Board Thread:News and Announcements/@comment-30238789-20180130035010/@comment-31651395-20180130150753

The beluga whale or white whale(Delphinapterus leucas) is an Arctic and sub-Arctic cetacean. It is one of two members of the family Monodontidae, along with the narwhal, and the only member of the genusDelphinapterus. This marine mammal is commonly referred to as the beluga, melonhead, or sea canary due to its high-pitched twitter.

It is adapted to life in the Arctic, so has anatomical and physiological characteristics that differentiate it from other cetaceans. Amongst these are its all-white colour and the absence of a dorsal fin. 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's and a true whale's, with males growing up to 5.5 m (18 ft) long and weighing up to 1,600 kg (3,530 lb). This whale has a stocky body. A large percentage of its weight is blubber, as is true of many cetaceans. Its sense of hearing is highly developed and its echolocation allows it to move about and find blowholes under sheet ice.

Belugas are gregarious and form groups of up to 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 700 m (2,300 ft) 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 150,000. They 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 commercially during the 19th century and part of the 20th century. Whale hunting has been under international control since 1973. Currently, only certain Inuit and Alaska Native groups are allowed to carry out subsistence huntingof belugas. Other threats include natural predators (polar bears and killer whales), contamination of rivers (as with PCBs which bioaccumulate up the food chain), and infectious diseases. From a conservation perspective, 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, however, is considered critically endangered and is under the prote

The beluga was first described in 1776 by Peter Simon Pallas.[1]  It is a member of the Monodontidae family, which is in turn part of the parvorder Odontoceti(toothed whales).[1]  The Irrawaddy dolphin was once placed in the same family; recent genetic evidence suggests these dolphins belong to the Delphinidaefamily.[3] [4]  The narwhal is the only other species within the Monodontidae besides the beluga.[5]  A skull has been discovered with intermediate characteristics supporting the hypothesis that hybridization is possible between these two families.[6]

The name of the genus, Delphinapterus, means "dolphin without fin" (from the Greek δελφίν (delphin), dolphin and απτερος (apteros), without fin) and the species name leucas means "white" (from the Greek λευκας (leukas), white).[7]  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 белуха (belukha), which derives from the word белый (bélyj), meaning "white".[7]  The name beluga in Russian refers to an unrelated species, a fish, beluga sturgeon.

The whale is also colloquially known as the sea canary on account of its high-pitched squeaks, squeals, clucks, and whistles. A Japanese researcher says he taught a beluga to "talk" by using these sounds to identify three different objects, offering hope that humans may one day be able to communicate effectively with sea mammals.[8]  A similar observation has been made by Canadian researchers, where a beluga which died in 2007 "talked" when he was still a subadult. Another example is NOC, a beluga whale that could mimic the rhythm and tone of human language. Beluga whales in the wild have been reported to imitate human voices.[9]

ction of the United States' Endangered Species Act. Of seven Canadian beluga populations, the two inhabiting eastern Hudson Bay and Ungava Bay 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 popular with the public due to their colour and expression.

studies have shown modern cetaceans last shared a common ancestor between 30 and 34 million years ago.[10]  The family Monodontidae separated relatively early from the other odontoceti; it split from the Delphinoidea between 11 and 15 million years ago, and from the Phocoenidae, its closest relatives in evolutionary terms, more recently still.[11]  In 2017 the genome of a beluga whale was sequenced, comprising 2.327 Gbp of assembled genomic sequence that encoded 29,581 predicted genes.[12]  The authors estimated that the genome-wide sequence similarity between beluga whales and killer whales to be 97.87% ± 2.4 × 10−7% (mean ± standard deviation).

The beluga's earliest known ancestor is the prehistoric Denebola brachycephala from the late Miocene period (9–10 million years ago).[13] [14]  A single fossil from the Baja California Peninsula indicates the family once inhabited warmer waters.[15]  The fossil record also indicates, 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.<sup id="cite_ref-16">[16]  Counter-evidence to this theory comes from the finding in 1849 of fossilised beluga bones in Vermont in the United States, 240 km (150 mi) 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 10 ft (3.0 m) 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 150 mi (240 km) 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.<sup id="cite_ref-17">[17]  Today, the Charlotte whale is the official Vermont State Fossil (making Vermont the only state whose official fossil is that of a still extant animal).<sup id="cite_ref-18">[18]

Its body is round, particularly when well fed, and tapers less smoothly to the head than the tail. The sudden tapering to the base of its neck gives it the appearance of shoulders, unique among cetaceans. The tailfin grows and becomes increasingly and ornately curved as the animal ages. The flippers are broad and short—making them almost square-shaped.

Preliminary investigations suggested a beluga's life expectancy was rarely more than 30 years.<sup id="cite_ref-19">[19]  The method used to calculate the age of a beluga is based on counting the layers of dentin 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.<sup id="cite_ref-20">[20]  A 2006 study using radiocarbon dating of the dentine layers showed the deposit of this material occurs with a lesser frequency (once per year) than was previously thought. The study therefore estimated belugas can live for 70 or 80 years.<sup id="cite_ref-21">[21]

Size[edit]
The species presents a moderate degree of sexual dimorphism, as the males are 25% longer than the females and are sturdier.<sup id="cite_ref-cms_22-0">[22]  Adult male belugas can range from 3.5 to 5.5 m (11 to 18 ft), while the females measure 3 to 4.1 m (9.8 to 13.5 ft).<sup id="cite_ref-princeton_23-0">[23]  Males weigh between 1,100 and 1,600 kg (2,430 and 3,530 lb), occasionally up to 1,900 kg (4,190 lb) while females weigh between 700 and 1,200 kg (1,540 and 2,650 lb).<sup id="cite_ref-audubon_24-0">[24] <sup id="cite_ref-25">[25] They rank as mid-sized species among toothed whales.<sup id="cite_ref-26">[26]

Individuals of both sexes reach their maximum size by the time they are 10 years old.<sup id="cite_ref-ridgway_27-0">[27]  The beluga's body shape is stocky and fusiform (cone-shaped with the point facing backwards), and they frequently have folds of fat, particularly along the ventral surface.<sup id="cite_ref-seaworldphy_28-0">[28]  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.<sup id="cite_ref-paine_29-0">[29] <sup id="cite_ref-30">[30]  The fat forms a layer that covers all of the body except the head, and it can be up to 15 cm (5.9 in) 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.<sup id="cite_ref-31">[31]