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 beloye meaning white.
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.
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 is derived from the Russian word belukha, meaning white. It is sometimes refered 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.
This gregarious 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 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 favor 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.
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. Wikipedia
