Types of seals. How many kinds of seals exist

Seals are a common name for marine mammals, which unites representatives of two families: real and eared seals. Quite clumsy on land, they are excellent swim under water. Their traditional habitat is the coastal zones of the southern and northern latitudes. The species of seals that exist in nature vary greatly, but at the same time, their appearance, habits and way of life have many common features.

The Origin of Seals

It is known that the ancestors of pinnipeds of mammals once walked freely on the ground. Later, perhaps, due to the deterioration of climatic conditions, they were forced to descend into the water. In this case, most likely, these and eared seals have originated from different animals.

Scientists believe that the ancestors of this, or ordinary, seal were otter-like creatures that fifteen million years ago met in the North Atlantic. The eared seal is more ancient - its ancestors, dog-like mammals, twenty five million years ago lived in the northern latitudes of the Pacific Ocean.

Differences in the structure of the body

The unrelated origin of these two groups of seals confirms a significant difference in the structure of their skeleton. So, an ordinary seal on land is almost helpless. On the shore, he lies on his stomach, his front flippers stick out on each side, and the rear ones are dragged along the ground like a fish tail. To move forward, the beast is forced to constantly bounce, moving its very heavy body.

The eared seal, unlike him, firmly rests on all four limbs. At the same time, his front fins have a sufficiently powerful musculature, allowing to withstand a fairly solid body weight, and the rear ones are not dragged behind, but are deployed forward and located under the belly. Usually this beast "waddles", using all the flippers in the process of walking, and if necessary can "hobble" at a very decent speed. Thus, a sea cat is able to run on a rocky shore even faster than a person.

How the seals swim

The front fins of these seals are much smaller than the rear fins. The latter are always stretched back and do not bend in the heel joint. They are unable to serve as a support for movement on land, but in the water the animal swims due to them, making powerful strokes.

The eared seal moves in the water quite differently. He swims like a penguin, sweeping his forelegs. The rear fins in it perform only the function of the helm.

general description

Different kinds of seals essentially differ in length (from almost one and a half to six meters) and in body weight (males - from seventy kilograms to three tons). The largest among the seals of ordinary - sea elephants, and the smallest - ringed seals. Eared seals, as a rule, are not so big. The largest of them, sea lion, can grow to four meters and weigh a little more than a ton. The smallest, the Kerch seal, is a seal weighing only about a hundred pounds and reaching a length of one and a half meters. Seals develop sexual dimorphism - their males significantly exceed females in weight and body size.

The shape of the body of the seals is ideally adapted to the convenient movement in the water. They all have an elongated trunk, a long and flexible neck, a short but well-defined tail. The head, as a rule, is small, and the auricles are clearly visible only in eared seals; The real hearing organs are small holes on the sides of the head.

Combines all seals with a thick layer of subcutaneous fat, which allows you to keep the heat in cold water well. Seals of many species are born, covered with thick fur, which is no more than three weeks (its color, as a rule, white). Seal present (adult) has a coarse hairline, which has no pronounced podpushki, and sea elephants and completely deprived it almost completely. As for eared seals, they have a downy podpushka, on the contrary, it can be quite dense, while in fur seals and in adulthood a dense fur coat remains.

Lifestyle

Most of the seals live in coastal areas - where underwater currents from the bottom rise masses of water that abound in microscopic creatures. There are many small water fauna in these places. It, in turn, is eaten by the fish, which serve as food for the seals.

This carnivore. The seal has a tooth structure similar to a predatory mammal. Hunt he prefers, diving to depth. In addition to fish, seals feed on cancers, crabs, cephalopods. The sea leopard sometimes attacks penguins and other, smaller ones, seals.

These creatures are perfectly adapted to low temperatures. They lead a predominantly aquatic life, getting out on land for sleeping and during moulting and breeding. When the seal dives, its nostrils and auditory holes tighten tightly, preventing water from getting inside. Most seals have poor eyesight, but the eyes are adapted to observe movement in the water in low light.

Reproduction

During the breeding season, most species of real seals create pairs. Polygamous of them are only elephants and long-sea seals. Pregnancy of the female lasts from 280 to 350 days, after which a baby appears - already sighted and fully formed. The mother feeds him with fatty milk from a few weeks to one month, stopping feeding already when the baby is still unable to produce food. Some time the kids starve, surviving from the accumulated reserves of fat.

Due to thick white fur covering the skin and almost invisible against the background of snow, the newborn baby seal was nicknamed "white". The seal, however, is not always born white: cubs of sea hares, for example, olive-brown color. As a rule, females try to hide the kids in the "holes" from the snow between the ice hummocks, which contributes to their better survival.

Long-eared seals in the breeding season gather quite large herds in secluded coastal areas and islands. The first to appear on the shore are males, who, trying to seize larger areas, arrange fights with each other. Then females appear at the rookery. After a while, each of them gives birth to a cub, and soon afterwards again mates with a male, who continues to protect his territory. The aggression of male eared seals fades with the end of the breeding season. Then these animals begin to spend more and more time in the water. In colder latitudes, they migrate to winter where they are slightly warmer, and in more favorable conditions can stay near the site of their rookeries all year round.

The most famous species of true seals

In the family of true seals, according to various data, consists of eighteen to twenty-four species.

They include:

• Seal-monks (white, Hawaiian, Caribbean);
• Sea elephants (northern and southern);
• The seal of Ross;
• Weddell seal;
• A crab-seal seal;
• Sea leopard;
• Lakhtak (sea hare);
• Hooded;
• Common and spotted seals;
• Seal (Baikal, Caspian and ringed);
• Long-tailed seal;
• Harp seal;
• Lionfish (striped seal).

All kinds of seals of this family are represented in the fauna of Russia.

Eared Seals

Modern fauna consists of fourteen or fifteen species of eared seals. They are united into two large groups (subfamilies).

The first group includes seals, including:

• Northern (the only one of the same name);
• Southern (South American, New Zealand, Galapagos, Kerguelen, Fernandez, Cape, Guadeloupe, Subantarctic).

The second group is formed by sea lions :

• Sea lion (northern);
• Californian;
• The Galapagos;
• Japanese;
• Southern;
• Australian;
• New Zealand.

In the waters of Russia, the seals of this family are represented by sea lions and northern fur seals.

Protected species of seals

As a result of active human intervention in the life of nature, many species of animals, including seals, are now on the verge of extinction.

So, several species of seals are listed in the Red Data Book of Russia. This Steller's sea lion, inhabiting the Kurile Islands and the Commander Islands and in the region of Kamchatka. A spotted seal, or lagra, inhabiting the Far East is also called rare. Protected at the present time is considered to be a gray long-legged seal , or tevyak. It is found in the Baltic Sea and on the Murmansk coast. On the verge of extermination was a ringed seal - a valuable Far Eastern fishing seal.

The Red Book of Ukraine contains a record of a monk seal. The nature protection status of this species is designated as "missing". This extremely shy animal has a low reproductive potential and does not stand up to the close presence of a person. Only about ten pairs of monk seals live in the Black Sea, and in the world today, their number is no more than five hundred individuals.

Ordinary seal

The common seal is widely distributed on the coasts of the northern seas of Europe. This species lives relatively settled, choosing usually stony or sandy areas of the coastal zone, islets, shallows and streamers in the bays and estuaries of rivers. The main food for him is fish, as well as aquatic invertebrates.

Cubs of these seals are usually born on the shore in May-July, and several hours after birth they go into the water. Mother's milk they eat about a month and manage to gain on this nutritious diet to thirty kilograms. However, due to the fact that a large amount of heavy metals and pesticides get into the milk of a seal's female because of the fish it has eaten, many cubs get sick and die.

Despite the fact that this species is not included in protected, like, for example, spotted seal or ringed seal, it also requires careful treatment of itself, as its population is inexorably shrinking.

Crabtail Seal

Antarctic kraboyd seal is considered today the most numerous species of seal in the world. According to various estimates, its number reaches from seven to forty million individuals - this is four times greater than the number of all other seals.

The size of adults is up to two and a half meters, they weigh two or three hundred kilograms. It is interesting that females of this species of seals are somewhat larger than males. These animals live in the Southern Ocean, drifting around the coast in summer, and migrating to the north with the onset of autumn.

They feed mainly on krill (small Antarctic crustaceans), this is facilitated by the special structure of their jaws.

The main natural enemies of seal-crabs are the sea leopard and killer whale. The first is a threat mainly for young and inexperienced animals. From the killer whale, the seals escape, with incredible dexterity jumping out onto the ice floes from the water.

Sea Leopard

This sea seal is not in vain is the "namesake" of the formidable predator of the cat family. Insidious and ruthless hunter, he is not content with exclusively fish: his victims are penguins, skuas, loons and other birds. Often he attacks even small seals.

The teeth of this animal are small, but very sharp and strong. There are cases of attacks by sea leopards on humans. Like the "land" leopard, the sea predator has a spotted skin: black spots are scattered randomly on a dark gray background.

Along with the killer whale, the sea leopard is considered one of the most important predators of the southern polar region. The seal, reaching more than three and a half meters in length and weighing more than four hundred and fifty kilograms, is capable of moving at an astonishing speed along the edge of the drifting ice. In prey, as a rule, he attacks the water.

Sea Leopard - the only one of the seals, the basis of the diet is made by warm-blooded creatures.