Sperm Whale

The sperm whale is among the largest mammals living on the planet. They are marine mammals, sperm whale size ranges about 24 meters (about 78 feet) in size. Sperm whales are easily distinguishable from their counterparts as they possess an enormous square head which is followed by a relatively narrower lower body. They are toothed mammals, sperm whales are more often also referred to as the cachalot. In this article, we will learn the details about the sperm whale, their size, sperm whale habitats, life cycle, and reproduction pattern of the organism, and the common sperm whale vs blue whale differences.

Morphology of the Sperm Whale

Sperm whales are also referred to as cachalot. Sperm whales are the currently residing largest mammals with the tooth. Sperm whale vs blue whale has the main difference that blue is the largest mammal on the planet but they are toothless, whereas sperm whales are toothed mammals. Sperm whales have the characteristic feature of the large square head, the head of the sperm whale is filled with a substance called spermaceti. The biological role of this compound is still unknown but it is because of the presence of this compound this mammal is named the sperm whale.

Sperm whale size can range about 24 meters which are about 78 feet for an adult grown male, whereas the female of the group is generally smaller compared to the male counterpart. The adult female sperm whale size can range from about 14 meters to 14.5 meters which is about 45.9 feet. As the size of the males is larger compared to the females, they also weigh more than females. An adult sperm whale can weigh up to 55 tons whereas the female sperm whale can weigh less than 27 to 28 tons. The sperm whales have a unique square-shaped head, they are generally grey in colour with a generally smooth skin texture, sometimes the back of the mammal is rough. 

Sperm whales also have a blowhole that is used in breathing, the blowhole apparatus is situated just below the front head they are slightly tilted towards the left of the whale.  The sperm whales are considered to be a widely dimorphic species, the dimorphism can be attributed to the sperm whale size, or their weight and colour. The sperm whales are seen to have patchy skin on the belly, they generally develop white coloured patches on the belly. The interesting facts about sperm whales are the presence of the spermaceti in the head, another point is the commercial value of the sperm vomit, both of these compounds have large commercial values.

Taxonomy of the Sperm Whale

Sperm whales are known to be among the largest mammals, the taxonomic classification of the organism is important to understand the position of the species in the evolutionary history of toothed mammals. The scientific name of the organism is Physeter macrocephalus. 

According to the taxonomic classification, the Physeter macrocephalus or commonly known as the sperm whale belongs to the kingdom Animalia, they belong to the phylum Chordata, the Chordata phylum includes all the organisms that has the backbone, that is the organism that consists of the vertebral column.  They are classified under the class Mammalia, the characteristic feature of this class is that they give birth to the young ones, they generally have internal fertilization. Internal fertilization refers to the fertilization of male and female gametes inside the reproductive system of the female. They follow the path of direct development that is they do not undergo metamorphosis or transitional state during their development. 

Sperm whales belong to the order Artiodactyla. This modern classification system is known as the Cetartiodactyla. This order consists of all the animals like pigs, peccaries, hippopotamuses, antelopes, mouse deer, deer, giraffes, camels, llamas, alpacas, sheep, goats, and cattle. The characteristic feature of this order is to have the ungulates hoofed animal. The order is further classified in the infraorder, sperm whale belongs to Cetacea, this infraorder consists of all the whales, dolphins, and porpoises. The characteristic feature of this infra order is the carnivorous diet of the mammals, they generally are large and have a slender body. 

These features are common for all the members of this infra order including the sperm whales. They are even further grouped as Odontoceti, this subdivision of the infra order, this group contains all the toothed marine mammals like dolphins and whales. They are classified under the family Physeteridae. This superfamily contains all the three extant species of whales, containing the sperm whale,  pygmy sperm whale, and dwarf sperm whale. The sperm whale discussed here belongs to the genus Physeter, the last stage of the taxonomic classification is the species the sperm whale belongs to Macrocephalus.

Anatomical Feature of the Sperm Whale

Apart from its unique morphological features, there are some relevant anatomical features that help in the survival of the sperm whale, the anatomical features discussed here are the skeleton, jaws, and teeth of the sperm whale. 

Skeleton of the Sperm Whale 

The sperm whale belongs to the phylum Chordata. The facts about the sperm whale skeleton are the presence of ribs, the ribs are made up of cartilage, the cartilage joins the rib to the spine. The reason for the evolution of the cartilage is to support the high-pressure living conditions of the sperm whale. The presence of the cartilage allows the ribs to collapse in high pressure rather than breaking. Some of the studies have revealed the presence of pitting signals in the bones. These pitting signals are the indicator of the decompression disease of the bones which is found in humans. 

It is an interesting fact that there is no sign of decompression disease in the skeleton of newborn or young sperm whales. It is an indicator that this disease is caused because of the continuous deep diving of the whales. There are some evolutionary modifications made in the spine of the sperm whale, these modifications are made to adapt to the mammal living in the very deep seas, one of the modifications of the spine observed in sperm whales is the reduced zygapophysial joints. The zygapophysial joint reduction results in decreased dorsal bending while promoting the increase in the dorsoventral bending. The increased dorsoventral bending is important for the adaptation of the whale to high pressure and water currents of the ocean. 

It is also to be noted that this reduction is a common feature among all the members of the cetaceans family.  Another modification that is helpful for the survival of the sperm whale is the unjoined vestigial pelvis. The pelvis bone in the sperm whale does not perform any function thus is considered as a vestigial organ, this vestigial pelvis is not attached to the spine, thus rendering it a unique feature of the spine among the phylum chordates. Generally, all the chordates have their pelvic girdle or pelvic joint attached to the spine of the body.

Jaws of the Sperm Whale

It is the presence of the tooth that has marked and led to the formation of different subgroups in the taxonomic classification. If the difference in sperm whale vs blue whale is studied apart from the sperm whale size comparison the presence of the teeth is the most important difference prevailing in this comparison. There are about 18 to 26 teeth on each side of the lower jaws. These teeth fit on the upper jaw. It is important to note that the teeth even though present in the buccal cavity do not necessarily play the role in the mastication of the food. 

It is believed the teeth are more of the rudimentary organ, teeth in adult sperm whales are used to prove their dominance and aggression. It is also important to note that the upper jaw does not have teeth. The upper jaw may contain some vestigial teeth but they do not develop into the teeth. The teeth are a sign of age in the sperm whale group. As the adult of the group has an increased layer of the cementum and dentine, these layers are generally referred to calculate the age of the individual. A full-grown tooth in the adult sperm whale can weigh up to 1 kg of weight. 

Spermaceti

Spermaceti is the organ from which the name of the sperm whale is derived, spermaceti has a kind of waxy texture found specifically in sperm whales. Because of the presence of these compounds, sperm whales are subjected to enormous whaling. Whaling can be defined as whale hunting. The spermaceti biological significance is not yet completely understood but it has commercial importance; they are used as burning fuels in lamps and used in lubrication. They were sold as lubricating wax. 

According to sperm whale facts, spermaceti organs present in a single sperm whale can store up to 550 gallons of this compound. There are two theories regarding the biological significance of the spermaceti in sperm whales. The first theory suggests that it is this organ that maintains the buoyancy in the sperm whale during high-pressure deep-sea dive. The spermaceti can act as a buoyancy regulator by evacuating the muscle and absorbing nitrogen at extreme underwater pressure prior to the deep dive in the high-pressure water. It can also cushion to protect the sperm whale's snout, which is a delicate organ susceptible to damage during a deep-diving condition. 

Another hypothesis about the organ is that they help in the communication among the other sperm whales or different whale species. Whales communicate with each other by using echolocation. The spermaceti is believed to add an internal echo or sonar that helps in the echolocation. This helps sperm whales to capture their food, when biosonar or echo are released with the change in speed or position there is a change in the reflected sonar. This change is sensed by the sperm whales allowing them to capture the prey and gain information about the direction of the prey. Apart from using it for predation, they are also a means of communication in whales. 

Diet of Sperm Whale

Sperm whales are mainly carnivorous; they generally feed on squid. The organism that the sperm whale prey on includes the octopus and smaller squids. Some of the minor examples of organisms that are preyed on by the sperm whale include the following ock fishes, cod, sharks, rag fish, skate, dory-type fish, ling, lumpsucker. It is an interesting fact about sperm whales that among the various organisms they prey on, the most preferable prey is the giant squid. Since the upper jaws of the whale do not have teeth and the lower jaw teeth are not used for mastication, the digestion of the food is completely dependent on the gastric juices of the sperm whale. The indigestible part of the diet like the beak of the gain squid resides in the intestine of the mammal food sometimes, which is ultimately vomited out. This substance that is vomited out is known as the ambergris. 

Ambergris is the combination of solid undigested food and secretion of bile ducts which produces the bile juices and the gastric juice. They are also considered as one of the commercially important substances of the sperm whale. Ambergris is used in the fragrance industry as a conjugate to lengthen the time of fragrance to dissipate. 

The sperm whales are sometimes seen to consume the food at a deeper sea level and exerted on a comparatively upper surface this leads to the fertilization of the phytoplanktons. The consumption of nutrients at the deep sea and transporting those nutrients to the oceans' surface when they defecate, leads to the fertilization of the phytoplankton layer. This phenomenon is also known as the whale pump. 

Habitat and Group of Sperm Whale

Sperm whales reside in the depth of the sea or ocean, they come up to the surface to dive. The most favourable habitat for this mammal is about  3,300 feet deep, they do not prefer living in the ice-filled region. They can be easily spotted in the regions like underwater canyons, and the edges of continental shelves. Sperm whales are distributed over the tropical and temperate oceans, the sperm whales generally live in groups. The group of sperm whales is referred to as pods. The pods contain about 15 to 20 members. It is important to note that the adult male sperm whale is not generally seen with the pod every time. The pod usually consists of female and younger members. The females nurture and protect their progeny. It is also important to note that parental care in this species is very high. The parent whale takes care of the young members for over a decade. 

Communication in Pods

The group of sperm whales is known as pods. Sperm whales are generally considered as groups that maintain the social hierarchy and structure. They interact with each other and with other groups of whales. The principal way of communication in whales is through echolocating. During echolocating, the sperm whales produce a very specific sound, the minor differences in the sound are detected by the other sperm whales. The term used to describe such sound produced by the sperm whale is clicks. Each click has its particular frequency and vibration pattern that enables deciphering the meaning of it by other pod members. Echolocation is also used for determining the location of prey, detecting a potential threat, and communicating with related groups of organisms. 

Life Cycle and Reproduction Pattern

They are k- selected species, that is they provide enough parental care, they have a longer life span, they produce fewer offsprings. The average lifespan of the sperm whale is about 70 years, as described earlier sperm whales are social animals that follow a hierarchical structure. The male of the group generally does not interact with the female till mating season. There is often competition and display of aggressive behaviour indicating the intraspecies competition among males for mating probability. The strongest male mates with the female multiple times. 

Females of the group attain their reproductive maturity at the age of nine. The last recorded data suggest that the reproductive capacity of the males can last up to 41 years of age. Contrary to this males attain their reproductive features somewhat late, the male is shown to attain reproductive maturity till 19 years of age.. the male sperm whale is often known as bulls, they are polygamous in nature. They do not highly participate in parental care. The gestation period in the females can last up to 14 to 16 months, after which the young one needs care for a long time, generally over a decade. The lactation period in baby sperm whales can last up to 19 to 42 months. Once the calves become strong and attain their reproductive maturity the male moves to higher latitudes and continues their life cycle. 

Facts About Sperm Whale Etymology

The name sperm whale is often misunderstood and thought to be derived from the whale semen or sperm. But in fact, the name is of Greek origin and is derived from the name of organ spermaceti which stores whale oil. Another misconception that is followed by sperm whales is the whale semen forms the tidal foam around the coast. It is partially true that the blue whale sperm ejaculation at a single instant unloads 20 litres of sperm. But even with the amount of ejaculation of blue whale sperm, it is very rare to form such tidal foams. The real reason behind the formation of tidal foam is coagulation in sea waves. 

Sperm Whale Vs Blue Whale

There are many similarities and differences between these two groups, some of the major differences are listed below.

Conclusion 

Sperm whales are the largest known toothed mammals, whose diet is primarily carnivorous which include giant squids and octopus, similar to all the K-selected species they give birth to the young ones and provide parental care. They follow the hierarchical system and live in groups called pods. They are classified into vulnerable species due to the extensive whaling of the species because of their commercial valuable sperm whale oil.