” 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 genus Delphinapterus. 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.
Commercial whaling by European and American whalers during the 18th and 19th centuries decreased beluga populations in the Canadian Arctic. The animals were hunted for their meat and blubber, while the Europeans used the oil from the melon as a lubricant for clocks, machinery, and lighting in lighthouses. Mineral oil replaced whale oil in the 1860s, but the hunting of these animals continued unabated. In 1863, the cured skin could be used to make horse harnesses, machine belts for saw mills, and shoelaces. These manufactured items ensured the hunting of belugas continued for the rest of the 19th century and the beginning of the 20th century. Between 1868 and 1911, Scottish and American whalers killed more than 20,000 belugas in Lancaster Sound and Davis Strait.
Killer whales are able to capture both young and adult belugas. They live in all the seas of the world and share the same habitat as belugas in the sub-Arctic region. Attacks on belugas by killer whales have been reported in the waters of Greenland, Russia, Canada, and Alaska. A number of killings have been recorded in Cook Inlet, and experts are concerned the predation by killer whales will impede the recovery of this subpopulation, which has already been badly depleted by hunting. The killer whales arrive at the beginning of August, but the belugas are occasionally able to hear their presence and evade them. The groups near to or under the sea ice have a degree of protection, as the killer whale’s large dorsal fin, up to 2 m in length, impedes their movement under the ice and does not allow them to get sufficiently close to the breathing holes in the ice.
Papillomaviruses have been found in the stomachs of belugas in the Saint Lawrence River. Animals in this location have also been recorded as suffering infections caused by herpesviruses and in certain cases to be suffering from encephalitis caused by the protozoan Sarcocystis. Cases have been recorded of ciliate protozoa colonising the spiracle of certain individuals, but they not thought to be pathogens or at least they are not very harmful.” https://en.wikipedia.org/wiki/Beluga_whale#Threats