SPERM WHALE: CHARACTERISTICS, CLASSIFICATION, HABITAT, FEEDING, REPRODUCTION - BIOLOGY - 2025

The sperm whale (Physeter macrocephalus) is a marine mammal that belongs to the Physeteridae family. Within the group of toothed whales, it is the largest species, the adult male being able to measure up to 20.5 meters and weigh almost 57 tons. The female is much smaller, having a length of 12 meters.

It has a large block-shaped head that distinguishes this cetacean from the rest of the members of the order to which it belongs. The blowhole is located near the front of the head, slightly offset to the left. The skin on the back has a rough appearance. As for its coloration, it is gray. However, under sunlight it turns brown.

Sperm whale Source: Mother_and_baby_sperm_whale.jpg: Gabriel Barathieuderivative work: Tomer T

In relation to distribution, this pelagic mammal has a great global reach. Thus, it lives in those marine waters that are not under the ice and whose depth is greater than 1,000 meters. However, it does not live in the Black Sea or the Red Sea.

The dives

The sperm whale is one of the marine mammals that dive deeper. It usually goes down to 400 meters in just 35 minutes. However, it could be submerged to a much greater distance, being able to cover up to almost three kilometers.

Adaptations

This species has adaptations that allow it to withstand the drastic changes that the body undergoes, in the face of the strong pressure variations produced by diving.

In this sense, the rib cage is flexible, which allows lung collapse. This reduces the entry of nitrogen into the tissues and decreases metabolism, thus conserving oxygen.

Another factor that increases the effectiveness of the respiratory process is the presence in the blood of large amounts of myoglobin. This protein is responsible for storing oxygen at the muscle level. In addition, the density of red blood cells is high, so hemoglobin is abundant, which functions as an oxygen carrier.

On the other hand, when oxygen levels are low, oxygenated blood can go exclusively to the brain and other essential organs.

Although the Physeter macrocephalus is well adapted to diving in the deep sea, repeated dives have long-term adverse effects. This is evidenced in bone level injuries caused by rapid decompression.

characteristics

Size

Within the group of toothed whales, the sperm whale is the largest. Also, it is one of the cetaceans with a marked sexual dimorphism.

The young of both sexes are born having almost the same size, however, when they mature there is a notable difference. The male is 30 to 50% longer and up to 3 times larger than the female.

Thus, the male reaches 20.5 meters, while the female is 12 meters long. In terms of weight, the adult male can weigh up to 57 tons.

Body

This species has a distinctive appearance, its head is very large and block-shaped. It can measure between a quarter and a third of the total length of the animal. On the front of the head it has a blowhole, with the appearance of S.

The tail lobes are thick, flexible and triangular. When the animal dives, they protrude out of the water. Instead of a dorsal fin, the sperm whale has a series of ridges, located in the dorsal caudal third. The largest crest is called a hump, due to its similarity to a dorsal fin.

Bone structure

The ribs of this cetacean are attached to the spine through flexible cartilage. In this way, the rib cage does not break when it is subjected to the high pressure generated by the immersion.

The skull is triangular and asymmetrical. Within the basin of this, the openings corresponding to the bony narial tubes are inclined to the left. As for the jaws, they are large and make up most of the bone structure of the head.

The spinal column is made up of 49 vertebrae, divided into four groups: cervical, thoracic, lumbar and caudal. Like the rest of the cetaceans, this bone structure has reduced zygapophyseal joints

This modification makes the spine much more flexible than that of terrestrial vertebrates, but it also makes it weaker.

Teeth

The teeth are cone-shaped and each one could weigh up to one kilogram. The lower jaw of the Physeter macrocephalus is narrow and long. On each side, it has between 18 and 26 teeth, which fit perfectly into the cavities of the upper jaw.

In the upper jaw there are also rudimentary pieces, although they rarely emerge. The teeth are functional, but the sperm whale probably does not use them to capture or eat their prey.

This is based on the fact that researchers have found some animals of this species without teeth and with problems in jaws, which are well fed. Experts suggest that teeth are used in aggression between males, who frequently display scars produced in these fights.

Brain

The Physeter macrocephalus brain is the largest of any extinct or modern animal, with an average weight of 7.8 kilograms and an approximate volume of 8,000 cm3. The olfactory area is reduced, while the auditory area is well developed.

The breathing

Between each dive, the sperm whale rises to the surface for 8 minutes to breathe. Like the rest of the odontocetes, it breathes through a single blowhole, which is S-shaped. The blowing is noisy, with a jet of water that can rise high above the surface.

When the animal is at rest, it breathes 3 to 5 times per minute, increasing up to 7 times per minute after submerging.

Digestive system

The sperm whale has a stomach that is divided into several chambers. The former has very thick muscular walls and does not secrete any type of gastric juice. In this cavity the prey that the animal has ingested are crushed.

The second cavity, larger than the previous one, is where digestion occurs. The action of gastric juices acts on food, degrading organic compounds so that they can be assimilated by the body.

However, squid beaks are not digested, so a large part of these are expelled through the mouth and the rest passes into the intestine. According to experts, to facilitate the passage of these spikes and other indigestible parts (such as the cuticle of nematodes), the liver secretes bile.

This bile secretion is known as ambergris and is used in the perfume industry, in gastronomy as a flavoring, as well as in traditional medicine.

Spermaceti organ

This structure is located in the head of the Physeter macrocephalus, occupying almost 90% of its total mass. Inside it is spermaceti oil, a compound made up of wax esters and triglycerides.

Many are the functions that are attributed to this organ, such as functioning as a buoyancy mechanism.

During the immersion, the cold water solidifies the spermaceti oil, which induces an increase in its density. This generates a downward force of approximately 40 kilograms, thus allowing the animal to descend more easily.

Conversely, while hunting, increased oxygen consumption generates heat, which melts the oil. Thus, buoyancy is increased and the cetacean can return to the surface more easily.

Another function of this organ is echolocation. In this sense, variations in the shape of the spermaceti organ amplify or reduce the sounds emitted. Also, it contributes to the transmission of ultrasound.

Taxonomy and classification

-Kingdom: Anima.

-Subreino: Bilateria.

-Filum: Cordate.

-Subfilum: Vertebrate.

-Infrafilum: Gnathostomata

-Superclass: Tetrapoda.

-Class: Mammal.

-Subclass: Theria.

-Infraclass: Eutheria.

-Order: Cetacea.

-Suborder: Odontoceti.

-Family: Physeteridae.

-Gender: Physeter.

-Species: Physeter macrocephalus.

Habitat and distribution

The sperm whale is widely distributed in almost all marine waters that are not covered with ice and that have a depth greater than 1,000 meters. Within its extensive habitat the Red Sea and the Black Sea are excluded.

Both sexes live in oceans and in temperate and tropical seas. However, females and their young tend to be restricted to lower latitudes, with waters whose temperature is greater than 15 ° C. As for adult males, they generally prefer higher latitudes.

Physeter macrocephalus populations are densest near canyons and continental shelves. However, they are frequently sighted near the coast, in areas where the continental shelf is small, suddenly dropping to depths between 310 and 920 meters.

Feeding

This marine mammal is a carnivore that requires the equivalent of 3% of its weight to be ingested daily. Their diet is varied, and can include various species of fish and octopus.

However, the diet is mainly based on squid of various genera, such as Histioteuthis, Ancistrocheirus, and Octopoteuthis. Thus, they hunt giant or colossal squid, but basically they consume the medium squid.

The male usually feeds at a greater depth than the female. In this way, it can consume benthic organisms such as crabs and fish (Allocyttus sp. And Lophius sp). As for the female, it generally remains further from the coast, where the male can also live.

Both sexes feed mesopelagically, consuming crustaceans of the order Mysida, fish of the species Ruvettus sp., And mesopelagic cephalopods. A study carried out indicates that adult males eat large cephalopods more frequently compared to those ingested by females or by young males.

Hunting methods

To hunt for prey, the sperm whale dives from 300 to 800 meters. If necessary, it could go almost three kilometers deep. Also, according to the data provided by the researchers, sperm whales can work together to capture Humboldt squid.

Likewise, when the cetacean is in a deep dive, it usually hunts upside down. On some occasions, the prey is captured directly or could be accidentally taken, while ingesting other marine species.

Considering that the Physeter macrocephalus frequently inhabits shallow depths, where light is scarce, echolocation is a very effective technique for hunting. In this, the cetacean emits waves, which collide with the object. When they bounce, they are taken up by the spermaceti organ, which transmits them to the brain.

In this organ of the nervous system, stimuli are interpreted, providing the animal with information about the location of the prey.

Reproduction

In the sperm whale, the female becomes fertile when she reaches nine years of age and can be pregnant until at least 41 years of age. In relation to the male, he is sexually mature at 18 years of age.

At that time, the male migrates to higher latitudes, where feeding is more productive for him. The female remains in the lower latitudes and where she can give birth every 4 to 20 years.

To mate with a female, males often fight each other. These can mate with several females during the same reproductive period, but that does not make them dominant within the group.

Breeding

The duration of gestation is 14 to 16 months, producing a single offspring. The birth is a social event, since both the mother and the young need the rest of the group to protect them from predators.

The mother breastfeeds the calf between 19 and 42 months, although cases of youngsters who are weaned at 13 years have been reported.

As in other whales, the mother's milk of the sperm whale contains a high degree of fat, more than in terrestrial mammals. Thus, cow's milk has 4% fat, while that of this cetacean has 36%.

This particular characteristic gives it a consistency similar to cottage cheese, which prevents it from dissolving in the water before the young person drinks it. In addition, its energy value is very high, reaching 3,840 kcal / kg, compared to cow's milk, which only has 640 kcal / kg.

Behavior

The social unit is a grouping of sperm whales that live and travel together. This can vary in size, being able to be formed between 6 and 9 cetaceans, although they tend to have more than 20. Within this group, the Physeter macrocephalus does not show a tendency to associate with its relatives, an aspect that does occur in orcas.

Juvenile males and females live and stay together in groups, while adult males leave their natal grouping when they are between 4 and 21 years old. Sometimes they form groups of singles, with others the same size and age, but as they become more adults, they live alone.

Females and young spend about a quarter of their time socializing and three quarters feeding. To defend a vulnerable member of the group, the sperm whales organize and adopt the daisy formation.

Thus, they surround the most defenseless members of the group, placing their body in position with the tail fins facing out. In this way, they keep the predator away.

References

1. Wikipedia (2019). Sperm whale. Recovered from en.wikipedia.org.
2. ITIS (2019). Physeter macrocephalus. Recovered from itis.gov.
3. B. Best (2010). Food and feeding of sperm whales Physeter macrocephalus off the west coast of South Africa. Recovered from tandfonline.com.
4. Hal Whitehead (2018). Sperm Whale: Physeter microcephalus. Recovered from sciencedirect.com.
5. Peter Rudolph, Chris Smeenk (2009). Indo-West Pacific Marine Mammals. Recovered from sciencedirect.com.
6. EDGE (2019). Sperm Whale. Physeter macrocephalus Recovered from edgeofexistence.org.
7. Christopher M. Johnson, Lynnath E. Beckley, Halina Kobryn, Genevieve E. Johnson, Iain Kerr, Roger Payne. (2016). Crowdsourcing Modern and Historical Data Identifies Sperm Whale (Physeter macrocephalus) Habitat Offshore of South-Western Australia. Recovered from frontiersin.org.