Beluga Whale

Beluga, (or Delphinapterus leucas) is also referred to as belukha and white whale. It is a small toothed whale that may be found primarily in the Arctic Ocean's coastal waters and surrounding seas, as well as deep offshore waters and rivers. It is a very vocal cetacean and therefore has also been known as the “canary of the sea.” Also, this whale can proficiently mimic a diverse range of sounds. The beluga has been kept in captivity since the 1860s and is easily caught in shallow water, and its adaptability and colouration have made it popular at oceanariums.

About Beluga and Beluga Whale Facts

Adult belugas hold broad flippers with upward-curving tips, but there exists no dorsal fin. Belugas have extremely plastic facial features and a rounded forehead, enabling the whales to change the external shape of their head at will. Female belugas will experience menopause, with a significant portion of their 35–50-year life span can be spent in the post-reproductive phase.

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Arctic Populations of Beluga

Beluga whales’ Arctic populations are at home in pack ice but should migrate to warmer waters when the sea completely freezes over. Usually, they live in the groups of 5 to pods of above 1,000, feeding on cephalopods, crustaceans, fish, and worms.

In the Arctic regions, the beluga is hunted as food for dogs and humans. During the 19th and the early 20th centuries, it was commercially taken for its flesh, oil, and hides that provided industrial leather, shoelaces and belts. In the Gulf of St. Lawrence, the beluga population was approximately exterminated for its hides, and a few other beluga populations are endangered by the pollution.

Beluga Whales

Beluga whales are related to the narwhal, and the two species together constitute the family Monodontidae of the suborder Odontoceti (which are the toothed whales). The name beluga derives from the Greek word delphinos, which means dolphin, mixed with apteron, which refers to the lack of a dorsal fin. The particular epithet leucas has derived from the Greek leukos, which means “white.” The common name, at times, spelt belukha, has derived from the Russian belyi, again meaning “white.” Also, beluga is the common name for the unrelated great white sturgeon of the caviar fame.

Taxonomy

Beluga vs Dolphin

First, the beluga was described by Peter Simon Pallas in 1776. It belongs to the Monodontidae family, which is, in turn, a subfamily of the Odontoceti (or toothed whales). The Irrawaddy dolphin was once classed in the same family as the bottlenose dolphin, but recent genetic research reveals that these dolphins belong to the Delphinidae family. Besides the beluga, the narwhal is the only other species within the Monodontidae. The discovery of a skull with intermediate traits lends credence to the theory that hybridization between these two species is possible.

Delphinapterus is the genus name, which means "dolphin without fin" (derived from the Greek (delphin), dolphin, and (apteros), without fin), and leucas is the species name, which means "white" (derived from the Greek term (leukas), white). White whales and belugas are both common names on the Red List of Threatened Species, albeit the former is more prominent presently. The English name has come from the Russian (belukha), which derives from the word bélyj, which means "white". The term beluga in Russian refers to the unrelated species, the beluga sturgeon, a fish.

Evolution

Mitochondrial DNA studies have demonstrated that modern cetaceans last shared a common ancestor between the years of 25 and 34 millions. The superfamily Delphinoidea (that contains dolphins, monodontidae and porpoises) split from the other toothed whales, odontoceti, between the years 11 and 15 million ago. Then, monodontidae split from the dolphins (Delphinidae) and after that, from porpoises (Phocoenidae), their closest relatives in evolutionary terms. In 2017 the beluga genome whale was sequenced by comprising 2.327 Gbp of assembled genomic sequence, which encoded 29,581 predicted genes. Also, the authors have estimated that the similarity of genome-wide sequence between the killer whales and beluga whales is 97.87% ± 2×10−7% (which means, ± standard deviation).

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The prehistoric Denebola brachycephala from the late Miocene epoch (i.e., 9–10 million years ago) and the Bohaskaia monodontoides from the early Pliocene (i.e., 3–5 million years ago) are the earliest known separate progenitors of beluga. The family formerly lived in warmer waters, according to fossil evidence found in Virginia and Baja California. From five million years ago, a fossil of the monodontid Casatia thermophila, provides the strongest evidence that monodontids once inhabited the warmer waters, as the fossil was found alongside the fossils of tropical species such as tiger sharks and bull.

Description of Belugas

Its body is round, specifically when well-fed, and tapers less smoothly to the head compared to the tail. Its rapid tapering to the base of its neck gives it the impression of shoulders, which is unusual among cetaceans. As the animal gets older, the tail-fin develops and becomes more ornately curled. The flippers are short and broad—making them almost as square-shaped.

Longevity

Preliminary investigations suggested that a life of beluga expectancy was rarely above 30 years. The method used to calculate the beluga’s age is completely based on counting the layers of dental and dentin cement in the teeth of the specimen, which were originally thought to be deposited either once or twice a year. The layers may be readily identified as one layer consists of an opaque dense material and the other layer is less dense and transparent. Therefore, it is possible to estimate the individual age by extrapolating the layers count identified and the estimated frequency with which the deposits are laid down.

Size

The males are 25% longer and sturdier than the females, indicating a moderate degree of sexual dimorphism in the species. Male belugas can grow to be 3.5 to 5.5 metres long (11 to 18 feet), while females grow to be 3 to 4.1 metres long (9.8 to 13.5 ft). Males weigh between 1,100 and 1,600 kg (2,430 and 3,530 lb), with some reaching 1,900 kg (4,190 lb), while females weigh between 700 and 1,200 kg (2,430 and 3,530 lb) (1,540 and 2,650 lb). Among toothed whales, they are a medium-sized species.

Colour

Because it is either totally white or whitish-grey in colour, the adult beluga is rarely mistaken for any other species. Usually, the calves are born grey, and by the time they are a month old, have turned blue grey or dark grey. Then, they progressively start to lose their pigmentation until they attain the distinctive white colouration, at the age of 9 in males and 7 years in females. The skin’s white colouration is an adaptation to life in the Arctic, which allows belugas to camouflage themselves in the polar ice caps as protection against their primary predators, killer whales and polar bears.

Unlike the other cetaceans, the belugas shed their skin seasonally. During the winter, the epidermis thickens and turns yellow, especially on the fins and back. When they migrate to the estuaries at the time of summer, they themselves rub on the gravel of the riverbeds to remove cutaneous covering.

Head and Neck

It, like the majority of toothed whales, has a compartment in the centre of the forehead that houses an organ for echolocation known as a melon that stores fatty tissue. The beluga’s head shape is unlike that of any other cetacean, because the melon is very bulbous, visible as a large frontal prominence and lobed. The other distinctive characteristic that it possesses is the melon is malleable; its shape is changed at the time of sound emission.

To focus on emitted sounds, the beluga can modify the form of its head by blowing air around its sinuses. This organ has fatty acids, primarily isovaleric acid (60.1%) and the long-chain branched acids (16.9%), which is a very different composition from its body fat and that could play a main role in its echolocation system.

Fins

The fins will retain the bony vestiges of the mammalian ancestors of the belugas, and they are firmly bound together by the connective tissues. The fins are oar-shaped, rounded, and somewhat curved at the tips, and are modest in comparison to the size of the body. These versatile extremities are majorly used as a rudder to control the direction and to work in synchrony with the tailfin and for the agile movement in shallow waters around 3 m (9.8 feet) deep.

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The arteries that feed the fin's muscles are bordered by veins that dilate or contract to acquire or lose heat, therefore the fins include a system for controlling body temperature. The tailfin is made up of thick, hard, and fibrous connective tissue and is flat with two oar-like lobes. It does not hold any bones and is made up of thick, hard, and fibrous connective tissue. The tailfin contains a distinctive curvature along the lower edge. Both the ascending and descending movement of the tailfin, which has the same thermoregulation process as the pectoral fins, is provided by the back's longitudinal muscles.

Senses

The beluga has a highly developed auditory brain and a specialised sense of hearing. It may hear sounds within the range of 1.2 - 120 kHz, having the greatest sensitivity between 10 - 75 kHz, whereas, the average hearing range for humans is given as 0.02 to 20 kHz. The majority of the sounds are most probably received by the lower jaw and are transmitted towards the middle ear. The lower jawbone of a toothed whale is large, with a hollow at its base that expands towards where it connects the cranium.

Inside this small cavity, a fatty deposit connects to the middle ear. Furthermore, toothed whales have a small external auditory hole located a few millimetres beyond their eyes, which communicates with an eardrum and external auditory conduit. If these organs are functional or simply vestigial, it is not known.