Beluga whale, white whale (Delphinapterus leucas)
An albino marine mammal with a sizeable melon responsible for echolocation. The white whale is unmistakable among any other marine animals. As recognizable as a killer whale, as friendly as a dolphin.
Classification
- Class: Mammalia
- Order: Cetartiodactyla
- Family: Monodontidae
- Genus: Delphinapterus
- Species: Beluga whale, white whale (Delphinapterus leucas)
Areas of occurrence
It inhabits the cold Arctic and sub-Arctic waters, swimming in the deep coastal waters near Alaska, Northern Canada, Western Greenland and Northern Russia during summer. In the summer it can be observed in the St. Lawrence River, in close proximity to the Shantar Islands and Sakhalin Island (in the Sea of Okhotsk) plus the Amur River estuary.
The beluga whale migrates on a seasonal basis – when the areas it inhabits in summer are frozen still with the turn of autumn, for winter it moves to the open sea covered only with cracked drift ice, or even waters topped with ice packs, drawing breath only from the natural air holes, which allow them to resurface from time to time.
In summer, after thaw it migrates to more shallow, coastal waters (1 – 3 m of depth (3 – 10 ft)), yet it sometimes happens to choose deeper areas – up to 800 m (2600 ft) deep. During summer it also inhabits the continental shelf areas and often swims into river estuaries. Belugas swimming hundreds or even thousands of kilometers from the ocean were multiply recorded.
The white whale also observes the fish migration (especially salmon). Rivers are a safe haven for baby whales, for their nemesis – killer whales – usually keep away from the inland waters.
Characteristics
Its fusiform, elongated body tapers to a greater extent in the caudal area than in the cephalic region. The narrowing at the base of skull (neck) creates the impression of having shoulders, which makes beluga’s appearance extraordinary among other cetaceans. The pectoral fins spread widely, being short and rounded. The tail fin is heart-shaped and orientated horizontally.
As most toothed whales a beluga also has a melon located in its forehead, which allows it to benefit from echolocation. The melons holds a semi-fluid fat tissue. As opposed to other cetaceans, its melon’s outline is very distinctive – it has a bulb-like shape. Interestingly, the melon is deformative – its shape changes along with the emitted sounds.
Unlike dolphins’ the beluga’s cervical vertebrae are not conjoined, it allows the animal to twist its head without turning the whole body. As a result it has a larger field of vision, hunts more effectively and can dodge predators’ attacks. Its mouth holds small, blunt and slightly crooked teeth, a total of 36 – 40 in every jaw. They are not designated for chewing, rather for catching the prey, which is swallowed whole.
At the top of beluga’s head, behind the melon, a single spiracle is visible, surrounded by smooth muscles which allow the animal to close it tightly when underwater. The thyroid gland is much larger than land mammals’ glands – it is 3 times as heavy as a horse’s thyroid, allowing the whale to boost its metabolism during summer, when living in the river estuaries. The dorsal fin disappeared leaving a noticeable ‘hump’ which, combined with the head – allows furrowing air holes in ice up to 8 cm thick (3 in).
Hearing
One of the most developed senses of that species. It can hear sounds ranging from 1.2 – 120 kHz, being most sensitive to frequencies from 10 to 75 kHz (the average human hearing range is 0.02 -20 kHz).
Sight
It sees well both over- and underwater, tough beluga’s sight is rather poor when compared to dolphins’. Eyes are best adapted to seeing underwater, yet in contact with atmospheric air the vision system accommodates to different environment. Its seeing abilities resemble the characteristics of the nearsighted.
The eye has both rod and cone cells, so presumably the animal is able to see even in low light situations. The glands located in the interior corners of the eyes secrete a fatty, jelly-like substance which greases the eyeball and allows to remove foreign objects.
Touch, taste, smell
It has been observed that belugas like to remain in physical contact (not to be mistaken with sexual relations) with other belugas. Their mouths hold so called chemoreceptors, allowing to distinguish various tastes. Furthermore a beluga whale can sense the taste of blood in the water – in such situation it reacts with panic. Similarly to other toothed whales, it lacks smell-brain and olfactory nerves, which suggests it does not have a sense of smell.
Color
An adult animal is unmistakable for any other species, for only this whale is completely white or white-to-grey. However calves are born grey, becoming black or blue-grey after a month. They gradually drop their coloration finishing with a bright white color. The final coloration is reached at 7 (females) and 9 (males) years of age.
The coloration is a result of adapting to life in the Arctic for it provides camouflage in the polar ice cap, protecting belugas from killer whales and polar bears – main predators hunting for those beautiful mammals.
The epidermis thickens in winter: the skin becomes yellowish, mostly in the dorsal area and on fins. During summer, after migrating to the river estuaries belugas rub themselves against gravelly river bed to get rid of the old skin coating. To rephrase: beluga sheds it skin, being the only cetacean to do so.
Lifestyle
Diet
Beluga whale is an opportunistic species – it hunts for whatever prey is the easiest and quickest to catch. Its dietary habits depend on the subpopulation and season of the year. The Beaufort Sea whales can eat Arctic cods, while those found in the Greenland area hunt for rose fish, northern prawns (Pandalus borealis) and Greenland halibuts.
Alaskan subpopulations mostly prefer Pacific salmons. Besides those species beluga eagerly hunts for capelins, flounders, smelts, salmons, squids, clams, sea snails, octopi, polychaetes and other deep-sea species.
It usually hunts in depths ranging from 20 to 40 meters (65 – 130 ft), yet it can dive up to 700 m (2300 ft) deep. A flexible neck assures a full range of motion during food search at the bottom of the sea. It often hunts in groups containing around 5 whales to drive fish shoals to shallow waters, attacking them subsequently.
Diving
It normally dives up to 20 meters (65 ft) deep, though it is able to penetrate much greater depths – ranging from 400 to 700 meters (1300 – 2300 ft). The deepest beluga diver was recorded at the depth of 872 m (2860 ft). One dive routinely lasts for 3 – 5 minutes, yet it can stretch to 15 – 18 minutes. In the shallow river estuaries an average dive is about 2 minutes long: a sequence consists of 5 – 6 quick shallow dives, followed by a deeper dive, typically around 1 minute. Beluga dives 31 – 51 times a day.
During a dive the animal’s heart rate drops from the initial 100 beats per minute to 12 – 20 bpm. Only the most vital organs are supplied with blood: brain, heart and lungs, requiring constant oxygen flow. Furthermore beluga’s muscles have very high levels of a certain protein – myoglobin, which is responsible for storing the oxygen inside the muscles. The concentration of this protein in beluga’s muscles is several times as high as in case of land mammals, which helps avoiding oxygen deficiency during a dive.
Social behavior
Much as a common bottlenose dolphin (Tursiops truncatus) beluga is a highly sociable animal – it frequently forms small groups containing up to 25 whales, yet usually one group holds about 10 animals. However these groups are not permanent and certain whales happen to change their affiliation. A group consists of both males and females, the groups are not sex-based. It is lead by a dominant male.
When in pod, belugas chase each other, seemingly for entertainment. In captivity they are highly curious towards humans and often swim close to the aquarium glass to take a good look of them. It is common for belugas to spit at their trainers or aquarium keepers, they even try to spit at people behind the aquarium glass. This phenomenon has not been fully explained, yet it is believed that spitting is a result of their habit of blowing sand off the crustaceans at the sea bottom.
Wild-living whales also show remarkable interest towards humans and often swim in their company. Beluga tends to play not only with the animate creatures (humans, plants), but also with… non-animate objects (sticks, dead fish, air bubbles which it creates by itself). In the breeding season adult whales swam with plants, nets or even a dead reindeer skeleton placed on their head or back. Females which lost their offspring were commonly seen swimming e.g. ‘accompanied’ by a buoy.
Breeding
Pregnancy lasts from 12 to 14.5 months, but a female pregnancy lasting over 15 months (475 days) was recorded. A female gives birth to one calf normally once every 3 years. The breeding season takes place between February and May, yet some animals (or even whole populations) mate in other seasons of the year. Females reach sexual maturity between 4 and 7 years of age, while males 4 – 9 years.
Female beluga gives birth for the first time around 8 years of age, the level of fertility drops after reaching 25 years. Beluga can delay implantation (implanting the fertilized ovum in the womb). The babies – depending on the inhabited area – are born between March and September, at the end of June or between late July and early August.
The birth takes place in the river estuaries and bays, where the water is warm – 10 – 15oC (50 – 59 ºF). The calf is about 1.5 m (4ft 11in) long and weighs around 80 kg (176 lb), it has a grayish skin color. It swims alongside its mother right after being born. The baby is dependent from its mother for approximately 1 year, until all its teeth grow out. After this time prawns and small fish are added to its menu.
Most mothers breastfeed their offspring until 20 months of age, despite the calf’s solid food diet. It is not uncommon for lactation to last over 2 years. In captivity it has been observed that calves are taken care of by females other than their mothers. Perhaps a similar phenomenon also takes place in the wild.
Detailed characteristic / size
Beluga whale / white whale (Delphinapterus leucas)
- Length:
- males: 3,5 – 5.5 m (11ft 6in – 18ft)
- females: 3 – 4.1 m (9ft 10in – 13ft 5in)
- Weight:
- males: 1100 – 1600 kg (2425 – 3527 lb), sometimes 1900 kg (4188 lb)
- females: 700 – 1200 kg (1543 – 2645 lb)
- Lifespan: 25 – 30 years
Beluga whale, white whale – interesting facts
- It has been proven that being in a river environment, this mammal’s metabolism is boosted, helping the seasonal epidermis regeneration.
- Calves often return to the same estuary as their mothers.
- Beluga has a remarkably large thyroid gland, which may result in frequent overgrowth of this gland, or neoplastic lesions.
- Supposedly a white whale can see in color, yet this information has not yet been confirmed.
- These mammals in captivity eat 2.5 – 3 % of their body mass on a daily basis – this means 18.2 – 27.2 kg (40 – 59 lb) of fish.
- Normally it swims rather slowly: 3 – 9 km/h (1.9 – 5.6 mph), yet it can reach a maximum speed of 22 km/h, which can be maintained for even 15 minutes.
- Beluga can swim backwards.
- Despite being a close relative with a common bottlenose whale, it customarily does not leap over the water surface.
- 40 – 50 % of its body mass is fat tissue.
- In the XIX century beluga whales were called ‘sea canaries’ due to the high-pitched sounds it creates.
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