Dolphins and sea pigs
Though ancestors of dolphins and sea pigs lived on a land, they evolved in the graceful and strong water animals who have got variety of unique abilities.
Dolphins and sea pigs are evolution miracle. A structure of their bodies same, as well as at other mammals, including the person, but for 50 million years of adaptation they became almost indistinguishable from object of the hunting - fishes. Their bodies have accepted a streamline, and they have learnt to float quickly by means of a tail reminding a fin. On speed and quickness they do not concede in water to sharks - to the most terrible enemies - and even surpass them in it. Nevertheless, they have kept all prominent features of the overland ancestors: teplokrovnost, lungs to breathe air, and ability to bring up cubs milk. Dolphins and sea pigs is not that other, as small zubatye whales, basically eating fish and squids though greatest of them - dolphins-kasatki - hunt also on seals and other dolphins.
The Difference between a dolphin and a sea pig is insignificant: at a sea pig flat, lopatochnye a teeth (instead of conic as at a dolphin), and at it is not present fleshy "Ё№ыічр" characteristic for many kinds of dolphins. In the rest they are very similar on anatomy, on appearance and habits.
the Life in water
Dolphins and sea pigs so adapted for a life in water that now are almost helpless out of native elements.
The Most obvious result of adaptation - the body form. As water is much more dense than air, obtekaemost bodies is very important for bolshej speeds of movement. Therefore at dolphins and sea pigs cigar-shaped bodies with a minimum quantity of acting parts. They do not have auricles more, genitals (at males and at females) are usually hidden in a body, back finitenesses have completely disappeared, and lobbies have turned to the hydrowings providing stability and management. Tails were extended and transformed to wide, rigid tail fins which, thanks to powerful muscles of a back, allow them so surprisingly dexterously to move in water.
At them the silky skin completely deprived of a scalp that allows them to slide easily in water, and all roughnesses of a body are smoothed by a thick grease layer which also allows to reduce heat losses - so, and energy - in water (temperature of sea water almost always below a body temperature of warm-blooded animals even on equator.)
Obtekaemost of the form of a body of a dolphin is obvious, but there are subtleties which not so are appreciable. Simple obtekaemost never happens absolute as water all the same creates turbulentsiju and, hence, resistance because of pressure changes. The skin of a dolphin automatically interferes with it thanks to small cross-section folds which extinguish turbuletnost at its occurrence. Besides, the skin extraordinary intensively dumps the top layer of cages (to 12 times a day) and allocates fat droplets. All it provides smoothness of sliding of animals in water. As result, the sea pig of Dallja, one of the fastest among the relatives, can float the big distances with a speed to 50 km/hour.
The Effective habit of dolphins jump out of water can to be connected with desire to reduce resistance to movement as in air to move easier, than in water. Jumps also allow them to breathe. Thus they exhale air through dyhalo in the top part of a head and quickly inhale before again to plunge into water. Dolphins seldom deeply dive, therefore usually the oxygen large supply is not required to them: half-seconds over water suffice for its replenishment. If the dolphin dives, it types in lungs of much more oxygen, than we, and stores it in red blood little bodies. At the majority of dolphins and sea pigs of blood more than at land mammals of comparable size that allows them to increase an oxygen stock as much as possible.
Dolphins and sea pigs usually hunt in pripoverhnostnyh, the layers of ocean shined with the sun, is frequent in pure water, therefore for them sight is important. Very sensitive crystalline lens of an eye allows to focus sight in air and under water. Dlinnorylye kinds (for example, afalina) possess the good binocular sight necessary for a correct estimation of distance. However sight is not vital: all who observed of the tricks executed by trained dolphins blindfold, know that they have other, not less effective ways of orientation.
the World of sounds
The Basic sense organs of a dolphin are ears. Them it is not visible outside almost - only small apertures behind eyes, but they are very effective and well adapted for perception of sounds extending under water. Feature of an ear of a dolphin is ability to accept stereosignals thanks to what they define a sound direction.
The Person is not capable of it as under water sound waves pass directly through a head and simultaneously influence both ears. And at dolphins and sea pigs each department of an internal ear is shipped in foam which isolates it from a skull. It allows an animal to fix time interval between the moment of achievement by a sound of one party of a head, and then another - and thus precisely to define a site of a source of a sound.
It is very important, as dolphins live in peace the sounds published as other beings, and them. Dolphins are guided in water with the help eholokatora. Like bats, they continuously send a stream of short sound impulses which are reflected from firm objects and come back in a kind ehosignalov. Time between a message and Signal reception specifies distance to object, and the thin stereophonic hearing of a dolphin helps to define its site.
As a matter of fact, these signals not that other as a series of clicks, but such short and fast that they remind a sound of an opened creaking door more likely. It seems that clicks arise in dyhale an animal, are reflected from a concave lobby of a surface of a skull and focused acoustic "ышэчющ" the formed fatty fabric over a snout - so-called "ф№эхщ" because of which at many kinds a convex forehead. Analyzing the reflected echo-signals, the dolphin or a sea pig receive a full sound picture of surrounding conditions, avoid obstacles and precisely define, where there is a potential extraction.
Processing of this information demands connection of a great number of cages of a brain that, possibly, is the main reason of why the brain of a dolphin so is great (a brain adult afaliny weighs about 2 kg in comparison with 1,5 kg at the adult person). There is no doubt that they are reasonable and possess well developed ability to knowledge.
a Food and dialogue
The Majority of dolphins and sea pigs eat fishes and squids. Korotkorylye kinds with smaller quantity of a teeth prefer squids, while dlinnorylye, a having numerous small teeth, basically rybojadny. An exception of a rule is kasatka - very big dolphin attacking warm-blooded sea animals, such as seals, penguins and other kinds kitoobraznyh. There were cases when the group kasatok attacked a blue whale. Rybojadnye hunt on everything that can catch, but some kinds (for example, dlinnorylye dolphins) like to hunt in coastal waters while stenelly and other dolphins gravitate to ocean open spaces. Sea pigs usually hunt small flights (on 2-4 individuals), but ocean kinds often form herds to 1000 and more animal and comb exhausting with the wide chain which each link consists of several small groups. These groups quite often remain invariable within weeks and even months, however the herd structure as a whole constantly varies, as the whole groups and separate animals that join herd leave it.
The Greatest congestions of dolphins are observed in the basic places of feeding, especially there where ocean currents lift a cold sheet of water rich with food from a sea-bottom and mix it with warm blankets, creating perfect conditions for plankton reproduction. It involves the big jambs of fishes (mojvy and an anchovy), and those, in turn, involve dolphins. Having found out with the help eholokatsii a jamb of fish, dolphins start to describe round it circles, compressing a ring more and more, forcing down fishes in a heap and forcing them to rise to a surface. Than more dolphins participates in it, especially effectively they operate, and if all goes normally, all jamb is superseded to a surface where fishes already have to disappear. Dolphins snatch on a jamb, fishes suffice and swallow them entirely. In Pacific ocean stenelly and bolshelobye prodolphins hunt together and while one kind eats, another guards in time to warn about occurrence of predators - kasatok or the big white sharks.
Such mixed herds are often accompanied by jambs zheltoperyh tunas - the big and fast predatory fishes eating the same as also dolphins. Tunas follow dolphins to take advantage of their ability to eholokatsii, and then take away the share of extraction which, as a rule, suffices on all. Tunas can thank dolphins, warning them in advance about an attack of sharks. Unfortunately, sharks not the most dangerous predators in the sea. Tunas are under constant threat from outside the fishery vessels trading on all space of Pacific ocean. Therefore over the dolphins conducting behind self jambs of tunas, danger of death often hangs. Fishermen look out in the sea of dolphins, and then throw koshelkovyj a seine for catching floating below tunas. The bottom part of a seine is tightened and forms a huge mesh bag which is gradually closed round a jamb of fish, grasping thus and dolphins. When fish together with dolphins lift aboard a vessel, dolphins perish either from lebedok, or under weight of the network. It is supposed that in 1986 thus, were lost about 130 thousand dolphins.
During the last years thanks to powerful campaign in protection of dolphins it was possible to achieve some progress in fishery. In 1998 12 countries which are in the lead in a craft of a tuna, have passed the Law on protection of dolphins. As well as all mammals breathing by air, at dolphins have not enough time for getting out of a network and not to sink.
The Majority of dolphins and sea pigs - chaotic manufacturers. Mother feeds a unique cub with milk till two years though it begins, is firm food some months prior to a full excommunication from mother. All this time it is under its guardianship.
The community Organization kasatok closer. The successful male has a harem consisting from three-four polovozrelyh of females, and remains with them during all life, growing up in this time some broods of cubs. Thus, each family group (flight) includes a little still unripe and absolutely young males and females who participate in hunting, thus skilled dolphins train others that they need to do.