Definitions

sea canary

sea canary

sea canary: see beluga.

The Beluga or White Whale (Delphinapterus leucas) is an Arctic and sub-Arctic species of cetacean. It is one of two members of the family Monodontidae, along with the Narwhal. This marine mammal is commonly referred to simply as the Beluga or Sea Canary due to its high-pitched twitter. It is up to 5 m (15 ft) in length and an unmistakable all white in color with a distinctive melon-shaped head.

Taxonomy and evolution

The beluga whale was first described by Peter Simon Pallas in 1776. It is a member of the Monodontidae family, which is in turn part of the toothed whale suborder. The Irrawaddy dolphin was also once considered to be in the same family; however, recent genetic evidence suggests otherwise.

The earliest known ancestor of the beluga is the prehistoric Denebola brachycephala from the late Miocene period. One single fossil has been found on the Baja California peninsula, indicating that the family once existed 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.

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 белуга (beluga) or белуха (belukha) which derives from the word белый (belyy), meaning "white". 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, clucks and whistles.

A Japanese researcher says he has taught a beluga whale to "talk" by using these sounds to identify three different objects, offering hope that humans may one day be able to hold conversations with sea mammals.

Description

This small whale can be up to 5 metres (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 1,360 kg (3,000 lb) and females about 900 kg (one short ton).

Newly-born belugas are about 1.5 m (5 ft) long and weigh 80 kilograms (176 lb).The baby beluga is usually born grey but not always. 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 head 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 belugas mouth is called the rostrum. The rostrum has about 8 to 10 teeth on each side of the jaw.

The absence of the dorsal fin is reflected in the genus name of the species - apterus is the Greek word for "wingless". The evolutionary preference for a dorsal ridge rather than a fin is believed by scientists to be adaptation to under-ice conditions, or possibly as a way of preserving heat. Like in other cetaceans the thyroid gland is relatively large compared to terrestrial mammals (three times per weight as a horse) and may help to sustain higher metabolism during the summer estuarine occupations.

The body of the Beluga is round, 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. Seasonally polyestrus females give birth to a single calf in the spring after a gestation period of fifteen months with ranges found from 14.5 in the wild to 15-17 months in captivity. 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 period is about two years in length. The mating process is not properly understood. Testosterone levels in males have been found to be lowest in September and then rose to be highest in march with peak sperm production thought to occur perhaps in May or June if their physiology mimics other mammals. 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 occurs at other times, leaving open the possibility of delayed implantation. Belugas can live for up to fifty years. Females in captivity have been found to conceive as old as 20 years.

Distribution

The beluga inhabits a discontinuous circumpolar distribution in Arctic and sub-Arctic waters ranging from 50° N to 80° N, particularly along the coasts of Alaska, Canada, Greenland and Russia. The southernmost extent of the range includes isolated populations in the St. Lawrence River estuary and the Saguenay fjord, around the village of Tadoussac, Quebec, in the Atlantic and the Amur River delta, the Shantar Islands and the waters surrounding Sakhalin Island in the Sea of Okhotsk.

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 slivers of open water where the dense ice pack may cover more than 96% 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 was found in the Tanana River near Fairbanks in central Alaska, nearly 1,700 kilometres (1,100 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.

Behavior

Belugas are highly sociable creatures. Groups of males may number in the hundreds, but mothers with calves generally mix in slightly smaller groups. When pods do 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. Nursing times of 2 years have been observed and lactational anestrus may not occur. Calves often return to the same estuary as their mother in the summer, meeting with their mother sometimes even after becoming fully mature.

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. Unlike most whales, they are capable of swimming backwards.

Diet

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. Generally a feeding dive will last 3-5 minutes, but belugas have been observed submerged for up to 20 minutes at a time.

Population, threats, and human interactions

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, 25,045 in Hudson Bay, 18,500 in the Bering Sea and 28,008 in the Canadian Low Arctic. The population in the St. Lawrence estuary is estimated to be around 1000. They are considered an excellent sentinel species and indicator of the health of, and changes in, the environment. This is as they are long lived, on top of the food web, with large amounts of fat and blubber, relatively well studied for a cetacean, and still somewhat common.

The beluga's natural predators are polar bears, who hunt when the whales become encircled by ice during winter. In these cases many miles of ice separate groups of Belugas from the open ocean, and as a result they are unable to leave until the ice melts in spring. During this period belugas do not offer much resistance to bear attacks due to their low energy reserves.

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 as a result of the St. Lawrence River pollution. The bodies of the Beluga inhabiting this area contain so many contaminants that their carcasses are treated as toxic waste. Reproductive pathology has been discovered in the population here and many suspect organochlorines to be responsible. Levels between 240 ppm and 800 ppm of PCBs have been found, with males typically having higher levels. It is not known what the long-term effects of this pollution will be on the affected populations.

Erysipelothrix rhusiopathiae gram positive/variable bacilli, likely from contaminated fish in the diet, can endanger the beluga causing anorexia, dermal plaques, and lesions. This may lead to death if not diagnosed early and treated with antibiotics. Cetaceans seem quite vulnerable to pneumonia, and various species of the aerobic actinomycete Nocardia, likely more problematic when anything causes more soil or dust to become airborne, (spreading the organisms to the water or air the belugas breath), can be worrisome and can lead to death.

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 Asia. Their popularity there with visitors reflects their attractive color, and their range of facial expressions. While most cetacean "smiles" are fixed, the extra movement afforded by the beluga's unfused cervical vertebrae allows a greater range of expression. Most beluga found in aquariums are caught in the wild, though captive breeding programs have enjoyed some success.

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.

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 left the populations in great peril. Indigenous whaling continues in these areas, and some populations continue to decline. 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 1995.

The Beluga population from Cook Inlet Alaska is a U.S. National Marine Fisheries Service Species of Concern. In addition, the Cook Inlet Beluga population was proposed to be listed as Endangered under the ESA in April 2007. A final decision was expected in April 2008, but the NMFS used a one-time 6 month extension request in order to perform the 2008 survey and digest the data. A decision is now expected in October 2008.

Both the United States Navy and the Russian Navy have used belugas in anti-mining operations in Arctic waters.

Papillomaviruses

Papillomaviruses have been found in the gastric compartments of belugas in the St. Lawerence River. Herpesvirus as well has been detected on occasion in belugas. Encephalitis has sometimes been observed and the protozoa Sarcocystis can infect the animals. Ciliates have been observed to colonize the blowhole yet may not be pathogenic or especially harmful.

Gallery

See also

References

  • Marine Mammal Medicine, Leslie Dierauf & Frances Gulland, CRC Press 2001, ISBN 0-8493-0839-9

Further reading

  • Outridge, P. M., K. A. Hobson, R. McNeely, and A. Dyke. 2002. "A Comparison of Modern and Preindustrial Levels of Mercury in the Teeth of Beluga in the Mackenzie Delta, Northwest Territories, and Walrus at Igloolik, Nunavut, Canada". Arctic. 55: 123-132.

External links

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