Seals - the common name of marine mammals, brings together representatives of two families: the present and the eared seals.Suffice clumsy on land, they are perfectly swim under water.Traditional their natural habitat - coastal zones of southern and northern latitudes.Types of seals that exist in nature, are very different, but at the same time in their appearance, habits and lifestyle a lot in common.
Origin seals
known that the ancestors of mammals pinnipeds freely once walked the earth.Later, perhaps due to the deteriorating weather conditions, they were forced to go down into the water.This is likely true and eared seals evolved from different animals.
Scientists believe that the ancestors of the present, or ordinary, seals were creatures like otters that fifteen million years ago occurred in the North Atlantic.Otariids more ancient - his ancestors, cynomolgus mammals, twenty-five million years ago, lived in the northern latitudes of the Pacific Ocean.
differences in body structure
unrelated origin of these two groups of seals confirms a significant difference in the structure of their skeleton.Thus, the common seal on land almost helpless.On the beach he lies on his stomach, his front flippers sticking to the sides and rear while driving dragged along the ground like a fish tail.To move forward, the animal is forced to constantly jumping, moving your body is very heavy.
eared seals, in contrast, rests firmly on all four limbs.Moreover, its front fins are powerful enough muscle to withstand a fairly substantial body weight, while the rear is not dragged behind, and deployed forward and placed under the belly.Typically, this beast goes "waddling", using all fins in the process of walking, and if necessary, may "hobble" a very decent speed.Thus, the seal is able to run along the rocky shore, even faster than a human.
as floating seals
front flippers of seals is much smaller than the rear.The latter always pull back and do not bend in the heel joint.They are unable to serve as a support when moving on land, but the animal is swimming in the water because of them, making a powerful strokes.
otariids moves in the water very differently.It floats like a penguin, boldly working forelegs.Rear fins he only acts as a rudder.
General description
Different types of seals are substantially different in length (by almost one and a half to six meters) and body weight (males - from seventy kilos to three tonnes).The biggest among seals ordinary - sea elephants, the youngest - the ringed seals.Otariidae usually not as great.The largest of them, the sea lions can grow up to four meters and weigh a little more than a ton.The smallest, Kerch fur seal - the seal, weighing only about one hundred kilograms and reach a length of one and a half meters.At seals developed sexual dimorphism - males significantly outperform their female weight and body size.
body shape seals perfectly adapted for easy movement in the water.All of them have an elongated body, long and flexible neck, a short but well-defined tail.The head is usually small, and ears clearly visible only otariids;at this same hearing are small holes on the sides of the head.
unites all seals the presence of a thick layer of subcutaneous fat, which allows the well to keep warm in cold water.Tyulenyata many species are born, covered with dense fur, which are no more than three weeks (its color, usually white).Seal real (adult) has a rough scalp with no pronounced podpushka and elephant seals altogether deprived of it almost completely.As for the eared seals, they have downy podpushka, by contrast, can be sufficiently dense, while seals and persists into adulthood thick fur coat.
Lifestyle
Most seals inhabit the coastal areas - where underwater currents rise from the bottom of a body of water teeming with microscopic creatures.In these places, I found a lot of shallow water fauna.She, in turn, eaten by fish, which are eaten by seals.
This carnivore.Seal has the structure of teeth, similar to predatory mammals.He prefers to hunt by diving into the depths.Apart from fish, seals eat crayfish, crabs, cephalopods.Sea Leopard sometimes attack penguins and other, smaller, seals.
These creatures are perfectly adapted to low temperatures.They are mostly water lifestyle, getting out on the land to sleep and during periods of moulting and breeding.When the seal dives, his nostrils and ear openings are closed tightly, not allowing water to enter.Most seals poor eyesight, but the eyes are adapted to observe the movement of the water with a small light.
Breeding During the breeding season, most species of true seals create a pair.Polygamous are only elephant seals and gray seal.Pregnancy lasts for females from 280 to 350 days, after which the light appears one cub - sighted and already fully formed.His mother feeds him fat milk from a few weeks to a month, stopping breastfeeding at the time when tyulenёnok still unable to produce their own food.For a while the kids are hungry, surviving at the expense of the accumulated reserves of fat.
Due to the thick white fur covering skins and almost invisible against the background of snow, newborn tyulenёnok earned the nickname "belёk."The seal, however, is not always born white: cubs sea birds, for example, olive-brown color.Generally, females try to hide the children in the "holes" of snow between the ice hummocks, which contributes to their better survival.
Eared seals during the breeding season are going quite large herds on secluded coastal areas and islands.The first to appear on the banks of the males, which are trying to seize more sites, arrange fights with each other.Then, at the rookery appear female.After some time, each of them gives birth to a cub, and shortly thereafter again paired with a male who continues to protect its territory.Aggression males otariids extinguished with the end of the breeding season.Then all the animals begin to spend more time in the water.In colder latitudes, they migrate to spend the winter there, which is a bit warmer and more favorable conditions may stay near their rookeries places throughout the year.
most famous types of seals
The family of seals, according to various sources, is from eighteen to twenty-four species.
These include:
- monk seal (white-bellied, Hawaii, the Caribbean);
- elephant seals (north and south);
- Ross seal;
- Weddell seals;
- crabeater seals;
- leopard seal;
- bearded seal (bearded seal);
- hooded seals;
- ordinary and spotted seals;
- seals (Baikal, Caspian and ringed);
- gray seal;
- harp seals;
- cape (striped seal).
All seal species of this family are represented in the fauna of Russia.
Eared seals
modern fauna includes fourteen or fifteen species of eared seals.They are grouped into two groups (subfamily).
The first group includes seals, including:
- north (the only kind of the same name);
- south (South American, New Zealand, Galapagos, Kerguelen, fernandessky, cape, Guadalupe, subantarctic).
second group formed sea lions:
- Steller sea lions (North);
- California;
- Galapagos;
- Japanese;
- south;
- Australian;
- New Zealand.
Russia seals in the waters of this family presented Steller sea lions and northern fur seals.
Protected species of seals
As a result, active human intervention in the life of nature, many species of animals, including seals, today in danger of extinction.
Thus, in the Red Book of Russia recorded several species of seals.This sea lions living on the Kuril and Commander Islands and Kamchatka area.Rare is named as the spotted seal, or Larga, living in the Far East.Protected currently considered the gray seal dlinnomordy or tevyak.It is found in the Baltic Sea and the Murmansk coast.On the verge of extermination was the ringed seal - Far valuable fishing seal.
Red Book of Ukraine contains a record of the monk seal.Conservation status of the species is listed as "missing".This is an extremely shy animal has a low reproductive potential and did not withstand close human presence.Only about ten pairs of monk seals inhabit the Black Sea, and in the world today their number has more than five hundred individuals.
harbor seals common seals are widely distributed on the coasts of the northern seas of Europe.This kind of relatively sedentary lives, choosing usually rocky or sandy areas of the coastal zone, islands, shoals and spit in the bays and estuaries.The main food it serves fish and aquatic invertebrates.
Cubs these seals are usually born on the shores between May and July, and a few hours after birth are sent into the water.They are fed breast milk for about a month and manage to score on this nutritious diet to thirty kilograms.However, due to the fact that the milk of the female seal gets a large amount of heavy metals and pesticides because of the fish eaten it many cubs are sick and dying.
Despite the fact that this species is not protected is brought in, as, for example, spotted seal and ringed seal, it also requires careful attitude to himself, because his strength is inexorably shrinking.
crabeater
Antarctic crabeater seal is now regarded as the most numerous species of seal in the world.According to various estimates, the number of its reach from seven to forty million individuals - it is four times more than the number of all the other seals.
size adults - up to two and a half meters, they weigh two to three hundred kilograms.Interestingly, the females of this species of seals are somewhat larger than males.These animals live in the Southern Ocean, drifting near the coast in the summer and into the fall migrating north.
They feed primarily on krill (small crustaceans Antarctic), this contributes to the special structure of their jaws.
main natural enemies of crabeater seals are leopard seal and the killer whale.The first is a threat primarily to the young and inexperienced animals.From whales saved the seals, with incredible agility jumping on the ice floes of the water.
Sea Leopard
This marine seal is not in vain "namesake" a formidable predator of the cat family.Cunning and ruthless hunter, he is not satisfied with only the fish, his victims are penguins, skuas, loons and other birds.Often he even attacks on small seals.
teeth of the beast small but very sharp and durable.There are cases of Leopard attacks on humans.Like the "land" leopard predator in the sea just as spotty skin: on a dark gray background randomly scattered black spots.
Along with killer whale marine leopard is considered one of the main predators of the southern polar region.Seal, reaching more than three and a half meters in length and weighing more than four hundred and fifty kilograms, is able to move at breakneck speed along the edge of the pack ice.In the production, as a rule, he attacked in the water.
Sea Leopard - the only one of the seals, which constitute the basis of the diet of warm-blooded creatures.
