Blue Whale: Characteristics, Habitat, Nutrition, Reproduction

The blue whale ( Balaenoptera musculus ) is a placental mammal belonging to the order of the cetaceans. It is the largest species in the entire animal kingdom, being around 33 meters long and weighing about 150 tons.

Its skin is bluish gray, but under water it looks a more intense blue color. Despite its large size, its streamlined body and powerful fins allow it to be a fast swimmer. They normally travel between 19 and 22 km / h, but when threatened they could swim at about 30 km / h.

In the early twentieth century this species inhabited almost all oceans, but due to indiscriminate hunting its population has been reduced to the northeast Pacific, the Indian Ocean and the Antarctic. There are also small groups in the North Atlantic and in the southern hemisphere.

Their diet is based on krill, a crustacean similar to a shrimp. To capture its prey it can go to the surface or descend to about 100 meters.

During this dive, the blue whale could turn its body 360 ° with the intention of locating its prey. Then she quickly reorients herself and lunges through the krill banks.

Danger of extinction

Indiscriminate hunting of blue whales has been the main cause of their near extermination. They are captured for the commercialization of their meat and the oil that comes from their body fat.

The populations that inhabited the North Atlantic were aggressively attacked since 1868. Because it is a very difficult animal to catch, whaling boats were built, which were equipped with large harpoons to catch these cetaceans.

Towards the end of the Second World War the population had declined significantly. Due to this, in 1946 the first international trade restrictions of these Mysticetes were established.

It was in 1966 when its population was very reduced, giving the International Whaling Commission (IWC) world protection to these animals, prohibiting their hunting.

Conservation actions

The International Union for Conservation of Nature has listed Balaenoptera musculus as an endangered species. Due to this, countries have formulated a series of conservation policies in favor of their preservation.

In those regions where the cetacean migrates to reproduce, a series of actions are organized that allow the population to admire these beautiful aquatic mammals, without endangering their lives.

This is how the government of Mexico prepares and executes plans in the Bahía de Loreto National Park, in Baja California Sur.

Some of the regulations that must be met for passive viewing of the blue whale refer to the use of boats, which must be at a distance of no less than 100 meters and keep the engine off.

The recovery of the population has been slow, in recent years there have been certain indications that the number of individuals has increased.

Current threats

At present, the blue whale is threatened by the collision with the ships that sail through the area. This may be due to the animals becoming disoriented, a product of the sonic contamination that affects their echolocation.

Global warming is also affecting this group of cetaceans. The increase in water temperature causes the krill population to decrease. Therefore, the blue whale must migrate to more distant territories to find them, involving a greater expenditure of energy.

Industries that develop around habitats may be dumping their waste into these waters, causing significant chemical alteration. This could cause the death of the animal by poisoning the products.

General characteristics


On average, the length of the erect penis varies, but generally ranges from 2.4 meters. This is found internally and when erect it leaves the body through the genital cleft. It is a very resistant and fibrous organ, compared to that of any other mammal.

Sometimes the size of the penis could be taken as an indicator of the maturity of the animal. In this way they would be divided into immature, pubescent and mature.


The blue whale has two holes on the top of its head, which it uses for breathing. When carbon dioxide is expelled outside, it is usually accompanied by water.

There is really no water coming out of your lungs. What happens is that the air inside the body is warmer than the air outside. In this way, the released gas condenses and turns into water.

Another characteristic of the blowhole is that it has muscle flaps on the inside. These act as a kind of plug, keeping the water out of the lungs. During breathing, these muscles open, giving way to oxygen. Then they relax, closing the breathing hole.


Although the Balaenoptera musculus brain is not one of the largest within animals, its complexity makes it one of the most powerful.

An example of this control of actions, by the brain, is breathing. In these animals it is carried out in a conscious and voluntary way, thanks to the orders issued by the brain and which are transmitted by the nervous network.


The heart of the blue whale has four chambers and weighs about 900 kg. According to studies, it beats every 10 seconds, allowing it to pump around 220 liters of blood.


The light blue-gray color of the skin gives this species its name. When submerged underwater, the refraction of the sun’s rays makes these marine mammals appear a more intense blue color than they really are. On their body they have light gray specks, which form large spots.

The underside of some specimens has a yellowish hue, which is caused by diatom algae that live on their bodies.


His eyes are small compared to his body. They do not have eyelashes or tear glands.


Despite the fact that this animal lacks external ears, they have a good sense of hearing. They can detect sounds thanks to a system of bones and air sinuses.

Body size and shape

Most blue whales measure between 24 and 27 meters, although species of up to 33 meters have been recorded. They usually weigh more than 150 tons. The females are larger than the males, and can weigh up to 160 tons.

The species that inhabit the northern hemisphere are smaller than those of the southern ocean, around Antarctica .

Despite its large size, its body is slim and oval. Its aerodynamic structure allows it to swim an average of 5 mph. However, when threatened they could travel up to 25 miles per hour.

Dorsal fin

The dorsal fin of Balaenoptera musculus can be of several different shapes: triangular, falcate, rounded or just be a very small protrusion. Compared to its large dimensions, the size is much smaller than that of other species of whales.

They are slightly projected on the back of the body. The underside of the fins can be white or light gray.


The blue whale does not have teeth, but rather keratinized structures. Beards consist of a series of hard plates interspersed with equally tough bristles. They are arranged in the upper jaw, like vertical blinds.

When they are born, the young have very small beards or absolutely lack them, thus facilitating lactation. This structure begins to develop slowly, becoming fully functional between 6 and 12 months, once the calf has been weaned.


Beards consist of transversely oriented keratin plates, which are attached to the lateral area of ​​the upper jaw. In this way, a portion of the palate is left open, along the entire midline. Thus, two masses are formed that hang from the upper jaw in the form of a comb

The plates that are closest to the labial border are the largest and are known as major. Beside these, the plates gradually decrease in size, being called accessory plates. The association between these two plates forms a transverse row, shaped like a triangle.

The lingual area is smooth and consists only of main plates. Those that are oriented towards the oral cavity have two main plates and the accessory plates have a series of bristles.

These structures are of continuous growth. The plates that are located towards the inside of the mouth wear out much faster than the bristles. This makes them stick out and interlock, forming a filter.

This allows the water to flow, but the different prey that make up its diet are retained very efficiently.


Its head is wide and flattened, U-shaped. The size is less than a quarter of the total size of the cetacean. In it, a very prominent ridge stands out, which goes from the respiratory orifice to the upper lip. Its mouth, in the front part, is thick.

Their tongue can weigh about 2.7 tons. When the blue whale opens its mouth fully, it can hold up to 90 tons of water and food. However, despite its large mouth, its throat is thin, allowing it to swallow only small animals.

It has about 70 and 120 furrows, known as ventral folds. These go all the way down your throat, parallel to the length of your body. The function of these furrows is to contribute to the exit of the water from the mouth, where it entered as a product of having captured large amounts of krill.


Animal Kingdom.

Subkingdom Bilateria.

Chordate Phylum.

Vertebrate Subfilum.

Mammal class.

Subclass Theria.

Order Cetacea.

Balaenopteridae family.

Genus Balaenoptera

Balaenoptera musculus species 

Habitat and distribution

These large marine mammals live in the deep waters of cold areas, probably due to the abundance of krill, a crustacean that forms the basis of their diet.

Within the life cycle of Balaenoptera musculus there are two seasons, the mating season and the feeding season. These provoke migratory movements in search of the best climatic conditions for the adequate development of each stage.

In order to feed and store large supplies of nutrients, the blue whale finds itself in polar waters, feeding on krill. In the mating season, they migrate to warmer regions, close to the equator.


The range of distribution extends from the peripheral zone of ice in the polar seas to the tropics. However, it is absent in some seas, such as the Bering, Mediterranean and Okhotsk.

It has a seasonal migratory pattern, between winter and summer, although some species may remain in the same area throughout the year.

The Balaenoptera musculus  is divided into three populations: one in the North Atlantic, one in the Southern Hemisphere and one in the North Pacific. The pygmy species is abundant in southwestern Australia and on the Madagascar plateau in the Indian Ocean.

In the North Atlantic, during the summer, this animal is distributed from Canada, in the Davis Strait, to the Scottish shelf, and in the east it includes Iceland, Svalbard and the Straits of Denmark and Svalbard.

In relation to the eastern Pacific, the blue whale is located all year round from Chile to Costa Rica. In the northern region of the Pacific Ocean it is found throughout the coastal area of ​​Oregon to the Kuril Islands and north to the Aleutian Islands.

Regarding Antarctica, there is no specific migratory destination for these animals during the cold winter. Some blue whales head north, others prefer African waters, India, or the eastern Pacific Ocean.


The Balaenoptera musculus  is a carnivorous animal. Their diet is based almost exclusively on krill, a crustacean found mainly in the Arctic seas. Sometimes it could also consume red crab and small fish, among which are herring and capelin.

They could also capture few portions of copepods, whose species vary by habitat.

As part of their diet, the species Thysanoessa raschii, Meganyctiphanes norvegica, Thysanoessa longicaudata and Thysanoessa inermis inhabit the northern part of the Atlantic Ocean  .

In the North Pacific Ocean, you can find Thysanoessa longipes, Euphausia pacifica, Thysanoessa inermis, Nematoscelis megalops, and Thysanoessa spinifera .

In the southern hemisphere region there are Euphausia superba, Euphausia valentini, Euphausia crystallorophias and Nyctiphanes australis.

Digestive system

Blue whales lack teeth, instead they have baleen. These are similar to a brush and are made of keratin, which gives them their hardness.

The stomach has three chambers: the anterior cavity, the main chamber, and a connecting channel. All the organic compounds that the animal has ingested are stored in the anterior chamber.

Since this cavity does not have glands to aid digestion, the food will start the digestive process thanks to the muscular contractions of the stomach muscles and the anaerobic bacteria found there.

Once the food bolus reaches the main stomach, the pepsin and acids begin to act, which continue the process of food degradation. These two chambers, the main and the previous one, work at the same time as the pyloric stomach, since they have digestive substances and acid glands.

The task of these structures is arduous, digesting krill, like any other crustacean, involves processing its tough exoskeleton. Once this occurs, the gastric juices easily process the soft tissues that make up the interior of these crustaceans.

When the krill decomposition process is complete, the digestive material reaches the intestines through the connecting channel.

All nutrients are absorbed in the intestine, becoming part of the blue whale’s bloodstream. The waste material is stored in the large intestine and later expelled through the anus.

Filtration nutrition

Since these animals cannot grasp or chew their prey due to the lack of teeth, they use filter feeding.

Despite its large size, the blue whale feeds on small organisms, especially the crustacean called krill. Specialists argue that one of the reasons why  Balaenoptera musculus  consumes tiny animals could be because their esophagus is very small. Furthermore, they cannot chew or cut prey into pieces.

The krill are grouped in large schools, where the blue whale catches them. To do this, it opens its huge mouth, where it not only consumes the crustacean, but also small fish and a large amount of water.

Then he partially closes his jaws, pressing his tongue forward, causing the water in his mouth to escape. Subsequently, the blue whale swallows all the remaining animals.

At times it can dive under a krill cloud and expel bubbles as it spirals forward. In this way the krill is forced to go to the center, a moment that is used by the blue whale. It rises towards the center, opens its mouth and swallows the group of crustaceans in one bite.

Their eating habits are seasonal. Before migrating to their hatcheries, in the warm waters of the equator, blue whales can eat between 3 and 4 tons of krill per day. In this way they accumulate energy to be used when they are in areas where their basic food is scarce.


Sexual organs

The blue whale has the longest penis of all species in the animal kingdom. Cetaceans lack scrotum, so they have developed other ways to maintain an adequate temperature in the testes, thus allowing sperm viability.

When the blood circulates through the fins it loses heat and, upon reaching the testes, cools the sperm below body temperature.

In the vaginal slit, located at the base of the belly, females have the vulva located. Next to the cleft the skin forms a kind of fold, where the nipples meet. With these the mother will suckle the young.

Reproductive process

Blue whales reach their sexual maturity around 5 and 10 years of age. However, they usually reproduce only 3 or 4 years later. Before starting the courtship, these cetaceans travel to the hot equatorial arctic waters in search of a mate.

The mating ritual is very similar to a dance. Females and males swim together for a time, then dive deep. Then they line up belly to belly, so close together that they look like a single animal. The copulation process then occurs, where the vagina receives the male sexual organ and the ejaculated sperm could fertilize the ovum.

After being fertilized, the female returns to her feeding place, towards the northern Arctic. Because the gestation period is long, from 9 months to a year, the female has to save a lot of energy.

This is why before mating, he has accumulated large reserves of fat, for the maintenance of his developing young and hers.

The blue whale is a placental mammal, so the fetus develops in the womb, in a temporary organ known as the placenta. The growth of the fetus is rapid, from the seventh month it could already measure almost four meters. The young are born on their tails, then rushing to the surface to breathe.

Many females only get to have babies once, due to a shortage of males, unsuccessful attempts at fertilization and the long time it takes to reproduce. These are some of the reasons that prevent the rapid recovery of the species, from its terrible destruction during the whaling season.


Since its birth, the blue whale is a very large animal, measuring around 8 meters. The calf is suckled with milk with a high fat content, consuming about 180 liters per day. This allows you to gain an approximate 90 kg per day. Weaning occurs in the eighth month after birth.

Mother and son stay together for about a year. Later they separate, the young blue whale starting life as an independent animal.


Blue whales are usually alone or with a partner. These animals, unlike the other species of baleen whales, do not form large groups. In those places where there is an abundance of food, up to 50 individuals can be found, however, they are scattered in the area.


Smell and vision are very limited, but they have a keen sense of hearing. This allows them to communicate and have a better perception of their environment.

Balaenoptera musculus  produces a variety of low-frequency sounds. The male produces long calls, which are associated with the location of his prey, with communication between members of his species, and with courtship.

The vocalizations are the lowest of any baleen whale, vocalizing at 14 Hz, with a volume of up to 200 decibels. Sounds can travel long distances deep in the ocean.

These characteristics allow them not only to communicate, but the vocalizations can be used to navigate. This is because they create a sonic image, which offers them a reference to the characteristics of the environment where it is located.

The duration can be between 10 and 30 seconds. On the coast of Sri Lanka, recordings of some “songs” lasting up to two minutes have been obtained.

Recent research indicates that males vocalize more frequently and intensely than females. Males make individual sounds and “songs.” The unique sounds could be meant for his partner to stick with him while feeding.

Short calls are used to communicate with blue whales that are nearby.

Knowing and analyzing the context in which blue whales perform their vocalizations is of utmost importance, because in addition to contributing to the knowledge of the species, it helps to understand the ecosystem as a whole.


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