Ladoga seals live and breed in the lake of the same name. Interestingly, this is their only habitat. But seals are the species to which the Ladoga seal belongs - marine animals. How do they manage to exist in a fresh water reservoir and how did they end up in this lake?
About 11, 000 years ago, when the ice age ended, the water level changed. Thus, these mammals fell into fresh water.
Ladoga seal. Description
This animal has another name. It is also called the ringed seal, because the fur has a gray color with dark rings on it. Abdomen is light. The external structure of the Ladoga seal reminds the constitution of its other relatives, it differs from them in its small size. It reaches 1.2 meters in length and weighs 50-80 kilograms. The seal looks fat and short. She has virtually no neck. The head is small and slightly flattened. Powerful back flippers help to move both in water and on land. Her hearing and sense of smell are wonderful. Ladoga seals live for about 30-35 years, and growth ends in 10 years.
These mammals feed on small fish and crustaceans, whose body length does not exceed 20 cm. The menu includes perch, roach, smelt and vendace. In total, this predator needs 3-4 kilograms of fish. In the summer, when the time of molting comes, Ladoga seals prefer the northern shore of the lake, especially the islands of the Valaam archipelago: Saint, Lembos, Lysiy, Krestovy and others. In the warm season, they like to arrange rookery on the rocks, their number in one place can reach 600-650 individuals. And in winter, they like the southern, western and eastern shores.
Underwater life
Ladoga seal in water, even in cold, feels better than on land. Her elongated body is specially adapted for active swimming. In addition, flippers help her in this. Freezing does not give a thick layer of subcutaneous fat and the fact that the coat does not get wet. Cleverly diving to a depth of 300 meters, the seal can hold its breath for 40 minutes. This is possible due to the fact that her body is able to slow down the metabolism, and, therefore, it requires less oxygen. Moreover, vital organs are intensely supplied with blood: the head, liver and brain. Endurance of the seal allows it to swim several tens of kilometers at a speed of 20 km / h.
How to breed
For mating, these animals choose the cold season - January-March. They are ready for the process of procreation, having reached 6 years of age. A baby is born also when snow is lying. Usually ringed seal gives birth to one baby. It weighs only 4 kilograms, and its body has a length of 0.6 meters. His fur is white, so it is less noticeable to predators: foxes and wolves.
The mother feeds him milk for 1.5-2 months, her milk is so oily that the newborn adds 1 kilogram per day. After that, he begins to eat on his own. Nerpa is very fond of drifting ice floes. In them, she finds manholes and arranges for posterity. During pregnancy, she makes several shelters in the ice, they have a hole through which you can go down into the water, as well as holes for breathing. Such a "house" does not have an exit to the surface, therefore the cubs are protected from attack by external enemies. When the time comes, they, like the mother, go down the manhole into the water.
Why disappear
In recent years, the Ladoga seal has also become an animal whose population is rapidly declining. The Red Book of Russia has already included it in its list. This is mainly due to extermination by man. Previously, 20-30 thousand individuals lived in Lake Ladoga, but at present only 2-3 thousand seals live in it. The skin, lard, meat of this animal are of value, therefore they hunt it, but not on an industrial scale.
In the 20th century, the extermination of seals was not controlled, and today the state fish inspection is engaged in this. Fishing limits set. The destruction of the seal is also justified by the fact that it eats valuable species of fish in the lake. And this is despite the fact that scientists have proved that because of the small mouth of the seal in Lake Ladoga, it can’t eat large prey, which means that the population, for example, salmon did not decrease because of it. Opponents argue that these mammals eat fish entangled in the net, since they do not need to swallow it, but only tear off a piece of it, which they sometimes do for fun.
Additional factors
Ladoga seals also die because they get entangled in strong nets established to fish, from which they cannot get out on their own. In addition, the very fact of a person's presence on the lake gives them inconvenience and makes them worry, which also does not contribute to an increase in their numbers. Another factor affecting the reduction in the number of Ladoga seals is the pollution of the lake with sewage. After the waste began to get into it, these mammals began to get sick more often, their immunity decreased. Lake Ladoga may soon survive an environmental disaster.
Is it time to stop?
Hazardous substances, toxic compounds, salts of heavy metals have been discharged into the lake for several years. In addition, polluted precipitation falls into the water. At the bottom of Lake Ladoga, areas were found where invertebrates do not live. Some fish were on the verge of extinction, for example, the Atlantic sturgeon listed in the Red Book. And this means a reduction in food for the seal and the gradual extinction from hunger. Also, warming, and, therefore, a decrease in snow cover, also has a bad effect on these animals. After all, they need ice floes, if only in order to have somewhere to hide the cubs and take cover themselves.
