Beluga whale
The beluga whale, is an Arctic and sub-Arctic cetacean. It is one of two living members of the family Monodontidae, along with the narwhal, and the only member of the genus Delphinapterus. It is also known as the white whale, as it is the only cetacean to regularly occur with this colour; the sea canary, due to its high-pitched calls; and the melonhead, though that more commonly refers to the melon-headed whale, which is an oceanic dolphin.
The beluga is adapted to life in the Arctic, with anatomical and physiological characteristics that differentiate it from other cetaceans. Amongst these are its all-white colour and the absence of a dorsal fin, which allows it to swim under ice with ease. It possesses a distinctive protuberance at the front of its head which houses an echolocation organ called the melon, which in this species is large and deformable. The beluga's body size is between that of a dolphin and a True's beaked whale, with males growing up to long and weighing up to. This whale has a stocky body. Like many cetaceans, a large percentage of its weight is blubber. Its sense of hearing is highly developed and its echolocation allows it to move about and find breathing holes under sheet ice.
Belugas are gregarious and form groups of 10 animals on average, although during the summer, they can gather in the hundreds or even thousands in estuaries and shallow coastal areas. They are slow swimmers, but can dive to below the surface. They are opportunistic feeders and their diets vary according to their locations and the season. The majority of belugas live in the Arctic Ocean and the seas and coasts around North America, Russia, and Greenland; their worldwide population is thought to number around 200,000. Belugas are migratory and the majority of groups spend the winter around the Arctic ice cap; when the sea ice melts in summer, they move to warmer river estuaries and coastal areas. Some populations are sedentary and do not migrate over great distances during the year.
The native peoples of North America and Russia have hunted belugas for many centuries. They were also hunted by non-natives, primarily Europeans, during the 19th century and part of the 20th century. Hunting of belugas is not controlled by the International Whaling Commission, and each country has developed its own regulations in different years. Currently, some Inuit in Canada and Greenland, Alaska Native groups and Russians are allowed to hunt belugas for consumption as well as for sale, as aboriginal whaling is excluded from the International Whaling Commission 1986 moratorium on hunting. The numbers have dropped substantially in Russia and Greenland, but not in Alaska and Canada. Other threats include natural predators, contamination of rivers, climate change and infectious diseases. The beluga was placed on the International Union for Conservation of Nature's Red List in 2008 as being "near threatened"; the subpopulation from the Cook Inlet in Alaska is considered critically endangered and is under the protection of the United States' Endangered Species Act. Of all seven extant Canadian beluga populations, those inhabiting eastern Hudson Bay, Ungava Bay, and the St. Lawrence River are listed as endangered.
Belugas are one of the most commonly kept cetaceans in captivity and are housed in aquariums, dolphinariums and wildlife parks in North America, Europe and Asia. They are considered charismatic because of their docile demeanour and characteristic smile, communicative nature, and supple, graceful movement.
Etymology
The name of the genus, Delphinapterus, means "dolphin without fin", dolphin and απτερος and the species name leucas means "white". The Red List of Threatened Species gives both beluga and white whale as common names, though the former is now more popular. The English name comes from the Russian белу́га, which derives from the word белый, meaning "white". The whale is also colloquially known as the "sea canary" on account of its high-pitched squeaks, squeals, clucks, and whistles.Taxonomy
The beluga was first described in 1776 by Peter Simon Pallas. It is a member of the family Monodontidae, which is in turn part of the parvorder Odontoceti. The Irrawaddy dolphin was once placed in the same family, though recent genetic evidence suggests these dolphins belong to the family Delphinidae. The narwhal is the only other species within the Monodontidae. A skull has been discovered with intermediate characteristics supporting the hypothesis that hybridisation is possible between these two species.Evolution
studies have shown modern cetaceans last shared a common ancestor between 25 and 34 million years ago The superfamily Delphinoidea split from other toothed whales, odontoceti, between 11 and 15 million years ago. Monodontids then split from dolphins and later from porpoises, their closest relatives in evolutionary terms. In 2017 a study was completed where the genome of a beluga whale was sequenced, comprising 2.327 Gbp of assembled genomic sequence that encoded 29,581 predicted genes. The authors of this study estimated that the genome-wide sequence similarity between beluga whales and killer whales is 97.87%.The beluga's earliest known distinctive ancestors include the prehistoric Denebola brachycephala from the late Miocene epoch, and Bohaskaia monodontoides, from the early Pliocene. Fossil evidence from Baja California and Virginia indicate the family once inhabited warmer waters. A fossil of the monodontid Casatia thermophila, from five million years ago, provides the strongest evidence that monodontids once inhabited warmer waters, as the fossil was found alongside fossils of tropical species such as bull and tiger sharks.
The fossil record also indicates that, in comparatively recent times, the beluga's range varied with that of the polar ice packs expanding during ice ages and contracting when the ice retreated. Counter-evidence to this theory comes from the finding in 1849 of fossilised beluga bones in Vermont in the United States, from the Atlantic Ocean. The bones were discovered during construction of the first railroad between Rutland and Burlington in Vermont, when workers unearthed the bones of a mysterious animal in Charlotte. Buried nearly below the surface in a thick blue clay, these bones were unlike those of any animal previously discovered in Vermont. Experts identified the bones as those of a beluga. Because Charlotte is over from the nearest ocean, early naturalists were at a loss to explain the presence of the bones of a marine mammal buried beneath the fields of rural Vermont.
The remains were found to be preserved in the sediments of the Champlain Sea, an extension of the Atlantic Ocean within the continent resulting from the rise in sea level at the end of the ice ages some 12,000 years ago. Today, the Charlotte whale is the official Vermont State Fossil.
Description
Belugas have a round and muscular body that is tapered at both ends. The tapering begins at the base of its neck, which gives the beluga the appearance of shoulders. This trait is unique compared to other cetaceans. Beluga whales do not have fused neck vertebrae. The neck of a beluga is narrower when compared to other extant whales. The unusual vertebrae traits in a beluga allow it to move its head and nod.Longevity
Preliminary investigations suggested a beluga's life expectancy was rarely more than 30 years. The method used to calculate the age of a beluga is based on counting the layers of dentine and dental cement in a specimen's teeth, which were originally thought to be deposited once or twice a year. The layers can be readily identified as one layer consists of opaque dense material and the other is transparent and less dense. It is therefore possible to estimate the age of the individual by extrapolating the number of layers identified and the estimated frequency with which the deposits are laid down. A 2006 study using radiocarbon dating of the dentin layers showed the deposit of this material occurs with a lesser frequency than was previously thought. The study therefore estimated belugas can live for 70 or 80 years. In 2022, researchers at Kent State University and Northeast Ohio Medical University were able to determine that the Beluga whale gains one extra dentin layer each year below the teeth of their enamel, which provides a method of detecting the age of the beluga whale. The oldest living beluga whale was 79 years old.Size
The species presents a moderate degree of sexual dimorphism, as the males are 25% longer than the females and are sturdier. Adult male belugas can range from, while the females measure. Males weigh between, and occasionally up to while females weigh between. They rank as mid-sized species among toothed whales. The newborn calf will often measure approximately, and weigh from at their time of birth.Individuals of both sexes reach their maximum size by the time they are 10 years old. The beluga's body shape is stocky and fusiform, and they frequently have folds of fat, particularly along the ventral surface. Between 40% and 50% of their body weight is fat, which is a higher proportion than for cetaceans that do not inhabit the Arctic, where fat only represents 30% of body weight. The fat forms a layer that covers all of the body except the head, and it can be up to thick. It acts as insulation in waters with temperatures between 0 and 18 °C, as well as being an important reserve during periods without food.