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| {{otheruses}} | |||
| {{Taxobox | |||
| | | |||
| | name = Crocodile | |||
| | fossil_range = ] - Recent | |||
| | image = NileCrocodile.jpg | |||
| | image_caption = ] | |||
| | regnum = ]ia | |||
| | phylum = ] | |||
| | classis = ] | |||
| | ordo = ] | |||
| | familia = '''Crocodylidae''' | |||
| | familia_authority = ], 1807 | |||
| | subdivision_ranks = Genera | |||
| | subdivision = | |||
| * '']'' | |||
| * '']'' | |||
| '''See ].''' | |||
| }} | |||
| A '''crocodile''' is any ] belonging to the ] '''Crocodylidae''' (sometimes classified instead as the ] '''Crocodylinae'''). The term can also be used more loosely to include all members of the ] ]: i.e. the true crocodiles, the ]s and ]s (family ]) and the ]s (family ]), or even the ] which includes prehistoric crocodile relatives and ancestors. Crocodiles are large aquatic ]s that live throughout the ] in ], ], the ] and ]. Crocodiles tend to congregate in freshwater habitats like ]s, ]s, ]s and sometimes in ] water. They feed mostly on ]s like ], ]s, and ]s, sometimes on ]s like ]s and ]s, depending on species. They are an ancient lineage, and are believed to have changed little since the time of the dinosaurs. They are believed to be 200 million years old whereas dinosaurs became extinct 65 million years ago; crocodiles survived great extinction events.<ref name=ausfauna>Grigg, Gordon and Gans, Carl (1993) Morphology And Physiology Of The Crocodylia, in Fauna of Australia Vol 2A Amphibia and Reptilia, chapter 40, pages 326-336. Australian Government Publishing Service, Canberra. </ref> | |||
| ==Description== | |||
| :''Crocodiles are similar to alligators and caiman; for their common biology and differences between them, see ].'' | |||
| ]'']] | |||
| Crocodiles are among the more biologically complex reptiles despite their prehistoric look. Unlike other reptiles, they incorporate muscles used for aquatic locomotion into respiration (e.g. ''M. diaphragmaticus''; giving them the functional equivalent of a diaphragm),<ref name="Uriona & Farmer, 2008">Uriona TJ, Farmer CG. 2008. Recruitment of the diaphragmaticus, ischiopubis and other respiratory muscles to control pitch and roll in the American alligator (''Alligator mississippiensis''). ''Journal of Experimental Biology'' '''211''': 1141-1147.</ref> ] and four-chambered ]. Their external morphology on the other hand is a sign of their aquatic and predatory lifestyle. A crocodile’s physical traits allow it to be a successful ]. They have a streamlined body that enables them to swim swiftly. Crocodiles also tuck their feet to their sides while swimming, which makes them faster by decreasing water resistance. They have webbed feet which, although not used to propel the animal through the water, allow it to make fast turns and sudden moves in the water or initiate swimming. Webbed feet are an advantage in shallower water where the animals sometimes move around by walking. | |||
| Crocodiles have a palatal flap, a rigid tissue at the back of the mouth that blocks the entry of water. The palate has a special path from the nostril to the glottis that bypasses the mouth. The nostrils are closed during submergence. Like other ]s, crocodilians are ], although their post-temporal ] are reduced. The walls of the braincase are bony but they lack supratemporal and postfrontal bones.<ref name=ausfauna/> | |||
| Crocodilian scales have pores that are believed to be sensory, analogous to the ] in fishes. They are particularly seen on their upper and lower jaws. Another possibility is that they are secretory, as they produce an oily substance that appears to flush mud off.<ref name=ausfauna/> | |||
| Crocodiles are very fast over short distances, even out of water. They have extremely powerful jaws capable of biting down with immense force, by far the strongest bite of any animal. The crocodile's bite force is more than {{convert|5000|psi|atm}},<ref>National Geographic documentary; "Bite Force", Brady Barr.</ref> compared to just {{convert|335|psi|atm}} for a ], {{convert|400|psi|atm}} for a large ], or {{convert|800|psi|atm}} to {{convert|1000|psi|atm}} for a ]. They have sharp teeth for tearing and holding onto flesh, but cannot open their mouth if it is held closed. Since crocodiles feed by grabbing and holding onto their prey, they have evolved powerful muscles that close the jaws and hold them shut. The jaws are opened, however, by a very weak set of muscles. Crocodiles can thus be subdued for study or transport by ] their jaws or holding their jaws shut with large ]s cut from automobile ]s. All crocodiles have sharp and powerful claws. They have limited lateral (side-to-side) movement in their neck. | |||
| ===Age=== | |||
| There is no reliable way of measuring crocodile age, although several techniques are used to derive a reasonable guess. The most common method is to measure lamellar growth rings in bones and teeth—each ring corresponds to a change in growth rate which typically occurs once a year between dry and wet seasons.<ref>Britton Adam. . Retrieved 9/11/2006.</ref> Bearing these inaccuracies in mind, the oldest crocodilians appear to be the largest species. ''C. porosus'' is estimated to live around 70 years on average, and there is limited evidence that some individuals may exceed 100 years. One of the oldest crocodiles recorded died in a zoo in Russia. A male freshwater crocodile at the ] is estimated to be 130 years old. He was rescued from the wild by ] and ] after being shot twice by hunters. As a result of the shootings, this crocodile (known affectionately as "Mr. Freshy") has lost his right eye.<ref>, accessed ] ]</ref> | |||
| ===Size=== | |||
| ] in captivity in Australia]] | |||
| Size greatly varies between species, from the ] to the ]. Species of ''Palaeosuchus'' and ''Osteolaemus'' grow to an adult size of just {{convert|1|m|ft}} to {{convert|1.5|m|ft}}. Larger species can reach over {{convert|4.85|m|ft}} long and weigh well over {{convert|1200|kg|lb}}. Crocodilians show pronounced ] with males growing much larger and more rapidly than females.<ref name=ausfauna/> Despite their large adult size, crocodiles start their life at around {{convert|20|cm|in}} long. The largest species of crocodile is the ], found in northern Australia, throughout ], and in the surrounding waters. | |||
| The largest recorded crocodile is a giant saltwater crocodile measured at {{convert|8.6|m|ft}} and {{convert|1352|kg|lb}} shot in ], ] in 1957. A "replica" of this crocodile has been made as a tourist attraction.<ref name = NGeographicCroc/> The largest living crocodile known is a {{convert|7.1|m|ft}} long ], in ], India. It lives in ] and in June 2006, was entered in the Guinness Book of World Records.<ref>{{Cite news|url=http://in.today.reuters.com/news/newsArticle.aspx?type=topNews&storyID=2006-06-16T161028Z_01_NOOTR_RTRJONC_0_India-255100-1.xml| | |||
| title=Orissa crocodile recognised as world's largest| | |||
| publisher=Reuters| | |||
| date=2006-06-16| | |||
| accessdate = 2006-06-18}} </ref> | |||
| Two larger certifiable records are both of {{convert|6.2|m|ft}} crocodiles. The first crocodile was shot in the ] in the ] of ] in 1974 by poachers and measured by wildlife rangers.{{Fact|date=September 2008}} The second crocodile was killed in 1983 in the ], ]. In the case of the second crocodile it was actually the skin that was measured by zoologist Jerome Montague, and as skins are known to underestimate the size of the actual animal, it is possible this crocodile was at least another 10 cm longer.{{Fact|date=September 2008}} | |||
| ], a large saltwater crocodile that attacked boats]] | |||
| The largest crocodile ever held in captivity is an Estuarine–Siamese hybrid named Yai ({{lang-th|ใหญ่}}, meaning ''big'') (born ] ]) at the famous ], ]. This animal measures {{convert|6|m|ft}} in length and weighs {{convert|1114.27|kg|lb}}. | |||
| The largest captive crocodile alive in the US is located in South Carolina. In June 2002, Alligator Adventure introduced Utan. At {{convert|20|ft|m}} long and weighing in at more than a ton, "Utan", the largest crocodile to ever be exhibited in the United States, made his new home in Myrtle Beach. | |||
| Another huge captive specimen was a ] named ]. Gomek was captured by George Craig in Papua New Guinea and sold to St. Augustine Alligator Farm in ], ]. Gomek died of heart disease in February 1997. When he died, he was {{convert|5.5|m|ft}} long—as confirmed by St. Augustine Alligator Farm{{Fact|date=July 2008}}—and probably between 70 and 80 years old. | |||
| Yet another enormous crocodile, named ] by the Africans who have seen him, is responsible for over 300 human deaths, and allegedly ate an entire adult ]. He also stars in a film titled '']''. The crocodile's length is said to be anywhere between {{convert|20|ft|m}} to {{convert|30|ft|m}} long. He lives along the ] in Africa. | |||
| Wildlife experts, however, argue that the largest crocodile so far found in the Bhitarkanika was almost {{convert|25|ft|m}} long, which could be traced from the skull preserved by the Kanika Royal Family. The crocodile was shot near Dhamara in 1926 and later its skull was preserved by the then Kanika King. Crocodile experts estimate the animal at about {{convert|7.62|m|ft}} long, as the size of the skull was measured one seventh of the total length of the body. | |||
| ] treading on a crocodile (], ])]] | |||
| ===Etymology=== | |||
| {{wiktionary}} | |||
| The word ''crocodile'' comes from the ] κροκόδīλος (''crocodiilos'') "lizard", used in the phrase ''ho crocodiilos ho potámios'', "the lizard of the river" to refer to crocodiles in the current English sense. | |||
| There are several variant Greek forms of the word attested, including the later form κροκόδειλος (''crocodeilos'')<ref>http://perseus.mpiwg-berlin.mpg.de/cgi-bin/vor?lookup=krokodeilos&lang=greek</ref> found cited in many English reference works.<ref>http://dictionary.reference.com/browse/crocodile</ref> In the ] of ] times, ''crocodiilos'' and ''crocodeilos'' would have been pronounced identically, and either or both may be the source of the ] form ''crocodīlus'' used by the ancient ]. | |||
| ''Crocodiilos/crocodeilos'' itself is described in reference sources as a corruption of ''crocè'' ("pebbly"), and ''driilos/dreilos'' supposedly meaning "worm" although attested only as "(man with circumcized) penis".<ref>http://dictionary.com/browse/crocodile</ref> It is unclear how well supported this analysis is. The meaning of ''crocè'' is explained as describing the skin texture of lizards (or crocodiles) in most sources, but is alternately claimed to refer to a supposed habit of (lizards or crocodiles) basking on pebbly ground.<ref>http://etymonline.com/index.php?search=crocodile</ref> | |||
| The form ''crocodrillus'' is attested in ].<ref>http://dictionary.com/browse/crocodile</ref> It is not clear whether this is a medieval corruption or derives from alternate Greco-Latin forms (late Greek ''corcodrillos'' and ''corcodrillion'' are attested). | |||
| A (further) corrupted form ''cocodrille'' is found in ] and was borrowed into ] as ''cocodril(le)''. The ] form ''crocodile'' was adapted directly from the Classical Latin ''crocodīlus'' in the 16th Century, replacing the earlier form. | |||
| The use of -y- in the scientific name '']'' (and forms derived from it) is a corruption introduced by ] (1768). | |||
| ==Biology and behaviour== | |||
| Crocodiles are ambush hunters, waiting for fish or land animals to come close, then rushing out to attack. As cold-blooded predators, they are ], therefore survive long periods without food, and rarely need to actively go hunting. Despite their slow appearance, crocodiles are top predators in their environment, and various species have been observed attacking and killing ]s.<ref name = NGeographicCroc></ref> A famous exception is the ] which is said to enjoy a ] relationship with the crocodile. According to unauthenticated reports, the plover feeds on parasites that infest the crocodile's mouth and the reptile will open its jaws and allow the bird to enter to clean out the mouth (Richford and Mead 2003). | |||
| Many large crocodilians swallow stones (called gastroliths or stomach stones) and they are believed to be of use in acting as ballast to balance their body. Other suggestions have been made that they may have a function similar to that of grit in birds, which is in crushing food.<ref name=ausfauna/> | |||
| ]s are present in the tongues of most crocodylids and they have a pore opening on the surface of the tongue. They appear to be similar to those in marine turtles, however these seem to be absent in Alligatoridae.<ref name=ausfauna/> | |||
| Crocodilians can produce sounds during distress and in aggressive displays. They can also hear well and the tympanic membranes are concealed by flat flaps that may be raised or lowered by muscles.<ref name=ausfauna/> | |||
| ]]] | |||
| Crocodiles eat fish, birds, mammals and occasionally smaller crocodiles. | |||
| Crocodiles are protected in many parts of the world, but they also are farmed commercially. Their hide is tanned and used to make leather goods such as shoes and ]s, whilst crocodile meat is also considered a delicacy. The most commonly farmed species are the Saltwater and Nile crocodiles, while a hybrid of the Saltwater and the rare ] crocodile is also bred in Asian farms. Farming has resulted in an increase in the Saltwater crocodile population in ], as eggs are usually harvested from the wild, so landowners have an incentive to conserve crocodile habitat. | |||
| Crocodiles are more closely related to birds and dinosaurs than to most animals classified as reptiles, the three being included in the group ] ('ruling reptiles'). See ] for more information. | |||
| Crocodile embryos do not have sex chromosomes, and unlike humans sex is not determined genetically. Sex is determined by temperature, with males produced at around 31.6 °C, and females produced at slightly lower and higher temperatures. The average incubation period is around 80 days, and also is dependent upon temperature.<ref>Britton, Adam. . ''Crocodilians: Natural History Conservation: Crocodiles, Caimans, Alligators, Gharials.'' Retrieved 4 January 2007.</ref> | |||
| It has been observed that crocodiles may possess a form of ]. Three rogue saltwater crocodiles were relocated 400 kilometres by ] in northern ] but had returned to their original locations within three weeks, based on data obtained from tracking devices attached to the reptiles.<ref>Read MA, Grigg GC, Irwin SR, Shanahan D, Franklin CE (2007) Satellite Tracking Reveals Long Distance Coastal Travel and Homing by Translocated Estuarine Crocodiles, ''Crocodylus porosus''. PLoS ONE 2(9): e949. doi:10.1371/journal.pone.0000949</ref> | |||
| The ] record for a crocodile is 17 km/h (11 mph) measured in a galloping ]. <ref>{{cite web | |||
| | last = Britton | |||
| | first = Adam | |||
| | title = Crocodilian Biology Database FAQ, "How fast can a crocodile run?" | |||
| | url=http://www.flmnh.ufl.edu/cnhc/cbd-faq-q4.htm | |||
| | accessdate = 2008-02-02 }} | |||
| </ref> Maximum speed varies from species to species. Certain types of crocodiles can indeed gallop, including Cuban crocodiles, New Guinea crocodiles, ] and even smaller ]. For most species, the fastest they can move is a kind of "belly run", where the body moves in a snake-like fashion, limbs splayed out to either side paddling away frantically while the tail whips to and fro. Crocodiles can reach speeds of 10 or 11km/h (around 7 mph) when they "belly run", and often faster if they're slipping down muddy tidal riverbanks. Another form of locomotion is the "high walk" where the body is raised clear off the ground. | |||
| ] sleeping with its mouth open to pant.]] | |||
| Crocodiles do not have sweat glands, so they release heat through their mouths. Consequently, they often sleep with their mouth open and may even pant like a dog.<ref>{{cite web | |||
| | last = Anitai | |||
| | first = Stefan | |||
| | title = 14 Amazing Facts About Crocodiles - Living dinosaurs | |||
| | url=http://news.softpedia.com/news/14-Amazing-Facts-About-Crocodiles-69931.shtml | |||
| | publisher= Softpedia | |||
| | accessdate = 2008-04-01}}</ref> | |||
| ===Danger to humans=== | |||
| {{Citations missing|section|date=June 2008}} | |||
| {{Main|Crocodile attacks}} | |||
| The larger ] of crocodiles are very dangerous to humans. The main danger that crocodiles pose is not their ability to run after a person but their ability to strike before the person can react. The ] and ]s are the most dangerous, killing hundreds of people each year in parts of ] and ]. ]s and possibly the endangered ] are also very dangerous to humans. ]s are less aggressive and rarely assault humans without provocation. The most deaths in a single crocodile attack incident may have occurred during the ], on February 19, 1945, in ]. Nine hundred soldiers of an ] unit, in an attempt to retreat from the ] and rejoin a larger battalion of the Japanese ], crossed through {{convert|16|km|mi}} of ]s which contained Saltwater Crocodiles. Twenty Japanese soldiers were captured alive by the ], and almost five hundred are known to have escaped Ramree. Many of the remainder may have been eaten by the crocodiles, although gunfire from the British troops was undoubtedly a contributory factor. | |||
| == Taxonomy of the Crocodylidae == | |||
| ].]] | |||
| ] | |||
| ]]] | |||
| Most species are grouped into the ] ''Crocodylus''. The other ] genus, '']'', is ] (as is '']'', if recognized). | |||
| * Family Crocodylidae | |||
| ** '''Subfamily †]''' (extinct) | |||
| ** '''Subfamily Crocodylinae''' | |||
| *** Genus '']'' | |||
| **** '']'', ] | |||
| **** '']'', ] (studies in ] and ] suggest that this species may be more ] than '']'', and therefore belongs in its own genus, '']'')<ref>McAliley, Willis, Ray, White, Brochu & Densmore (2006). ''Are crocodiles really monophyletic?—Evidence for subdivisions from sequence and morphological data.'' Molecular Phylogenetics and Evolution 39:16-32.</ref> | |||
| **** '']'', ] | |||
| **** '']'', ] | |||
| **** '']'', ] | |||
| **** '']'', ] or Mexican Crocodile | |||
| **** '']'', ] or African Crocodile (the subspecies found in Madagascar is sometimes called the ]) | |||
| **** '']'', ] | |||
| **** '']'', ], Marsh Crocodile, or Indian Crocodile | |||
| **** '']'', ] or Estuarine Crocodile | |||
| **** '']'', ] | |||
| **** '']'', ] | |||
| *** Genus '']'' | |||
| **** '']'', ] (there has been controversy whether or not this is actually two species; current thinking is that there is one species with 2 subspecies: ''O. tetraspis tetraspis'' & ''O. t. osborni'') | |||
| *** Genus †'']'' | |||
| *** Genus †'']'' (formerly ''Crocodylus lloydi'') | |||
| *** Genus †'']'' | |||
| Some of the extinct relatives of true crocodiles, members of the larger group ], were herbivorous. | |||
| ==Crocodile products== | |||
| ] | |||
| Crocodile leather can be made into goods such as wallets, briefcases, purses, handbags, belts, hats, and shoes. | |||
| Crocodile is consumed in some countries, such as Australia, Ethiopia, Thailand, South Africa and also Cuba (in pickled form); it can also be found in specialty restaurants in some parts of the United States. The meat is white and its nutritional composition compares favourably with that of other meats{{Fact|date=August 2008}}. It tends to have a slightly higher cholesterol level than other meats{{Fact|date=August 2008}}. Crocodile meat has a delicate flavour; some describe it as a cross between chicken and crab{{Fact|date=August 2008}}. Cuts of meat include backstrap and tail fillet. | |||
| Crocodile oil has been used for centuries as a natural healing skin balm. | |||
| ==References== | |||
| {{reflist}} | |||
| ==Further reading== | |||
| * Iskandar, DT (2000). ''Turtles and Crocodiles of Insular Southeast Asia and New Guinea''. ITB, Bandung. | |||
| * Crocodilian Biology Database, FAQ. {{sic}} Adam Britton. | |||
| * Crocodilian Biology Database, FAQ. Adam Britton. | |||
| * {{cite book | author = Richford, Andrew S., and Christopher J. Mead | year = 2003 | title = Firefly Encyclopedia of Birds | chapter = Pratincoles and Coursers | editor = ] (Ed.) | pages = 252–253 | publisher = Firefly Books | isbn = 1-55297-777-3}} | |||
| == See also == | |||
| {{Wikispecies|Crocodilia}} | |||
| {{commons|Crocodilia}} | |||
| {{Wikiversity}} | |||
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| == External links == | |||
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Revision as of 03:22, 20 November 2008
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