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Beluga Whale / White Whale (Delphinapterus leucas) - Wiki
| Subject: | Beluga Whale / White Whale (Delphinapterus leucas) - Wiki
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Date: 2006:03:07 19:47:20
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[Photo] White Whale or Beluga Whale (Delphinapterus leucas) from Churchill River near Hudson Bay (Canada). Photo taken by Ansgar Walk. Date created July 03, 1999
The Beluga Whale or White Whale (Delphinapterus leucas) is an Arctic and sub-arctic species of cetacean. This marine mammal is commonly referred to simply as the Beluga - the word derives from the Russian word for white.
Taxonomy and evolution
The Beluga was first described by Peter Simon Pallas in 1776. It is a member of the Monodontidae taxonomic family alongside the Narwhal. The Irrawaddy Dolphin was also once considered to be in the same family though recent genetic evidence suggests otherwise.
The earliest known genetic ancestor of the Beluga is the now-extinct Denebola brachycephala from the late Miocene period. A single fossil has been found on the Baja California peninsula, indicating that the family once thrived in warmer waters. The fossil record also indicates that in comparatively recent times the Beluga's range has varied with that of the ice pack ??? expanded during ice ages and contracting when the ice retreats.
Naming
The Red List of Threatened Species gives both Beluga and White Whale as common names, though the former is now more popular. The name Beluga may be derived from the Russian words beloye or belukha, meaning white or white-one. It is sometimes referred to by scientists as the Belukha Whale in order to avoid confusion with the Beluga sturgeon. The whale is also colloquially known as the "Sea Canary" on account of the high-pitched squeaks, squeals and whistles.
Physical description
This large whale can be up to 5m (16 ft) long, larger than all but the largest dolphins but smaller than most other toothed whales. Males are generally larger than the female - males can weigh 1.5 tons and females about one ton. Newly-born Beluga are about 1.5m long and weigh 80kg. This whale is unmistakable when adult: it is all white and has a dorsal ridge rather than a fin. The head is also unlike that of any other cetacean - its melon is extremely bulbous and even malleable. The beluga is able to change the shape of its melon by blowing air around its sinuses. Again unlike many dolphins and whales, the vertebrae in the neck are not fused together, allowing the animal flexibility to turn its head laterally.
The absence of the dorsal fin is reflected in the genus name of the species - apterus is the Latin for "finless". The evolutionary preference for a dorsal ridge in favour of a fin is believed by scientists to be adaptation to under-ice conditions, or possibly as a way of preserving heat.
The body of the Beluga is rotund, particularly when well-fed, and tapers smoothly to both the head and tail. The tail fin grows and becomes increasingly ornately curved as the animal ages. The flippers are broad and short - making them almost square-shaped.
Males become sexually mature at eight years, females at five. Females give birth to a single calf in the spring after a gestation period of fifteen months. Young Belugas are uniformly dark grey in colour. The grey steadily lightens as they grow up - reaching their distinctive pure white colour by the age of seven in females and nine in males. The nursing periods is about two years. The mating process is not properly understood. Mating certainly does occur during the winter or early spring, when the animals are still in their winter grounds or have begun their migration. However, mating does occur at other times too; leaving open the possibility of delayed implantation. Belugas live for up to forty years.
Distribution
The Beluga moves in Arctic and sub-Arctic waters ranging from 50° N to 80° N. There is also an isolated population which travels in the St. Lawrence River estuary and the Saguenay fjord, around the village of Tadoussac, Quebec. In the spring beluga move to their summer grounds, bays, estuaries and other shallow inlets. These summer sites are detached from one another and a mother will usually return to the same site year after year. As their summer homes become clogged with ice during autumn, beluga move away for winter. Most travel in the direction of the advancing ice-pack and stay close to the edge of it for the winter months. Others stay under the iced area - surviving by finding ice leads and polynyas (patches of open water in the ice) in which they can surface to breathe. Beluga may also find pockets of air trapped under the ice. The remarkable ability of the beluga to find the thin slithers of open water where the dense ice pack may cover more than 95% of the sea surface is still a source of mystery and great interest to scientists. It is clear that the echo-location capabilities of the Beluga are highly adapted to the peculiar acoustics of the sub-ice sea and it has been suggested that Beluga can sense open water through echo-location.
On June 9, 2006, the carcass of a young beluga whale was found in the Tanana River near Fairbanks in central Alaska, nearly 1,000 miles from its nearest natural ocean habitat. As Beluga sometimes follow migrating fish, Tom Seaton, an Alaska state biologist, speculated that it had followed migrating salmon up the river at some point in the prior fall.
Behaviour
Beluga are highly sociable creatures. They move in pods which commonly contain animals of the same gender and age. Groups of males may number in the hundreds. Mothers with calves generally mix in slightly smaller groups. When pods aggregate in estuaries they may number in the thousands. This can represent a significant proportion of the entire Beluga population and is the time when they are most vulnerable to hunting.
Beluga pods tend to be unstable, meaning that belugas tend to move from pod to pod. Pod membership is rarely permanent. Radio-tracking has shown belugas can start out in a pod and within a few days be hundreds of miles away from that pod. The closest social relationship between belugas is the mother-calf relationship. Calves often return to the same estuary as their mother in the summer, meeting with their mother sometimes even after becoming fully mature.
Belugas are slow-swimming mammals which feed mainly on fish. They also eat cephalopods (squid and octopus) and crustaceans (crab and shrimp). Foraging on the seabed typically takes place at depths of up to 1,000 feet, but they can dive at least twice this depth.
Beluga exhibit a wide range of vocalizations including clicks, squeaks, whistles, squarks and a bell-like clang. One noted researcher in the field likens a noisy Beluga pod to the string section of an orchestra tuning up before a concert. Researchers have recorded 50 distinct sounds; most in the range of 0.1 to 12 kHz.
Their main natural predators are polar bears, especially when the whales become encircled and trapped by ice. The Bears club the trapped whale with a paw and then drag it on ice for a feast. Beluga are easily small enough to also be a target for an orca.
Beluga are also known for being rather playful, as well as spitting at humans or other whales. It is not unusual for an aquarium handler to be sprayed down by one of his charges whilst tending a beluga tank. Some researchers believe that this skill may be utilized to blow away sand from crustaceans at the sea bottom.
Population and human interaction
The global population of Beluga today stands at about 100,000. Although this number is much greater than that of other cetaceans, it is much smaller than historical populations before decades of over-hunting. There are estimated to be 40,000 individuals in the Beaufort Sea, 25,000 in Hudson Bay, 18,000 in the Bering Sea and 28,000 in the Canadian High Arctic. The population in the St. Lawrence estuary is estimated to be around 1000.
Because of their predictable migration pattern and high concentrations, Beluga have been hunted by indigenous Arctic peoples for centuries. In many areas a pattern of hunting, believed to be sustainable, continues to this day. However, in other areas, such as the Cook Inlet, Ungava Bay and off west Greenland previous commercial catches (now banned under the general moratorium on whaling) left the populations in great peril. Although not formally allowed, indigenous whaling continues in these areas too, and it is thought the populations may never recover. These areas are the subject of intensive dialogue between Inuit communities and national governments aiming to create a sustainable hunt and are the reason that the Beluga has been listed as vulnerable on the IUCN Red List of Threatened Species since 1994.
Because beluga congregate in river estuaries, human-caused pollution is proving to be a significant danger to their health. Incidents of cancer have been reported to be rising in the St. Lawrence River pollution. The bodies of the Belugas resident in this area contain so many contaminants that their carcasses are treated as toxic waste. It is not known what the long-term effects of this pollution will be on the affected populations.
Indirect human disturbance may also be a threat to the species. While some populations have come to tolerate small boats, others have been known to actively try to avoid ships. Whale-watching Beluga has become a huge and booming activity in the St. Lawrence and Churchill River areas.
Belugas were amongst the first whale species to be brought into captivity. The first Beluga was shown at Barnum's Museum in New York in 1861. Today it remains one of the few whale species kept at aquaria and sea life parks across North America, Europe and Japan. Their popularity there with visitors reflects their attractive colour, and their range of facial expressions. Whilst most dolphin "smiles" are fixed, the extra movement afforded by their unfused cervical vertebrae allows a greater range of expression. Most beluga found in aquariums are caught in the wild, though captive breeding programmes have enjoyed some success.
Both the United States Navy and the navy of the former Soviet Union have used beluga in anti-mining operations in Arctic waters.
http://en.wikipedia.org/wiki/Beluga
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Scientific Name: Delphinapterus leucas (Pallas, 1776)
Common Names:
English – Beluga, White Whale
French – Dauphin blanc, Bélouga, Delphinaptère blanc, Marsouin blanc
Spanish – Ballena Blanca
Taxonomic Notes: Specimens that appear to be hybrids between Narwhals and Belugas have been described from nature (Heide-Jørgensen and Reeves 1993). An alternative common name is White Whale. |
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