Blue whales (Balaenoptera musculus) are the largest animals ever known to have lived on Earth.
Blue whales are baleen whales – a suborder of whales that can filter tiny organisms out of the sea with their bristly baleen mouth combs.
The blue whale has a truly global distribution, occurring in all oceans except the Arctic, and enclosed seas. But despite this, they are one of the rarest of the whales, numbering between 10,000-25,000.
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.
The blue whale has an average lifespan of 80 to 90 years. A way to tell a whale’s age is to look at growth layers in their ear plug. The oldest whale estimated using this method was 110 years.
Blue whales can grow to be up to 33.3 meters (109 ft) in length and may weigh up to 181 tonnes (200 US tons).
By comparison, one of the largest known dinosaurs of the Mesozoic Era was Argentinosaurus, which is estimated to have weighed up to 90 tonnes (99 short tons), comparable to the average blue whale.
A blue whale’s heart is the size of a Volkswagen Beetle and pumps 9 tonnes (10 US tons) of blood through the massive blue whale body. A blue whale aorta (the main blood vessel) alone is large enough for a human to crawl through.
A blue whale’s tongue weighs around 2.7 tonnes (3 US tons) and, when fully expanded, its mouth is large enough to hold up to 90 tonnes (99 US tons) of food and water.
Blue whales look true blue underwater, but on the surface their coloring is more a mottled bluish gray. Their underbellies take on a yellowish hue from the millions of microorganisms that take up residence in their skin.
The blue whale has a long tapering body that appears stretched in comparison with the stockier build of other whales.
A small triangular-shaped dorsal fin is located on the blue whale’s back. This fin measures only 30 centimeters (1 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.
The head is flat, U-shaped and has a prominent ridge running from the blowhole to the top of the upper lip.
The front part of the mouth is thick with baleen plates; around 300 plates, each around one meter (3 ft) long.
Blue whales filter their food through their baleen plates. Blue whales feed almost exclusively on krill, though they also take small numbers of copepods. A blue whale can eat up to 3,600 kilograms (7,900 lb) of krill in a single day. It is estimated to take 1,000 kilograms (2,200 lbs.) of food to fill a blue whale’s stomach.
When breathing, the whale emits a vertical single-column spout, typically 9 meters (30 ft) high, but reaching up to 12 meters (39 ft). Its lung capacity is 5,000 liters (1,300 US gal). Blue whales have twin blowholes shielded by a large splashguard.
Blue whales can dive for up to an hour at a time, but their dive will generally last about 10 to 20 minutes.
Blue whales can dive to depths of 500 meters (1,640 feet), but they usually feed around depths of less than 100 meters (330 feet).
These whales swim at speeds of approximately 22.5 kilometers (14 miles) per hour but they can get up to 48 kilometers (30 miles) per hour during a quick burst or sprint.
Blue whales can usually be seen traveling alone or in groups made up of 2 to 4 individuals.
In locations where there is a high concentration of food, as many as 50 blue whales have been seen scattered over a small area.
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 blue whale can produce the loudest sound of any animal. At 188 decibels, the noise can be detected over 800 kilometers (500 miles) away. A passenger jet at take off makes a noise that is between 120 and 140 decibels.
A blue whale vocalizes by means low-frequency moans, pulses, buzzes, rasps, and ultrasonic clicks.
Scientists think they use these vocalizations not only to communicate, but, along with their excellent hearing, to sonar-navigate the lightless ocean depths.
Mating starts in late autumn and continues to the end of winter. Females typically give birth once every two to three years at the start of the winter after a gestation period of 10 to 12 months. Young are born in warm, low latitude waters. A baby blue whale weighs about 2.5 tonnes (2.8 US tons) and is around 7 meters (23 ft) in length. Blue whale babies drink 380–570 liters (100–150 US gallons) of milk a day. They grow at a rate of 90 kg (198 pounds) per day and wean after 7-8 months, once they have reached about 15 meters (49 feet) in length, and are able to follow the normal migration pattern alone.
The whales’ only natural predator is the orca. Studies report that as many as 25% of mature blue whales have scars resulting from orca attacks.
Blue whales were abundant in nearly all the oceans on Earth until the beginning of the twentieth century. For over a century, they were hunted almost to extinction by whalers until protected by the international community in 1966.
The global population was reduced by more than 99% during the 20th century.
The total world population was estimated to be between 5,000 and 12,000 in 2002; there are high levels of uncertainty in available estimates for many areas. A more recent estimate by the IUCN puts the global population at 10,000–25,000.
The IUCN Red List counts the blue whale as “endangered”, as it has since the list’s inception.
Blue whales may be encountered (but rarely) on whale-watching cruises in the Gulf of Maine and are the main attractions along the north shore of the Gulf of Saint Lawrence and in the Saint Lawrence estuary.