Where is the crocodile. Sea crocodile as a lifeguard. The biggest crocodile in the world

Crocodiles are semi-aquatic predators, belong to the order of aquatic vertebrates and are considered the largest specimens of the group of reptiles. In the detachment of crocodiles, there are more than twenty species, among which are caiman and alligator. These cold-blooded animals live in tropical and subtropical latitudes, regardless of the continent: they can be seen in America, Africa (the largest - nile crocodile), in Asia and Oceania (here lives the largest crocodile in the world - comby).

Crocodiles appeared more than 250 million years ago and are direct descendants of dinosaurs (a subclass of archosaurs).

True, their ancestors were larger: their length reached thirteen meters. Another interesting fact about crocodiles is that over the past millennia, this species has changed little, and therefore, being closer to dinosaurs than to modern reptiles, its representatives are unique animals, giving some idea of ​​how the ancient inhabitants of our planet looked like .

Crocodiles have a common land ancestor with birds. They even by some features of their internal structure are much closer to feathered than to reptiles.

Description

Adapting to the water, the crocodiles acquired an appropriate look: their head was flat, with a very long muzzle, the body was flattened, the legs were very short. The toes are interconnected by swimming membranes (there are five of them on the front paws, four on the hind paws: there is no pinky).

The eyes of the reptile are located on the head in such a way that only the eyes and nostrils can be seen above the surface (this allows them to remain undetected for prey). When an animal goes under water, its nostrils and ears are closed with valves, and the eye has a third transparent eyelid, so that the reptile perfectly sees under water and does not experience any difficulties. Since the mouth of crocodiles is not completely closed due to the lack of lips, so that water does not enter the stomach, the entrance to the esophagus when the animal is in the water is blocked by the palatine curtain.

The elongated body shape allows reptiles to maneuver superbly in the aquatic environment, and the animal uses a flat and strong tail instead of a motor organ. The length of the reptile, depending on the species, ranges from one and a half to six and a half meters. The largest crocodile of the captured and measured reptiles belongs to the ridge: its length is 6.4 meters, it weighs more than a ton and lives on the Philippine Islands.

But the most small crocodile  lives in the west of equatorial Africa: length land crocodile  ranges from one and a half to two meters.

The reptile's greenish-brown color helps it to be perfectly camouflaged in the water. Depending on the temperature of the environment, the reptile skin can change color (the hotter it is, the greener it is). Crocodile skin is covered with strong rectangular horn plates that hold tight throughout the reptile's life: unlike many reptiles, crocodiles do not shed, and their skin grows with the body (they grow throughout their life).

Reptile temperature

Like all reptiles, crocodiles are cold-blooded animals, and their body temperature ranges from 30 to 35 degrees. Although the temperature of the bodies of these reptiles depends on water and air, it still differs from their indicators. Unlike many freshwater ones, the crocodile has a four-chamber heart (although, when leaving the ventricles, the arterial blood rich in oxygen is partially mixed with venous blood, where there is little oxygen).

Horny plates on the skin of a crocodile heat up in a day and collect heat, which allows maintaining metabolism at a rather high level. Therefore, the temperature of the predator, regardless of the time of day, is almost always the same (in summer its fluctuations are about 1 ° C, in the winter - 1.5 ° C, for small animals - about 5 ° C).

They should not be confused with warm-blooded representatives of the animal world either, since in those the body temperature is maintained by its own metabolism, while crocodiles retain it due to their large size, large mass and specific behavior (they get warm in the sun, are cooled in water). Therefore, in larger specimens, fluctuations in body temperature are less than in smaller representatives.

Difference from alligator

The structure of teeth differs from its closest relatives, alligators, crocodiles: when the mouth is closed, the fourth tooth is visible in the lower jaw, while alligators have no teeth at all. The structure of the muzzle is also different: in alligators it is more dull, in crocodiles it is sharp.

Crocodiles have the best salt metabolism: they remove excess salt through the glands located on the tongue, as well as through the tear glands (the famous “crocodile tears”). Due to this, they are able to live not only in river, but also in sea water, while alligators - only in fresh water. Among crocodiles there are species that live both there and there, for example, despite the fact that the Nile crocodile prefers to live in rivers and lakes, it is also often found near the sea coast, in the mouths of rivers.

Way of life

Crocodiles prefer to live mainly in freshwater bodies, and some species: Nile crocodile, crested, African narrow-eared are found off the coast of the seas. All the time these animals spend in the water, they come out on land in the morning or in the evening to bask in the sun and accumulate heat in the horn plates. For example, the Nile crocodile prefers air temperature from 32 to 35 ° C, if the figures are higher, it is not even shown on land. During droughts, some species of crocodiles pull pits at the bottom of drying reservoirs and hibernate.

On land, these animals are slow-moving and sluggish, therefore they prefer to move exclusively in the water. If necessary, they are able to move to another reservoir through the land, breaking several kilometers.

Interestingly, they usually move with their legs wide apart, then at a speed (not more than 11 km / h for short distances), reptiles put their feet under the body. But in the water reptiles swim much faster, at a speed of about 40 km / h. Despite its impressive size, it is able to jump out of the water by two meters.

Crocodiles live in packs, and this life is peculiar: they are completely capable of eating their kindred, and the males often destroy babies. In each group there is a dominant male, who jealously guards his territory from such large individuals as he, making a loud roar. These reptiles can express their emotions in various ways: they hiss, grunts, growls and even croak hoarsely.

Hunting and nutrition

Despite the fact that crocodiles prefer to hunt at night, in the afternoon, if the prey is near them, it is not left without attention. They receive information about a potential victim due to receptors on the jaws, which are able to sense prey, even at a great distance.

They feed mainly on fish, but if they come across other prey that they can handle, they hunt for it too. How dangerous they are to humans depends on the species. For example, the Nile crocodile is a cannibal, but gavial (also of large size) is absolutely not dangerous.

The food preferences of the crocodile largely depend on its age and size: young individuals prefer invertebrate animals, adults prefer amphibians, small mammals, reptiles, and birds.

But large individuals (the same Nile crocodile) are able to cope even with victims far exceeding their size: the Nile crocodile catches wildebeest when they cross the river during the migration, the predator in the rainy season opens the hunt for cattle, Madagascar manages to catch a lemur, and in search of water, it crawls into caves (in the drought you can only find it here). If necessary, these animals are able to eat and their relatives.

These reptiles cannot chew, and therefore, having caught the victim, break it up with their teeth and swallow it in parts. If the food is too large for this, they can leave it for a while at the bottom and wait until it is soaked. With food, the animal is assisted in coping with the stones that it has swallowed, which they rub down on food. These stones often have quite significant dimensions: it is known for sure that the Nile crocodile is able to swallow a five-kilogram block.

Crocodiles eat very rarely, and rotten food does not tolerate at all. Reptiles eat a lot: they are able to swallow food weighing about 25% of their body weight at a time. Since 60% of food is stored in fat, if necessary, they are able to starve from one to one and a half years.

Breeding

If we take into account that crocodiles live from 50 to 110 years, then they reach puberty quite early: at the age of 8 to 10 years. Crocodiles are polygamous animals: a male may well have a harem consisting of twelve females.

The female does not give birth, and lays eggs (for the night about fifty pieces). To do this, it goes to the coast and pulls out a hole, the size of which largely depends on the light: in the sun - deeper, in the shade - smaller, after it falls asleep them with sand or leaves. So that the eggs hatched kids, takes about three months. All this time, the female spends near them, not going anywhere and not even feeding.

Who exactly will hatch depends largely on the temperature parameters of the air: if they exceed 32 ° C, a male will appear, from 28 to 30 ° C - the female. Before breaking the shell, then one or the other small crocodile begins to give grunting sounds. For the female, this is a signal, and she first digs them out, then, rolling in her mouth, frees the babies.

Crocodiles born into the world are small: their length is only 28 centimeters. Over time, the mother collects about two dozen babies in her mouth and transfers them to a small size reservoir in advance, where they spend about eight weeks, after which they disperse to the surroundings in search of water bodies unoccupied by other crocodiles. Because of this, the mortality rate among crocodiles is very high: many are eaten by birds, monitor lizards and other predators. Those that survived as they grow older first feed on insects, then begin to catch frogs and fish from reservoirs, and from the age of ten they begin to hunt large vertebrates.

Reptiles and people

Speaking about crocodiles, it is better for a person to take into account that he should avoid meetings with these animals: almost all of them are dangerous to humans. True, there are species that never attack people (gavial), while others do so at every opportunity (combed).

The hunt for crocodiles in their habitats is also popular: they eat meat, and from the skin they create textiles and haberdashery. As soon as crocodile skin products became popular in fashion, the number of animals began to decline very quickly: the hunt for crocodiles did its job.

According to the data, in the 20s of the last century only about one million reptiles were killed every year in South America, so if governments did not come to their senses in time and in the 40s would not adopt laws according to which crocodile hunting was banned, they would have been destroyed long ago. The largest crocodile in Africa, the Nile crocodile, also disappeared from its usual habitats, and captive breeding saved the Indian gavial from extinction (today there are about 1.5 thousand individuals).

Another factor that puts these reptiles on the verge of extinction in South America and Asia is the construction of dams. Huge forest areas were cut down for their construction, as a result of which many reservoirs inhabited by crocodiles dried up.

This situation is disturbing not only because a unique species dies out, but also due to the fact that with the disappearance of these animals the ecosystem of the region is disturbed. For example, in Florida, crocodiles hunt pike, which, without a natural enemy, would destroy all valuable fish, primarily bream and perch. These reptiles enable many animals to survive the drought: water accumulates in the holes dug by them, forming small bodies of water where the fish take refuge during the drought and animals and birds come to drink.

The largest crocodile is the saltwater crocodile (Crocodylus porosus), which is found in India, northern Australia and the Fiji Islands. Its length can reach 7 meters, and weight - 1 ton! Five-meter individuals weigh at least half a ton. At the same time, the eggs, which the female lays, are no larger than a goose.

These amazing animals lived in the days of dinosaurs and they are one of those who could survive that difficult time. They love warm water, in which they spend almost all their time. They feed mainly on fish, mammals and reptiles. And their age can be determined by the rings on the cut bone, as well as the tree.

The smallest crocodile is dwarf (Osteolaemus tetraspis), adults barely reach 190 cm in length. It is more land than waterfowl.

The expression "crocodile tears" refers to ostentatious remorse and remorse. This myth happened because crocodiles were thought to cry in the process of eating people. In fact, crocodiles really cry when they eat, but this happens for quite biological reasons. The air, swallowed by a crocodile in the process of feeding, in a special way is mixed with the contents of the lacrimal glands and is excreted in the form of abundant foam "tears".

Crocodile skin is considered one of the best for making various leather products (in general, it is cruel, but unfortunately, there is such a business). Industrially used only skin of the abdomen, as having softness and elasticity. Other places, especially the skin of the limbs and back, are not suitable for this - it is very strong and solid, and often withstands a direct hit by a bullet. In many cultures of the world, crocodile skin is considered a sign of prosperity and a high position in society. A crocodile skin bag can cost 10-20 thousand dollars and more, because of this, a large number of crocodiles are killed by poachers every year. In a number of countries, hunting for crocodiles in nature is prohibited, and to get crocodile skins grown on special farms.

In some cultures, the crocodile was considered a sacred animal, for example in Ancient egypt. Even nowadays, in some tribes of New Guinea, the crocodile is a totem symbol, and men undergo the painful procedure of deforming their skin, after which it becomes scarred, which makes it look like a crocodile. The most interesting thing is that some tribes of Australian aborigines are considered to be masters of crocodile hunting, while other tribes of the same Australian aborigines consider crocodile hunting to be blasphemy.

Crocodile aggression increases during the breeding season, which is associated with the rainy season.

The jaw of a crocodile contains 24 sharp teeth, capable of holding and eating prey, but not chewing. Therefore, they often swallow small stones that help them to grind the contents of the stomach. These stones also work as a ballast, helping the crocodile to dive into the water. Teeth are constantly updated throughout the life of the animal. The force of compression of the jaws of a crocodile is enormous, but the muscles opening the mouth are so weak that the effort of one hand is enough to prevent it from opening. The crocodile is capable of very precisely controlling the force of compression of the jaws, and can both snack on the thigh bones of large animals and carry its offspring from the nest into the water. The tail of a crocodile is also not a gift - its blows are very strong.

You can often see crocodiles lying for a long time with an open mouth. This is not an expression of aggression, but simple cooling. The dog in this case sticks out his tongue, and the crocodile opens its mouth - the excess heat and sweat comes out with the breath.

A crocodile that has just hatched from an egg is three times longer than the same egg.

In the village of Sabu in the African state of Burkina Faso there is a pond with “tame” sacred crocodiles. Locals feed them chicken, and they quietly allow them and the tourists themselves to the tail and sit on their backs.

The crocodile can run at speeds of up to 11 miles per hour.

The average life expectancy is 50 years. Long-livers live to 100.

China has long loved to feast on crocodile meat. On the banks of the Yangtze, small crocodiles were caught and fattened until the tail reached the desired length. Thus, the reptile became a pet, and, moreover, performed the functions of a watchdog. The fact is that the crocodile was kept at the entrance to the courtyard in a box like a doghouse, where he was firmly chained to the back leg with a rather long chain.

An antibiotic was found in the blood of a crocodile. This is an important scientific discovery made ... journalists. BBC reporters during the filming of the life of crocodiles living in salt water, drew attention to the fact that crocodiles often fight and inflict terrible wounds on each other, but they never have inflammation or gangrene. The journalists managed to get a crocodile blood sample, and its analysis showed that one of the previously unknown substances present in the blood of a reptile effectively kills bacteria by penetrating their membranes. British reporters called this substance "crocodiline." Now this substance is being studied in order to cure people of various infectious diseases.

Crocodiles do not use a lot of energy, so many months can go without food.

The saltwater crocodile, sometimes, swims into the sea for 600 kilometers from the coast (there is evidence of 1,100 kilometers).

Sometimes crocodiles are able to climb trees.

People have long appreciated a lot in crocodiles: meat, skin, and musk secreted by the nasal and prianal glands. Crocodile meat is extremely appreciated in Malaysia, as a lean and dietary product.

Estuary (estuarine) crocodile - the largest of all 26 species of crocodiles.

The name "crocodile" means "stone worm" (from the other Greek. "Croco" - stone, "Dilo" - worm).

Less well known is the fact that musk from crocodile glands is widely used in the perfume industry.

Alligator females lay about 40 eggs, of which crocodiles appear in 60-70 days.

These reptiles can jump out of the water at a height of 2 meters.

Even a very old and already toothless crocodile is still deadly; its jaws slam with a force of several tons, grinding the victim's body and bones.

In 1899, during the excavations in Egypt, mummies of crocodiles were found (in the era of the pharaohs, these animals were revered as sacred).

More people died in Africa from crocodiles than from lions.

Sometimes, having found someone else's egg-laying, or just hatched small crocodiles, the crocodile with cruel indifference devours its own kind.

The crocodile deals with victims unusually - it drowns them and leaves them soak in water for a few days, because the crocodile does not know how to chew.

Crocodiles suffer from cannibalism. They have the ability to eat smaller members of their own species.

These reptiles have no lips and their mouth cannot close completely.

Crocodiles have a four-chamber heart, like birds (their closest relatives) and mammals. When a crocodile sinks under water, its heart begins to work like a three-chamber, giving the animal more time under water.

The sex of the young crocodile is determined by the temperature in the nest and how deeply the eggs are hidden.

Young crocodiles are still inside the eggs, by the time of hatching make croaking sounds.

All modern crocodiles are adapted to a semi-aquatic lifestyle. Although more than 3000 years ago, land crocodiles were found in New Caledonia.

What is the difference between crocodiles and alligators? If its extreme teeth are visible even with the mouth closed, it is a crocodile. In alligators, they are completely hidden in a special groove on the opposite jaw. Crocodiles have salt glands in their mouths, so they can be found in salt water, unlike alligators. This gives crocodiles much more habitat, including in mangroves and estuaries. Crocodiles are more active and aggressive than alligators, but they suffer less cold. Alligators are such “Nordic guys”, and can even be found in subtropical areas, and crocodiles - only in hotter ones.

On the surface of the jaws of the crocodile are numerous pressure receptors that allow him to feel the vibration emanating from animals that are in the water at a great distance.

Crocodiles have a third eyelid, a membrane that closes their eyes while diving under the water - thus, the crocodile protects the eyes from the effects of water, while not losing the ability to see.

99% of crocodile offspring dies, eaten by fish, monitor lizards, herons and adult crocodiles. During the first weeks of life, crocodiles feed on the contents of the eggs from which they are born. Crocodile eggs are also a treat for monitor lizards, hyenas, storks, and even humans. The female usually lays 20-80 eggs in nests built from plant materials, and protects them for three months. The crocodile in captivity reaches a length of one and a half meters per year, and its wild brother spends almost three years on it, as it does not have permanent source of food.

The crocodile can swim at a speed of up to 40 km / h with the help of its tail, and be under water for up to two to three hours. On land, the crocodile can also make short throws, but gets tired very quickly. These animals can even jump out of the water, flying several meters.