Crocodile
Overview
A crocodile is any species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 belonging to the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Crocodylidae (sometimes classified instead as the subfamily Crocodylinae). The term can also be used more loosely to include all extant members of the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...

: i.e. the true crocodiles, the alligator
Alligator
An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. There are two extant alligator species: the American alligator and the Chinese alligator ....

s and caiman
Caiman
Caimans are alligatorid crocodylians within the subfamily Caimaninae. The group is one of two subfamilies of the family Alligatoridae, the other being alligators. Caimans inhabit Central and South America. They are relatively small crocodilians, with most species reaching lengths of only a few...

s (family Alligatoridae
Alligatoridae
Alligatoridae is a family of crocodylians that includes alligators and caimans.- True alligators :Alligators proper occur in the fluvial deposits of the age of the Upper Chalk in Europe, where they did not die out until the Pliocene age. The true alligators are now restricted to two species, A...

) and the gharial
Gharial
The gharial , , also called Indian gavial or gavial, is the only surviving member of the once well-represented family Gavialidae, a long-established group of crocodilians with long, slender snouts...

s (family Gavialidae
Gavialidae
Gavialidae is a family of reptiles within the order Crocodilia. Gavialidae consists of only one surviving species, the gharial , which is native to India. Many extinct species are also known...

), as well as the Crocodylomorpha
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...

 which includes prehistoric crocodile relatives and ancestors.

Member species of the family Crocodylidae are large aquatic reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s that live throughout the tropics in Africa, Asia, the Americas and Australia.
Encyclopedia
A crocodile is any species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 belonging to the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Crocodylidae (sometimes classified instead as the subfamily Crocodylinae). The term can also be used more loosely to include all extant members of the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...

: i.e. the true crocodiles, the alligator
Alligator
An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. There are two extant alligator species: the American alligator and the Chinese alligator ....

s and caiman
Caiman
Caimans are alligatorid crocodylians within the subfamily Caimaninae. The group is one of two subfamilies of the family Alligatoridae, the other being alligators. Caimans inhabit Central and South America. They are relatively small crocodilians, with most species reaching lengths of only a few...

s (family Alligatoridae
Alligatoridae
Alligatoridae is a family of crocodylians that includes alligators and caimans.- True alligators :Alligators proper occur in the fluvial deposits of the age of the Upper Chalk in Europe, where they did not die out until the Pliocene age. The true alligators are now restricted to two species, A...

) and the gharial
Gharial
The gharial , , also called Indian gavial or gavial, is the only surviving member of the once well-represented family Gavialidae, a long-established group of crocodilians with long, slender snouts...

s (family Gavialidae
Gavialidae
Gavialidae is a family of reptiles within the order Crocodilia. Gavialidae consists of only one surviving species, the gharial , which is native to India. Many extinct species are also known...

), as well as the Crocodylomorpha
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...

 which includes prehistoric crocodile relatives and ancestors.

Member species of the family Crocodylidae are large aquatic reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s that live throughout the tropics in Africa, Asia, the Americas and Australia. Crocodiles tend to congregate in freshwater habitats like rivers, lakes, wetlands and sometimes in brackish water. They feed mostly on vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s like fish, reptiles, and mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s, sometimes on invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s like molluscs and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s, depending on species. They first appeared during the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 epoch, about 55 million years ago.

Etymology

The word crocodile comes from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

 κροκόδιλος (crocodilos), "lizard," used in the phrase ho krokódilos ho potamós, "the lizard of the (Nile
Nile
The Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...

) river."

There are several variant Greek forms of the word attested, including the later form κροκόδειλος (crocodeilos) found cited in many English reference works. In the Koine Greek
Koine Greek
Koine Greek is the universal dialect of the Greek language spoken throughout post-Classical antiquity , developing from the Attic dialect, with admixture of elements especially from Ionic....

 of Roman
Roman Empire
The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....

 times, crocodilos and crocodeilos would have been pronounced identically, and either or both may be the source of the Latinized
Classical Latin
Classical Latin in simplest terms is the socio-linguistic register of the Latin language regarded by the enfranchised and empowered populations of the late Roman republic and the Roman empire as good Latin. Most writers during this time made use of it...

 form crocodīlus used by the ancient Romans.

Crocodilos/crocodeilos itself is a compound of krokè ("pebbles"), and drilos/dreilos ("worm"). It is ascribed to Herodotus, supposedly to describe the basking habits of the Egyptian crocodile. However the word drilos is only attested as a colloquial term for "penis". The meaning of krokè is explained as describing the skin texture of lizards (or crocodiles) in most sources, but is alternately claimed to refer to a supposed habit of (lizards or crocodiles) basking on pebbly ground.

The form crocodrillus is attested in Medieval Latin
Medieval Latin
Medieval Latin was the form of Latin used in the Middle Ages, primarily as a medium of scholarly exchange and as the liturgical language of the medieval Roman Catholic Church, but also as a language of science, literature, law, and administration. Despite the clerical origin of many of its authors,...

. It is not clear whether this is a medieval corruption or derives from alternate Greco-Latin forms (late Greek corcodrillos and corcodrillion are attested).

A (further) corrupted form cocodrille is found in Old French
Old French
Old French was the Romance dialect continuum spoken in territories that span roughly the northern half of modern France and parts of modern Belgium and Switzerland from the 9th century to the 14th century...

 and was borrowed into Middle English
Middle English
Middle English is the stage in the history of the English language during the High and Late Middle Ages, or roughly during the four centuries between the late 11th and the late 15th century....

 as cocodril(le). The Modern English
Modern English
Modern English is the form of the English language spoken since the Great Vowel Shift in England, completed in roughly 1550.Despite some differences in vocabulary, texts from the early 17th century, such as the works of William Shakespeare and the King James Bible, are considered to be in Modern...

 form crocodile was adapted directly from the Classical Latin crocodīlus in the 16th Century, replacing the earlier form.

The use of -y- in the scientific name Crocodylus
Crocodylus
Crocodylus is one of three genera from the Crocodylinae subfamily extending from the Crocodylidae family.Established species include three extinct species:* † Crocodylus acer - probably represents a distinct genus....

(and forms derived from it) is a corruption introduced by Laurenti
Josephus Nicolaus Laurenti
Josephus Nicolaus Laurenti was an Austrian naturalist of Italian origin.Laurenti is considered the auctor of the class Reptilia through his authorship of on the poisonous function of reptiles and amphibians...

 (1768).

Description

Crocodiles are similar to alligators and caiman; for their common biology and differences between them, see Crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...

.


Crocodiles are among the more biologically complex reptiles despite their prehistoric look. Unlike other reptiles, they have a cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...

; a four-chambered heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

; and the functional equivalent of a diaphragm, by incorporating muscles used for aquatic locomotion into respiration (e.g. M. diaphragmaticus); Their external morphology on the other hand is a sign of their aquatic and predatory lifestyle. A crocodile’s physical traits allow it to be a successful predator. They have a streamlined body that enables them to swim swiftly. Crocodiles also tuck their feet to their sides while swimming, which makes them faster by decreasing water resistance. They have webbed feet which, although not used to propel the animal through the water, allow it to make fast turns and sudden moves in the water or initiate swimming. Webbed feet are an advantage in shallower water where the animals sometimes move around by walking.

Crocodiles have a palatal flap, a rigid tissue at the back of the mouth that blocks the entry of water. The palate has a special path from the nostril to the glottis that bypasses the mouth. The nostrils are closed during submergence. Like other archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...

s, crocodilians are diapsid
Diapsid
Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...

, although their post-temporal fenestrae
Fenestrae
Fenestræ is a Latin word that means "window".* In histology, fenestræ are small pores in endothelial cells that allow for rapid exchange of molecules between sinusoid blood vessels and surrounding tissue...

 are reduced. The walls of the braincase are bony but they lack supratemporal and postfrontal bones. Their tongues are not free but held in place by a membrane which limits movement; as a result, crocodiles are unable to stick out their tongues.

Crocodilian scales have pores that are believed to be sensory, analogous to the lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...

 in fishes. They are particularly seen on their upper and lower jaws. Another possibility is that they are secretory, as they produce an oily substance that appears to flush mud off.

Crocodiles are very fast over short distances, even out of water. Since crocodiles feed by grabbing and holding onto their prey, they have evolved
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

 sharp teeth for tearing and holding onto flesh, and powerful muscles that close the jaws and hold them shut. These jaws can bite down with immense force, by far the strongest bite of any animal. The pressure of the crocodile's bite is more than 5000 pound per square inches (34,473.8 kPa), compared to just 335 pound per square inches (2,309.7 kPa) for a rottweiler
Rottweiler
The Rottweiler is a medium to large size breed of domestic dog that originated in Rottweil, Germany. The dogs were known as "Rottweil butchers' dogs" because they were used to herd livestock and pull carts laden with butchered meat and other products to market...

, 400 pound per square inches (2,757.9 kPa) for a large great white shark
Great white shark
The great white shark, scientific name Carcharodon carcharias, also known as the great white, white pointer, white shark, or white death, is a large lamniform shark found in coastal surface waters in all major oceans. It is known for its size, with the largest individuals known to have approached...

, 800 pound per square inches (5,515.8 kPa) to 1000 pound per square inches (6,894.8 kPa) for a hyena
Hyena
Hyenas or Hyaenas are the animals of the family Hyaenidae of suborder feliforms of the Carnivora. It is the fourth smallest biological family in the Carnivora , and one of the smallest in the mammalia...

, or 2000 pound per square inches (13,789.5 kPa) for a large alligator
Alligator
An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. There are two extant alligator species: the American alligator and the Chinese alligator ....

. The jaws are opened, however, by a very weak set of muscles. Crocodiles can thus be subdued for study or transport by taping
Duct tape
Duct tape, or duck tape, is cloth- or scrim-backed pressure sensitive tape often sealed with polyethylene. It is very similar to gaffer tape but differs in that gaffer tape was designed to be cleanly removed, while duct tape was not. It has a standard width of and is generally silver or black...

 their jaws or holding their jaws shut with large rubber band
Rubber band
A rubber band is a short length of rubber and latex formed in the shape of a loop and is commonly used to hold multiple objects together...

s cut from automobile inner tube
Tire
A tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...

s. They have limited lateral (side-to-side) movement in their neck.

Biology and behaviour

Crocodiles are ambush hunters, waiting for fish or land animals to come close, then rushing out to attack. As cold-blooded predators, they have a very slow metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

, and thus can survive long periods without food. Despite their appearance of being slow, crocodiles are top predators in their environment, and various species have been observed attacking and killing shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s.

Herodotus
Herodotus
Herodotus was an ancient Greek historian who was born in Halicarnassus, Caria and lived in the 5th century BC . He has been called the "Father of History", and was the first historian known to collect his materials systematically, test their accuracy to a certain extent and arrange them in a...

 claimed that Nile crocodiles have a symbiotic relationship
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

 with certain birds like the Egyptian plover
Egyptian Plover
The Egyptian Plover is a wader, the only member of the genus Pluvianus. Formerly placed in the pratincole and courser family, Glareolidae, it is now regarded as the sole member of its own monotypic family Pluvianidae....

, which enter the crocodile's mouth and pick leech
Leech
Leeches are segmented worms that belong to the phylum Annelida and comprise the subclass Hirudinea. Like other oligochaetes such as earthworms, leeches share a clitellum and are hermaphrodites. Nevertheless, they differ from other oligochaetes in significant ways...

es that have been feeding on the crocodile's blood, but there is no evidence of this interaction actually occurring in any crocodile species, and it is most likely mythical or allegorical fiction.

Many large crocodilians swallow stones (called gastroliths or stomach stones) which may act as ballast to balance their body or assist in crushing food, similar to grit in birds.

Salt gland
Salt gland
The salt gland is an organ for excreting excess salts. It is found in elasmobranchs, seabirds, and some reptiles. In sharks, salt glands are found in the rectum, but in birds and reptiles, they are found in or on the skull, in the area of the eyes, nostrils or mouth. In crocodiles, the salt is...

s are present in the tongues of most crocodylids and they have a pore opening on the surface of the tongue. They appear to be similar to those in marine turtles; they seem to be absent in Alligatoridae.

Crocodilians can produce sounds during distress and in aggressive displays. They can also hear well and the tympanic membranes are concealed by flat flaps that may be raised or lowered by muscles.
Crocodiles eat fish, birds, mammals and occasionally smaller crocodiles.

Crocodiles are protected in many parts of the world, but they also are farmed commercially. Their hide is tanned and used to make leather goods such as shoes and handbag
Handbag
A handbag, or purse in American English, is a handled medium-to-large bag that is often fashionably designed, typically used by women, to hold personal items such as wallet/coins, keys, cosmetics, a hairbrush, pepper spray, cigarettes, mobile phone etc....

s, whilst crocodile meat is also considered a delicacy. The most commonly farmed species are the Saltwater and Nile crocodiles, while a hybrid of the Saltwater and the rare Siamese Crocodile
Siamese Crocodile
Siamese crocodile is a freshwater crocodile native to Indonesia , Brunei, East Malaysia, Laos, Cambodia, Burma, Thailand, and Vietnam...

 is also bred in Asian farms. Farming has resulted in an increase in the Saltwater crocodile population in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, as eggs are usually harvested from the wild, so landowners have an incentive to conserve crocodile habitat.

Crocodiles are more closely related to birds and dinosaurs than to most animals classified as reptiles, the three being included in the group Archosauria ('ruling reptiles'). See Crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...

 for more information.

Crocodile embryos do not have sex chromosomes, and unlike humans sex is not determined genetically. Sex is determined by temperature
Temperature-dependent sex determination
Temperature-dependent sex determination is type of environmental sex determination in which the temperatures experienced during embryonic development determine the sex of the offspring. It is most prevalent and common among amniote vertebrates that are classified under the reptile class, but is...

, with males produced at around 31.6 °C (89 °F), and females produced at slightly lower and higher temperatures. The average incubation period is around 80 days, and also is dependent upon temperature.

Crocodiles may possess a form of homing instinct. Three rogue saltwater crocodiles were relocated 400 kilometres by helicopter
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...

 in northern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 but had returned to their original locations within three weeks, based on data obtained from tracking devices attached to the reptiles.

The land speed
Land speed
An object's speed across land is measured by difference in movement between the object and the land beneath it. Atmospheric pressure and aerodynamics must be considered when attempting to calculate possible speeds from the force applied.-Units:...

 record for a crocodile is 17 km/h (11 mph) measured in a galloping Australian freshwater crocodile
Freshwater Crocodile
The freshwater crocodile , also known as the Australian freshwater crocodile, Johnston's crocodile or colloquially as freshie, is a species of reptile endemic to the northern regions of Australia...

. Maximum speed varies from species to species. Certain types of crocodiles can indeed gallop, including Cuban crocodiles, New Guinea crocodiles, African dwarf crocodiles
Dwarf Crocodile
The dwarf crocodile is an African species of crocodile. It is also the smallest extant crocodile species in the world. Recent sampling has identified three genetically distinct populations...

, and even small Nile crocodiles. The fastest means by which most species can move is a kind of "belly run", where the body moves in a snake-like fashion, limbs splayed out to either side paddling away frantically while the tail whips to and fro. Crocodiles can reach speeds of 10 or 11 km/h (around 7 mph) when they "belly run", and often faster if they're slipping down muddy riverbanks. Another form of locomotion is the "high walk" where the body is raised clear off the ground.

Crocodiles do not have sweat glands and release heat through their mouths. They often sleep with their mouths open and may even pant like a dog.

It is reported that when the Nile crocodile
Nile crocodile
The Nile crocodile or Common crocodile is an African crocodile which is common in Somalia, Ethiopia, Uganda, Kenya, Egypt, Tanzania, Zambia, Zimbabwe, Gabon, South Africa, Malawi, Sudan, Botswana, and Cameroon...

 has lurked a long time underwater to catch prey, and thus has built up a big oxygen debt, when it has caught and eaten that prey, it closes its right aortic arch
Aortic arch
The arch of the aorta or the transverse aortic arch is the part of the aorta that begins at the level of the upper border of the second sternocostal articulation of the right side, and runs at first upward, backward, and to the left in front of the trachea; it is then directed backward on the left...

 and uses its left aortic arch to flush blood loaded with carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 from its muscles directly to its stomach; the resulting excess acidity in its blood supply makes it much easier for the stomach lining to secrete more stomach acid to quickly dissolve bulks of swallowed prey flesh and bone.

Size

Size greatly varies between species, from the dwarf crocodile
Dwarf Crocodile
The dwarf crocodile is an African species of crocodile. It is also the smallest extant crocodile species in the world. Recent sampling has identified three genetically distinct populations...

 to the saltwater crocodile
Saltwater Crocodile
The saltwater crocodile, also known as estuarine or Indo-Pacific crocodile, is the largest of all living reptiles...

. Species of Palaeosuchus and Osteolaemus grow to an adult size of just 1 metres (3.3 ft) to 1.5 metres (4.9 ft). Larger species can reach over 4.85 metres (15.9 ft) long and weigh well over 1200 kilograms (2,645.5 lb). Crocodilians show pronounced sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...

 with males growing much larger and more rapidly than females. Despite their large adult size, crocodiles start their life at around 20 centimetres (7.9 in) long. The largest species of crocodile is the saltwater crocodile
Saltwater Crocodile
The saltwater crocodile, also known as estuarine or Indo-Pacific crocodile, is the largest of all living reptiles...

, found in eastern India, northern Australia, throughout south-east Asia, and in the surrounding waters.

Two larger certifiable records are both of 6.2 metres (20.3 ft) crocodiles. The first crocodile was shot in the Mary River
Mary River (Northern Territory)
The Mary River flows in the Northern Territory of Australia and is a site of the Mary River National Park. Its lower reaches form part of the Adelaide and Mary River Floodplains Important Bird Area.-External links:**...

 in the Northern Territory
Northern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...

 of Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 in 1974 by poachers and measured by wildlife rangers. The second crocodile was killed in 1983 in the Fly River
Fly River
The Fly at , is the second longest river, after the Sepik, in Papua New Guinea. The Fly is the largest river in Oceania, the largest in the world without a single dam in its catchment, and overall ranks as the twenty-fifth largest river in the world by volume of discharge...

, Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...

. In the case of the second crocodile it was actually the skin that was measured by zoologist Jerome Montague, and as skins are known to underestimate the size of the actual animal, it is possible this crocodile was at least another 10 cm longer.

The largest crocodile ever held in captivity is an Estuarine–Siamese hybrid named Yai (born 10 June 1972) at the famous Samutprakarn Crocodile Farm and Zoo
Samutprakarn Crocodile Farm and Zoo
The Samutprakarn Crocodile Farm and Zoo is an internationally renowned crocodile zoo in Bangkok, Thailand. It claims to hold the Guinness Book of Records Largest Captive Crocodile measuring six meters and weighing 1114.27 kilograms...

, Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...

. This animal measures 6 m (19.69 ft) (19 ft 8 in) in length and weighs 1114.27 kg.

The longest crocodile captured alive is Lolong
Lolong
Lolong is the largest crocodile in captivity. A male Indo-Pacific or Saltwater crocodile , he weighs 2,370 pounds and is 20 feet 3 inches long, making him one of the largest crocodiles ever measured snout-to-tail.In November 2011, Australian crocodile expert Dr...

 which was measured at 6.096 metres (20 ft 3 in) by a National Geographic team in Agusan del Sur Province, Philippines. The largest captive crocodile alive in the US is located in South Carolina
South Carolina
South Carolina is a state in the Deep South of the United States that borders Georgia to the south, North Carolina to the north, and the Atlantic Ocean to the east. Originally part of the Province of Carolina, the Province of South Carolina was one of the 13 colonies that declared independence...

. In June 2002, Alligator Adventure introduced Utan, born in 1964 in Thailand. At 20 feet (6.1 m) long and weighing in at more than a ton, "Utan", the largest crocodile to ever be exhibited in the United States, made his new home in Myrtle Beach.

Wildlife experts, however, argue that the largest crocodile so far found in the Bhitarkanika was almost 23 feet (7 m) long, which could be traced from the skull preserved by the Kanika Royal Family. The crocodile was shot near Dhamara in 1926 and later its skull was preserved by the then Kanika King. Crocodile experts estimate the animal was between 20 feet (6.1 m) and 23 feet (7 m) long, as the size of the skull was measured one ninth of the total length of the body.

Age

There is no reliable way of measuring crocodile age, although several techniques are used to derive a reasonable guess. The most common method is to measure lamellar growth rings in bones and teeth—each ring corresponds to a change in growth rate which typically occurs once a year between dry and wet seasons. Bearing these inaccuracies in mind, the oldest crocodilians appear to be the largest species. C. porosus is estimated to live around 70 years on average, and there is limited evidence that some individuals may exceed 100 years. One of the oldest crocodiles recorded died in a zoo in Russia. A male freshwater crocodile at the Australia Zoo
Australia Zoo
Australia Zoo is a zoo located in the Australian state of Queensland on the Sunshine Coast near Beerwah/Glass House Mountains. It is a member of the Zoo and Aquarium Association , and is owned by Terri Irwin, the widow of Steve Irwin, whose wildlife documentary series The Crocodile Hunter made the...

 is estimated to be 130 years old. He was rescued from the wild by Bob Irwin
Bob Irwin
Robert "Bob" Irwin is an Australian naturalist, animal conservationist, and a pioneering herpetologist who is also famous for his conservation and husbandry work with apex predators and reptiles...

 and Steve Irwin
Steve Irwin
Stephen Robert "Steve" Irwin , nicknamed "The Crocodile Hunter", was an Australian television personality, wildlife expert, and conservationist. Irwin achieved worldwide fame from the television series The Crocodile Hunter, an internationally broadcast wildlife documentary series which he co-hosted...

 after being shot twice by hunters. As a result of the shootings, this crocodile (known affectionately as "Mr. Freshy") has lost his right eye.

Skin

Crocodiles have smooth skin on their belly and side, while their dorsal surface is armoured with large osteoderms. The armoured skin has scales and is thick and rugged, providing some protection. They are still able to absorb heat through this thick, rugged armour as a network of small capillaries push blood through the scales to absorb heat.

Taxonomy of the Crocodylidae

Most species are grouped into the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Crocodylus. The other extant genus, Osteolaemus, is monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

 (as is Mecistops, if recognized).
  • Family Crocodylidae
    • Subfamily †Mekosuchinae (extinct)
    • Subfamily Crocodylinae
      • Genus Crocodylus
        Crocodylus
        Crocodylus is one of three genera from the Crocodylinae subfamily extending from the Crocodylidae family.Established species include three extinct species:* † Crocodylus acer - probably represents a distinct genus....

        • Crocodylus acutus, American Crocodile
          American Crocodile
          The American crocodile is a species of crocodilian found in the Neotropics. It is the most widespread of the four extant species of crocodiles from the Americas. Populations occur from the Atlantic and Pacific coasts of southern Mexico to South America as far as Peru and Venezuela. It also lives...

        • Crocodylus cataphractus, Slender-snouted Crocodile
          Slender-snouted Crocodile
          The African Slender-snouted Crocodile is a species of crocodile. Recent studies in DNA and morphology suggest that it may belong in its own genus, Mecistops, but at present most continue to use Crocodylus for this species.African Slender-snouted Crocodile are native to freshwater habitats in...

           (studies in DNA
          DNA
          Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

           and morphology
          Morphology (biology)
          In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

           suggest that this species may be more basal
          Basal (phylogenetics)
          In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

           than Crocodylus
          Crocodylus
          Crocodylus is one of three genera from the Crocodylinae subfamily extending from the Crocodylidae family.Established species include three extinct species:* † Crocodylus acer - probably represents a distinct genus....

          , and therefore belongs in its own genus, Mecistops)
        • Crocodylus intermedius, Orinoco Crocodile
          Orinoco Crocodile
          The Orinoco crocodile, Crocodylus intermedius, is a critically endangered crocodile found in freshwater in northern South America, in particular the Orinoco River. Typical measurements for adults range from 3 to 4.8 m . Typical weight for mature females is 200 kg and 380 kg for males...

        • Crocodylus johnsoni, Freshwater Crocodile
          Freshwater Crocodile
          The freshwater crocodile , also known as the Australian freshwater crocodile, Johnston's crocodile or colloquially as freshie, is a species of reptile endemic to the northern regions of Australia...

          , or Johnstone's Crocodile
        • Crocodylus mindorensis, Philippine Crocodile
          Philippine crocodile
          The Philippine crocodile is a crocodile found in the Philippines. It is also known as the Mindoro crocodile and the Philippine freshwater crocodile. In the Philippines, it is strictly prohibited to kill a crocodile, but its status is critically endangered from exploitation and unsustainable...

        • Crocodylus moreletii, Morelet's Crocodile
          Morelet's Crocodile
          Morelet's crocodile, also known as the Mexican crocodile, is a modest sized crocodilian found only in fresh waters of the Atlantic regions of Mexico, Belize and Guatemala. It usually grows to about in length. It is an endangered species.-History:...

           or Mexican Crocodile
        • Crocodylus niloticus, Nile Crocodile
          Nile crocodile
          The Nile crocodile or Common crocodile is an African crocodile which is common in Somalia, Ethiopia, Uganda, Kenya, Egypt, Tanzania, Zambia, Zimbabwe, Gabon, South Africa, Malawi, Sudan, Botswana, and Cameroon...

           or African Crocodile (the subspecies found in Madagascar is sometimes called the Black Crocodile)
        • Crocodylus novaeguineae, New Guinea Crocodile
          New Guinea Crocodile
          The New Guinea crocodile is a small species of crocodile found on the island of New Guinea.-Description:Crocodylus novaeguineae grows to a length of up to for males and for females, although most specimens are rather smaller. The body is grey-brown in colour, with dark brown to black markings on...

        • Crocodylus palustris, Mugger Crocodile
          Mugger Crocodile
          The mugger crocodile , also called the Indian, Indus, Persian, or marsh crocodile, is found throughout the Indian subcontinent and the surrounding countries...

          , Marsh Crocodile, or Indian Crocodile
        • Crocodylus porosus, Saltwater Crocodile
          Saltwater Crocodile
          The saltwater crocodile, also known as estuarine or Indo-Pacific crocodile, is the largest of all living reptiles...

           or Estuarine Crocodile
        • Crocodylus rhombifer, Cuban Crocodile
          Cuban crocodile
          The Cuban crocodile is a small species of crocodile found only in Cuba's Zapata Swamp and the Isle of Youth, and highly endangered, though it formerly ranged elsewhere in the Caribbean...

        • Crocodylus siamensis, Siamese Crocodile
          Siamese Crocodile
          Siamese crocodile is a freshwater crocodile native to Indonesia , Brunei, East Malaysia, Laos, Cambodia, Burma, Thailand, and Vietnam...

           (may be extinct in the wild)
        • Crocodylus suchus, Desert Crocodile
          Desert Crocodile
          The desert crocodile, Northwest African crocodile, or West African crocodile is a species of crocodile distantly related to the Nile crocodile . The crocodile inhabits the Republic of Congo, Uganda, Gambia, Senegal, Mauritania, Burkina Faso, Ivory Coast, the Democratic Republic of Congo, Chad...

           or Sacred Crocodile (Recent (2011) DNA analysis indicates this is distinct from the eastern population of the Nile Crocodile.)
      • Genus Osteolaemus
        • Osteolaemus tetraspis, Dwarf Crocodile
          Dwarf Crocodile
          The dwarf crocodile is an African species of crocodile. It is also the smallest extant crocodile species in the world. Recent sampling has identified three genetically distinct populations...

           (There has been controversy whether or not this is actually two species; recent (2010) DNA analysis indicates that there are three distinct species: O. tetraspis, O. osborni, and a third currently unnamed.)
      • Genus †Euthecodon
        Euthecodon
        Euthecodon is an extinct genus of longirostrine crocodyline crocodilian. It was common throughout much of Africa during the Neogene, with fossils being especially common in Kenya. It existed from the Early Miocene to the Early Pleistocene.-Description:...

      • Genus †Rimasuchus
        Rimasuchus
        Rimasuchus is an extinct genus of crocodile from the Neogene period of Africa and the Middle East. Its name comes from the Latin words rima, meaning "crack" and suchus, which means "crocodile"...

        (formerly Crocodylus lloydi)
      • Genus †Voay
        Voay
        Voay is an extinct genus of crocodylid crocodilian. Numerous subfossils have been found from Madagascar, including complete skulls as well as vertebrae and osteoderms from such places as Ambolisatra and Antsirabe. The genus is thought to have become extinct relatively recently during the Holocene...

        Brochu, 2007 (formerly Crocodylus robustus)


Some of the extinct relatives of true crocodiles, members of the larger group Crocodylomorpha
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...

, were herbivorous.

Phylogeny

Cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...

 after Brochu C. A., Njau J., Blumenschine R. J., Densmore L. D. (2010).

Danger to humans

The larger species of crocodiles are very dangerous to humans. The main danger that crocodiles pose is not their ability to run after a person but their ability to strike before the person can react. The saltwater crocodile
Saltwater Crocodile
The saltwater crocodile, also known as estuarine or Indo-Pacific crocodile, is the largest of all living reptiles...

 and Nile crocodile
Nile crocodile
The Nile crocodile or Common crocodile is an African crocodile which is common in Somalia, Ethiopia, Uganda, Kenya, Egypt, Tanzania, Zambia, Zimbabwe, Gabon, South Africa, Malawi, Sudan, Botswana, and Cameroon...

 are the most dangerous, killing hundreds of people each year in parts of south-east Asia and Africa. The mugger crocodile
Mugger Crocodile
The mugger crocodile , also called the Indian, Indus, Persian, or marsh crocodile, is found throughout the Indian subcontinent and the surrounding countries...

, American crocodile
American Crocodile
The American crocodile is a species of crocodilian found in the Neotropics. It is the most widespread of the four extant species of crocodiles from the Americas. Populations occur from the Atlantic and Pacific coasts of southern Mexico to South America as far as Peru and Venezuela. It also lives...

, American alligator
American Alligator
The American alligator , sometimes referred to colloquially as a gator, is a reptile endemic only to the Southeastern United States. It is one of the two living species of alligator, in the genus Alligator, within the family Alligatoridae...

 and black caiman
Black Caiman
The black caiman is a crocodilian. It is a carnivorous reptile that lives along slow-moving rivers and lakes, in the seasonally flooded savannas of the Amazon basin, and in other freshwater habitats in South America. Once common, it was hunted to near extinction primarily for its commercially...

 are also dangerous to humans.

Crocodile products

Crocodile leather can be made into goods such as wallets, briefcases, purses, handbags, belts, hats, and shoes.

Crocodile meat is consumed in some countries, such as Australia, Ethiopia, Thailand, South Africa and also Cuba (in pickled form); it can also be found in specialty restaurants in some parts of the United States. The meat is white and its nutritional composition compares favourably with that of other meats. It tends to have a slightly higher cholesterol level than other meats. Crocodile meat has a delicate flavour; some describe it as a cross between chicken and crab. Cuts of meat include backstrap and tail fillet.

See also

  • Alligator
    Alligator
    An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. There are two extant alligator species: the American alligator and the Chinese alligator ....

  • Crocodile exoskeleton
    Crocodile exoskeleton
    The crocodile exoskeleton consists of the protective dermal and epidermal components of the integumentary system in animals of the order Crocodilia. It is a form of armour.-Structure and anatomy:...

  • Crocodiles in sewers
  • The Crocodile Hunter
    The Crocodile Hunter
    The Crocodile Hunter was a wildlife documentary television series that was hosted by Steve Irwin and his wife Terri. The show became a popular franchise due to its unconventional approach and Irwin's approach to wildlife...


Further reading

  • Iskandar, DT (2000). Turtles and Crocodiles of Insular Southeast Asia and New Guinea. ITB, Bandung.
  • Crocodilian Biology Database, FAQ. FLMNH.ufl.edu, "How long do crocodiles live for?" Adam Britton.
  • Crocodilian Biology Database, FAQ. FLMNH.ufl.edu, "How fast can a crocodile run?" Adam Britton.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK