143-546: 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 in sub-Saharan Africa , occurring mostly in the eastern, southern, and central regions of the continent, and lives in different types of aquatic environments such as lakes, rivers, swamps and marshlands . It occasionally inhabits deltas , brackish lakes and rarely also saltwater. Its range once stretched from
286-484: A crown group (as opposed to a stem-based group ), Crocodylia is now restricted to only the last common ancestor of today's crocodilians and all of its descendants (living or extinct ). Crocodilia appears to be a Latinizing of the Greek κροκόδειλος ( crocodeilos ), which means both lizard and Nile crocodile . Crocodylia, as coined by Wermuth, in regards to the genus Crocodylus appears to be derived from
429-413: A "high walk" position, traveling with their legs erect rather than sprawling. Crocodilians have thick skin covered in non-overlapping scales. They have conical, peg-like teeth and a powerful bite. Like birds, crocodilians possess a four-chambered heart and lungs with unidirectional airflow. Like most other reptiles, they are ectotherms . Crocodilians are found mainly in the warmer and tropical areas of
572-508: A crocodile would kill most vertebrates. However, exertion by crocodilians can lead to death due to increasing lactic acid to lethal levels, which in turn leads to failure of the animal's internal organs. This is rarely recorded in wild crocodiles, normally having been observed in cases where humans have mishandled crocodiles and put them through overly extended periods of physical struggling and stress. The mouths of Nile crocodiles are filled with 64 to 68 sharply pointed, cone-shaped teeth (about
715-445: A crocodilian shut tight. All species have a palatal valve, a membranous flap of skin at the back of the oral cavity that protects the oesophagus and trachea when the animal is underwater. This enables them to open their mouths underwater without drowning. Crocodilians typically remain underwater for fifteen minutes or less at a time, but some can hold their breath for up to two hours under ideal conditions. The maximum diving depth
858-726: A dark bronze colouration above, with faded blackish spots and stripes variably appearing across the back and a dingy off-yellow on the belly, although mud can often obscure the crocodile's actual colour. The flanks, which are yellowish-green in colour, have dark patches arranged in oblique stripes in highly variable patterns. Some variation occurs relative to environment; specimens from swift-flowing waters tend to be lighter in colour than those dwelling in murkier lakes or swamps, which provides camouflage that suits their environment, an example of clinal variation. Nile crocodiles have green eyes. The colouration also helps to camouflage them; juveniles are grey, multicoloured, or brown, with dark cross-bands on
1001-399: A different way from those of other reptiles, a feature they share with some early archosaurs. One of the upper row of ankle bones, the ankle bone , moves with the tibia and fibula , while the heel bone moves with the foot and is where the ankle joint is located. The result is that the legs can be held almost vertically beneath the body when on land, and the foot swings during locomotion as
1144-567: A distinct species, the West African (or desert) crocodile. The distributional boundaries between these species were poorly understood, but following several studies, they are now better known. West African crocodiles are found throughout much of West and Central Africa, ranging east to South Sudan and Uganda where the species may come into contact with the Nile crocodile. Nile crocodiles are absent from most of West and Central Africa, but range into
1287-416: A dozen less than alligators have). For most of a crocodile's life, broken teeth can be replaced. On each side of the mouth, five teeth are in the front of the upper jaw ( premaxilla ), 13 or 14 are in the rest of the upper jaw ( maxilla ), and 14 or 15 are on either side of the lower jaw ( mandible ). The enlarged fourth lower tooth fits into the notch on the upper jaw and is visible when the jaws are closed, as
1430-629: A few became herbivores . The earliest stage of crocodilian evolution was the protosuchians in the late Triassic and early Jurassic. They were followed by the mesosuchians , which diversified widely during the Jurassic and the Tertiary. The eusuchians first appeared during the Early Cretaceous , and includes modern crocodilians. Protosuchians were small, mostly terrestrial animals with short snouts and long limbs. They had bony armor in
1573-464: A few reports of sandpipers removing leeches from the mouth and gular scutes and snapping at insects along the reptile's body." Crocodilia Crocodylia ( / k r ɒ k ə ˈ d ɪ l i ə / ) is an order of semiaquatic , predatory reptiles known as crocodilians . They first appeared during the Late Cretaceous and are the closest living relatives of birds . Crocodilians are
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#17327909013751716-454: A flashlight. It is found to be active day and night. It can stay submerged underwater for more than 30 minutes, and can reach speeds of up to 30 km/h (19 mph) in short bursts. On land, it is often observed basking motionless in the sun , often with its mouth agape. Compared to the Nile crocodile , which can grow over 5 m (16 ft 5 in) in length, the West African crocodile
1859-401: A higher surface-area-to-volume ratio . The kidneys and excretory system are much the same as in other reptiles, but crocodilians do not have a bladder . In fresh water, the osmolality (the concentration of solutes that contribute to a solution's osmotic pressure ) in the plasma is much higher than it is in the surrounding water. The animals are well-hydrated, and the urine in the cloaca
2002-790: A large number of gastroliths. One crocodile measuring 3.84 m (12 ft 7 in) and weighing 239 kg (527 lb) had 5.1 kg (11 lb) of stones in its stomach, perhaps a record gastrolith weight for a crocodile. Specimens shot near Mpondwe on the Semliki River had gastroliths in their stomach despite being shot miles away from any sources for the stones; the same holds true for specimens from Kafue Flats , Upper Zambezi and Bangweulu Swamp , all of which often had stones inside them despite being nowhere near stony regions. Cott (1961) felt that gastroliths were most likely serving as ballast to provide stability and additional weight to sink in water, this bearing great probability over
2145-454: A left and right aorta which are connected by a hole called the Foramen of Panizza . Like birds and mammals, crocodilians have separate vessels that direct blood flow to the lungs and the rest of the body respectively. They also have unique cog-teeth-like valves that, when interlocked, direct blood to the left aorta and away from the lungs, and then back around the body. This system may allow
2288-616: A member of the 'thoracosaurs', recovered as a sister taxon of Thoracosaurus within Gavialoidea, though it is uncertain whether 'thoracosaurs' were true gavialoids. Definitive alligatoroids first appeared during the Santonian - Campanian stages, while definitive longirostres first appeared during the Maastrichtian stage. The earliest known alligatoroids and gavialoids include highly derived forms, which indicates that
2431-545: A period of time, but hunt by themselves and are not fed by the parents. The Nile crocodile is one of the most dangerous species of crocodile and is responsible for hundreds of human deaths every year. It is common and is not endangered, despite some regional declines or extirpations in the Maghreb . The binomial name Crocodylus niloticus is derived from the Greek κρόκη, kroke ("pebble"), δρῖλος, drilos ("worm"), referring to its rough skin; and niloticus , meaning "from
2574-439: A powerful bite that is unique among all animals, and sharp, conical teeth that sink into flesh, allowing a grip that is almost impossible to loosen. They can apply high force for extended periods of time, a great advantage for holding down large prey underwater to drown. Nile crocodiles are relatively social. They share basking spots and large food sources, such as schools of fish and big carcasses . Their strict hierarchy
2717-414: A protector and source of pharaonic power. C. suchus was known to be more docile than the Nile crocodile and was chosen by the ancient Egyptians for spiritual rites , including mummification. DNA testing found that all sampled mummified crocodiles from the grotto of Thebes , grotto of Samoun, and Upper Egypt belonged to this species whereas the ones from a burial pit at Qubbet el-Hawa are believed on
2860-471: A revision of many reptilian and amphibian names—argued strongly for "Crocodylia". However, it was not until the advent of cladistics and phylogenetic nomenclature that a more solid justification for one spelling over the other was proposed. Prior to 1988, Crocodilia was a group that encompassed the modern-day animals, as well as their more distant relatives now in the larger groups called Crocodylomorpha and Pseudosuchia . Under its current definition as
3003-699: A role in the crushing of food. Digestion takes place more quickly at higher temperatures. When digesting a meal, CO2-rich blood towards the lungs is redirected to the stomach, supplying more acid for the oxyntic glands . Compared to crocodiles, alligators digest more carbohydrates relative to protein. Crocodilians have a very low metabolic rate and consequently, low energy requirements. They can withstand extended fasting, living on stored fat . Even recently hatched crocodiles are able to survive 58 days without food, losing 23% of their bodyweight during this time. Crocodilians are ectotherms , relying mostly on their environment to control their body temperature. The sun's heat
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#17327909013753146-499: A separate species). In a study of the morphology of the various populations, including C. (n.) suchus , the appearance of the Nile crocodile sensu lato was found to be more variable than that of any other currently recognized crocodile species, and at least some of these variations were related to locality. For example, a study on Lake Turkana in Kenya (informally this population would be placed in C. n. pauciscutatus ) found that
3289-534: A similar length. As an example of the body mass increase undergone by mature crocodiles, one of the larger crocodiles handled firsthand by Cott (1961) was 4.4 m (14 ft 5 in) and weighed 414.5 kg (914 lb), while the largest specimen measured by Graham and Beard (1973) was 4.8 m (15 ft 9 in) and weighed more than 680 kg (1,500 lb). One of the largest known specimens from South Africa , caught by J. G. Kuhlmann in Venda , which
3432-525: A single olfactory chamber and the vomeronasal organ disappears when they reach adulthood. 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 . They appear to have lost their pineal organ , but still show signs of melatonin rhythms. The skin of crocodilians
3575-668: A single source of the introduction. This source remains unclear, as their genetics do not match samples collected from captives at various zoos and theme parks in Florida. When compared to Nile crocodiles from their native Africa, the Florida wild specimens are most closely related to South African Nile crocodiles. It is unknown how many Nile crocodiles are currently at large in Florida. The animals likely were either brought there to be released or are escapees. Generally, Nile crocodiles are relatively inert creatures, as are most crocodilians and other large, cold-blooded creatures. More than half of
3718-743: A sinuous fashion, and they can sustain this form of movement much longer than on land, with a maximum known swimming speed of 30 to 35 km/h (19 to 22 mph). Nile crocodiles have been widely known to have gastroliths in their stomachs, which are stones swallowed by animals for various purposes. Although this is clearly a deliberate behaviour for the species, the purpose is not definitively known. Gastroliths are not present in hatchlings, but increase quickly in presence within most crocodiles examined at 2–3.1 m (6 ft 7 in – 10 ft 2 in) and yet normally become extremely rare again in very large specimens, meaning that some animals may eventually expel them. However, large specimens can have
3861-458: A specialization at hunting sizeable prey, such as large mammals and freshwater turtles, the latter much larger than any in present-day Africa. Studies have since shown these other African crocodiles to be only more distantly related to the Nile crocodile. Below is a cladogram based on a 2018 tip dating study by Lee & Yates simultaneously using morphological , molecular ( DNA sequencing ), and stratigraphic ( fossil age) data, as revised by
4004-461: A specimen measuring 5.36 m (17 ft 7 in) in total length (with a considerable portion of its tail tip missing). The weight of this specimen was estimated to be 838 kg (1,847 lb), making it one of the largest crocodiles ever to be captured and released alive. The bulk and mass of individual crocodiles can be fairly variable, some animals being relatively slender, while others being very robust; females are often bulkier than males of
4147-618: A study of habitat use by the three crocodile species in Liberia (West African, slender-snouted and dwarf ), it was found that the West African crocodile typically occupied larger, more open waterways consisting of river basins and mangrove swamps, and was the species most tolerant of brackish waters. In comparison, the slender-snouted crocodile typically occupies rivers within forest interiors, while dwarf crocodiles are distributed in smaller rivers (mainly tributaries), streams and brooks also within forested areas. The West African crocodile
4290-541: A study resurrected C. suchus as a valid species, and this was confirmed by several other studies in 2011–2015. Despite the long history of confusion, genetic testing has revealed that the two are not particularly close. The closest relatives of the Nile crocodile are the Crocodylus species from the Americas, while the West African crocodile is basal to the clade of Nile and American crocodiles. Below
4433-434: A suitable concentration of salt in body fluids. Osmoregulation is related to the quantity of salts and water exchanged with the environment. Intake of water and salts takes place across the lining of the mouth, when water is drunk, incidentally while feeding, and when present in foods. Water is lost during breathing, and both salts and water are lost in the urine and faeces, through the skin, and via salt-excreting glands on
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4576-629: A time, but can swim under water up to 30 minutes if threatened. If they remain fully inactive, they can hold their breath for up to 2 hours (which, as aforementioned, is due to the high levels of lactic acid in their blood). They have a rich vocal range and good hearing . Nile crocodiles normally crawl along on their bellies, but they can also "high walk" with their trunks raised above the ground. Smaller specimens can gallop , and even larger individuals are capable of occasional, surprising bursts of speed, briefly reaching up to 14 km/h (8.7 mph). They can swim much faster, moving their bodies and tails in
4719-502: A type of crocodylomorph pseudosuchian , a subset of archosaurs that appeared about 235 million years ago and were the only survivors of the Triassic–Jurassic extinction event . The order includes the true crocodiles (family Crocodylidae), the alligators and caimans (family Alligatoridae ), and the gharial and false gharial (family Gavialidae ). Although the term "crocodiles" is sometimes used to refer to all of these, it
4862-526: A valid species in 2011. Consequently, captives have typically been confused with other species, especially the Nile crocodile. In Europe, breeding pairs of West African crocodiles live in Copenhagen Zoo , Lyon Zoo and Vivarium de Lausanne , and offspring of the first pair are in Dublin Zoo and Kristiansand Zoo . A study in 2015 that included 16 captive "Nile crocodiles" in 6 US zoos (almost
5005-406: A variety of prey, with a diet consisting mostly of different species of fish, reptiles, birds, and mammals . As ambush predators , they can wait for hours, days, and even weeks for the suitable moment to attack. They are agile predators and wait for the opportunity for a prey item to come well within attack range. Even swift prey are not immune to attack. Like other crocodiles, Nile crocodiles have
5148-1213: Is a cladogram based on a 2018 tip dating study by Lee & Yates simultaneously using morphological , molecular ( DNA sequencing ), and stratigraphic ( fossil age) data, as revised by the 2021 Hekkala et al. paleogenomics study using DNA extracted from the extinct Voay . Voay † Crocodylus anthropophagus † Crocodylus thorbjarnarsoni † Crocodylus palaeindicus † Crocodylus Tirari Desert † Crocodylus johnstoni , freshwater crocodile [REDACTED] Crocodylus novaeguineae , New Guinea crocodile Crocodylus mindorensis , Philippine crocodile Crocodylus porosus , saltwater crocodile [REDACTED] Crocodylus siamensis , Siamese crocodile [REDACTED] Crocodylus palustris , mugger crocodile [REDACTED] Crocodylus checchiai † Crocodylus falconensis † Crocodylus suchus , West African crocodile Crocodylus niloticus , Nile crocodile [REDACTED] Crocodylus moreletii , Morelet's crocodile Crocodylus rhombifer , Cuban crocodile [REDACTED] Crocodylus intermedius , Orinoco crocodile Crocodylus acutus , American crocodile [REDACTED] The muzzle
5291-425: Is a species of crocodile related to, and often confused with, the larger and more aggressive Nile crocodile ( C. niloticus ). The species was named by Étienne Geoffroy Saint-Hilaire in 1807, who discovered differences between the skulls of a mummified crocodile and those of Nile crocodile ( C. niloticus ). This new species was, however, long afterwards regarded as a synonym of the Nile crocodile. In 2003,
5434-572: Is abundant and dilute, nitrogen being excreted as ammonium bicarbonate . Sodium loss is low and mainly takes place through the skin in freshwater conditions. In seawater, the opposite is true. The osmolality in the plasma is lower than the surrounding water, which is dehydrating for the animal. The cloacal urine is much more concentrated, white, and opaque, with the nitrogenous waste being mostly excreted as insoluble uric acid . West African crocodile The West African crocodile , desert crocodile , or sacred crocodile ( Crocodylus suchus )
5577-417: Is clad in non-overlapping scales known as scutes which are covered with in beta-keratin . Many of the scutes are strengthened by bony plates known as osteoderms . They are most numerous on the back and neck of the animal. The belly and underside of the tail possess rows of broad, flat and square-shaped scales. In between crocodilian scales are hinge areas which consist mainly of alpha-keratin . Underneath
5720-480: Is determined by size. Large, old males are at the top of this hierarchy and have first access to food and the best basking spots. Crocodiles tend to respect this order; when it is infringed, the results are often violent and sometimes fatal. Like most other reptiles, Nile crocodiles lay eggs ; these are guarded by the females but also males, making the Nile crocodiles one of few reptile species whose males contribute to parental care. The hatchlings are also protected for
5863-456: Is diversity in snout and tooth shape, all crocodilian species have essentially the same body morphology. They have solidly built lizard-like bodies with wide, cylindrical torsos, flat heads, long snouts, short necks and tails compressed from side-to-side. Their limbs are reduced in size; the front feet have five mostly non-webbed digits, and the hind feet have four webbed digits and an extra fifth. The pelvis and ribs of crocodilians are modified;
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6006-441: Is less aggressive than the Nile crocodile, but several attacks on humans have been recorded, including fatal ones. Mauritanian traditional peoples who live in close proximity to West African crocodiles revere them and protect them from harm. This is due to their belief that, just as water is essential to crocodiles, so crocodiles are essential to the water, which would permanently disappear if they were not there to inhabit it. Here
6149-508: Is less ambiguous to use "crocodilians". Extant crocodilians have long flat heads with long snouts and tails compressed on the sides, with their eyes, ears, and nostrils at the top of the head. Alligators and caimans tend to have broader U-shaped jaws, that when closed, only show the upper teeth, while crocodiles usually have narrower V-shaped jaws with both rows of teeth visible when closed. Gharials have extremely slender and elongated jaws. All crocodilians are good swimmers and can move on land in
6292-418: Is not fully understood, but it has been suggested that they may be mechanosensory organs. There are prominent paired integumentary glands in skin folds on the throat, and others in the side walls of the cloaca. Various functions for these have been suggested. They may play a part in communication, as indirect evidence suggest that they secrete pheromones used in courtship or nesting. The skin of crocodilians
6435-560: Is permanently erect and relies on cloacal muscles to protrude it out and elastic ligaments and a tendon to pull it back in. The gonads are located near the kidneys . Crocodilians range in size from the Paleosuchus and Osteolaemus species, which reach 1–1.5 m (3 ft 3 in – 4 ft 11 in), to the saltwater crocodile and Nile crocodile, which reach 6 m (20 ft) and weigh up to 1,000 kg (2,200 lb), though some prehistoric species such as
6578-469: Is short and thick. The distance between the eyes and the tip of the muzzle is 1.5 to 2 times longer than the width of the muzzle at the level of the front edge of the eyes (1.2 to 1.5 times in case of juveniles). The coloration is generally brown to olive . Juveniles are paler, with black bandings , especially on the tail. Like all other species of crocodiles , the West African crocodile's eyes reflect light at night allowing it to be spotted easily through
6721-503: Is smaller. It typically grows between 2 and 3 m (6 ft 7 in and 9 ft 10 in) in length, with an occasional male growing over 4 m (13 ft 1 in) in rare cases. Adults weigh between 90 and 250 kg (200 and 550 lb), with particularly large male specimens exceeding 300 kg (660 lb) in weight. The West African crocodile inhabits much of West and Central Africa , ranging east to South Sudan and Uganda , and south to Democratic Republic of
6864-399: Is the case with all true crocodiles. Hatchlings quickly lose a hardened piece of skin on the top of their mouths called the egg tooth , which they use to break through their eggshells at hatching. Among crocodilians, the Nile crocodile possesses a relatively long snout, which is about 1.6 to 2.0 times as long as broad at the level of the front corners of the eyes. As is the saltwater crocodile,
7007-477: Is the largest predator in Africa, and may be considered the second-largest extant reptile in the world, after the saltwater crocodile ( Crocodylus porosus ). Size is sexually dimorphic , with females usually about 30% smaller than males. The crocodile has thick, scaly, heavily armoured skin. Nile crocodiles are opportunistic apex predators ; a very aggressive crocodile, they are capable of taking almost any animal within their range. They are generalists , taking
7150-416: Is the main means of warming for any crocodilian, while immersion in water may either raise its temperature via conduction , or cool the animal in hot weather. The main method for regulating its temperature is behavioural. Temperate-living alligators may start the day by basking in the sun on land, and move into the water for the afternoon, with parts of the back breaking the surface so it can still be warmed by
7293-443: Is tough and can withstand damage from conspecifics , and the immune system is effective enough to heal wounds within a few days. In the genus Crocodylus the skin contains chromatophores , allowing them to change color from dark to light and vice versa. The crocodilian has perhaps the most complex vertebrate circulatory system . It has a four-chambered heart and two ventricles , an unusual trait among extant reptiles, and both
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#17327909013757436-501: Is unknown, but crocodiles can dive to at least 20 m (66 ft). Vocalizing is produced by vibrating vocal folds in the larynx . The folds of the American alligator have a complex morphology consisting of epithelium , lamina propria and muscle, and according to Riede et al. (2015), "it is reasonable to expect species-specific morphologies in vocal folds/analogues as far back as basal reptiles". Crocodilian vocal folds lack
7579-468: Is usually maintained between 25 and 35 °C (77 and 95 °F), and mainly stays in the range 30 to 33 °C (86 to 91 °F). Both the American and Chinese alligator can be found in areas that sometimes experience periods of frost in winter. In cold weather, they remain submerged with their tails in deeper, less cold water and their nostrils just projecting through the surface. If ice forms on
7722-477: The Americas , Africa , Asia and Oceania . They usually inhabit freshwater habitats , but some can live in saltier environments and even swim out to sea. They have a largely carnivorous diet. Some species like the gharial are specialized feeders, while others like the saltwater crocodile have generalized diets. Crocodilians are generally solitary and territorial , though they sometimes hunt in groups. During
7865-705: The Central African Republic , the Democratic Republic of the Congo , Equatorial Guinea , Tanzania, Rwanda , Burundi , Zambia, Zimbabwe , Gabon , Angola , South Africa, Malawi , Mozambique , Namibia , Sudan , South Sudan , Botswana , and Cameroon . The Nile crocodile's current range of distribution extends from the regional tributaries of the Nile in Sudan and Lake Nasser in Egypt to
8008-749: The Cunene river of Angola, the Okavango Delta of Botswana, and the Olifants River in South Africa. Isolated populations also exist in Madagascar , which were supposed to have likely colonized the island very recently, after the extinction of the endemic crocodile Voay within the last 2000 years . However in 2022 a skull of Crocodylus from Madagascar was found to be around 7,500 years old based on radiocarbon dating, suggesting that
8151-741: The Isle of Wight in the United Kingdom. It was followed by crocodilians such as the Planocraniidae , the so-called 'hoofed crocodiles', in the Palaeogene . Spanning the Cretaceous and Palaeogene periods is the genus Borealosuchus of North America, with six species, though its phylogenetic position is not settled. The three primary branches of Crocodilia had diverged by the Late Cretaceous . The possible earliest-known members of
8294-614: The Nile Delta throughout the Nile River . Lake Turkana in Kenya has one of the largest undisturbed Nile crocodile populations. Generally, the adult male Nile crocodile is between 3.5 and 5 m (11 ft 6 in and 16 ft 5 in) in length and weighs 225 to 750 kg (496 to 1,653 lb). However, specimens exceeding 6.1 m (20 ft) in length and 1,000 kg (2,200 lb) in weight have been recorded. It
8437-409: The cartilaginous processes of the ribs allow the thorax to collapse when submerging and the structure of the pelvis can accommodate large amounts of food, or more air in the lungs. Both sexes have a cloaca , a single chamber and outlet near the tail into which the intestinal , urinary and genital tracts open. It houses the penis in males and the clitoris in females. The crocodilian penis
8580-442: The eardrums are protected by flaps that can be opened or closed by muscles. Crocodilians have a wide hearing range , with sensitivity comparable to most birds and many mammals. Hearing in crocodilians does not degrade as the animal gets older as they can regrow and replace hair cells . The well-developed trigeminal nerve allows them to detect vibrations in the water (such as those made by potential prey). Crocodilians have just
8723-529: The pancreas , spleen , small intestine , and liver also function more efficiently. When submerged, a crocodilian's heart may beat at only one or two beats a minute, with little blood flow to the muscle. When it rises and takes a breath, its heart rate almost immediately speeds up, and the muscles receive newly oxygenated blood. Unlike many marine mammals , crocodilians have little myoglobin to store oxygen in their muscles. During diving, an increasing concentration of bicarbonate ions causes haemoglobin in
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#17327909013758866-406: The pterygoid bones . This allowed the animal to breathe through its nostrils while its mouth was open underwater. The eusuchians continued this process with the interior nostrils now opening through an aperture in the pterygoid bones. The vertebrae of eusuchians had one convex and one concave articulating surface. The oldest known eusuchian is Hylaeochampsa vectiana from the Early Cretaceous of
9009-561: The saltwater crocodile . Typical size has been reported to be as much as 4.5 to 5.5 m (14 ft 9 in to 18 ft 1 in), but this is excessive for actual average size per most studies and represents the upper limit of sizes attained by the largest animals in a majority of populations. Alexander and Marais (2007) give the typical mature size as 2.8 to 3.5 m (9 ft 2 in to 11 ft 6 in); Garrick and Lang (1977) put it at from 3.0 to 4.5 m (9 ft 10 in to 14 ft 9 in). According to Cott (1961),
9152-584: The 1920s, museums continued to obtain West African crocodile specimens from the White Nile , but today the species has disappeared from this river. In Mauritania the species has adapted to the arid desert environment of the Sahara – Sahel by staying in caves or burrows in a state of aestivation during the driest periods, leading to the alternative common name desert crocodile. When it rains, these desert crocodiles gather at gueltas . In much of its range,
9295-1020: The 2021 Hekkala et al. paleogenomics study using DNA extracted from the extinct Voay . Voay † Crocodylus anthropophagus † Crocodylus thorbjarnarsoni † Crocodylus palaeindicus † Crocodylus Tirari Desert † Crocodylus johnstoni Freshwater crocodile [REDACTED] Crocodylus novaeguineae New Guinea crocodile Crocodylus mindorensis Philippine crocodile Crocodylus porosus Saltwater crocodile [REDACTED] Crocodylus siamensis Siamese crocodile [REDACTED] Crocodylus palustris Mugger crocodile [REDACTED] Crocodylus checchiai † Crocodylus falconensis † Crocodylus suchus West African crocodile Crocodylus niloticus Nile crocodile [REDACTED] Crocodylus moreletii Morelet's crocodile Crocodylus rhombifer Cuban crocodile [REDACTED] Crocodylus intermedius Orinoco crocodile Crocodylus acutus American crocodile [REDACTED] Adult Nile crocodiles have
9438-477: The Congo (in all three countries it may come into contact with Nile crocodiles). Other countries where it is found include Mauritania , Benin , Liberia , Guinea-Bissau , Nigeria , Niger , Cameroon , Chad , Sierra Leone , the Central African Republic , Equatorial Guinea , Senegal , Mali , Guinea , Gambia , Burkina Faso , Ghana , Gabon , Togo , Ivory Coast and the Republic of Congo . As late as
9581-858: The East African Nile crocodile), C. n. chamses (the West African Nile crocodile), C. n. cowiei (the South African Nile crocodile), C. n. madagascariensis (the Malagasy or Madagascar Nile crocodile, regionally also known as the croco Mada , which translates to Malagasy crocodile), C. n. niloticus (the Ethiopian Nile crocodile; this would be the nominate subspecies), C. n. pauciscutatus (the Kenyan Nile crocodile) and C. (n.) suchus (now widely considered
9724-814: The Mediterranean coast in Libya , Tunisia , Algeria , Morocco , the Nile Delta of Egypt and across the Red Sea in Palestine and Syria . The Nile crocodile has historically been recorded in areas where they are now regionally extinct. For example, Herodotus recorded the species inhabiting Lake Moeris in Egypt. They are thought to have become extinct in the Seychelles in the early 19th century (1810–1820). Today, Nile crocodiles are widely found in, among others, Somalia , Ethiopia , Uganda , Kenya, Egypt,
9867-1086: The Nile River". The Nile crocodile is called timsah al-nil in Arabic , mamba in Swahili , yaxaas in Somali , garwe in Shona , ngwenya in Ndebele , ngwena in Venda , kwena in Sotho and Tswana , and tanin ha-yeor in Hebrew . It also sometimes referred to as the African crocodile , Ethiopian crocodile , and common crocodile . Although no subspecies are currently formally recognized, as many as seven have been proposed, mostly due to variations in appearance and size noted in various populations throughout Africa. These have consisted of C. n. africanus (informally named
10010-430: The Nile crocodile is a quadruped with four short, splayed legs, a long, powerful tail , a scaly hide with rows of ossified scutes running down its back and tail, and powerful, elongated jaws . Their skin has a number of poorly understood integumentary sense organs that may react to changes in water pressure , presumably allowing them to track prey movements in the water. The Nile crocodile has fewer osteoderms on
10153-469: The Nile crocodile is considered a species with medium-width snout relative to other extant crocodilian species. In a search for the largest crocodilian skulls in museums, the largest verifiable Nile crocodile skulls found were several housed in Arba Minch , Ethiopia , sourced from nearby Lake Chamo , which apparently included several specimens with a skull length more than 65 cm (26 in), with
10296-456: The Nile crocodile: C. anthropophagus from Plio-Pleistocene Tanzania and C. thorbjarnarsoni from Plio-Pleistocene Kenya . C. anthropophagus and C. thorbjarnarsoni were both somewhat larger, with projected total lengths up to 7.5–7.6 m (24 ft 7 in – 24 ft 11 in). As well as being larger, C. anthropophagus and C. thorbjarnarsoni , as well as Rimasuchus spp., were all relatively broad-snouted, indicating
10439-573: The Nile in Lower Egypt along with the Nile crocodile. Herodotus wrote that the Egyptian priests were selective when picking crocodiles. Priests were aware of the difference between the two species, C. suchus being smaller and more docile, making it easier to catch and tame. Herodotus also indicated that some Egyptians kept crocodiles as pampered pets. In Sobek's temple in Arsinoe, a crocodile
10582-466: The West African crocodile may come into contact with other crocodile species and there appears to be a level of habitat segregation between them. The Nile crocodile typically prefers large seasonal rivers in savannah or grassland, while the West African crocodile generally prefers lagoons and wetlands in forested regions, at least where the two species may come into contact. The details of this probable segregations remains to be confirmed for certain. In
10725-486: The ancient Greek κρόκη ( kroke )—meaning shingle or pebble—and δρîλος or δρεîλος ( dr(e)ilos ) for "worm". The name may refer to the animal's habit of resting on the pebbled shores of the Nile . Crocodilians, and birds, are members of the Archosaur clade. Archosaurs are distinguished from other reptiles particularly by two sets of extra openings in the skull: the antorbital fenestra located in front of
10868-428: The animal needs to stop or steer in a different direction, the limbs are splayed out. Swimming is normally achieved with gentle sinuous movements of the tail, but they can move faster when pursuing or being pursued. Crocodilians are less well-adapted for moving on land, and are unusual among vertebrates in having two different means of terrestrial locomotion: the "high walk" and the "low walk". Their ankle joints flex in
11011-642: The animal's eye socket and the mandibular fenestra on the jaw. Archosaurs comprise two main groups: the Pseudosuchia (crocodilians and their relatives), and the Avemetatarsalia ( dinosaurs , pterosaurs , and their relatives). The split between these two is assumed to have happened close to the Permian–Triassic extinction event (informally known as the Great Dying). Crocodylomorpha ,
11154-462: The animals to remain submerged for a longer period, but this explanation has been questioned. Other possible reasons for the peculiar circulatory system include assistance with thermoregulatory needs, prevention of pulmonary oedema , or faster recovery from metabolic acidosis . Retaining carbon dioxide within the body permits an increase in the rate of gastric acid secretion and thus the efficiency of digestion, and other gastrointestinal organs such as
11297-403: The ankle rotates. The limbs move much the same as in other quadrupeds , with the left forelimb moving first, followed by the right hindlimb, then right forelimb, and finally left hindlimb, and repeat. The high walk of crocodilians, with the belly and most of the tail held off the ground and the limbs held directly under the bodies, resembles that of mammals and birds. The low walk is similar to
11440-478: The average female specimen would weigh 40 to 250 kg (88 to 551 lb). An old male individual, named "Big Daddy", housed at Mamba Village Centre, Mombasa , Kenya , is considered to be one of the largest living Nile crocodiles in captivity. It measures 5 m (16 ft 5 in) in length and weighs 800 kg (1,800 lb). In 2007, at the Katavi National Park , Brady Barr captured
11583-535: The average length and weight of Nile crocodiles from Uganda and Zambia in breeding maturity was 3.16 m (10 ft 4 in) and 137.5 kg (303 lb). Per Graham (1968), the average length and weight of a large sample of adult crocodiles from Lake Turkana (formerly known as Lake Rudolf), Kenya was 3.66 m (12 ft 0 in) and body mass of 201.6 kg (444 lb). Similarly, adult crocodiles from Kruger National Park reportedly average 3.65 m (12 ft 0 in) in length. In comparison,
11726-659: The basis of anatomy to consist of a mix of the two species. Sobek was depicted as a crocodile, as a mummified crocodile, or as a man with the head of a crocodile. The center of his worship was in the Middle Kingdom city of Arsinoe in the Faiyum , known as " Crocodilopolis " by the Greeks . Another major temple to Sobek is in Kom Ombo ; other temples were scattered across the country. Historically, C. suchus inhabited
11869-443: The belly outward, and the diaphragmaticus pulls the liver back. When exhaling, the internal intercostal muscles push the ribs inward, while the rectus abdominis pulls the hips and liver forwards and the belly inward. Crocodilians can also use these muscles to adjust the position of their lungs, controlling their buoyancy in the water. An animal sinks when the lungs are pulled towards the tail and floats when they move back towards
12012-400: The belly, which are much more conspicuous on some of the more modestly sized crocodilians. The species, however, also has small, oval osteoderms on the sides of the body, as well as the throat. The Nile crocodile shares with all crocodilians a nictitating membrane to protect the eyes and lachrymal glands to cleanse its eyes with tears. The nostrils , eyes, and ears are situated on the top of
12155-404: The blood from the calcium and magnesium in these dermal bones act as a buffer during prolonged submersion when increasing levels of carbon dioxide would otherwise cause acidosis . Some scutes contain a single pore known as an integumentary sense organ. Crocodiles and gharials have these on large parts of their bodies, while alligators and caimans only have them on the head. Their exact function
12298-604: The blood to release oxygen for the muscles. Crocodilians were traditionally thought to breathe like mammals, with airflow moving in and out tidally, but studies published in 2010 and 2013 conclude that crocodilians breathe more like birds , with airflow moving in a unidirectional loop within the lungs. When a crocodilian inhales, air flows through the trachea and into two primary bronchi , or airways, which split off into narrower secondary passageways. The air continues to move through these, then into even narrower tertiary airways, and then into other secondary airways which were bypassed
12441-587: The breeding season, dominant males try to monopolize available females. Females lay their eggs in holes or mounds, and similar to many birds, care for their hatched young. Some species of crocodilians (particularly the Nile crocodile ) are known to have attacked humans . Humans are the greatest threat to crocodilian populations through activities that include hunting, poaching, and habitat destruction , but farming of crocodilians has greatly reduced unlawful trading in wild skins. Artistic and literary representations of crocodilians have appeared in human cultures around
12584-614: The crocodile's blood. Guggisberg (1972) had seen examples of birds picking scraps of meat from the teeth of basking crocodiles (without entering the mouth) and prey from soil very near basking crocodiles, so felt it was not impossible that a bold, hungry bird may occasionally nearly enter a crocodile's mouth, but not likely as a habitual behaviour. MacFarland and Reeder, reviewing the evidence in 1974, found that: "Extensive observations of Nile crocodiles in regular or occasional association with various species of potential cleaners (e.g. Plovers , Sandpipers , water dikkop ) ... have resulted in only
12727-403: The crocodiles live in apparent peace with the humans, and are not known to attack swimmers. The people of ancient Egypt worshiped Sobek , a crocodile-god associated with fertility , protection, and the power of the pharaoh . They had an ambivalent relationship with Sobek, as they did (and do) with C. suchus : sometimes they hunted crocodiles and reviled Sobek, and sometimes they saw him as
12870-478: The crocodiles observed by Cott (1961), if not disturbed, spent the hours from 9:00 a.m. to 4:00 p.m. continuously basking with their jaws open if conditions were sunny. If their jaws are bound together in the extreme midday heat, Nile crocodiles may easily die from overheating. Although they can remain practically motionless for hours on end, whether basking or sitting in shallows, Nile crocodiles are said to be constantly aware of their surroundings and aware of
13013-475: The crocodiles of the Americas, namely the American ( C. acutus ), Cuban ( C. rhombifer ), Morelet's ( C. moreletii ), and Orinoco crocodiles ( C. intermedius ). The fossil species C. checchiai from the Miocene in Kenya was about the same size as the extant African Nile crocodiles and shared similar physical characteristics to this specific species. At one time, the fossil species Rimasuchus lloydi
13156-485: The elasticity of mammalian ones; but the larynx is still capable of complex motor control similar to birds and mammals and can adequately control its fundamental frequency . Crocodilian teeth can only hold onto prey, and food is swallowed unchewed. The stomach consists of a grinding gizzard and a digestive chamber. Indigestible items are regurgitated as pellets. The stomach is more acidic than that of any other vertebrate and contains ridges for gastroliths , which play
13299-542: The extinction of Voay post-dates the arrival of Nile crocodiles on Madagascar. Nile Crocodiles occur in the western and southern parts of Madagascar from Sambirano to Tôlanaro . They have been spotted in Zanzibar and the Comoros in modern times, but occur very rarely. The species was previously thought to extend in range into the whole of West and Central Africa, but these populations are now typically recognized as
13442-596: The eye clean. When a crocodilian leaves the water and dries off, this substance is visible as "tears". While eyesight is fairly good in air, it is significantly weakened underwater. Crocodilians appear to have gone through a "nocturnal bottleneck" early in their history with their eyes losing traits like sclerotic rings , an annular pad of the lens and colored cone oil droplets , giving them dichromatic vision (red-green colorblindness). Since then, some crocodilians appear to have re-evolved full colour vision . The ears are adapted for hearing both in air and underwater, and
13585-571: The female is 3.05 m (10 ft 0 in), at which females would average about 116 kg (256 lb). This gives the Nile crocodile somewhat of a size advantage over the next largest non-marine predator on the African continent, the lion ( Panthera leo ), which averages 188 kg (414 lb) in males and 124 kg (273 lb) in females, and attains a maximum known weight of 313 kg (690 lb), far less than that of large male crocodiles. Nile crocodiles from cooler climates, like
13728-413: The first time. The air then flows back into the primary airways and is exhaled. The lungs of crocodilians are attached to the liver and the pelvis by the diaphragmaticus muscle ( analogous of the diaphragm in mammals). During inhalation, the external intercostal muscles expand the ribs, allowing the animal to take in more air, while the ischiopubis muscle causes the hips to swing downwards and push
13871-419: The form of two rows of plates extending from head to tail; this armor would still be found in later species. Their vertebrae were convex on the two main articulating surfaces, and the secondary palate was little developed as it consisted only of a maxilla . The mesosuchians saw a fusion of the palatine bones to the secondary palate and a great extension of the nasal passages behind the palatine and in front of
14014-486: The group may be Portugalosuchus and Zholsuchus from the Cenomanian - Turonian stages. The classification of Portugalosuchus has been disputed by some researchers who claimed that it may be outside the crown group crocodilians. The morphology-based phylogenetic analyses based on the new neuroanatomical data obtained from its skull using micro-CT scans suggested that this taxon is a crown group crocodilian and
14157-616: The group that later give rise to modern crocodilians, emerged in the Late Triassic . While the most basal crocodylomorphs were large, the ones that gave rise to crocodilians were small, slender, and leggy. This evolutionary grade, the so-called " sphenosuchians " first appeared around Carnian of the Late Triassic . They ate small, fast prey and survived into the Late Jurassic . As the Triassic ended, crocodylomorphs became
14300-505: The head, so the rest of the body can remain concealed under water. They have a four-chambered heart , although modified for their ectothermic nature due to an elongated cardiac septum, physiologically similar to the heart of a bird, which is especially efficient at oxygenating their blood. As in all crocodilians, Nile crocodiles have exceptionally high levels of lactic acid in their blood, which allows them to sit motionless in water for up to 2 hours. Levels of lactic acid as high as they are in
14443-409: The head. This allows them to move through the water without creating disturbances that could alert potential prey. They can also spin and twist by moving their lungs laterally. Swimming and diving crocodilians appear to rely on lung volume more for buoyancy than oxygen storage. Just before diving, the animal exhales to reduce its lung volume and reach negative buoyancy. When diving, the nostrils of
14586-488: The high walk, but without the body being raised, and is quite different from the sprawling walk of salamanders and lizards. The animal can change from one walk to the other instantaneously, but the high walk is the usual means of locomotion on land. The animal may push its body up and use this form immediately, or may take one or two strides of low walk before raising the body higher. Unlike most other land vertebrates, when crocodilians increase their pace of travel they increase
14729-459: The hind limbs launching the body forward and the fore limbs subsequently taking the weight. Next, the hind limbs swing forward as the spine flexes dorso-ventrally , and this sequence of movements is repeated. During terrestrial locomotion, a crocodilian can keep its back and tail straight, since the scales are attached to the vertebrae by muscles. Whether on land or in water, crocodilians can jump or leap by pressing their tails and hind limbs against
14872-554: The jaws are closed as their teeth fit into grooves along the outside lining of the upper jaw. By contrast the lower teeth of alligators and caimans normally fit into holes along the inside lining of the upper jaw. Thus they are hidden when the jaws are closed. Crocodilians are homodonts , meaning each of their teeth are all of the same type (they do not possess different tooth types, such as canines and molars) and polyphyodonts are able to replace each of their approximately 80 teeth up to 50 times in their 35- to 75-year lifespan. They are
15015-436: The jaws are larger and more powerful than the ones that open them, and a crocodilian's jaws can be held shut by a person fairly easily. Conversely, the jaws are extremely difficult to pry open. The powerful closing muscles attach at the middle of the lower jaw and the jaw hinge attaches behind the atlanto-occipital joint , giving the animal a wide gape. A folded membrane holds the tongue stationary. Crocodilians have some of
15158-407: The larger the crocodilian gets, the stronger its bite is likely to be. Therefore, a male saltwater crocodile, which had attained a length around 4.59 m (15 ft 1 in), was found to have the most powerful biting force ever tested in a lab setting for any type of animal. The Nile crocodile is the largest crocodilian in Africa, and is generally considered the second-largest crocodilian after
15301-1169: The largest Nile crocodiles ever recorded. It was estimated to weigh 1,082 kg (2,385 lb). Like all crocodiles, they are sexually dimorphic , with the males up to 30% larger than the females, though the difference is considerably less compared to some species, like the saltwater crocodile. Male Nile crocodiles are about 30 to 50 cm (12 to 20 in) longer on average at sexual maturity and grow more so than females after becoming sexually mature, especially expanding in bulk after exceeding 4 m (13 ft 1 in) in length. Adult male Nile crocodiles usually range in length from 3.3 to 5.0 m (10 ft 10 in to 16 ft 5 in) long; at these lengths, an average sized male may weigh from 150 to 750 kg (330 to 1,650 lb). Very old, mature ones can grow to 5.5 m (18 ft 1 in) or more in length (all specimens over 5.5 m (18 ft 1 in) from 1900 onward are cataloged later). Large mature males can reach 1,000 kg (2,200 lb) or more in weight. Mature female Nile crocodiles typically measure 2.2 to 3.8 m (7 ft 3 in to 12 ft 6 in), at which lengths
15444-567: The largest one being 68.6 cm (27.0 in) in length with a mandibular length of 87 cm (34 in). Nile crocodiles with skulls this size are likely to measure in the range of 5.4 to 5.6 m (17 ft 9 in to 18 ft 4 in), which is also the length of the animals according to the museum where they were found. However, larger skulls may exist, as this study largely focused on crocodilians from Asia. The detached head of an exceptionally large Nile crocodile (killed in 1968 and measuring 5.87 m (19 ft 3 in) in length)
15587-425: The late Cretaceous Deinosuchus were even larger at up to about 11 m (36 ft) and 3,450 kg (7,610 lb). They tend to be sexually dimorphic , with males much larger than females. Crocodilians are excellent swimmers. During aquatic locomotion , the muscular tail undulates from side to side to drive the animal through the water while the limbs are held close to the body to reduce drag . When
15730-869: The latter region in eastern and southern Democratic Republic of Congo, and along the Central African coastal Atlantic region (as far north to Cameroon). Likely a level of habitat segregation occurs between the two species, but this remains to be confirmed. Nile crocodiles may be able to tolerate an extremely broad range of habitat types, including small brackish streams, fast-flowing rivers, swamps , dams, and tidal lakes and estuaries . In East Africa, they are found mostly in rivers, lakes, marshes , and dams, favoring open, broad bodies of water over smaller ones. They are often found in waters adjacent to various open habitats such as savanna or even semi-desert but can also acclimate to well-wooded swamps, extensively wooded riparian zones , waterways of other woodlands and
15873-532: The local crocodiles have more osteoderms in their ventral surface than other known populations, and thus are of lesser value in leather trading, accounting for an exceptionally large (possibly overpopulated) local population there in the late 20th century. The segregation of the West African crocodile ( C. suchus ) from the Nile crocodile has been supported by morphological characteristics, studies of genetic materials and habitat preferences. The separation of
16016-699: The long-snouted gavialids more closely related to crocodiles than to alligators, with the new grouping of gavialids and crocodiles named Longirostres . Below is a cladogram from 2021 showing the relationships of the major extant crocodilian groups. This analysis was based off mitochondrial DNA , including that of the recently extinct Voay robustus : Caiman [REDACTED] Melanosuchus [REDACTED] Paleosuchus [REDACTED] Alligator [REDACTED] Crocodylus [REDACTED] † Voay Mecistops [REDACTED] Osteolaemus [REDACTED] Gavialis [REDACTED] Tomistoma [REDACTED] Though there
16159-414: The longest there being 3.65 m (12 ft 0 in). Crocodiles in aestivation are lethargic, entering a state similar to animals that hibernate . Only the largest individuals engaging in aestivation leave the burrow to sun on the warmest days; otherwise, these crocodiles rarely left their burrows. Aestivation has been recorded from May to August. Nile crocodiles usually dive for only a few minutes at
16302-420: The most common crocodilian in Africa. Among crocodilians today, only the saltwater crocodile occurs over a broader geographic area, although other species, especially the spectacled caiman ( Caiman crocodilus ) (due to its small size and extreme adaptability in habitat and flexibility in diet), seem to actually be more abundant. This species’ historic range, however, was even wider. They were found as far north as
16445-405: The muscular tendons used to shut the jaws are similar in proportional size. Only the gharial ( Gavialis gangeticus ) (and perhaps some of the few very thin-snouted crocodilians) is likely to have noticeably diminished bite force compared to other living species due to its exceptionally narrow, fragile snout. More or less, the size of the tendons used to impart bite force increases with body size and
16588-456: The only non-mammalian vertebrates with tooth sockets . Next to each full-grown tooth there is a small replacement tooth and an odontogenic stem cell in the dental lamina , which can be activated when required. Tooth replacement slows and eventually stops as the animal ages. The eyes, ears and nostrils of crocodilians are at the top of the head. This allows them to stalk their prey with most of their bodies underwater. When in bright light,
16731-473: The only surviving pseudosuchians. During the early Jurassic period, the dinosaurs became dominant on land, and the crocodylomorphs underwent major adaptive diversifications to fill ecological niches vacated by recently extinguished groups. Mesozoic crocodylomorphs had a much greater diversity of forms than modern crocodilians. Some became small fast-moving insectivores , others specialist fish-eaters , still others marine and terrestrial carnivores , and
16874-508: The perimeter of forests. In Madagascar, the remnant population of Nile crocodiles has adapted to living within caves. Nile crocodiles may make use of ephemeral watering holes on occasion. Although not a regular sea-going species as is the American crocodile , and especially the saltwater crocodile , the Nile crocodile possesses salt glands like all true crocodiles (i.e., excluding alligators and caimans), and does on occasion enter coastal and even marine waters . They have been known to enter
17017-424: The presence of other animals. However, mouth-gaping (while essential to thermoregulation) may also serve as a threat display to other crocodiles. For example, some specimens have been observed mouth-gaping at night, when overheating is not a risk. In Lake Turkana , crocodiles rarely bask at all through the day, unlike crocodiles from most other areas, for unknown reasons, usually sitting motionless partially exposed at
17160-401: The pupils of a crocodilian contract into narrow slits, whereas in darkness they become large circles. This is typical for animals that hunt at night. Crocodilians also possess a tapetum lucidum which enhances vision in low light. When the animal completely submerges, the nictitating membranes cover its eyes. In addition, glands on the nictitating membrane secrete a salty lubricant that keeps
17303-428: The saltwater crocodile and gharial reportedly both average around 4 m (13 ft 1 in), so are about 30 cm (12 in) longer on average, and the false gharial ( Tomistoma schlegelii ) may average about 3.75 m (12 ft 4 in), so may be slightly longer, as well. However, compared to the narrow-snouted, streamlined gharial and false gharial, the Nile crocodile is more robust and ranks second to
17446-408: The saltwater crocodile in total average body mass among living crocodilians, and is considered to be the second-largest extant reptile. The largest accurately measured male, shot near Mwanza, Tanzania, measured 6.45 m (21 ft 2 in) and weighed about 1,043–1,089 kg (2,300–2,400 lb). Another large male measuring 5.8 m (19 ft 0 in) in total length (Cott 1961) was among
17589-473: The sea in some areas, with one specimen having been recorded 11 km (6.8 mi) off St. Lucia Bay in 1917. Nile crocodiles have been recently captured in South Florida , though no signs that the population is reproducing in the wild have been found. Genetic studies of Nile crocodiles captured in the wild in Florida have revealed that the specimens are all closely related to each other, suggesting
17732-521: The southern tip of Africa, may be smaller, reaching maximum lengths of only 4 m (13 ft 1 in). A crocodile population from Mali , the Sahara Desert , and elsewhere in West Africa reaches only 2 to 3 m (6 ft 7 in to 9 ft 10 in) in length, but it is now largely recognized as a separate species, the West African crocodile . The Nile crocodile is presently
17875-424: The speed at which the lower half of each limb (rather than the whole leg) swings forward, so stride length increases while stride duration decreases. Though typically slow on land, crocodilians can produce brief bursts of speed, and some can run at 12 to 14 km/h (7.5 to 8.7 mph) for short distances. In some small species such as the freshwater crocodile , a running can progress to galloping. This involves
18018-868: The strongest bite forces in the animal kingdom. In a study published in 2003, an American alligator's bite force was measured at up to 2,125 lbf (9.45 kN). In a 2012 study, a saltwater crocodile's bite force was measured even higher, at 3,700 lbf (16 kN). This study also found no correlation between bite force and snout shape. Nevertheless, the gharial's extremely slender jaws are relatively weak and built more for quick jaw closure. The bite force of Deinosuchus may have measured 23,000 lbf (100 kN), even greater than that of theropod dinosaurs like Tyrannosaurus . Crocodilian teeth vary from dull and rounded to sharp and pointy. Broad-snouted species have teeth that vary in size, while those of slender-snouted species are more consistent. In general both rows of teeth are visible on crocodiles and gharials when
18161-585: The subject of debate and conflicting results. Many studies and their resulting cladograms , or "family trees" of crocodilians, have found the "short-snouted" families of Crocodylidae and Alligatoridae to be close relatives, with the long-snouted Gavialidae as a divergent branch of the tree. The resulting group of short-snouted species, named Brevirostres , was supported mainly by morphological studies which analyzed skeletal features alone. However, recent molecular studies using DNA sequencing of living crocodilians have rejected this distinct group Brevirostres, with
18304-450: The substrate and launching themselves into the air. A fast entry into water from a muddy bank can be effected by plunging to the ground, twisting the body from side to side and splaying out the limbs. The snout shape of crocodilians varies between species. Alligators and caimans generally have wider, U-shaped snouts while those of crocodiles are typically narrower and V-shaped. The gharial's are extremely elongated. The muscles that close
18447-406: The sun. At night it remains submerged, and its temperature slowly falls. The basking period is longer in winter. Tropical crocodiles bask briefly in the morning but then move into the water for rest of the day. They may also move to land at nightfall, as it is cooler. Gaping with the mouth can provide cooling by evaporation from the mouth lining. By these means, the temperature range of crocodilians
18590-889: The surface in shallows, with no apparent ill effects from the lack of basking on land. In South Africa, Nile crocodiles are more easily observed in winter because of the extensive amount of time they spend basking at this time of year. More time is spent in water on overcast, rainy, or misty days. In the southern reaches of their range, as a response to dry, cool conditions that they cannot survive externally, crocodiles may dig and take refuge in tunnels and engage in aestivation . Pooley found in Royal Natal National Park that during aestivation, young crocodiles of 60 to 90 cm (24 to 35 in) total length would dig tunnels around 1.2 to 1.8 m (3 ft 11 in to 5 ft 11 in) in depth for most, with some tunnels measuring more than 2.7 m (8 ft 10 in),
18733-463: The surface, the dermis is thick with collagen . Both the head and jaws lack actual scales and are instead covered in tight keratinised skin that is fused directly to the bones of the skull and which over time develop a pattern of cracks as the skull develops. The skin on the neck and sides is loose. The scutes contain blood vessels and may act to absorb or release heat during thermoregulation . Research also suggests that alkaline ions released into
18876-408: The tail and body. The underbelly of young crocodiles is yellowish green. As they mature, Nile crocodiles become darker and the cross-bands fade, especially those on the upper-body. A similar tendency in coloration change during maturation has been noted in most crocodile species. Most morphological attributes of Nile crocodiles are typical of crocodilians as a whole. Like all crocodilians, for example,
19019-473: The theories that they assist in digestion and staving off hunger. However, Alderton (1998) stated that a study using radiology found that gastroliths were seen to internally aid the grinding of food during digestion for a small Nile crocodile. Herodotus claimed that Nile crocodiles have a symbiotic relationship with a bird named the Trochilus which enter the crocodile's mouth and pick leeches feeding on
19162-678: The time of the actual divergence between the three lineages must have been a pre-Campanian event. Additionally, scientists conclude that environmental factors played a major role in the evolution of crocodilians and their ancestors, with warmer climate being associated with high evolutionary rates and large body sizes. Crocodylia is cladistically defined as the last common ancestor of Gavialis gangeticus (the gharial ), Alligator mississippiensis ( American alligator ), and Crocodylus rhombifer (the Cuban crocodile ) and all of its descendants. The phylogenetic relationships of crocodilians has been
19305-415: The tongue, though these are only present in crocodiles and gharials. The skin is a largely effective barrier to both water and ions, and gaping causes water loss by evaporation. Large animals are better able to maintain homeostasis at times of osmotic stress than smaller ones. Newly hatched crocodilians are much less tolerant of exposure to salt water than are older juveniles, presumably because they have
19448-451: The two is not recognized by the IUCN as their last evaluations of the group was in 2008 and 2009, years before the primary publications supporting the distinctiveness of the West African crocodiles. Although originally thought to be the same species as the West African crocodile , genetic studies using DNA sequencing have revealed that the Nile crocodile is actually more closely related to
19591-477: The use of duct tape to bind the jaws together. The broadest snouted modern crocodilians are alligators and larger caimans . For example, a 3.9 m (12 ft 10 in) black caiman ( Melanosuchus niger ) was found to have a notably broader and heavier skull than that of a Nile crocodile measuring 4.8 m (15 ft 9 in). However, despite their robust skulls, alligators and caimans appear to be proportionately equal in biting force to true crocodiles, as
19734-419: The water, they maintain ice-free breathing holes, and there have been occasions when their snouts have become frozen into the ice. Temperature sensing probes implanted in wild American alligators have found that their core body temperatures can descend to around 5 °C (41 °F), but as long as they remain able to breathe they show no ill effects when the weather warms up. All crocodilians need to maintain
19877-418: The world since Ancient Egypt . "Crocodilia" and "Crocodylia" have been used interchangeably for decades starting with Schmidt's redescription of the group from the formerly defunct term Loricata . Schmidt used the older term "Crocodilia", based on Owen 's original name for the group. Wermuth opted for "Crocodylia" as the proper name, basing it on the type genus Crocodylus ( Laurenti , 1768). Dundee—in
20020-499: Was 5.5 m (18 ft 1 in) long weighed 905.7 kg (1,997 lb). On the other hand, another individual measuring 5.87 m (19 ft 3 in) in length was estimated to weigh between 770–820 kg (1,700–1,800 lb). In attempts to parse the mean male and female lengths across the species, the mean adult length was estimated to be reportedly 4 m (13 ft 1 in) in males, at which males would average about 280 kg (620 lb) in weight, while that of
20163-409: Was found to have weighed 166 kg (366 lb), including the large tendons used to shut the jaw. The bite force exerted by an adult Nile crocodile has been shown by Brady Barr to measure 22 kN (5,000 lbf). However, the muscles responsible for opening the mouth are exceptionally weak, allowing a person to easily hold them shut, and even larger crocodiles can be brought under control by
20306-538: Was kept in the pool of the temple, where it was fed, covered with jewelry, and worshipped. When the crocodiles died, they were embalmed, mummified, placed in sarcophagi , and then buried in a sacred tomb. Many mummified C. suchus specimens and even crocodile eggs have been found in Egyptian tombs. Spells were used to appease crocodiles in ancient Egypt, and even in modern times Nubian fishermen stuff and mount crocodiles over their doorsteps to ward against evil. The West African crocodile only received wider recognition as
20449-457: Was thought to be the closest relative of the Nile crocodile, but more recent research has indicated that Rimasuchus , despite its very large size (about 20–30% bigger than a Nile crocodile with a skull length estimated up to 97 cm (38 in)), is more closely related to the dwarf crocodile ( Osteolaemus tetraspis ) among living species. Two other fossil species from Africa retained in the genus Crocodylus appear to be closely related to
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