The Blue Whale

by Antonia Kropp

Photo – Thanks to Chase Dekker for permission to use his photo.

Scientific Name:  Balaenoptera musculus

Size:  Blue whales are the largest living animals ever known (bigger than dinosaurs). Adults are 23-30 meters long, with females growing up to 10m larger than males. They weigh approximately 140,000kg-160,000kg. Their infants are about 8m long and weigh 4 tonnes.

Status: Endangered

Population count:  10,000 to 25,000 blue whales worldwide today

Identifying Features:  The blue whale is slender, streamlined and very big (23-30m). The head is broad and U-shaped when viewed from above and relatively flat cone-shaped from the side. Around the centre of the rounded rostrum is a single prominent ridge which ends in an impressive ‘splash guard’ around the two blowholes. It has approximately 90 ventral throat grooves, which reach the navel. The flippers are long and pointed while the dorsal fin is really small, variable shaped and about three-quarters of the way back from the snout tip. The broad fluke has a straight trailing edge and a prominent notch. Blue whales are bluish-grey from above and a bit lighter underneath. The head is uniformly blue but the back and sides are variably mottled (depends on basic colour if spots are lighter or darker than the rest). The yellowish colouring on their bottoms sometimes occurs because diatoms (microscopic, unicellular marine algae) accumulate there, and lead to the nickname “sulphur bottom whale”. The mouth contains 300-400 pairs of black, broad-based baleen plates on each side of the mouth (each less than 1m long). The blow is tall and slim, reaching 9m or more in height. The blue whale is in general bluish-gray, mottled, slender, long, relatively flat with (compared to body length) very small fins and fluke.

Habitat:  Blue whales prefer deeper ocean waters to coastal waters and come closer to the shore just for mating and birth. They dive to depths more than 100m (330ft) to feed during the day but stay at the surface at night. Their dive times are typically 10 minutes when feeding, though dives of up to 21 minutes are possible. They have a truly global distribution, occurring in all oceans except the Arctic and enclosed seas like the Bering seas. They migrate towards the poles (in colder waters) in summer to feed, but go back towards the equator (into warmer waters) in winter to breed (mostly in south Africa). Despite their wide spreading habit they are one of the rarest whales existing with a population of 10.000-25.000.

Food (prey):  A baby blue whale consumes milk during its first 6-18 months after birth and can drink as much as 150 gallons per day. This feeding will continue until the young whale is able to hunt for food and survive on its own. Blue whales are filter feeders who eat krill, copepods and small fish. Their stomach can hold one tonne of krill and it needs to eat about four tonnes everyday, which means he consumes around 40 million krill each day while summer feeding season. The blue whale expands its throat plates and takes in ocean water (with krill and other food in it obviously) for feeding. It then pushes the water out of its mouth by lifting its huge tongue. Krill, copepods and small fish stay inside and get swallowed. Through a blue whale’s 10-20 minutes dive at depths less than 100m, it can eat about 3 000 000 (3 million) krill. These giant animals need to feed constantly in order to have enough energy to move their bodies and swim. One of the most common natural causes of death for a blue whale is loss of energy due to undereating. This means that they don’t have enough energy to hunt and regain their strength, so they end up dying because of a lack of energy.

Predators:  The only animals that dare to attack a blue whale are a group of killer whales. While these attacks are very rare, there have been people who confirmed witnessing such attacks and even a few videos have been recorded showing a group of killer whales attacking a young blue whale. The biggest threat to them are humans though. They have been almost hunted down completely in the major time of whale hunting (1920-1940) because of the many treasures that just one of these giants holds. After almost extincting these mammals, new laws prevented them from dying out (international whaling commission declared them to be a protected species in 1966). They recovered a bit but are still endangered and face new threats today. These are chemical and sound pollution, habit loss, overfishing of krill, ship strikes and becoming entangled in fishing gear for example. Those are all slow and painful deaths to many blue whales in just one sudden strike of these causes. Due to climate change, the “colder” waters are getting warmer and warmer which causes the krill to move further south and so do the whales in order to feed on them. These longer migration paths can increase the energy cost of migration and cause energy loss way faster than normal. The lack of food in these areas then lead to death of whole pods (group of whales). Most of these threats are connected to the impact of humans, which means humans are in almost every way the cause of death to blue whales. Their only defense is the gigantic size and the thick layer of blubber under the skin (2-14 inches) because it has no teeth, toxin or sting. A hit from it’s fluke can be deadly tho.

Life cycle:  After mating, the female blue whale will carry the baby for one year. The infant will be born with the tail first (as all cetaceans) near the shore in shallow water. It will start to search the surface 10 seconds after birth with the help of the mother who pushes the newborn up, for its first breath of air. At birth, a blue whale calf is already the largest baby on earth; approximately 8m long and weighing about 4 tonnes. They grow at a rate of 90kg per day. With about 150 gallons of milk per day, they reach an enormous size in no time. They are able to follow the normal migration pattern of a blue whale alone at about 15m in length. They reach sexual maturity at 5-10 years and start mating through the breeding season in the tropic zones around the equator. Blue whales usually give birth to just one calf (rarely twins) and with every female giving birth approximately every, to every second year just once, the number of population is keeping itself relatively low. Many human impacts on habit and life of a blue whale makes breeding very hard (pollution, ship sounds, shrinking habit). Without any of these dangers, a whale has a lifespan of about 40-70 years, though it is really hard to tell the age of these whales because they have baleen instead of teeth.

Interesting facts:

The blue whale’s heart is the size of a small car and its beat can be detected two miles away

Lifespan: 40 to 70 years but hard to tell because they have no teeth

Blue whales are the loudest animals on earth, with calls reaching levels up to 188 decibel. This low-frequency whistle can be heard for hundreds of miles. The blue whale is louder than a starting jet, which reaches only 140 decibels

A human could crawl through its aorta (major blood vessel)

Despite their size are blue whales very fast swimmers with an average speed of 3-20 mph (4.8-32 kph). In case of danger are bursts of even 24-30 mph (38-48 kph) possible

It is very hard to tell their weight because they are too big for any scale. The measured weight is very inaccurate when only pieces of a blue whale are weighed because they loose most of their body fluids in the process of cutting. Scientists guess that only their body fluids (like blood) weigh about 2000kg

The oil you can make out of the blubber (fat layer under the skin) of a whale, was very valuable during the whale hunting period because it is a long-lasting fuel for fire (used as light in every household)

Before whaling, the largest population was in the Antarctic, numbering approximately 239,000 (today 10.000-25.000)

They live in pods (group of whales) with three to hundreds of blue whales together

Blue whales are very social and look out for each other like a family


Blue whale (balaenoptera musculus). (n.d.). Retrieved January 19, 2018, from

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Forsyth, A. (1988). Mammals of the Canadian wild. Camden East, Ontario: Camden House.

Harbo, R. M. (2011). Whelks to whales: Coastal marine life of the Pacific Northwest. Madeira Park, B.C.: Harbour Pub.

Jefferson, T. A., Leatherwood, S., & Webber, M. A. (n.d.). Blue whale (balaenoptera musculus). Retrieved from

Keyes, L. (2015, November 12). Life cycle of a blue whale. Retrieved January 18, 2018, from

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