At first sight all seals look, is not identical almost, but, having looked narrowly, see that they share on two various groups and that only at representatives of one of them the sign which has entitled an animal has remained. It is a question of the big, well appreciable ears.
Generally ears are at all seals, but only at sea lions and seals ears long and trailing. At other, so-called present seals - and zoologists carry all polar seals to them, hook-nosed tevjakov and seals ordinary - ears represent no more than small apertures on each side heads; it gives to a body of an animal big obtekaemost.
so small distinction in appearance was formed by Ushastye as a result of separate evolutionary processes. Scientists believe that ordinary seals have occurred about 15 million years ago from the beings similar to otters living in Northern Atlantic, and the mammals living 25 million years ago in northern widths of Pacific ocean were ancestors ushastyh seals sobakopodobnye. The genetic relation with family of the dog has not passed without a trace: ushastye seals something look like dogs and are rather mobile on a land, unlike the majority of seals ordinary, almost helpless out of the water environment.
The Reason is simple. It having appeared on a land, the ordinary seal lies on a stomach, like the fish cast ashore, its lobbies lasty stick out on each side, and back are dragged on sand, as the fish tail; to move forward, the animal is compelled, jumping up, to move all hulk.
Circulation and swimming
Ushastyj a seal, unlike the bezuhih colleagues, strongly costs on all four; its lobbies lasty are supplied by the powerful muscles, allowing to maintain body weight, and back are not dragged behind, and developed forward and are under a belly. Usually ushastyj the seal goes waddlingly as if on tiptoe, making a start from the earth edges of finitenesses, and angered or frightened ushan is simply rushed forth, far throwing out lobbies lasty and hobbling after, as the cripple on crutches. Such gallop is unsightly, but is effective: speed of the seal running on stony coast, above speed of the running person.
Shustrost ushastogo a seal on a land is similar its manner to float. Unlike the ordinary seal floating for the account grebkov powerful back lastami, it ushastyj the relative moves in water as a penguin, widely working as lobbies lastami. Back lasty practically are not involved and serve only as a wheel. Thus, all muscular force ushastogo a seal is concentrated in a forward part of its body, about shoulders and a neck, therefore and on a land it moves quickly.
Like all other seals, ushastyj spends the most part of the life in water owing to what its body has found the forms promoting swimming. From the point of view obtekaemosti the body of a seal absolutely, also moves ahead in water it free and smoothly. Bones of the top finitenesses do not stick out, and bottom come to an end flat krylovidnymi lastami, allowing to make a start from water thickness, without causing any resistance.
The Smooth body of a seal has the small area of a surface that allows it to keep heat in cold water well. It is not necessary to forget, what even near to equator where fur seals, a water temperature sometimes considerably below a body temperature live galapagosskie.
Additional isolation and obtekaemost ushastym to seals is provided with a thick layer of hypodermic fat, and seals besides can brag of an excellent fur coat from the soft fur, protected from above a rigid scalp. Without fur ushastomu to a seal not to manage in any way on a land when on a polar wind the temperature falls to-100 °s; the fur coat and in water, since is useful to it. A subtlety of strands of wood in a combination to their water-repellent covering never give to cold water of access to a skin of an animal. Value of fur as isolating material decreases at deep diving when layers of warm air kept by fur it is compressed under the pressure of water weights; nevertheless, the inhabitant of Southern Africa a cape seal without ceremony pursues extraction on depth of hundred and more metres. The Californian sea lions have trained to dive even more deeply though by and large ushastye seals dive worse the presents. Why? First of all do not wish to hold the breath for a long time. The ordinary seal will hold on under water of minutes twenty, and even longer; it will release the lungs and will reserve a lot of oxygen in blood, in its red little bodies. The underwater respiratory technics ushastyh seals is not so perfect, and very few people from them manages to stay for time under water of more than five minutes.
Extraction and food
On a land the seal is awkward and clumsy, but in water - the prompt and quick hunter, with keenness and a grasp of a wolf and with dexterous dexterousness of predatory fishes.
All seals - animal predatory, but some subspecies differ special gastronomic predilections. Among ushastyh seals the choosiest is Greenland bolsheglazyj: he does not eat anything, except krilja, - tiny shrimps, miriadami teeming in northern seas. Kril also is a today's special of blue whales; probably that just their leaving from southern waters has served one of the reasons of prompt growth of number of seals. By the way, seals and sea lions are not painfully legible in meal - that will catch, will eat. The majority of kinds of seals live in regions where coastal undercurrents lift upward the ground water weights abounding with microscopic beings - a perennial spring of food for small water fauna which is eaten by fishes, so delicious, in turn, for seals.
As seals hunt
Ushastye seals hunt in depths of waters and on a sea-bottom. Their usual extraction consists of free-floating fish, squids and even penguins, and at times includes crabs, cancers and other ground inhabitants. To catch extraction, the seal uses all feelings well adapted for orientation under water. On a land the seal not bad sees on a shining sun, but in twilight when pupils extend, all around merges in stains, both the animal distinguishes only large and quickly moving subjects. In water all differently: the structure of the seal eye completely answers optical properties of water, and the animal sharp-sightedly sees all around even at a daylight total absence.
Some ushastye seals are at all blind, but their fattened kind proves that other feelings (among other, hearing) quite provide with it livelihood.
As they hear under water
Under water ushastyj the seal not only is better sees, but also hears is better. His ears are arranged so that it does not stir growth of force of sound waves in the water environment, and the special mechanism allows to set up an ear for work in depth, under the big pressure. The hearing of a seal even in dark and muddy water allows to define accurately, whence there is a sound and where there is its source.
The seal even can find Ushastyj extraction in full darkness and silence of sea depths to the touch. Its long as at a cat, moustaches perceive the fluctuations made by fishes floating nearby or other objects, and on a difficult network of nervous fibres transmit in a brain an exact signal about possible ulove.
For a continuation of the family all seals and sea lions gather in numerous herds - colonies; here they give rise to cubs, raise them, and then, upon termination of a marriage season, again leave in the sea.
One of the reasons on which seals get off in herds, - absence of enough of rookeries, suitable for vynashivanija and births of cubs. Ushastye seals are mobile enough on a land, but thus are an easy mark for large predators; therefore the females quitting water open spaces for product on world of posterity, gather in secluded places where feel in bolshej safety. As the female is ready to accept the male soon after the permission from the burden, each male can serve at once several and the chance does not miss: the male arrives on a rookery before occurrence of a female and declares the rights to a territory part - and all "т№ёрцштр¦Ёш§ё " there tjulenih.
Formation of harems inevitably leads to that many males remain off side, on a cold and a wind so struggle for a place on a beach, under the sun, inflames outright. Between males there are present fights. Thus, during firm natural selection males of seals become more and more.
Occurrence of females
Females start to arrive on a rookery in two-three weeks after males. The first new arrived all as one are pregnant - the organism of seals is arranged so that kids are born exactly in a year after copulation. During the day or two tjulenihi give birth, then days six look after a cub, and then, with approach techki, start to scurry about backwards-forward on a rookery, aiming obviously aside exhausting. Trying to return it "т ёхьі¦" the male understands that the female is again ready to copulation, and without losing time covers it then the female departures in the sea for ulovom, periodically coming back to feed the kid with milk; so proceeds almost three and a half a month.
Destruction of seals
Secluded rookeries protect seals from the majority of predatory animals, but not from the person. For example, the first open colonies of seals (in 1786, on islands near Alaska) have been completely exterminated by field men. The same destiny has comprehended the polar seals living at other American coasts. Getters first of all interested kotikovye the skins appreciated brilliant fluffy fur, and they not very much burdened themselves vybrakovkoj: seals killed successively, without discrimination, all who appeared near at hand, including pregnant females. It is not surprising that by 1910 fluffy northern seals have practically disappeared, and many other kinds were threatened seriously with a total disappearance.
Introduction of restrictions on catching and shooting has prevented uncontrolled destruction of many seal kinds, and laborious work on protection of flights has allowed to increase their livestock, and on occasion, as, for example, with the Greenland seal, to record indicators. Now populations of all kinds ushastyh seals steadily grow - unlike that occurs to the majority of other large mammals.