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Crocodiles ( family Crocodylidae) or true crocodiles are large semiaquatic
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s that live throughout the tropics in Africa, Asia, the
Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...
and
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
. The term crocodile is sometimes used even more loosely to include all
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...
members of the
order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
Crocodilia, which includes the alligators and caimans (family Alligatoridae), the
gharial The gharial (''Gavialis gangeticus''), also known as gavial or fish-eating crocodile, is a crocodilian in the family Gavialidae and among the longest of all living crocodilians. Mature females are long, and males . Adult males have a distinct b ...
and
false gharial The false gharial (''Tomistoma schlegelii''), also known by the names Malayan gharial, Sunda gharial and tomistoma is a freshwater crocodilian of the family Gavialidae native to Peninsular Malaysia, Borneo, Sumatra and Java. It is listed as Vu ...
(family Gavialidae) among other extinct taxa. Although they appear similar, crocodiles, alligators and the gharial belong to separate biological families. The gharial, with its narrow
snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, rostrum, or proboscis. The wet furless surface around the nostrils of the nose of many mammals is c ...
, is easier to distinguish, while morphological differences are more difficult to spot in crocodiles and alligators. The most obvious external differences are visible in the head, with crocodiles having narrower and longer heads, with a more V-shaped than a U-shaped snout compared to alligators and caimans. Another obvious trait is that the upper and lower jaws of the crocodiles are the same width, and the teeth in the lower jaw fall along the edge or outside the upper jaw when the mouth is closed; therefore, all teeth are visible, unlike an alligator, which possesses in the upper jaw small depressions into which the lower teeth fit. Also, when the crocodile's mouth is closed, the large fourth tooth in the lower jaw fits into a constriction in the upper jaw. For hard-to-distinguish specimens, the protruding tooth is the most reliable feature to define the species' family. Crocodiles have more webbing on the toes of the hind feet and can better tolerate saltwater due to specialized salt glands for filtering out salt, which are present, but non-functioning, in alligators. Another trait that separates crocodiles from other crocodilians is their much higher levels of
aggression Aggression is overt or covert, often harmful, social interaction with the intention of inflicting damage or other harm upon another individual; although it can be channeled into creative and practical outlets for some. It may occur either reacti ...
. Crocodile size, morphology,
behaviour Behavior (American English) or behaviour (British English) is the range of actions and mannerisms made by individuals, organisms, systems or artificial entities in some environment. These systems can include other systems or organisms as wel ...
and ecology differ somewhat among species. However, they have many similarities in these areas as well. All crocodiles are semiaquatic and tend to congregate in
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
habitats such as rivers, lakes, wetlands and sometimes in brackish water and saltwater. They are
carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...
animals, feeding mostly on vertebrates such as fish,
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s, birds and
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s, and sometimes on invertebrates such as
mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000  extant species of molluscs are recognized. The number of fossil species is esti ...
s and crustaceans, depending on species and age. All crocodiles are tropical species that, unlike alligators, are very sensitive to cold. They separated from other crocodilians during the Eocene epoch, about 55 million years ago. Many species are at the risk of extinction, some being classified as critically endangered.


Etymology

The word ''crocodile'' comes from the Ancient Greek () meaning 'lizard', used in the phrase , "the lizard of the ( Nile) river". There are several variant Greek forms of the word attested, including the later form () found cited in many English reference works. In the Koine Greek of Roman times, and would have been pronounced identically, and either or both may be the source of the Latinized form used by the ancient Romans. It has been suggested, but it is not certain that the word or is a compound of ('pebbles'), and ('worm'), although is only attested as a colloquial term for 'penis'. It is ascribed to Herodotus, and supposedly describes the basking habits of the Egyptian crocodile. The form is attested in Medieval Latin. It is not clear whether this is a medieval corruption or derives from alternative Greco-Latin forms (late Greek and are attested). A (further) corrupted form is found in Old French and was borrowed into Middle English as . The Modern English form ''crocodile'' was adapted directly from the Classical Latin in the 16th century, replacing the earlier form. The use of ''-y-'' in the scientific name ''
Crocodylus ''Crocodylus'' is a genus of true crocodiles in the family Crocodylidae. Taxonomy The generic name, ''Crocodylus'', was proposed by Josephus Nicolaus Laurenti in 1768. ''Crocodylus'' contains 13–14 extant (living) species and 5 extinct species ...
'' (and forms derived from it) is a corruption introduced by
Laurenti Laurenti is a surname. It may refer to: People *Adolfo Laurenti (1856-1944), Italian sculptor *Camillo Laurenti (1861–1938), Italian cardinal *Cesare Laurenti (engineer), Italian designer of submarines influencing HMS ''Swordfish'' (1916) *Cesar ...
(1768).


Species

A total of 18
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...
species have been recognized. Further genetic study is needed for the confirmation of proposed species under the genus ''
Osteolaemus ''Osteolaemus'' is a genus of crocodiles. They are small, secretive crocodiles that occur in wetlands of West and Middle Africa. They are commonly known as the African dwarf crocodiles. Unlike other crocodiles, ''Osteolaemus'' are strictly noctur ...
''.


Characteristics

A crocodile's physical traits allow it to be a successful predator. Its external morphology is a sign of its aquatic and predatory lifestyle. Its streamlined body enables it to swim swiftly; it also tucks its feet to the side while swimming, making it faster by decreasing water resistance. Crocodiles have
webbed feet The webbed foot is a specialized limb with interdigital membranes (webbings) that aids in aquatic locomotion, present in a variety of tetrapod vertebrates. This adaptation is primarily found in semiaquatic species, and has convergently evolved m ...
which, though not used to propel them through the water, allow them to make fast turns and sudden moves in the water or initiate swimming. Webbed feet are an advantage in shallow 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 The glottis is the opening between the vocal folds (the rima glottidis). The glottis is crucial in producing vowels and voiced consonants. Etymology From Ancient Greek ''γλωττίς'' (glōttís), derived from ''γλῶττα'' (glôtta), va ...
that bypasses the mouth. The nostrils are closed during submergence. Like other
archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian d ...
s, crocodilians are diapsid, although their
post-temporal fenestra The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...
e are reduced. The walls of the braincase are bony but lack supratemporal and postfrontal bones.Grigg, Gordon and Gans, Carl (1993
Morphology And Physiology Of The Crocodylia
, in Fauna of Australia Vol 2A Amphibia and Reptilia, chapter 40, pp. 326–336. Australian Government Publishing Service, Canberra.
Their tongues are not free, but held in place by a membrane that limits movement; as a result, crocodiles are unable to stick out their tongues. Crocodiles have smooth skin on their bellies and sides, while their dorsal surfaces are 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 armour, as a network of small capillaries allows blood through the scales to absorb heat. The osteoderms are highly vascularised and aid in calcium balance, both to neutralize acids while the animal cannot breathe underwater and to provide calcium for eggshell formation. Crocodilian tegument have pores believed to be sensory in function, analogous to the
lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...
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 which appears to flush mud off.


Size

Size greatly varies among species, from the
dwarf crocodile The dwarf crocodile (''Osteolaemus tetraspis''), also known as the African dwarf crocodile, broad-snouted crocodile (a name more often used for the Asian mugger crocodile) or bony crocodile, is an African crocodile that is also the smallest extan ...
to the saltwater crocodile. Species of the dwarf crocodile ''Osteolaemus'' grow to an adult size of just , whereas the saltwater crocodile can grow to sizes over and weigh over . Several other large species can reach over long and weigh over . Crocodilians show pronounced sexual dimorphism, with males growing much larger and more rapidly than females. Despite their large adult sizes, crocodiles start their lives at around long. The largest species of crocodile is the saltwater crocodile, found in eastern India, northern Australia, throughout South-east Asia, and in the surrounding waters. The brain volume of two adult crocodiles was 5.6 cm3 for a spectacled caiman and 8.5 cm3 for a larger Nile crocodile. The largest crocodile ever held in captivity is a saltwater–Siamese hybrid named Yai ( th, ใหญ่, meaning big; born 10 June 1972) at the
Samutprakarn Crocodile Farm and Zoo The Samutprakarn Crocodile Farm and Zoo ( th, ฟาร์ม จระเข้ สมุทรปราการ ) is a crocodile zoo in Samut Prakan Province, Thailand. The park claims to hold the world's largest crocodile in captivity, na ...
, Thailand. This animal measures in length and weighs . The longest crocodile captured alive was Lolong, a saltwater crocodile which was measured at and weighed at by a National Geographic team in Agusan del Sur Province, Philippines.


Teeth

Crocodiles are polyphyodonts; they are able to replace each of their 80 teeth up to 50 times in their 35- to 75-year lifespan. Next to each full-grown tooth, there is a small replacement tooth and an odontogenic
stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...
in the dental lamina in standby that can be activated if required.


Biology and behaviour

Crocodilians are more closely related to birds and dinosaurs than to most animals classified as reptiles, the three families being included in the group Archosauria ('ruling reptiles'). Despite their prehistoric look, crocodiles are among the more biologically complex reptiles. Unlike other reptiles, a crocodile has a cerebral cortex and a four-chambered heart. Crocodilians also have the functional equivalent of a diaphragm by incorporating muscles used for aquatic locomotion into respiration. Salt glands are present in the tongues of crocodiles and they have a pore opening on the surface of the tongue, a trait that separates them from alligators. Salt glands are dysfunctional in Alligatoridae. Their function appears to be similar to that of salt glands in marine turtles. Crocodiles do not have sweat glands and release heat through their mouths. They often sleep with their mouths open and may pant like a dog. Four species of freshwater crocodile climb trees to bask in areas lacking a shoreline.


Senses

Crocodiles have acute senses, an evolutionary advantage that makes them successful predators. The eyes, ears and nostrils are located on top of the head, allowing the crocodile to lie low in the water, almost totally submerged and hidden from prey.


Vision

Crocodiles have very good night vision, and are mostly
nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...
hunters. They use the disadvantage of most prey animals' poor nocturnal vision to their advantage. The light receptors in crocodilians' eyes include cones and numerous rods, so it is assumed all crocodilians can see colours. Crocodiles have vertical-slit shaped pupils, similar to those of domestic cats. One explanation for the evolution of slit pupils is that they exclude light more effectively than a circular pupil, helping to protect the eyes during daylight. On the rear wall of the eye is a tapetum lucidum, which reflects incoming light back onto the retina, thus utilizing the small amount of light available at night to best advantage. In addition to the protection of the upper and lower eyelids, crocodiles have a
nictitating membrane The nictitating membrane (from Latin '' nictare'', to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision. All ...
(sometimes called a "third eye-lid") that can be drawn over the eye from the inner corner while the lids are open. The eyeball surface is thus protected under the water while a certain degree of vision is still possible.


Olfaction

Crocodilian sense of smell is also very well developed, aiding them to detect prey or animal carcasses that are either on land or in water, from far away. It is possible that crocodiles use olfaction in the egg prior to hatching. Chemoreception in crocodiles is especially interesting because they hunt in both terrestrial and aquatic surroundings. Crocodiles have only one olfactory chamber and the vomeronasal organ is absent in the adults indicating all olfactory perception is limited to the olfactory system. Behavioural and olfactometer experiments indicate that crocodiles detect both air-borne and water-soluble chemicals and use their olfactory system for hunting. When above water, crocodiles enhance their ability to detect volatile odorants by gular pumping, a rhythmic movement of the floor of the pharynx. Crocodiles close their nostrils when submerged, so olfaction underwater is unlikely. Underwater food detection is presumably gustatory and tactile.


Hearing

Crocodiles can hear well; their tympanic membranes are concealed by flat flaps that may be raised or lowered by muscles.


Touch

The touch sensors, concentrated in crocodile skin, can be thicker than those in human fingerprints. Crocodiles can feel the touch on their skin. Cranial: The upper and lower jaws are covered with sensory pits, visible as small, black speckles on the skin, the crocodilian version of the
lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...
organs seen in fish and many amphibians, though arising from a completely different origin. These pigmented nodules encase bundles of nerve fibers innervated beneath by branches of the trigeminal nerve. They respond to the slightest disturbance in surface water, detecting vibrations and small pressure changes as small as a single drop. This makes it possible for crocodiles to detect prey, danger and intruders, even in total darkness. These sense organs are known as domed pressure receptors (DPRs). Post-Cranial: While alligators and caimans have DPRs only on their jaws, crocodiles have similar organs on almost every scale on their bodies. The function of the DPRs on the jaws is clear; to catch prey, but it is still not clear what the function is of the organs on the rest of the body. The receptors flatten when exposed to increased osmotic pressure, such as that experienced when swimming in sea water hyperosmotic to the body fluids. When contact between the integument and the surrounding sea water solution is blocked, crocodiles are found to lose their ability to discriminate salinities. It has been proposed that the flattening of the sensory organ in hyperosmotic sea water is sensed by the animal as "touch", but interpreted as chemical information about its surroundings. This might be why in alligators they are absent on the rest of the body.


Hunting and diet

Crocodiles are ambush predators, waiting for fish or land animals to come close, then rushing out to attack. Crocodiles mostly eat fish,
amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
s, crustaceans,
mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000  extant species of molluscs are recognized. The number of fossil species is esti ...
s, birds,
reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
s, and
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
s, and they occasionally
cannibalize Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, b ...
smaller crocodiles. What a crocodile eats varies greatly with species, size and age. From the mostly fish-eating species, like the slender-snouted and freshwater crocodiles, to the larger species like the Nile crocodile and the saltwater crocodile that prey on large mammals, such as buffalo, deer and wild boar, diet shows great diversity. Diet is also greatly affected by the size and age of the individual within the same species. All young crocodiles hunt mostly invertebrates and small fish, gradually moving on to larger prey. Being ectothermic (cold-blooded) predators, they have a very slow metabolism, so they can survive long periods without food. Despite their appearance of being slow, crocodiles have a very fast strike and are top predators in their environment, and various species have been observed attacking and killing other predators such as sharks and big cats. Crocodiles are also known to be aggressive
scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...
s who feed upon
carrion Carrion () is the decaying flesh of dead animals, including human flesh. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures, c ...
and steal from other predators. Evidence suggests that crocodiles also feed upon fruits, based on the discovery of seeds in stools and stomachs from many subjects as well as accounts of them feeding. Crocodiles have the most acidic stomach of any vertebrate. They can easily digest bones, hooves and horns. The BBC TV reported that a Nile crocodile that has lurked a long time underwater to catch prey builds up a large
oxygen debt Excess post-exercise oxygen consumption (EPOC, informally called afterburn) is a measurably increased rate of oxygen intake following strenuous activity. In historical contexts the term "oxygen debt" was popularized to explain or perhaps attempt t ...
. When it has caught and eaten that prey, it closes its right aortic arch and uses its left aortic arch to flush blood loaded with carbon dioxide 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. Many large crocodilians swallow stones (called gastroliths or stomach stones), which may act as ballast to balance their bodies or assist in crushing food, similar to grit ingested by birds. Herodotus claimed that Nile crocodiles had a symbiotic relationship with certain birds, such as the
Egyptian plover The Egyptian plover (''Pluvianus aegyptius''), also known as the crocodile bird, 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 ...
, which enter the crocodile's mouth and pick
leech Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodie ...
es feeding on the crocodile's blood; with no evidence of this interaction actually occurring in any crocodile species, it is most likely mythical or allegorical fiction.


Bite

Since they feed by grabbing and holding onto their prey, they have evolved sharp teeth for piercing and holding onto flesh, and powerful muscles to close the jaws and hold them shut. The teeth are not well-suited to tearing flesh off of large prey items as are the dentition and claws of many mammalian carnivores, the hooked bills and talons of raptorial birds, or the serrated teeth of sharks. However, this is an advantage rather than a disadvantage to the crocodile since the properties of the teeth allow it to hold onto prey with the least possibility of the prey animal escaping. Cutting teeth, combined with the exceptionally high bite force, would pass through flesh easily enough to leave an escape opportunity for prey. The jaws can bite down with immense force, by far the strongest bite of any animal. The force of a large crocodile's bite is more than , which was measured in a Nile crocodile, in the field; comparing to for a Rottweiler, for a
hyena Hyenas, or hyaenas (from Ancient Greek , ), are feliform carnivoran mammals of the family Hyaenidae . With only four extant species (each in its own genus), it is the fifth-smallest family in the Carnivora and one of the smallest in the clas ...
, for an American alligator, and for the largest confirmed great white shark. A long saltwater crocodile has been confirmed as having the strongest bite force ever recorded for an animal in a laboratory setting. It was able to apply a bite force value of , and thus surpassed the previous record of made by a long American alligator. Taking the measurements of several crocodiles as reference, the bite forces of 6-m individuals were estimated at . The study, led by Dr.
Gregory M. Erickson Gregory M. Erickson, Ph.D. in paleobiology at Florida State University. Erickson has published many papers on the ontogeny and growth patterns of alligators and dinosaurs, especially on the theropod ''Tyrannosaurus rex''. Erickson has also been ...
, also shed light on the larger,
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
species of
crocodilian Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...
s. Since crocodile anatomy has changed only slightly over the last 80 million years, current data on modern crocodilians can be used to estimate the bite force of extinct species. An Deinosuchus would apply a force of , nearly twice that of the latest, higher bite force estimations of Tyrannosaurus (). The extraordinary bite of crocodilians is a result of their anatomy. The space for the jaw muscle in the skull is very large, which is easily visible from the outside as a bulge at each side. The
muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...
is so stiff, it is almost as hard as bone to touch, as if it were the continuum of the skull. Another trait is that most of the muscle in a crocodile's jaw is arranged for clamping down. Despite the strong muscles to close the jaw, crocodiles have extremely small and weak muscles to open the jaw. Crocodiles can thus be subdued for study or transport by taping their jaws or holding their jaws shut with large rubber bands cut from automobile inner tubes.


Locomotion

Crocodiles can move quickly over short distances, even out of water. The land speed record for a crocodile is measured in a galloping
Australian freshwater crocodile The freshwater crocodile (''Crocodylus johnstoni''), also known as the Australian freshwater crocodile, Johnstone's crocodile or the freshie, is a species of crocodile endemic to the northern regions of Australia. Unlike their much larger Austr ...
. Maximum speed varies between species. Some species can gallop, including Cuban crocodiles, Johnston's crocodiles, New Guinea crocodiles, African dwarf crocodiles, and even small
Nile crocodiles The Nile crocodile (''Crocodylus niloticus'') is a large crocodilian native to freshwater habitats in Africa, where it is present in 26 countries. It is widely distributed throughout sub-Saharan Africa, occurring mostly in the central, easter ...
. The fastest means by which most species can move is a "belly run", in which the body moves in a snake-like (sinusoidal) fashion, limbs splayed out to either side paddling away frantically while the tail whips to and fro. Crocodiles can reach speeds of when they "belly run", and often faster if slipping down muddy riverbanks. When a crocodile walks quickly, it holds its legs in a straighter and more upright position under its body, which is called the "high walk". This walk allows a speed of up to 5 km/h. Crocodiles may possess a
homing instinct Homing is the inherent ability of an animal to navigate towards an original location through unfamiliar areas. This location may be either a home territory, or a breeding spot. Uses Homing abilities can be used to find the way back to home in a ...
. In northern Australia, three rogue saltwater crocodiles were relocated by helicopter, but returned to their original locations within three weeks, based on data obtained from tracking devices attached to them.


Longevity

Measuring crocodile age is unreliable, 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, it can be safely said that all crocodile species have an average lifespan of at least 30–40 years, and in the case of larger species an average of 60–70 years. The oldest crocodiles appear to be the largest species. ''C. porosus'' is estimated to live around 70 years on average, with limited evidence of some individuals exceeding 100 years. In captivity, some individuals are claimed to have lived for over a century. A male crocodile lived to an estimated age of 110–115 years in a Russian zoo in Yekaterinburg. Named Kolya, he joined the zoo around 1913 to 1915, fully grown, after touring in an animal show, and lived until 1995. A male freshwater crocodile lived to an estimated age of 120–140 years at the
Australia Zoo Australia Zoo is a zoo located in the Australian state of Queensland on the Sunshine Coast, Queensland, Sunshine Coast near Beerwah, Queensland, Beerwah/Glass House Mountains National Park, Glass House Mountains. It is a member of the Zoo and A ...
. Known affectionately as "Mr. Freshie", he was rescued around 1970 by
Bob Irwin Robert Eric Irwin (born 8 June 1939) is an Australian naturalist, animal conservationist, former zookeeper, and a herpetologist known for his conservation and husbandry work with apex predators and reptiles. He is the founder of the Queenslan ...
and Steve Irwin, after being shot twice by hunters and losing an eye as a result, and lived until 2010. Crocworld Conservation Centre, in
Scottburgh Scottburgh () is a coastal resort town located on the south coast of KwaZulu-Natal, South Africa. It situated south of the mouth of the Mpambanyoni River ''(confuser of birds).'' History Named after Natal Colony Governor John Scott, in 186 ...
, South Africa, claims to have a male Nile crocodile that was born in 1900. Named Henry, the crocodile is said to have lived in Botswana along the Okavango River, according to centre director Martin Rodrigues.


Social behaviour and vocalization

Crocodiles are the most social of reptiles. Even though they do not form social groups, many species congregate in certain sections of rivers, tolerating each other at times of
feeding Eating (also known as consuming) is the ingestion of food, typically to provide a heterotrophic organism with energy and to allow for growth. Animals and other heterotrophs must eat in order to survive — carnivores eat other animals, herbi ...
and basking. Most species are not highly territorial, with the exception of the saltwater crocodile, which is a highly
territorial A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal. In international politics, a territory is usually either the total area from which a state may extract power resources or a ...
and aggressive species: a mature, male saltwater crocodile will not tolerate any other males at any time of the year, but most other species are more flexible. There is a certain form of
hierarchy A hierarchy (from Greek: , from , 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) that are represented as being "above", "below", or "at the same level as" one another. Hierarchy is an important ...
in crocodiles: the largest and heaviest males are at the top, having access to the best basking site, while females are priority during a group feeding of a big kill or carcass. A good example of the hierarchy in crocodiles would be the case of the Nile crocodile. This species clearly displays all of these behaviours. Studies in this area are not thorough, however, and many species are yet to be studied in greater detail. Mugger crocodiles are also known to show toleration in group feedings and tend to congregate in certain areas. However, males of all species are aggressive towards each other during mating season, to gain access to females. Crocodiles are also the most vocal of all reptiles, producing a wide variety of sounds during various situations and conditions, depending on species, age, size and sex. Depending on the context, some species can communicate over 20 different messages through vocalizations alone. Some of these vocalizations are made during social communication, especially during
territorial A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal. In international politics, a territory is usually either the total area from which a state may extract power resources or a ...
displays towards the same sex and courtship with the opposite sex; the common concern being
reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual or ...
. Therefore most conspecific vocalization is made during the
breeding season Seasonal breeders are animal species that successfully mate only during certain times of the year. These times of year allow for the optimization of survival of young due to factors such as ambient temperature, food and water availability, and cha ...
, with the exception being year-round territorial behaviour in some species and quarrels during feeding. Crocodiles also produce different distress calls and in aggressive displays to their own kind and other animals; notably other predators during interspecific predatory confrontations over carcasses and terrestrial kills. Specific vocalisations include — * Chirp: When about to hatch, the young make a "peeping" noise, which encourages the female to excavate the nest. The female then gathers the hatchlings in her mouth and transports them to the water, where they remain in a group for several months, protected by the female * Distress call: A high-pitched call used mostly by younger animals to alert other crocodiles to imminent danger or an animal being attacked. * Threat call: A hissing sound that has also been described as a coughing noise. * Hatching call: Emitted by a female when breeding to alert other crocodiles that she has laid eggs in her nest. * Bellowing: Male crocodiles are especially vociferous. Bellowing choruses occur most often in the spring when breeding groups congregate, but can occur at any time of year. To bellow, males noticeably inflate as they raise the tail and head out of water, slowly waving the tail back and forth. They then puff out the throat and with a closed mouth, begin to vibrate air. Just before bellowing, males project an infrasonic signal at about 10 Hz through the water, which vibrates the ground and nearby objects. These low-frequency vibrations travel great distances through both air and water to advertise the male's presence and are so powerful they result in the water's appearing to "dance".


Reproduction

Crocodiles lay
egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...
s, which are laid in either holes or mound nests, depending on species. A hole nest is usually excavated in sand and a mound nest is usually constructed out of vegetation. Nesting periods range from a few weeks up to six months. Courtship takes place in a series of behavioural interactions that include a variety of snout rubbing and submissive display that can take a long time. Mating always takes place in water, where the pair can be observed mating several times. Females can build or dig several trial nests which appear incomplete and abandoned later. Egg-laying usually takes place at night and about 30–40 minutes. Females are highly protective of their nests and young. The eggs are hard shelled, but translucent at the time of egg-laying. Depending on the species of crocodile, 7 to 95 eggs are laid. Crocodile
embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
s do not have sex chromosomes, and unlike humans, sex is not determined genetically. Sex is determined by temperature, where at or less most hatchlings are females and at , offspring are of both sexes. A temperature of gives mostly males whereas above in some species continues to give males, but in other species resulting in females, which are sometimes called high-temperature females. Temperature also affects growth and survival rate of the young, which may explain the sexual dimorphism in crocodiles. The average incubation period is around 80 days, and also is dependent on temperature and species that usually ranges from 65 to 95 days. The eggshell structure is very conservative through evolution but there are enough changes to tell different species apart by their eggshell microstructure. Scutes may play a role in calcium storage for eggshell formation. At the time of hatching, the young start calling within the eggs. They have an
egg-tooth An egg tooth is a temporary, sharp projection present on the bill or snout of an oviparous animal at hatching. It allows the hatchling to penetrate the eggshell from inside and break free. Birds, reptiles, and monotremes possess egg teeth as hat ...
at the tip of their snouts, which is developed from the skin, and that helps them pierce out of the shell. Hearing the calls, the female usually excavates the nest and sometimes takes the unhatched eggs in her mouth, slowly rolling the eggs to help the process. The young is usually carried to the water in the mouth. She would then introduce her hatchlings to the water and even feed them. The mother would then take care of her young for over a year before the next mating season. In the absence of the mother crocodile, the father would act in her place to take care of the young. However, even with a sophisticated parental nurturing, young crocodiles have a very high mortality rate due to their vulnerability to predation. A group of hatchlings is called a pod or
crèche Crèche or creche (from Latin ''cripia'' "crib, cradle") may refer to: *Child care center, an organization of adults who take care of children in place of their parents *Nativity scene, a group of figures arranged to represent the birth of Jesus ...
and may be protected for months.


Cognition

Crocodiles possess some advanced cognitive abilities. 6 December 2013 9 December 2013 13 October 2014 They can observe and use patterns of prey behaviour, such as when prey come to the river to drink at the same time each day.
Vladimir Dinets Vladimir Dinets is an American zoologist known for his studies of Crocodilian behavior and of numerous rare animals in remote parts of the world, as well as for popular writings in English and Russian. Education Dinets was interested in zoolo ...
of the University of Tennessee, observed that crocodiles use twigs as bait for birds looking for nesting material. They place sticks on their snouts and partly submerge themselves. When the birds swooped in to get the sticks, the crocodiles then catch the birds. Crocodiles only do this in spring nesting seasons of the birds, when there is high demand for sticks to be used for building nests. Vladimir also discovered other similar observations from various scientists, some dating back to the 19th century. Aside from using sticks, crocodiles are also capable of cooperative hunting. Large numbers of crocodiles swim in circles to trap fish and take turns snatching them. In hunting larger prey, crocodiles swarm in, with one holding the prey down as the others rip it apart. According to a 2015 study, crocodiles engage in all three main types of play behaviour recorded in animals: locomotor play, play with objects and social play. Play with objects is reported most often, but locomotor play such as repeatedly sliding down slopes, and social play such as riding on the backs of other crocodiles is also reported. This behaviour was exhibited with conspecifics and mammals and is apparently not uncommon, though has been difficult to observe and interpret in the past due to obvious dangers of interacting with large carnivores.


Taxonomy and phylogeny

Crocodylidae is cladistically defined as a
crown group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...
composed of the last common ancestor of the Nile crocodile (''Crocodylus niloticus''), the
Dwarf crocodile The dwarf crocodile (''Osteolaemus tetraspis''), also known as the African dwarf crocodile, broad-snouted crocodile (a name more often used for the Asian mugger crocodile) or bony crocodile, is an African crocodile that is also the smallest extan ...
(''Osteolaemus tetraspis''), and all of its descendants. It contains two
subfamilies In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...
:
Crocodylinae Crocodylinae is a subfamily of true crocodiles within the family Crocodylidae, and is the sister taxon to Osteolaeminae ( dwarf crocodiles and slender-snouted crocodiles). Taxonomy Crocodylinae was cladistically defined by Christopher Brochu in ...
and
Osteolaeminae Osteolaeminae is a subfamily of true crocodiles within the family Crocodylidae containing the dwarf crocodiles and slender-snouted crocodiles, and is the sister taxon to Crocodylinae. Taxonomy Osteolaeminae was named by Christopher Brochu in ...
. Crocodylinae contains 13-14 living species, as well as 6
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
species. Osteolaeminae was named by Christopher Brochu in 2003 as a subfamily of Crocodylidae separate from Crocodylinae, and contains the two
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...
genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...
''
Osteolaemus ''Osteolaemus'' is a genus of crocodiles. They are small, secretive crocodiles that occur in wetlands of West and Middle Africa. They are commonly known as the African dwarf crocodiles. Unlike other crocodiles, ''Osteolaemus'' are strictly noctur ...
'' and '' Mecistops'', along with several extinct genera. The number of extant species within Osteolaeminae is currently in question. * Subfamily
Crocodylinae Crocodylinae is a subfamily of true crocodiles within the family Crocodylidae, and is the sister taxon to Osteolaeminae ( dwarf crocodiles and slender-snouted crocodiles). Taxonomy Crocodylinae was cladistically defined by Christopher Brochu in ...
** Genus ''
Crocodylus ''Crocodylus'' is a genus of true crocodiles in the family Crocodylidae. Taxonomy The generic name, ''Crocodylus'', was proposed by Josephus Nicolaus Laurenti in 1768. ''Crocodylus'' contains 13–14 extant (living) species and 5 extinct species ...
'' ***''
Crocodylus acutus ''Crocodylus'' is a genus of true crocodiles in the family Crocodylidae. Taxonomy The generic name, ''Crocodylus'', was proposed by Josephus Nicolaus Laurenti in 1768. ''Crocodylus'' contains 13–14 extant (living) species and 5 extinct spec ...
'', American crocodile ***'' Crocodylus halli'',
Hall's New Guinea crocodile ''Crocodylus halli'', also known as Hall's New Guinea crocodile, is a species of crocodile endemic to the island of New Guinea. It is found on the southern half of the island, south of the New Guinea highlands. It is named after Philip M. Hall, a ...
found South of the New Guinea Highlands ***''
Crocodylus intermedius The Orinoco crocodile (''Crocodylus intermedius'') is a critically endangered crocodile. Its population is very small, and they can only be found in the Orinoco river basin in Colombia and Venezuela. Extensively hunted for their skins in the 19 ...
'', Orinoco crocodile ***''
Crocodylus johnsoni The freshwater crocodile (''Crocodylus johnstoni''), also known as the Australian freshwater crocodile, Johnstone's crocodile or the freshie, is a species of crocodile endemic to the northern regions of Australia. Unlike their much larger Austr ...
'', freshwater crocodile, or Johnstone's crocodile ***'' Crocodylus mindorensis'', Philippine crocodile ***''
Crocodylus moreletii Morelet's crocodile ''(Crocodylus moreletii)'', also known as the Mexican crocodile or Belize crocodile, is a modest-sized crocodilian found only in fresh waters of the Atlantic regions of Mexico, Belize and Guatemala. It usually grows to abou ...
'', Morelet's crocodile or Mexican crocodile ***'' Crocodylus niloticus'', Nile crocodile or African crocodile (the subspecies found in Madagascar is sometimes called the black crocodile) ***''
Crocodylus novaeguineae The New Guinea crocodile (''Crocodylus novaeguineae'') is a small species of crocodile found on the island of New Guinea north of the New Guinea Highlands, mountain ridge that runs along the centre of the island. The population found south of the ...
'', New Guinea crocodile found North of the New Guinea Highlands ***''
Crocodylus palustris The mugger crocodile (''Crocodylus palustris'') is a medium-sized broad- snouted crocodile, also known as mugger and marsh crocodile. It is native to freshwater habitats from southern Iran to the Indian subcontinent, where it inhabits marshes ...
'', mugger, marsh or Indian crocodile ***'' Crocodylus porosus'', saltwater crocodile or estuarine crocodile ****''
Crocodylus raninus ''Crocodylus raninus'', the Borneo crocodile, is an enigmatic species of freshwater crocodile endemic to the Southeast Asian island of Borneo.Anon. From crocs to croaks: Borneo's reptiles and amphibians''. Accessed on: 03:41, 4 August 2011 (UT ...
'', the Borneo crocodile, is currently considered to be a synonym of ''Crocodylus porosus''; whether or not it is a distinct species remains unclear. ***'' Crocodylus rhombifer'', Cuban crocodile ***''
Crocodylus siamensis The Siamese crocodile (''Crocodylus siamensis'') is a medium-sized freshwater crocodile native to Indonesia (Borneo and possibly Java), Brunei, East Malaysia, Laos, Cambodia, Myanmar, Thailand and Vietnam. The species is critically endangered ...
'', Siamese crocodile (may be extinct in the wild) ***''
Crocodylus suchus The West African crocodile, desert crocodile, or sacred crocodile (''Crocodylus suchus'') is a species of crocodile related to – and often confused with – the larger and more aggressive Nile crocodile (''C. niloticus''). Taxonomy Compared ...
'', West African crocodile, desert or sacred crocodile ***''
Crocodylus anthropophagus ''Crocodylus anthropophagus'' is an extinct species of crocodile from the Pleistocene of Tanzania. It lived 1.84 million years ago. It was a large-sized predator reaching a length of . Etymology ''Crocodylus anthropophagus'' was first named by ...
'' ***''
Crocodylus checchiai ''Crocodylus checchiai'' is an extinct species of crocodile from the Miocene to Pliocene of Libya and Kenya. ''C. checchiai'' was named in 1947 based on a skull from the Sahabi Formation. Remains from the lower Nawata Formation in the Turkana Bas ...
'' ***''
Crocodylus falconensis ''Crocodylus falconensis'' is an extinct species of crocodile known from the early Pliocene of the lower part of the Vergel Member of the San Gregorio Formation of Venezuela. ''C. falconensis'' was named in 2013 after Falcón State and is though ...
'' ***''
Crocodylus palaeindicus ''Crocodylus palaeindicus'' is an extinct species of crocodile from southern Asia. ''C. palaeindicus'' lived from the Miocene to the Pliocene. It may be an ancestor of the living Mugger crocodile. History ''C. palaeindicus'' was first named by ...
'' ***'' Crocodylus thorbjarnarsoni'' ** Genus '' Voay'' ***''
Voay robustus ''Voay'' is an extinct genus of crocodile from Madagascar that lived during the Late Pleistocene to Holocene, containing only one species, ''V. robustus''. Numerous subfossils have been found, including complete skulls, noted for their distin ...
'' (formerly ''Crocodylus robustus'') * Subfamily
Osteolaeminae Osteolaeminae is a subfamily of true crocodiles within the family Crocodylidae containing the dwarf crocodiles and slender-snouted crocodiles, and is the sister taxon to Crocodylinae. Taxonomy Osteolaeminae was named by Christopher Brochu in ...
** Genus ''
Osteolaemus ''Osteolaemus'' is a genus of crocodiles. They are small, secretive crocodiles that occur in wetlands of West and Middle Africa. They are commonly known as the African dwarf crocodiles. Unlike other crocodiles, ''Osteolaemus'' are strictly noctur ...
'' *** ''
Osteolaemus tetraspis The dwarf crocodile (''Osteolaemus tetraspis''), also known as the African dwarf crocodile, broad-snouted crocodile (a name more often used for the Asian mugger crocodile) or bony crocodile, is an African crocodile that is also the smallest exta ...
'',
dwarf crocodile The dwarf crocodile (''Osteolaemus tetraspis''), also known as the African dwarf crocodile, broad-snouted crocodile (a name more often used for the Asian mugger crocodile) or bony crocodile, is an African crocodile that is also the smallest extan ...
(There has been controversy as to whether or not this is actually two species; recent (2010) DNA analysis indicate three distinct species: ''O. tetraspis'', ''O. osborni'' and a third, currently unnamed.) ** Genus '' Mecistops'' ***'' Mecistops cataphractus'' West African slender-snouted crocodile *** '' Mecistops leptorhynchus'' Central African slender-snouted crocodile ** Genus ''
Brochuchus ''Brochuchus'' is an extinct genus of crocodile known from the Early Miocene Hiwegi Formation of Rusinga Island in Lake Victoria, Kenya; it was originally named as a species of ''Crocodylus''. It contains two species, ''B. parvidens'' and ''B. pi ...
'' *** ''
Brochuchus pigotti ''Brochuchus'' is an extinct genus of crocodile known from the Early Miocene Hiwegi Formation of Rusinga Island in Lake Victoria, Kenya; it was originally named as a species of '' Crocodylus''. It contains two species, ''B. parvidens'' and ''B ...
'' (formerly ''Crocodylus pigotti'') *** ''
Brochuchus parvidens ''Brochuchus'' is an extinct genus of crocodile known from the Early Miocene Hiwegi Formation of Rusinga Island in Lake Victoria, Kenya; it was originally named as a species of ''Crocodylus''. It contains two species, ''B. parvidens'' and ''B. pi ...
'' ** Genus ''
Euthecodon ''Euthecodon'' is an extinct genus of long-snouted crocodile. It was common throughout much of Africa during the Neogene, with fossils being especially common in Kenya, Ethiopia, and Libya. Although superficially resembling that of gharials, the ...
'' *** ''
Euthecodon nitriae ''Euthecodon'' is an extinct genus of long-snouted crocodile. It was common throughout much of Africa during the Neogene, with fossils being especially common in Kenya, Ethiopia, and Libya. Although superficially resembling that of gharials, the ...
'' *** ''
Euthecodon brumpti ''Euthecodon'' is an extinct genus of long-snouted crocodile. It was common throughout much of Africa during the Neogene, with fossils being especially common in Kenya, Ethiopia, and Libya. Although superficially resembling that of gharials, the ...
'' *** ''
Euthecodon arambourgi ''Euthecodon'' is an extinct genus of long-snouted crocodile. It was common throughout much of Africa during the Neogene, with fossils being especially common in Kenya, Ethiopia, and Libya. Although superficially resembling that of gharials, the ...
'' ** Genus ''
Rimasuchus ''Rimasuchus'' is an extinct genus of crocodile from the Miocene of Egypt and possibly Libya. Only one species - ''Rimasuchus lloydi'' - is currently known. It was previously thought to be a species of ''Crocodylus'', but is now thought to be mo ...
'' *** ''
Rimasuchus lloydi ''Rimasuchus'' is an extinct genus of crocodile from the Miocene of Egypt and possibly Libya. Only one species - ''Rimasuchus lloydi'' - is currently known. It was previously thought to be a species of '' Crocodylus'', but is now thought to be ...
'' (formerly ''Crocodylus lloydi'')


Phylogeny

Recent molecular studies using
DNA sequencing DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. Th ...
have shown crocodiles to be more closely related to the gavialids rather than to alligators, contrary to prior theories based on morphological studies alone. Below is a cladogram showing the relationships of the major
extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...
crocodile groups based on molecular studies, excluding separate extinct taxa: Below is a more detailed cladogram of Crocodylidae, based on a 2021 study using paleogenomics that extracted DNA from the extinct '' Voay''. Alternatively, some morphological studies have recovered '' Mecistops'' as a
basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...
member of
Crocodylinae Crocodylinae is a subfamily of true crocodiles within the family Crocodylidae, and is the sister taxon to Osteolaeminae ( dwarf crocodiles and slender-snouted crocodiles). Taxonomy Crocodylinae was cladistically defined by Christopher Brochu in ...
, more closely related to ''
Crocodylus ''Crocodylus'' is a genus of true crocodiles in the family Crocodylidae. Taxonomy The generic name, ''Crocodylus'', was proposed by Josephus Nicolaus Laurenti in 1768. ''Crocodylus'' contains 13–14 extant (living) species and 5 extinct species ...
'' than to ''
Osteolaemus ''Osteolaemus'' is a genus of crocodiles. They are small, secretive crocodiles that occur in wetlands of West and Middle Africa. They are commonly known as the African dwarf crocodiles. Unlike other crocodiles, ''Osteolaemus'' are strictly noctur ...
'' and the other members of
Osteolaeminae Osteolaeminae is a subfamily of true crocodiles within the family Crocodylidae containing the dwarf crocodiles and slender-snouted crocodiles, and is the sister taxon to Crocodylinae. Taxonomy Osteolaeminae was named by Christopher Brochu in ...
, as shown in the cladogram below.


Relationship with humans


Danger to humans

The larger species of crocodiles are very dangerous to humans, mainly because of their ability to strike before the person can react. The saltwater crocodile and Nile crocodile are the most dangerous, killing hundreds of people each year in parts of Southeast Asia and Africa. The mugger crocodile and American crocodile are also dangerous to humans.


Crocodile products

Crocodiles are protected in many parts of the world, but are also farmed commercially. Their hides are tanned and used to make leather goods such as shoes and handbags; 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 is also bred in Asian farms. Farming has resulted in an increase in the saltwater crocodile population in
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, as eggs are usually harvested from the wild, so landowners have an incentive to conserve their habitat. Crocodile leather can be made into goods such as wallets, briefcases, purses, handbags, belts, hats, and shoes.
Crocodile oil Crocodile oil is extracted from the fatty tissues of crocodiles. Crocodile fat is a product of commercial farming, evident in Thailand. Historically, for centuries crocodile oil has been used by traditional practitioners across the globe, includi ...
has been used for various purposes. Crocodiles were eaten by Vietnamese while they were taboo and off limits for Chinese. Vietnamese women who married Chinese men adopted the Chinese taboo. Crocodile meat is consumed in some countries, such as Australia, Ethiopia, Thailand, South Africa,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
and also Cuba (in pickled form). It is also occasionally eaten as an "exotic" delicacy in the western world. Cuts of meat include backstrap and tail fillet. Due to high demand for crocodile products, TRAFFIC states that 1,418,487 Nile Crocodile skins were exported from Africa between 2006 and 2015.


In religion

Crocodiles have appeared in various forms in religions across the world. Ancient Egypt had Sobek, the crocodile-headed god, with his cult-city
Crocodilopolis Faiyum ( ar, الفيوم ' , borrowed from cop,  ̀Ⲫⲓⲟⲙ or Ⲫⲓⲱⲙ ' from egy, pꜣ ym "the Sea, Lake") is a city in Middle Egypt. Located southwest of Cairo, in the Faiyum Oasis, it is the capital of the modern Faiyum ...
, as well as Taweret, the goddess of childbirth and fertility, with the back and tail of a crocodile. The Jukun shrine in the Wukari Federation, Nigeria is dedicated to crocodiles in thanks for their aid during migration. In Madagascar various peoples such as the Sakalava and
Antandroy The Tandroy are a traditionally nomadic ethnic group of Madagascar inhabiting the arid southern part of the island called Androy, tracing their origins back to the East Africa mainland. In the 17th century however, the Tandroy emerged as a confe ...
see crocodiles as ancestor spirits and under local '' fady'' often offer them food;Campbell, Gwyn (2012). David Griffiths and the Missionary "History of Madagascar". Leiden, The Netherlands: Brill. . in the case of the latter at least a crocodile features prominently as an ancestor deity. Crocodiles appear in different forms in Hinduism. Varuna, a Vedic and Hindu god, rides a part-crocodile makara; his consort
Varuni Varuni () is the name of multiple goddesses associated with the Hindu god Varuna — his wife (also known as Varunani), his daughter (the goddess of wine), and the personification of his shakti (A matrika or mother goddess). Sometimes, these god ...
rides a crocodile. Similarly the goddess personifications of the
Ganga The Ganges ( ) (in India: Ganga ( ); in Bangladesh: Padma ( )). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international river to which India, Bangladesh, Nepal and China are the riparian states." is ...
and Yamuna rivers are often depicted as riding crocodiles. Also in India, in Goa, crocodile worship is practised, including the annual ''Mannge Thapnee'' ceremony.
Akali Nihang The Nihang or Akali (lit. "the immortals") is an armed Sikh warrior order originating in the Indian subcontinent. Nihang are believed to have originated either from Fateh Singh and the attire he wore or from the "Akali" (lit. Army of the Immor ...
Sikh Sikhs ( or ; pa, ਸਿੱਖ, ' ) are people who adhere to Sikhism, Sikhism (Sikhi), a Monotheism, monotheistic religion that originated in the late 15th century in the Punjab region of the Indian subcontinent, based on the revelation of Gu ...
warriors also have connections with crocodiles. ''Nihang'' may come from the Persian word for a mythical sea creature ( fa, نهنگ). The term owes its origin to
Mughal Mughal or Moghul may refer to: Related to the Mughal Empire * Mughal Empire of South Asia between the 16th and 19th centuries * Mughal dynasty * Mughal emperors * Mughal people, a social group of Central and South Asia * Mughal architecture * Mug ...
historians, who compared the ferocity of the Akali with that of crocodiles. The meaning of Akali in Sikhism however, is the immortal army of Akal (god). In Latin America,
Cipactli Cipactli ( nci, Cipactli "crocodile" or "caiman") was the first day of the Aztec divinatory count of 13 X 20 days (the '' tonalpohualli'') and ''Cipactonal'' "Sign of Cipactli" was considered to have been the first diviner. In Aztec cosmology, the ...
was the giant earth crocodile of the Aztec and other Nahua peoples.


Crocodile tears

The term " crocodile tears" (and equivalents in other languages) refers to a false, insincere display of emotion, such as a hypocrite crying fake tears of
grief Grief is the response to loss, particularly to the loss of someone or some living thing that has died, to which a bond or affection was formed. Although conventionally focused on the emotional response to loss, grief also has physical, cogni ...
. It is derived from an ancient anecdote that crocodiles weep in order to lure their prey, or that they
cry Crying is the dropping of tears (or welling of tears in the eyes) in response to an emotional state, or pain. Emotions that can lead to crying include sadness, anger, and even happiness. The act of crying has been defined as "a complex secreto ...
for the victims they are eating, first told in the '' Bibliotheca'' by
Photios I of Constantinople Photios I ( el, Φώτιος, ''Phōtios''; c. 810/820 – 6 February 893), also spelled PhotiusFr. Justin Taylor, essay "Canon Law in the Age of the Fathers" (published in Jordan Hite, T.O.R., & Daniel J. Ward, O.S.B., "Readings, Cases, Materia ...
. The story is repeated in bestiaries such as ''De bestiis et aliis rebus''. This tale was first spread widely in English in the stories of the ''Travels of
Sir John Mandeville Sir John Mandeville is the supposed author of ''The Travels of Sir John Mandeville'', a travel memoir which first circulated between 1357 and 1371. The earliest-surviving text is in French. By aid of translations into many other languages, the ...
'' in the 14th century, and appears in several of Shakespeare's plays. In fact, crocodiles can and do generate tears, but they do not actually cry.


The Surabaya Shark and Crocodile

The name of
Surabaya Surabaya ( jv, ꦱꦸꦫꦧꦪ or jv, ꦯꦹꦫꦨꦪ; ; ) is the capital city of the Provinces of Indonesia, Indonesian province of East Java and the List of Indonesian cities by population, second-largest city in Indonesia, after Jakarta. L ...
, Indonesia, is locally believed to be derived from the words "''suro"'' ( shark) and "''boyo"'' (crocodile), two creatures which, in a local
myth Myth is a folklore genre consisting of Narrative, narratives that play a fundamental role in a society, such as foundational tales or Origin myth, origin myths. Since "myth" is widely used to imply that a story is not Objectivity (philosophy), ...
, fought each other in order to gain the title of "the strongest and most powerful animal" in the area. It was said that the two powerful animals agreed for a truce and set boundaries; that the shark's domain would be in the sea while the crocodile's domain would be on the land. However one day the shark swam into the river estuary to hunt, this angered the crocodile, who declared it his territory. The Shark argued that the river was a water-realm which meant that it was shark territory, while the crocodile argued that the river flowed deep inland, so it was therefore crocodile territory. A ferocious fight resumed as the two animals bit each other. Finally the shark was badly bitten and fled to the open sea, and the crocodile finally ruled the estuarine area that today is the city. Another source alludes to a
Jayabaya Jayabhaya or Jayabaya ( Javanese spelled: Ratu Jayabaya) was the Javanese King of the Kediri Kingdom in East Java, Indonesia which ruled around 1135-1159 CE. With the title of ''abhiseka'' used is Sri Maharaja Sang Mapanji Jayabhaya Sri Warmesw ...
prophecy—a 12th-century psychic king of Kediri Kingdom—as he foresaw a fight between a giant
white shark The great white shark (''Carcharodon carcharias''), also known as the white shark, white pointer, or simply great white, is a species of large mackerel shark which can be found in the coastal surface waters of all the major oceans. It is nota ...
and a giant white crocodile taking place in the area, which is sometimes interpreted as a foretelling of the Mongol invasion of Java, a major conflict between the forces of the
Kublai Khan Kublai ; Mongolian script: ; (23 September 1215 – 18 February 1294), also known by his temple name as the Emperor Shizu of Yuan and his regnal name Setsen Khan, was the founder of the Yuan dynasty of China and the fifth khagan-emperor of th ...
, Mongol ruler of
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
, and those of
Raden Wijaya Raden Wijaya or Raden Vijaya (also known as Nararya Sangramawijaya, regnal name Kertarajasa Jayawardhana) (reigned 1293–1309) was a Javanese emperor, and the founder and first monarch of the Majapahit Empire.Slamet Muljana, 2005, ''Runtuhny ...
's
Majapahit Majapahit ( jv, ꦩꦗꦥꦲꦶꦠ꧀; ), also known as Wilwatikta ( jv, ꦮꦶꦭ꧀ꦮꦠꦶꦏ꧀ꦠ; ), was a Javanese people, Javanese Hinduism, Hindu-Buddhism, Buddhist thalassocracy, thalassocratic empire in Southeast Asia that was ba ...
in 1293. The two animals are now used as the city's symbol, with the two facing and circling each other, as depicted in a statue appropriately located near the entrance to the
city zoo ''City Zoo'' ( zh, t=摩天動物園) is the seventh studio album by Hong Kong singer-songwriter G.E.M., it was released on December 27, 2019, by Sony Music. As the executive producer, G.E.M. worked with producer Terrence Ma. The self-written al ...
(see photo on the
Surabaya Surabaya ( jv, ꦱꦸꦫꦧꦪ or jv, ꦯꦹꦫꦨꦪ; ; ) is the capital city of the Provinces of Indonesia, Indonesian province of East Java and the List of Indonesian cities by population, second-largest city in Indonesia, after Jakarta. L ...
page).


Crocodile (walking)

In the UK, a row of
schoolchildren A student is a person enrolled in a school or other educational institution. In the United Kingdom and most commonwealth countries, a "student" attends a secondary school or higher (e.g., college or university); those in primary or elementar ...
walking in pairs, or two by two is known as 'crocodile'.Angela Brazil


Fashion

The French clothing company Lacoste features its iconic crocodile in its logo. The American shoe company Crocs also uses this imagery in its logo.


See also

* Alligator meat *'' The Crocodile Hunter'' *
Crocodilian armor Crocodile armor consists of the protective dermal and epidermal components of the integumentary system in animals of the order Crocodilia. Structure and anatomy The epidermal exoskeleton of the alligator consists of oblong horny scales, arranged ...
*
Game (hunting) Game or quarry is any wild animal hunted for animal products (primarily meat), for recreation (" sporting"), or for trophies. The species of animals hunted as game varies in different parts of the world and by different local jurisdictions, thou ...
* Sewer alligator * Sobek – an ancient Egyptian deity associated with the Nile crocodile


References


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

"How fast can a crocodile run?" Adam Britton.


External links

*
Crocodilian Online



Crocodile Attacks in Australia

BBC news finds powerful agent in crocodile blood

World's most expensive handbag sells in Hong Kong for over US$377,000 – a Hermès white crocodile
(31 May 2017), ''
South China Morning Post The ''South China Morning Post'' (''SCMP''), with its Sunday edition, the ''Sunday Morning Post'', is a Hong Kong-based English-language newspaper owned by Alibaba Group. Founded in 1903 by Tse Tsan-tai and Alfred Cunningham, it has remained ...
''
292 New Guinea crocodiles massacred
in West Papua, Indonesia {{DEFAULTSORT:Crocodile Crocodylidae Reptiles of Asia Reptiles of Africa Crocodiles of Australia Reptiles of North America Reptiles of South America Extant Ypresian first appearances Taxa named by Georges Cuvier