Crocodiles. Anatomical structure of a crocodile Features of the structure of crocodiles

Crocodiles are often ranked among the most interesting animals, and many zoologists and animal lovers spend their entire lives studying the characteristics and diversity of crocodiles.

Crocodiles (Crocodilia) are reptiles from the order of aquatic vertebrates. Their usual habitats are in Australia, Northern and South America, Asia and Africa. Today, they are considered the most powerful among reptiles. There are about 23 modern species, which consist of 3 families: crocodiles, alligators and gharials. As a rule, these animals live from 60 to 70 years, but there are individuals that have crossed the 125-year mark.

The sizes of crocodiles are very different, but the largest crocodile in the world, which is also the heaviest, is‒ saltwater crocodile(Crocodylus porosus). Its length is 6.2 meters and its weight is 1200 kg. Its habitat is the waters of eastern India, South-East Asia and Northern Australia.

photo: Phil Simonson

(Osteolaemus tetraspis) on the contrary is the smallest. Found in tropical lowland waters south of the Sahara West Africa and Western Central Africa. They are only 1-2 meters long.

Being hunters, all crocodiles have very good vision. To begin with, they have the ability to keep their eyes open while diving. This gives them the opportunity to lurk underwater in anticipation of prey. On land, these reptiles are no less dangerous and fast, their speed reaches 43.5 km/h.

Due to its specific appearance, it is widely known (Gavialis gangeticus). The largest males reach a length of 5-6 m, and females are slightly more than 4 m. They have a long and thin snout, designed for catching fish, their main food product. Gharials live in the northern part of the Indian subcontinent, they live in clean freshwater rivers with a fast current.

Second modern look in the gharial family gharial crocodile(Tomistoma schlegelii) also has a long snout and large size. It lives in Malaysia and Indonesia, very rarely, but is also found in Thailand.

photo: Ted McGrath

The most common representative of the family of true crocodiles sharp-snouted crocodile(Crocodylus acutus). Quite a large species: average length: 3.5 m, maximum 6 m, weight 180-450 kg. It has a stocky body with a long, powerful tail. Lives along east coast Pacific Ocean from western Mexico south to Ecuador, and along the western Atlantic coast from Guatemala north to the southern tip of Florida.

Siamese crocodile(Crocodylus siamensis) is a small, freshwater crocodile with a relatively wide, smooth snout. It is one of the most endangered species in the wild, although it is widely bred in captivity. Adults feed primarily on fish, but may also eat amphibians, reptiles and small mammals.

photo: RonSpomer

Crocodiles are among the most well-adapted hunters among reptiles and more. To begin with, one jaw has about 24 teeth, which are ideal for capturing prey, but not for chewing. Damaged and broken teeth are constantly replaced with new ones. After the crocodile has caught its prey, it does not let go and pulls it into the water to drown it. Afterwards, it swallows the victim without chewing; if it is too large, it makes sharp movements from side to side to tear it into smaller pieces. All crocodiles are known as one of the most patient hunters because they can stay underwater just below the surface of the water, hiding for more than 8 hours waiting for prey.

One of the most dangerous animals in Africa and a famous cannibal is Nile crocodile(Crocodylus niloticus). Only where hippopotamuses live does it die more people than from this terrible reptile. Among the very dangerous representatives of the family is also swamp crocodile(Crocodylus palustris) and Mississippi alligator(Alligator mississippiensis). The first affects about 100 people a year, and the second attacks only 10 per year, but almost all cases are fatal.

photo: Vladislav Simonov

(Alligator sinensis) has only about 200 individuals, so it has the status of a very rare species. It hunts at night and its diet consists mainly of aquatic molluscs such as snails and mussels, as well as fish. Also feeds on occasional waterfowl and small mammals.

photo:muzina_shanghai

Male crocodiles grow much larger and faster than females. Depending on the species, a crocodile can live on average up to 70 years, with some species reaching a limit of 130 years.

photo:Profe Josema

The International Red Book contains caiman black(Melanosuchus niger), which occurs throughout much of the Amazon basin, but is much less common than several decades ago. This is the most large predator Amazon that grows up to 6 m in length. They also have protective status marsh crocodile(Crocodylus palustris), Orinoco(Crocodylus intermedius), sharp-snouted(Crocodylus acutus), narrow-snouted African(Crocodylus cataphractus) and gavial(Gavialis gangeticus).

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Crocodile - special kind reptiles whose lifestyle is semi-aquatic. In appearance, the crocodile resembles smooth stones, so people should be careful near bodies of water and vegetation, as the animal can quickly attack.

Thanks to their coloring, crocodiles are able to camouflage themselves perfectly in nature.

Crocodiles belong to the class of archosaurs; an adult can reach 3 meters in length, and some giants can reach 7 meters. Crocodiles weigh from 250-500 kg, with one head weighing 200 kg; as a rule, males are much larger than females.

Description of a cold-blooded animal

The entire body of the animal is covered with 9 cervical vertebrae, while the tail has 36 vertebrae, which help it turn, accelerate, and also maintain optimal body temperature.

The crocodile is a cold-blooded reptile, so its element is water. Due to the fact that his eyes and nose are located close to the top of his head, he can for a long time lie underwater waiting for their prey, while being able to clearly see from the water what is happening on land.

The most terrible thing about a crocodile is its huge mouth, with 80 sharp fangs.

The entire body of the reptile is covered with skin, which is formed by keratinized shields. The crocodile has strong ribs inside its body. The color of a crocodile can range from green to dark brown, depending on the species and habitat.

The crocodile has a four-chambered heart, and the blood contains a special antibiotic that prevents the crocodile’s body from becoming infected, because it is constantly in dirty water.

The stomach of a crocodile is not ordinary; it differs in that it contains special gastrolith stones inside, which help to process any solid food and also retain long body in equilibrium in water.

A crocodile grows throughout its life, as the cartilage tissue constantly changes in size. Their average lifespan is about 85 years.

The crocodile animal is considered a fearless animal; it has no enemies. The only enemy can be considered a person who, using special traps, catches middle-aged individuals.

Also, crocodile eggs can be eaten by turtles, monitor lizards, and herons.

Can crocodiles cry?

People say “cry crocodile tears” and for good reason. Crocodiles can really cry, but not from pain and resentment.

The peculiarity of the appearance of tears is that the animal has a special lacrimal gland; it removes salts from the body that have accumulated in excess in the crocodile.

So, crocodile tears are a natural process that occurs due to a large amount of harmful salts.

Where do crocodiles live?

Crocodiles can be found anywhere globe, where they are not bred independently, where there is no habitat favorable for them, they are bred artificially and all conditions for existence are created.

Most favorable climate for a crocodile this is Guatemala, countries of Asia, Africa, the Philippine Islands, Australia, America, etc.

Animals love fresh water bodies; they are willing to spend all their time in such places.

The reptile can also perfectly adapt to a salty body of water, since they have a good water-salt metabolism, so it can also be found in the seas.

How do crocodiles live?

All crocodiles live in water and lay eggs in the sand on land; this lifestyle is called semi-aquatic. The animal loves to be under the sun in the early morning or afternoon.

The body temperature of a crocodile always varies from environment. When it is very hot outside, the reptile opens its mouth to evaporate the water, at this time the birds can feast on the remains of food in their sharp teeth, after which they can be eaten by a crocodile.

Crocodiles are most often found directly near the water, but in search of prey they can pave a path of 4 kilometers, while moving at a speed of 15 km/h.

The crocodile's lifestyle allows it to move away from its main place and then return again.

What do crocodiles eat?

The diet of a crocodile depends primarily on its own body size. Thus, large individuals can swallow a large horned animal, while a smaller species is not able to consume such food.

The main diet of a crocodile is fish, birds, the bats, snakes, monitor lizards. A crocodile can even eat poisonous snakes.

Crocodiles living in the sea feed on dolphins, fish, shellfish; large species even eat sharks.

The reptile often hunts kangaroos, cheetahs, lions, monkeys, hares and other savannah animals. Crocodiles living near the village can eat domestic animals and even people.

Species of crocodiles

Nile crocodile

It is considered the largest representative of this genus. It lives in rivers, fresh water bodies, and lakes.

The main food of such animals is giraffes, hippos, and rhinoceroses.

Blunt crocodile

It is considered the smallest crocodile; an adult does not exceed one and a half meters in length.

The animal lives in fresh waters Africa, they are afraid of people, they hunt mainly at night. They feed on all types of fish and carrion.

Saltwater crocodile

This is the most big crocodile all over the planet. Such a crocodile is considered the most dangerous predator; people called it a man-eating crocodile.

It reaches 7 meters in length and weighs about 2 tons. This reptile lives in the sea, in Indonesia, in the Philippines.

It feeds on large animals, buffaloes, cows, goats, and domestic animals.

Photo of a crocodile

The crocodile is a semi-aquatic vertebrate wild animal, belongs to the phylum chordata, class reptiles, order crocodiles (lat. Crocodilia).

Yours Russian name The predator got its name from the Greek word “crocodilos,” which literally means “pebble worm.” Most likely, this is what the Greeks called the reptile, whose lumpy skin looks like a pebble, and whose long body and characteristic body movements resemble a worm.

IN sea ​​water The crocodile feeds on fish, saw-nosed stingrays and even stingrays, including white stingrays, the size of which is not inferior to, and often exceeds in length, the attacking crocodile. The menu consisting of mammals is especially varied. A successful hunt brings a crocodile for dinner, a monitor lizard, a wild boar, a buffalo or.

Often the prey of a crocodile becomes, and. Crocodiles also eat monkeys, raccoons, martens, etc. If given the opportunity to have a snack, they will not hesitate to attack any domestic animal, be it a large one or cattle. Some crocodiles eat each other, that is, they do not hesitate to attack their own kind.

How does a crocodile hunt?

Crocodiles spend most of the day in the water, and hunt only after dark. The reptile swallows small prey whole. In a duel with a large prey, the crocodile's weapon is brute force. Large land animals, such as deer and buffalo, are guarded by a crocodile at a watering hole, attacked suddenly and dragged into the water, where the victim is unable to resist. Large fish, on the contrary, are dragged into shallow water, where it is easier to deal with prey.

The massive jaws of a crocodile easily crush a buffalo’s skull, and strong jerks of the head and a special “deadly rotation” technique instantly tear the prey apart. Crocodiles do not know how to chew, therefore, after killing the victim, powerful jaws they twist out pieces of suitable flesh and swallow them whole. Crocodiles eat quite a lot: one lunch can account for up to 23% of the mass of the predator itself. Often crocodiles hide part of the prey, but the supply does not always remain intact, and is often consumed by other predators.

• The crocodile belongs to the crocodile family, the alligator belongs to the alligator family. Moreover, both reptiles belong to the order crocodiles.
• The main difference between a crocodile and an alligator is the structure of the jaw and the arrangement of the teeth. When the crocodile's mouth is closed, one or a pair of teeth on the lower jaw always stick out, while the alligator's upper jaw is completely covered by a predatory grin.

• Also, the difference between a crocodile and an alligator lies in the structure of the muzzle. The crocodile's muzzle is pointed and shaped English letter V, the alligator's muzzle is blunt and more like the letter U.

• Crocodiles have salt glands in the tongue and lacrimal glands in the eyes to remove excess salts from the body, so they can live in the sea. Alligators do not have such glands, so they mainly live in fresh water bodies.
• If you compare the size of a crocodile and an alligator, it is difficult to say which reptile is larger. Average length an alligator does not exceed the average length of a crocodile. But if we compare the largest individuals, the American (Mississippi) alligator has a maximum body length of no more than 4.5 meters (according to unofficial data, the only maximum recorded length of one individual was 5.8 meters). And the world's largest saltwater crocodile, with an average body length of 5.2 meters, can grow up to 7 meters in length.
• Average weight The Mississippi alligator (it is larger than the Chinese one) is 200 kg, while the maximum recorded weight reached 626 kg. The average weight of a crocodile depends on the species. Yet some species of crocodiles weigh much more than alligators. For example, the weight of a sharp-snouted crocodile reaches 1 ton, and the world's largest saltwater crocodile weighs about 2 tons.

What is the difference between a crocodile and a gharial?

• Both the crocodile and the gharial belong to the order Crocodiles. But the crocodile is part of the crocodile family, and the gharial belongs to the gharial family.
• The crocodile has salt glands located on the tongue and special lacrimal glands in the eye area: through them, excess salts are removed from the crocodile's body. This factor allows the crocodile to live in salty sea water. The gharial does not possess such glands, therefore it is a resident of absolutely fresh water bodies.
• It is easy to distinguish a crocodile from a gharial by the shape of its jaws: the gharial has rather narrow jaws, which is justified by hunting only fish. The crocodile has wider jaws.

• The gharial has more teeth than the crocodile, but they are much smaller and thinner: the gharial needs such sharp and thin teeth to tenaciously hold caught fish in its mouth. Depending on the species, a crocodile has 66 or 68 teeth, but the gharial can boast of having hundreds of sharp teeth.

• Another difference between a crocodile and a gharial: of the entire family of crocodiles, only the gharial spends the maximum time in the water, leaving the reservoir only to lay eggs and to bask a little in the sun. The crocodile spends about a third of its life in bodies of water, preferring water over land.
• Crocodiles and gharials differ very slightly in size. Male gharials usually have a body length of 3-4.5 meters, rarely reaching 5.5 meters in length. Crocodiles are not far behind their counterparts - the length of an adult male varies between 2-5.5 meters. And yet, seasoned males of some species of crocodiles often reach 7 meters in length. In terms of weight, crocodiles win this round: the saltwater crocodile can reach a mass of 2000 kg, and the Gangetic gharial has a modest weight of 180-200 kg.

What is the difference between a crocodile and a caiman?

• Although crocodiles and caimans belong to the order Crocodilia, caimans belong to the alligator family and crocodiles belong to the crocodilian family.
• The external differences between a crocodile and a caiman are as follows: crocodiles are distinguished by a pointed V-shaped snout, caimans are distinguished by a blunt and wide U-shaped muzzle.
• Another difference between reptiles is that crocodiles have special salt glands on their tongues. Through them, as well as through the lacrimal glands, crocodiles get rid of excess salts, so they feel equally good in both fresh and salt water. Caimans do not have this feature, therefore, with rare exceptions, they live only in clean fresh water bodies.

Types of crocodiles: names, descriptions, list and photos.

Modern classification divides the order of crocodiles into 3 families, 8 genera and 24 species.

Family of real crocodiles(lat. Crocodylidae). Some of its varieties are of particular interest:

• Saltwater crocodile (saltwater crocodile)(lat. Crocodylus porosus)- the largest crocodile in the world, a mega-predator firmly established at the top of the food chain. Other names for this reptile are submarine crocodile, man-eating crocodile, salty, estuarine and Indo-Pacific crocodile. The length of a saltwater crocodile can reach 7 meters and weigh up to 2 tons. The species got its name thanks to 2 massive bony ridges running along the snout from the edge of the eyes. In appearance The crocodile's colors are predominantly pale yellow-brown, with dark stripes and spots visible on the body and tail. The salt water lover is a typical inhabitant of rivers flowing into the ocean, and also lives in sea lagoons. Saltwater crocodiles often live in the open sea and are found on the northern Australian coast, in Indonesia, the Philippines, India and off the coast of Japan. Crocodiles' food is any prey that a predator can catch. These can be large land animals: buffalos, leopards, grizzlies, antelopes, pythons, monitor lizards. Also, medium-sized mammals often become prey for the crocodile: wild boars, tapirs, dingoes, kangaroos, many species of monkeys, including orangutans. Domestic animals can also become prey: goats, etc. Of the birds, mainly waterfowl species, as well as marine and freshwater, and many species fall into the mouth of the combed crocodile. Baby crocodile feeds on aquatic invertebrates, insects and small fish. Older individuals freely eat poisonous cane toads, big fish and crustaceans. Saltwater crocodiles practice cannibalism on occasion, never missing the opportunity to eat small or weak representatives of their species.

• Blunt crocodile(lat. Osteolaemus tetraspis)- This is the smallest crocodile in the world. The body length of an adult is only 1.5 meters. The male weighs about 80 kg, the female crocodiles weighs about 30-35 kg. The color of the reptile's back is black, its belly is yellow, with black spots. Unlike other types of crocodiles, the reptile has skin well armored with hard plates-growths, which compensates for the lack of growth. Blunt-snouted crocodiles live in fresh water bodies of West Africa, shy and secretive, leading night look life. They feed on fish and carrion.

• Nile crocodile(lat. Crocodylus niloticus)- the largest reptile of the family after the saltwater crocodile, lives in Africa. The average body length of males is from 4.5 to 5.5 meters, and the weight of a male crocodile reaches almost 1 ton. The color of the crocodile is gray or light brown, with dark stripes on the back and tail. The reptile is one of 3 species that live in African countries and have no equal in the water element. Even on land, conflicts over prey, such as with lions, involve a “tug-of-war,” and the crocodile still emerges victorious. - a typical inhabitant of rivers, lakes and swamps located south of the Sahara Desert, including the Nile River basin. The Nile crocodile feeds on fish: Nile perch, tilapia, black mullet, African pike and numerous representatives of cyprinids. And also mammals: antelopes, waterbucks, gazelles, oryx, warthogs, chimpanzees and gorillas. Often all types of domesticated animals become prey for the crocodile. Particularly large individuals attack buffaloes, and young African elephants. Young Nile crocodiles eat amphibians: the African toad, the changeable reed frog and the goliath frog. The young feed on insects (crickets), crabs and other invertebrates.

• Siamese crocodile(lat. Crocodylus siamensis) has a body up to 3-4 m long. The color of the crocodile is olive green, sometimes dark green. The weight of a male reaches 350 kg, the weight of females is 150 kg. This species of crocodiles is listed in the Red Book as endangered. Today the population numbers no more than 5 thousand individuals. The species' range extends through the countries of southeast Asia: Cambodia, Malaysia, Vietnam, Thailand, and is also found on the island of Kalimantan. The main food source of Siamese crocodiles is different kinds, small . In rare cases, the crocodile feeds on rodents and carrion.

• Sharp-snouted crocodile(lat. Crocodylus acutus)- the most common representative of the family. The species is distinguished by a narrow, characteristically pointed snout. Adult males grow up to 4 m in length, females up to 3 m. The weight of a crocodile is 500-1000 kg. The color of the crocodile is grayish or greenish-brown. Crocodiles live in swampy areas, rivers, and fresh and salt lakes in North and South America. Sharp-snouted crocodiles eat most types of freshwater and saltwater fish. A significant part of the diet consists of birds: pelicans, flamingos,. With a certain periodicity, crocodiles eat sea and livestock. Young reptiles feed on crabs, as well as insects and their larvae.

• Australian narrow-snoutedcrocodile (lat. Crocodylus johnstoni) is a freshwater reptile and is small in size: males grow no more than 3 meters in length, females up to 2 meters. The animal has an uncharacteristically narrow muzzle for a crocodile. The color of the reptile is brown with black stripes on the crocodile's back and tail. A population of about 100 thousand individuals inhabits freshwater bodies of northern Australia. The Australian narrow-snouted crocodile feeds primarily on fish. A small part of the diet of adults consists of waterfowl and small mammals.

Alligator family(lat. Alligatoridae), in which the subfamily alligators and the subfamily caimans are distinguished. This family includes the following varieties:

• Mississippi alligator (American alligator) (lat. Alligator mississippiensis) - large reptile(reptile), males of which grow up to 4.5 m in length with a body weight of about 200 kg. Unlike the crocodile, the American alligator can withstand the cold and can hibernate by freezing its body into the ice and leaving only its nostrils on the surface. These alligators live in fresh water bodies North America: dams, swamps, rivers and lakes. The Mississippi (American) alligator, unlike crocodiles, rarely attacks large animals. Adult alligators feed on fish, waterfowl, water snakes, and mammals such as nutria, muskrats, and raccoons. Baby alligators eat worms, as well as insects and their larvae. Some alligators do not have enough melanin pigment and are albino. True, a white crocodile is rarely found in nature.

White crocodile (albino)

• - a small species of alligator, which is also rare species. Only 200 individuals live in nature. The color of the alligator is yellow-gray, there are black spots on the lower jaw. The average length of an alligator is 1.5 meters, the maximum reaches 2.2 meters. The weight of the predator is 35-45 kg. Alligators live in China, in the Yangtze River basin. They feed on small birds and mammals, mollusks.

• Crocodile (spectacled) caiman(lat. Caiman crocodilus)- a relatively small alligator with a body length of up to 1.8-2 m and a weight of up to 60 kg. This species of crocodile is distinguished by a narrow snout and a characteristic bony growth between the eyes, shaped like glasses. Little cayman has yellow bodies with black spots, an adult crocodile has olive green skin. The reptile has the widest range of all alligators. The caiman lives in low-lying, stagnant bodies of fresh or salt water from Mexico and Guatemala to the Dominican Republic and the Bahamas. Due to its small size, the caiman feeds on mollusks, small fish, freshwater crabs, as well as small reptiles and mammals. Seasoned individuals occasionally attack large amphibians, for example, as well as wild boars and even other caimans.

• Black caiman(lat. Melanosuchus niger)- one of the largest reptiles. The body length of a mature male can exceed 5.5 m, and the body weight can be more than 500 kg. A pronounced bony ridge, typical of all caimans, runs from the eyes along the entire length of the muzzle. The modern population, consisting of approximately 100 thousand individuals, lives in large rivers and lakes of South America. Adult black caimans eat large quantities of fish, including piranhas

  Gharial family(lat. Gavialidae) consists of several genera and only 2 modern species:

  • Gangetic gharial(lat. Gavialis gangeticus)- a large representative of the order with a body growing up to 6 meters in length. Gharials, unlike real crocodiles, have a lighter constitution, so the weight of an adult individual generally does not exceed 200 kg. Gharials are distinguished by a characteristically narrow jaw shape, conveniently adapted for catching fish, as well as a maximum number of teeth - up to 100 pieces. Gharials live in the pools and knees of rivers in India, Pakistan and Bangladesh. The species is listed in the Red Book as especially rare and has been completely exterminated in Bhutan and Myanmar. Due to its predominantly aquatic lifestyle, the Gangetic gharial feeds mainly on fish. Particularly large individuals occasionally attack small mammals and happily eat carrion. Baby reptiles are content with invertebrate animals.

  

  • Gharial crocodile(lat. Tomistoma schlegelii)- the closest relative of the gharial, with the same long, narrow muzzle and gigantic size. The body length of a crocodile can exceed 6 meters, but on average reaches no more than 5 meters. The color of the crocodile is chocolate brown with stripes on the body. The weight of a crocodile varies from 93 kg for females to 210 kg for males. This species of reptile has endangered status. A small population of crocodiles, consisting of 2.5 thousand individuals, lives in shallow, swampy rivers and lakes in Indonesia and Malaysia. The gharial crocodile, unlike its closest relative, the Gangetic gharial, only partly consumes fish, shrimp and small vertebrates. Despite the narrow snout, the main diet of the predator consists of pythons and others, monitor lizards, monkeys, wild pigs, deer and otters.

  

Crocodiles are cold-blooded vertebrates that lead a semi-aquatic lifestyle. Water is their favorite medium, being more constant in temperature. It was thanks to her that the ancestors of crocodiles survived the global cooling of the Earth's climate. The body shape of crocodiles is lizard-shaped. The large head is flattened in the dorso-ventral direction, the muzzle is elongated or long, with strong elongated jaws, seated with sharp conical “fangs” up to 5 cm long, which grow throughout the life of the animal, replacing worn out and broken ones. The teeth are strengthened in individual bone cells of the jaws, the base of the tooth is hollow inside; The crocodile's bite is designed in such a way that opposite the largest teeth on the lateral edge of one jaw are the smallest teeth of the other. This design could turn the dental apparatus into a perfect weapon for attack. In narrow-snouted fish-eating gharials, the jaws can be compared to the jaws of tweezers, allowing them to grab small mobile prey in the water with a lateral movement of the head.

The jaw system of Chinese alligators (Alligator sinensis), distributed in Eastern China along the lower reaches of the Yangtze River, is structured differently. These are small reptiles ( maximum length 1.5 m), feeding mainly bivalves, water snails, crustaceans, as well as frogs and slow-moving fish species. Such coarse food is ground by the closely set back teeth with a flat crown surface. By rinsing their mouths in water, the fed alligators get rid of fragments of crushed shells and shells.

At the end of the crocodile's snout there are convex nostrils, and the eyes are also raised and located on the upper side of the head. This structural feature of the skull determines the favorite pose of the aquatic reptile: the body is blissful in the water - only the eyes and nostrils are visible from the outside.

Crocodiles have five fingers on their forelimbs and four on their hind limbs; they are connected by an interdigital membrane. The tail is long, laterally compressed, very powerful and multifunctional: it is a “steering control” and an “engine” when swimming, a support when moving on land, and when hunting it is like a stunning mace. When swimming, the limbs of crocodiles are laid back, the front ones are pressed to the sides, and the powerful flattened tail, bending, describes S-shaped movements. Lying in wait for large mammals at a watering hole, a huge saltwater crocodile (Crocodylus porosus) attacks suddenly, grabbing a zebra or antelope by the head and breaking its neck, or knocking the victim down with a terrible blow of his tail. During the breeding season, females compact the “building material” brought for the nest with their tail, splash it on the water, spraying the nest with masonry.

The entire surface of the crocodile's body is covered with large, regular-shaped horny scales. The dorsal scutes are thicker and bear convex spiny ridges that turn into serrations on the tail. Each scale develops independently and grows due to the underlying layers. Under the large scutes of skin on the back and tail, a real shell of bone plates, osteoderms, develops. The shields are elastically connected to each other, so they do not restrict the animal’s movements. The shape and surface pattern of the shell is individual for each species. On the head, osteoderms are fused with the bones of the skull. Thus, the animal wears real “armor” that effectively protects vital internal organs and the brain.

The structure of the skull is very unusual. The quadrate and articular bones are penetrated by air-bearing outgrowths of the middle ear cavity. Most of the posterior bones of the skull contain cavities of a highly expanded and complex branching system of eustachian tubes. The bones of the long muzzle and palate also contain significant voids: blind outgrowths of the nasal passage extend into them. Scientists believe that the systems of air cavities and passages that penetrate almost the entire huge skull of the crocodile significantly lighten it, allowing it to hold its head above the surface of the water without significant expenditure of muscle energy (for a silent and imperceptible dive, it is enough for the crocodile to reduce the pressure in the chest cavity and direct part of it into the lungs air from the air cranial passages).

All types of crocodiles have highly organized sense organs. Unlike snakes, they hear perfectly - the range of auditory sensitivity is very large and amounts to 100-4000 Hz. At the same time, crocodiles are deprived of the special “snake” Jacobson’s organ, which allows creepers to distinguish taste and smell with great accuracy. The eyes of crocodiles are adapted for night vision, but also serve well during the day. The retina of the eye contains mainly rod receptors that capture light photons. The pupil, like a cat’s, is capable of narrowing in the light into a narrow vertical slit, and at night the alligator’s eyes have a red-pink glow, which is often taken as constant proof of its bloodthirstiness. It should be said that although the hunting instincts of crocodiles are exacerbated in the dark, ferocious predatory eyes are only a consequence of the anatomical structure of the visual analyzer. In the dark, the vertical pupil dilates, and the bloody color is provided by the presence of a special pigment in animals - rhodopsin - on the retina, illuminated by reflected light. Underwater, the eyes of crocodiles are protected by a transparent nictitating membrane, which closes them when diving.

Everyone knows the expression “shed crocodile tears.” Indeed, crocodiles cry, but not from grief, pain or the desire to treacherously lull someone’s vigilance. In this way, animals are freed from excess organic salts contained in the body. Their muddy tears are unusually salty, but devoid of emotion. Salt glands are located in representatives of the family of true crocodiles, even under the tongue.

The respiratory system of crocodiles also has its own characteristics. The nostrils, like the external auditory openings, can be tightly closed by muscles - they automatically contract as soon as the animal dives. The lungs have a complex structure compared to the baggy lungs of snakes and are capable of holding a large supply of air. As a result of this, for example, a young Nile crocodile only 1 meter long is able to stay under water for about 40 minutes, without the slightest harm to its own health. As for large adult individuals, the duration of their “diving” can reach 1.5 hours. It should be noted that scaly reptiles unable to absorb oxygen through rough skin, as thin-skinned amphibians (frogs, newts) do.

The air inhaled through the nostrils passes through paired nasal passages, separated from oral cavity secondary bony palate, which serves as a kind of protection of the skull from the inside. In the case when a crocodile tries to swallow a large and severely mutilated victim, bone fragments and desperate resistance, jerks and blows of the doomed animal are not able to injure the vault of the oral cavity and damage the brain. Just before the choanae (inner nostrils), a muscular curtain descends from above, which presses against a similar outgrowth at the base of the tongue and forms a valve that completely separates the oral cavity from the respiratory tract. Thus, thanks to its anatomical structure, a crocodile is able to drown, tear and swallow prey without the risk of choking itself.

The mechanism of ventilation of the lungs is peculiar and unusual in crocodiles. If for most higher vertebrates the change in volume chest is produced through the movement of the ribs, then the volume of the lungs in crocodiles also changes with the movement of the liver. The latter is moved forward by contraction of the transverse abdominal muscles, causing an increase in pressure in the lungs and exhalation, and then moves backward by the longitudinal diaphragmatic muscles connecting the liver to the pelvis, causing a decrease in pressure in the lungs and, accordingly, inhalation. As researchers K. Hans and B. Clark proved, in crocodiles in water, the main role in ventilation of the lungs is played by the movements of the liver.

The heart of crocodiles consists of four chambers and is much more advanced than the three-chambered heart of other reptiles: oxygenated arterial blood does not mix with venous blood, which has already given oxygen to organs and tissues. The heart of crocodiles differs from the four-chambered heart of mammals in that the latter retain two aortic arches with an anastomosis (bridge) at the crossover. Thus, despite the fact that body temperature, metabolic rate, motor activity and appetite of crocodiles significantly depend on the ambient temperature, the process of gas exchange in their cells is more efficient than in lizards and turtles.

The digestive system of crocodiles is distinguished primarily by the absence of saliva in the oral cavity. In addition, there is another amazing adaptation: in the thick-walled muscular stomach of most adult crocodiles there is a certain amount of stones (the so-called gastrolites), which the animals specifically swallow. In Nile crocodiles, the weight of stones in the stomach reaches 5 kg. The role of this phenomenon is not entirely clear; it is assumed that the stones play the role of ballast and move the crocodile’s center of gravity in front downwards, giving greater stability when swimming and making it easier to dive, or they contribute to the grinding of food when the walls of the stomach contract, as in birds.

Crocodiles do not have a bladder, which is apparently due to life in water. Urine is excreted along with feces through a special organ that removes waste products, located on the abdominal side of the animal (it is called the cloaca). The cloaca has the appearance of a longitudinal slit, while in lizards and turtles it is of a transverse type. In its posterior part, males have an unpaired genital organ. The female lays fertilized eggs, protected on the outside by a dense calcareous shell, and on the inside by primary reserves of food and moisture sufficient for the development of the embryo.

On the sides of the cloaca, as well as under the lower jaw, crocodiles have large paired glands that secrete a brown secretion with a strong musky odor. The secretion of these glands is especially activated during the breeding season, helping sexual partners find each other.

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

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. One more interesting fact about crocodiles is that over the past millennia this species has changed little in appearance, and therefore, being closer to dinosaurs than to modern reptiles, its representatives are unique animals that give some idea of ​​what the ancient inhabitants of our planet looked like.

Crocodiles share a common land ancestor with birds. Even in some features of their internal structure much closer to birds than to reptiles.

Description

Having adapted to water, crocodiles acquired the corresponding appearance: their head is flat, with a very long muzzle, their body is flattened, and their legs are very short. The toes are connected to each other by swimming membranes (there are five on the front paws, four on the hind paws: the little finger is missing).

The reptile's eyes are located on the head in such a way that only the eyes and nostrils are visible above the surface (this allows them to remain unnoticed by prey). When the animal goes under water, its nostrils and ears close with valves, and the eye has a third transparent eyelid, thanks to which the reptile sees perfectly under water and does not experience any difficulties. Since the mouth of crocodiles, due to the absence of lips, does not close completely to prevent water from entering the stomach, the entrance to the esophagus, when the animal is in water, is blocked by the velum palatine.

The elongated shape of the body allows the reptile to maneuver perfectly in 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 reptiles captured and measured is a saltwater crocodile: it is 6.4 meters long, weighs more than a ton and lives in the Philippine Islands.

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

The greenish-brown color of the reptile helps it to camouflage perfectly in the water. Depending on the temperature of the environment, the skin of a reptile can change color (the hotter it is, the greener it is). The skin of a crocodile is covered with durable horny rectangular plates that hold tightly throughout the life of the reptile: unlike many reptiles, crocodiles do not shed, and their skin grows along with the body (they grow throughout their lives).

Reptile temperature

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

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

They should also not be confused with warm-blooded representatives of the animal world, since their own metabolism maintains a constant body temperature, while crocodiles maintain it due to their large size, large mass and specific behavior (basking in the sun, cooling in water). Therefore, larger specimens exhibit less fluctuations in body temperature than smaller specimens.

Difference from an alligator

What distinguishes crocodiles from their closest relatives, alligators, is primarily the structure of their teeth: when the mouth is closed, the fourth tooth is visible on the lower jaw, while in alligators no teeth are visible at all. The structure of the muzzle is also different: in alligators it is blunter, in crocodiles it is sharper.

Crocodiles have the best salt metabolism: they remove excess salts through the glands located on the tongue, as well as through the lacrimal glands (the famous “crocodile tears”). Thanks to this, they are able to live not only in river water, but also in sea water, while alligators can only live in fresh water. Among crocodiles there are species that live both here 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 river mouths.

Way of life

Crocodiles prefer to live mainly in fresh water bodies, and some species: Nile crocodile, combed crocodile, African narrow-snouted crocodile are found near the sea coast. These animals spend all their time in the water, coming to land in the morning or evening to bask in the sun and accumulate heat in their horny plates. For example, the Nile crocodile prefers air temperatures from 32 to 35 °C; if the readings are higher, it does not even show up on land. During drought, some species of crocodiles dig holes at the bottom of drying reservoirs and hibernate.

On land, these animals are inactive and clumsy, so they prefer to move exclusively in water. If necessary, they are able to move to another body of water through land, covering several kilometers.

It is interesting that they usually move with their legs spread wide apart, then developing speed (no more than 11 km/h for short distances), the reptiles place their paws under their body. But in water, reptiles swim much faster, at a speed of about 40 km/h. Despite their impressive size, they are quite capable of jumping two meters out of the water.

Crocodiles live in packs, and this life is unique: they are quite capable of eating their relatives, and the males often destroy the babies. In each group there is a dominant male, who jealously guards his territory from individuals as large as himself, emitting a loud roar. These reptiles can express their emotions different ways: They hiss, grunt, growl and even croak hoarsely.

Hunting and food

Despite the fact that crocodiles prefer to hunt at night, during the day, if the prey is not far from them, they do not leave it without attention. They receive information about a potential victim thanks to receptors located on their jaws, which are able to sense prey located even at a great distance.

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

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

But large individuals (the same Nile crocodile) are able to cope even with victims that are significantly larger than them in size: the Nile crocodile catches wildebeest when they cross rivers during migration, the combed predator opens a hunt for cattle during the rainy season, the Madagascan one succeeds catch a lemur, and in search of water he crawls into caves (during drought it can only be found here). If necessary, these animals are capable of eating their own relatives.

These reptiles cannot chew, and therefore, having caught the victim, they dismember it with their teeth and swallow it in parts. If the food is too large for this, they can leave it at the bottom for a while and wait until it gets soggy. The animal is helped to cope with food by swallowing stones, which grind the food. These stones are often quite large in size: it is known for sure that the Nile crocodile is capable of swallowing a five-kilogram block.

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

Reproduction

Considering that crocodiles live from 50 to 110 years, they reach sexual maturity quite early: at the age of 8 to 10 years. Crocodiles are polygamous animals: a male may well have a harem of twelve females.

The female does not give birth, but lays eggs (about fifty eggs per night). To do this, she goes to the coast and digs a hole, the size of which largely depends on the illumination: deeper in the sun, shallower in the shade, and then covers it with sand or leaves. It takes about three months. The female spends all this time near them, without going anywhere and not even feeding.

Who exactly hatches depends largely on temperature indicators air: if they exceed 32°C, a male will appear, from 28 to 30°C - a female. Before breaking the shell, one or the other small crocodile begins to make grunting sounds. This is a signal for the female, and she first digs them out, then rolls them in her mouth and releases the babies.

The crocodiles that are born are small: their length is only 28 centimeters. At a time, the mother collects about two dozen babies in her mouth and transfers them to a pre-selected small reservoir, where they spend about eight weeks, after which they scatter around the surrounding area in search of reservoirs 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 survive, 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 hunting large vertebrates.

Reptiles and people

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

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

According to data, in the 20s of the last century, about a million reptiles were killed annually in South America alone, so if governments had not come to their senses in time and in the forties had not passed laws according to which hunting crocodiles was prohibited, they would have been destroyed long ago. Also, the largest crocodile in Africa, the Nile crocodile, disappeared from its usual habitats, and captive breeding saved the Indian gharial from complete disappearance(today there are about 1.5 thousand individuals).

Another factor that puts these reptiles on the brink of extinction in South America and Asia is the construction of dams. To build them, huge areas of forests were cut down, as a result of which many reservoirs where crocodiles lived dried up.

This situation is alarming not only because a unique species is dying out, but also because with the disappearance of these animals the ecosystem of the region is disrupted. 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 drought: water accumulates in the holes they dig, forming small reservoirs where, during drought, fish find refuge, and animals and birds come to drink.