About the beluga
Delphinapterus leucas Pallas, 1776
Suborder: Toothed whales (Odontoceti)
Genus: Belugas (DelphinfpterusLaceped.1804)
The beluga population is divided according to places of estivation into 29 local herds, about 12 of which are in the territory of Russia. The distribution is circumpolar between 50 ° and 80 ° N, inhabiting all the Arctic, as well as the Bering and Okhotsk seas; in winter can enter the Baltic Sea. In pursuit of fish (salmon for spawning) the whale untill the middle of last century came in large rivers (Ob, Yenisei, Lena, Amur), sometimes rising upstream for hundreds of miles.
Sexual dimorphism is typical for belugas: males are usually larger than females of the same age. Weight: males reach 850-1500 kg, females 650-1360 kg with typical body length 3.6-4.2 m. Largest males reach 6 m in length and 2 tonns.
The head of the beluga is pherical, "foreheaded", lower jaw practically does not come forward without a beak. The vertebrae in the neck are not fused together, so the beluga unlike most whales can turn its head. This facilitates its orientation and maneuvering in the ice. The pectoral fins are small, oval-shaped. The dorsal fin is absent - it allows beluga move freely under the ice. Hence the Latin name of the genus is Delphin apterus leucas - «white dolphin without a dorsal fin."
Their skin with a loose layer of the epidermis (up to 12 mm thickness) resembles an external buffer and partly protects belugas from damage while swimming in the ice. A layer of subcutaneous fat is up to 10-12 cm thick, sometimes up to 18 cm – it is 40% of the beluga's body weight; this layer saves them from hypothermia. Skin color is monotonous. It varies with age: newborns are light brown due to the thick layer of the epidermis, which while a baby grows, fall off pieces and the lower part of the dermis with an abundance of dark pigment – melanin - rises to the surface. The general color is dark blue, growth and molting continue sothe youngs are gray, and then they become bluish-gray; individuals older than 4-7 years are pure white.
Behavior and lifestyle:
Some populations of belugas make regular migrations depending on the seasonal movements of fish stocks. Thus, the movement of the population from Cook Inlet in Alaska follows the movement of its main prey - the salmon.
In spring belugas start approaching the shore – to freshened shallow bays, fjords and estuaries of the northern rivers. They estivate along the coasts due to the presence of food there and the higher temperature of desalinated water. Warmer water improves conditions for molting and shedding the old layer of the epidermis. Often, in order to remove the lifeless surface layer of the skin, belugas rub against the bottom - sand in shallow water. Belugas are tied to the same places of estivation, visiting them from year to year. Tracking of individual animals showed that the beluga remembers the place of its birth and the path to it after winter.
In summer local populations (reproductive clusters) play a dual role in the biology of the species. Firstly, they provide reproduction of the population and isolation from neighboring local populations, and secondly, play a crucial role in the implementation of all kinds of individual contacts (sexual, game, etc.) between the members of the herd, maintaining hierarchical relationships and promoting education and training of young animals. This ensures the preservation of the social structure of a local population and and group status of its members.
Not all populations migrate. Their need is determined by the specific ice conditions and the presence of clusters of food.
In winter, belugas, as a rule, stay near the edge of the ice fields, but sometimes go far inside the zone of glaciers, where the winds and currents support cracks, divorces and ice opennings. In case of icing of vast areas they commit mass escape. Ice opennings, where belugas rise to breathe, can be a few kilometers from each other. Belugas find them using noise direction and sometimes location. But sometimes they find themselves trapped - in the ice trap, if the distance to clean water exceeds 3-4.5 km. The dorsal part of the body and the upper part of the head consist of thick and durable leather, which allows them to maintain ice-opennings, breaking the ice of a thickness of up to 4-6 cm.
The beluga is a social animals. A herd of belugas consists of clans and clans - of families, arranged according to the principle of matriarchy. The family consists of the primary family group: mothers and 1-2 cubs. Males in the herd play the role of clan guards and scouts to look for aggregations of fish. Large patches of fish sometimes attract several herds of belugas, and the feeding animals unite into flocksof hundreds or even thousands of animals.
Basis of the beluga's diet is fish, mainly gregarious (capelin, cod, polar cod, herring, saffron cod, plaice, salmon and whitefish species); to a lesser extent - crustaceans and cephalopods. Belugas do not snap their prey, especially bottom-dwelling organisms, they suck it. An adult can consume about 15 kg of food daily. But such a good day is rare.
In the Okhotsk Sea belugas copulate in April - May, in the Ob Bay - in July, in the Barents and Kara Seas - from May to August, in the Gulf of St. Lawrence - from February to August, and in the Hudson Bay females fertilization lasts from March to September. Thus, the mating season lasts about 6 months, but the bulk of the female is fertilized in a relatively short period of time - the end of April - early - mid July. In the rest of the year, in most cases only a few animals mate.
Childbearing period is extended, like the mating period, and they can deliver starting from early spring throughout the summer months. Thus, pregnancy lasts 11.5 months, there is an opinion that this period can be up to 13-14 months. As a rule, females give birth in estuaries, where the water is warmer. A female bears one calf, length 140-160 cm, very rarely - two. Lactation lasts about 12 months. Next pairing can happen in one or two weeks after birth.
Life expectancy in the wild - 32-40 years (known maximum age of a female - 44 years).
Population: The exact number is not known.
According to the International Union for Conservation of Nature, there are about 150,000 belugas in the world. Russian population, according to the International Whaling Commission, accounts for up to 27 000 individuals. The 3 most major groups of Okhotsk sea number 20,000.
Belugas’ enemy is the killer whale.
The main danger for these whales is toxic waste, polluting their environment, as well as industrial displacement of Arctic habitat, especially the core areas – where they breed and feed. In recent years noise pollution has sharply increased - due to the development of navigation and the increase of the wild tourists flows that interferes with normal reproduction and leads to a decrease in the number of calfs– ie to reduction of the number of herds.
In winter, belugas hunt cod, flounder, sculpin, pollock, making a deep dive – up to 300-1000m, and staying underwater for up to 25 minutes. Despite its mass, the beluga is adroit; it can float on its back, and even backwards. It usually swims at a speed of 3-9 km / h, if it gets scared it can make leaps up to 22 km / h.
For a variety of the sounds they make, in the 19th century the beluga was nicknamed "a sea canary», while in Russia there was an expression "beluga roar" - a characteristic roar of a male during rutting.
Researchers counted about 50 beluga sounds: whistling, screeching, chirping, screech, rattle, scream, roar, and others. Besides belugas use "body language" (slaps on the water with their with caudal fins), and even facial expressions when communicating.
Besides screams belugas make clicks in the ultrasonic range. They make them with the system of air sacs in the soft tissues of the head, and the radiation is focused with a special fat pad on the forehead - Malone (acoustic lens). Reflected from the surrounding objects, clicks back to the beluga; the lower jaw is an"Antenna", which transmits vibrations to the middle ear cavity. Analysis of the echo allows the animal to get an accurate representation of the surrounding space. The beluga has a great hearing and echolocation. These animals are able to hear a broad frequency range from 40-75 Hz and 30-100 kHz.
The beluga also has developed vision, both underwater and above the surface. Probably the beluga's vision is color, because its retina contains rods and cones - photoreceptor cells. However, researchers have not confirmed this yet.
Compiled by a member of the Board of the Council on Marine Mammals, Head of the Marine Mammal Laboratory of Institute of Oceanology, Ph.D. V.M. Bel'kovich
Marine Mammal Council