Crocodiles and alligators
Crocodiles and alligators belong to number of the most ancient inhabitants of the Earth, surpassing in age further dinosaurs. In the course of evolution their appearance has not changed almost, and nowadays the family of these largest reptiles totals about 20 kinds.
Crocodiles and alligators have appeared on a planet about 200 million years ago, on a decline of a great epoch of pangolins (evolution of the person has begun only about 7 million years ago). In those days they conducted especially overland, instead of a water way of life, as their present descendants. Feet at them were longer, and muzzles are shorter, than at acquaintances to us of crocodiles.
But if by the end of a mesozoic era, i.e. About 65 million years ago, many land I animals, including dinosaurs, have died out, crocodiles and alligators have managed to adapt to new conditions.
All crocodiles and alligators together with their near relations kajmanami and gavialami belong to group With rо codylia. They can be learnt on jashcheritseobraznoj to the body form, a protective armour from horn guards and to enormous powerful jaws with set of a terrible teeth. All of them live in hot regions of a planet.
Crocodiles share on three families - actually crocodiles, alligators and kajmanov. There is also a separate kind - Indian gavial. Crocodiles differ from kajmanov both alligators more graceful constitution and the extended muzzle. At the last heads are wider and shorter. The crocodile is easy for distinguishing and to that at it at the closed mouth from both parties the fourth teeth of the bottom jaw is well visible. At alligators they hide in a pole and consequently are imperceptible. Outwardly similar against each other, different kinds outwardly similar against each other nevertheless differ on dimensions - from 1,5 to almost 7м.
All crocodiles lodge at water - bogs, a pond, lake, the silent river or a channel where spend the most part of days. Being holodnokrovnymi, or pojkilotermnymi animals, they require water for maintenance of a constant body temperature. They spend the night usually in a reservoir, and all the day long are heated on the sun somewhere ashore. In the heat they get into a shade or slide off in cool water. In a midday sun it is often possible to see a crocodile with widely opened mouth. Without having potovyh some glands, they, like dogs, escape in such a way from an overheat thanks to evaporation of water from a mouth mucous membrane.
Peacefully getting on in the big groups, crocodiles nevertheless jealously protect the territory, and at group usually there is a dominating male. He of more time spends in water, patrolling borders of the site, driving away other large males and often publishing a loud roar. All crocodiles possess rich "ёыютрЁэ№ь чрярёюь" - grunt, hiss, hoarsely croak and growl, apparently, conducting the krokodili conversations.
Leaving on a land, crocodiles usually move slow razvalistoj gait on widely placed paws. In case of need they can pass to clumsy gallop or quietly creep on all fours on a belly. But they excellently float, making a start not short webby paws, and by means of a long strong tail. They can lie motionlessly long in water, having exposed on air only nostrils, eyes and the ears located in the top part of a head.
Crocodiles breathe atmospheric air, but can be long under water. When the crocodile dives, his ears and nostrils are closed special the valve mi, and eyes are protected by a thin film. In a pursuit of extraction or seeking safety in flight from the aggressive relative, it is capable, despite all weight, almost vertically to jump out of water.
All crocodiles are carnivorous. The wide quick jaws and an ominous grin they have won for a long time reputation of ruthless and aggressive predators. They everywhere direct horror, however the menu of crocodiles at people depends on their own dimensions and those living creatures which are found in district.
Cubs Hatching from eggs and young growth eat insects, tadpoles, snails, the small small fish, crabs both other Crustacea and molluscs. They grow in the beginning of a life quickly enough, and as during this period it on a teeth only small extraction and it is necessary to be supported often.
In process of growth of crocodiles increase both the sizes of extraction, and breaks between meals. First they eat large fish and reptiles, and later pass to mammals. Everything that appears within reach their terrible jaws - monkeys, buffalo s, zebras, snakes, even people - they consider as the lawful extraction, and not one careless animal, having approached to a watering place, falls a victim of a crocodile. They do not disdain and drop. But whatever sharp and impressive was the teeth of these reptiles, all of them are not capable to break off extraction on a part and to chew I write. Having tracked down a victim at water edge, the crocodile suffices it and tries to drag under water to drown. Then the dead animal should be pushed in any hole under coast and to wait, while its skin will soften, and meat will enough become rotten, that the successful hunter could tear off a piece behind a piece. There is also other way of hunting - having compressed jaws a victim, the crocodile twists a somersault in water, trying to tear off from it pieces of meat which swallows entirely. Large animals often serve as a dinner to the whole flight of crocodiles which in eager rivalry snip off tidbits.
crocodiles catch Fish, dexterously sufficing jaws or pressing to a bottom on shoal. It too swallow entirely, usually a head forward that gills and prickly fins have not damaged gentle covers krokodilej drinks. The majority of crocodiles swallows different subjects with food, it is probable to accelerate and without that prompt digestion.
At each kind krokodilego a tribe the special hunting receptions. One are excessively lazy and patiently wait, while extraction almost itself will fall down it in a mouth. Others - especially nilskie crocodiles - are much more aggressive, arranging ambushes or even pursuing the attracted victim. Sometimes they knock down a careless animal blow of a powerful tail. Most natatorial of crocodiles, gavial, is fed basically with fish. This skilful fisher simply rushes in water, twisting the opened mouth here and there to grasp more fishes.
All crocodiles postpone eggs which leave in due course completely generated kids. Pairing occurs in water at various times year depending on a kind and a habitat. Approximately in a month after pairing the female finds on a land a place for a laying. Some kinds dig out for this purpose a hole in sand, others - as the American alligator - suit a nest from a dirt and the semidecayed plants which the female collects and brings in a mouth.
The Female postpones with semiminute intervals from 20 to 80 oval eggs. Unlike the majority of reptiles, it regularly carries out parent duties and, having dug a laying, vigilantly it protects, rushing on any who will approach too close. The period inkubatsii lasts about three months, and all this time the female supports humidity in a nest, irrigating with its urine or immediately laying down on a nest after an exit from water. The American alligator if necessary even cleans a part of decaying vegetation to keep the necessary temperature. Usually all this time of a female of crocodiles fast, living at the expense of fatty accumulation in a back and a tail.
Ready to get out on light kids punch a shell the special tooth growing on a tip to graze. They warn mummy about the occurrence, publishing special croaking sounds, and that rakes a laying and helps to get out of eggs that who has tarried. Then it cautiously collects kids in a mouth and bears to water where lets out them "т ьшЁ".
Growing up posterity
Young krokodilchiki, tiny copies of the parents, the lives first some weeks eat from remained at them zheltkovogo a bag. Mummy continues to look after posterity and to protect it as kids while are absolutely defenceless and become easy can extraction of an otter, a raccoon, a stork, a turtle, the large big fish or a water snake. For a year cubs twice outgrow any of the potential enemies. Before to be started up in wanderings, they till one and a half years live in one reservoir with mother. At three-year age they leave a native bog and master own territory.
Depending on a kind the sexual maturity comes at crocodiles and alligators with achievement of certain length of a body, at the age from 5 till 15 years. All of them excellent long-livers. It is said that some individuals live at liberty till 100 years though it does not have authentic proofs.
As it is sad, but, safely having lived about 200 million the years, some kinds of crocodiles have been put today by the person on a total disappearance side. The hunter himself has turned to extraction, and now it is threatened with destruction almost in all zones of former dwelling, i.e. Across all Africa, Asia, Australia and the South America.
Since ancient times the person mortally was afraid and esteemed crocodiles and alligators, here and there even worshipping to them as to gods. In Ancient Egypt Sebek - god in an image of a crocodile was one of the pivotal gods, - and mummies of reptiles buried in tombs together with the high-ranking dignitaries. In other parts of the world - Africa, India, on Philippines and Borneo - the crocodile has been surrounded not by smaller worship, and the Australian natives believed that one of the largest rivers of continent has been created by a crocodile, which vygryz jaws its channel.
In the latest centuries the person was up in arms against crocodiles and alligators and the beginnings them everywhere to exterminate - partly trying to save from them livestock, and in many regions and in food. But only when all world was captured by a fashion on products from a crocodile leather, coincided on time with the invention of modern fire-arms, population of these animals of the beginning promptly to be reduced. Figures are simply monstrous. Annually in the South America killed to 1 million kajmanov; in 1929 190 000 skins of the American alligators have been sold; in 1950 in Tanzania it has been extracted 12 500 krokodilih skins. As believe, if in 1944 laws on protection of the American alligator have not been passed, this kind would be exterminated for a long time. In Africa nilsky the crocodile has disappeared from many traditional habitats in the north of continent. In 1970th Indian gaviala began to plant in bondage and only so have rescued from full extinction. Today in zakaznikah is about these 1500 animals.
Now almost everywhere in the world crocodiles are taken under protection, but trade in crocodile skins, unfortunately, still remains very profitable business. Such high prices pay for skins that poor natives of the South America are ready to risk a life to track down and kill an alligator.
Disappearance of habitats
It is one more factor inevitably putting crocodiles on a side of extinction, and in the same South America and South East Asia. At erection of dams and building of channels to the wild nature the irreparable loss is caused. Because of cutting down of jungle level of deposits, and those reservoirs in which crocodiles earlier were found decreases, completely dry up. Extinction of these animals causes serious alarm not only because the whole kind but also because it breaks ecological balance of region disappears. For example, in Florida reserve Everglejds alligators eat a spotty armour-clad pike with bony scales which, having lost the natural enemy, soon would exterminate here all perches and leshchej. Besides, alligators help to survive other animal in a droughty season. They dig out in the hole earth, creating small reservoirs where fish finds a refuge, and birds, reptiles and mammals - a watering place.