refreshed.

This type of sleep, called unihemispheric sleep, has also been documented in birds, allowing them to migrate long distances without stopping to sleep, or falling out of the air from exhaustion.

Conservation Status

Able to travel at speeds of up to 20 kilometres per hour, with tough hides, blue whales were beyond the reach of whalers until 1868, when the introduction of steam engines, explosive harpoons, and air compressors (for inflating freshly killed whales, to keep them at the surface) made them vulnerable to the industrial hunger for blubber and whalebone (baleen). The blubber was rendered for use in lighting, fine soapmaking, and machine lubrication. Whalebone, the keratin plates balleen whales use to strain food out of the ocean, was prized for corset stays, umbrella ribs, and carriage springs; applications where plastic or steel would now be used. For decades, the ocean giants were hunted without restraint, and their numbers dwindled from an estimated 350,000 to 1000-2000. The blue whale hunt peaked in 1931, with a take of over 29,000 animals. In 1966, the International Whaling Commission banned hunting of blue whales, and today their numbers are estimated at 4,500. Blue whales are on the IUCN Red List of Endangered Species, and are listed as Endangered under the Canadian Species-at-Risk Act.

Whaling bans are helping populations to recover. A whale survey conducted by the Cascadia Research group off the coast of BC in the summer of 2007 counted more blue whales than have been seen in the area in the past half-century.