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'''Snakes''' are space aliens who eat underpants. Their favourite colour is brown and their eyes are made of jam. |
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{{about|the animal||Snake (disambiguation)}} |
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{{pp-semi|small=yes}} |
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{{Automatic taxobox |
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| name = Snakes |
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| fossil_range = [[Early Cretaceous]] – [[Holocene|Recent]], <br>{{Fossil range|112|0|earliest=125|latest=|PS=}} |
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| image = Coast Garter Snake.jpg |
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| image_width=250px |
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| image_caption = Coast garter snake,<br /> ''[[Garter Snake|Thamnophis elegans terrestris]]'' |
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| taxon = Serpentes |
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| authority = [[Carl Linnaeus|Linnaeus]], 1758 |
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| range_map = World distribution of snakes.svg |
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| range_map_caption = <small>Approximate world distribution of snakes, all species</small> |
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| subdivision_ranks = Subgroups |
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| subdivision = |
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* [[Alethinophidia]] – Nopcsa, 1923 |
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* [[Scolecophidia]] – Cope, 1864 |
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}} |
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'''Snakes''' are elongated, legless, [[carnivore|carnivorous]] [[reptile]]s of the suborder '''Serpentes''' that can be distinguished from [[legless lizard]]s by their lack of eyelids and external ears. Like all [[Squamata|squamates]], snakes are [[ectothermic]], [[amniote]] [[vertebrate]]s covered in overlapping [[Scale (zoology)|scales]]. Many species of snakes have [[skulls]] with many more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads with their [[cranial kinesis|highly mobile jaws]]. To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of the other instead of side by side, and most have only one functional [[lung]]. Some species retain a [[pelvic girdle]] with a pair of [[vestigial]] claws on either side of the [[cloaca]]. |
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Living snakes are found on every continent except Antarctica, in the Pacific and Indian Oceans, and on most smaller land masses — exceptions include some large islands, such as Ireland and New Zealand, and many small islands of the Atlantic and central Pacific.<ref name=Bauchot>{{cite book|editor=Roland Bauchot|title=Snakes: A Natural History|year=1994|publisher=Sterling Publishing Co., Inc.|location=New York|isbn=1-4027-3181-7|page=220}}</ref> More than 20 [[Family (biology)|families]] are currently recognized, comprising about 500 [[Genus|genera]] and about 3,400 [[species]].<ref name="ITIS">{{ITIS |id=174118 |taxon=Serpentes |accessdate=3 December 2008}}</ref><ref name="NRDB-Cs">[http://reptile-database.reptarium.cz/search.php?taxon=snake&submit=Search snake species list] at the [http://reptile-database.org/ Reptile Database]. Accessed 22 May 2012.</ref> They range in size from the tiny, 10 cm-long [[Leptotyphlops carlae|thread snake]] to the [[Python reticulatus|Reticulated python]] of up to {{convert|8.7|m|ft|sp=us}} in length.<ref name=Mur97>{{cite book|last=Murphy; Henderson|first=JC; RW|title=Tales of Giant Snakes: A Historical Natural History of Anacondas and Pythons|year=1997|publisher=Krieger Pub. Co|location=Florida, USA|isbn=0-89464-995-7|page=221}}</ref><ref name=Meh87>{{cite book|last=Mehrtens|first=JM|title=Living Snakes of the World in Color|year=1987|publisher=Sterling Publishers|location=New York|isbn=0-8069-6460-X|page=480}}</ref> The fossil species ''[[Titanoboa cerrejonensis]]'' was {{convert|15|m|ft|sp=us}} long. Snakes are thought to have evolved from either burrowing or aquatic lizards during the mid-[[Cretaceous]] period, and the earliest known fossils date to around 112 [[Mega-annum|Ma]] ago. The diversity of modern snakes appeared during the [[Paleocene]] period (''c'' 66 to 56 Ma ago). The oldest preserved descriptions of snakes can be found in the [[Brooklyn Papyrus]]. |
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Most species are nonvenomous and those that have venom use it primarily to kill and subdue prey rather than for self-defense. Some possess venom potent enough to cause painful injury or death to humans. Nonvenomous snakes either swallow prey alive or kill by [[constriction]]. |
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==Etymology== |
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The English word ''snake'' comes from [[Old English]] ''snaca'', itself from [[Proto-Germanic]] ''*snak-an-'' (cf. [[Germanic languages|Germanic]] ''Schnake'' "ring snake", Swedish ''snok'' "grass snake"), from [[Proto-Indo-European language|Proto-Indo-European]] root ''*(s)nēg-o-'' "to crawl", "to creep", which also gave ''sneak'' as well as [[Sanskrit]] ''nāgá'' "snake".<ref>Proto-IE: *(s)nēg-o-, Meaning: snake, Old Indian: nāgá- m. "snake", Germanic: *snēk-a- m., *snak-an- m., *snak-ō f.; *snak-a- vb., Russ. meaning: жаба (змея), References: WP ([[Indogermanisches etymologisches Wörterbuch|Vergleichendes Wörterbuch der indogermanischen Sprachen]]) II 697 f.</ref> The word ousted ''adder'', as ''adder'' went on to narrow in meaning, though in Old English ''næddre'' was the general word for snake.<ref>''Online Etymology Dictionary'', s.v. "[http://www.etymonline.com/index.php?term=snake snake]", retrieved on 22 September 2009.</ref> The other term, ''serpent'', is from French, ultimately from Indo-European ''*serp-'' (to creep),<ref name="serpent">{{cite web | work=Merriam-Webster Online Dictionary | title=Definition of serpent |url=http://www.merriam-webster.com/dictionary/serpent| accessdate=12 October 2006}}</ref> which also gave [[Ancient Greek]] '' érpo'' (ερπω) "I crawl". |
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==Evolution== |
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{{Cladogram|title=A phylogenetic overview of the extant groups |
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|clades={{clade|style=font-size:88.888888%;line-height:100% |
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|label1=Modern snakes |
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|1={{clade |
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|label1=[[Scolecophidia]] |
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|1={{clade |
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|1=[[Leptotyphlopidae]] |
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|label2= |
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|2={{clade |
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|1=[[Anomalepididae]] |
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|2=[[Typhlopidae]] |
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}} |
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}} |
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|label2=[[Alethinophidia]] |
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|2={{clade |
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|1=''[[Anilius]]'' |
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|label2=Core Alethinophidia |
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|2={{clade |
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|label1=[[Uropeltidae]] |
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|1={{clade |
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|1=''[[Cylindrophis]]'' |
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|label2= |
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|2={{clade |
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|1=''[[Anomochilus]]'' |
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|2=Uropeltinae |
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}} |
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}} |
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|label2=Macrostomata |
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|2={{clade |
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|label1=[[Pythonidae]] |
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|1={{clade |
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|1=[[Pythoninae]] |
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|2=''[[Xenopeltis]]'' |
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|3=''[[Loxocemus]]'' |
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}} |
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|label2=[[Caenophidia]] |
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|2={{clade |
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|1=[[Colubridae]] |
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|2=''[[Acrochordidae]]'' |
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|3=[[Atractaspididae]] |
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|4=[[Elapidae]] |
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|5=[[Hydrophiidae]] |
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|6=[[Viperidae]] |
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}} |
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|label3=[[Boidae]] |
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|3={{clade |
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|1=[[Erycinae]] |
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|2=[[Boinae]] |
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|3=''[[Calabaria]]'' |
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}} |
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|4=[[Ungaliophiinae]] |
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}} |
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|3=[[Tropidophiinae]] |
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}} |
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}} |
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}} |
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}} |
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|caption=Note: the tree only indicates relationships, not evolutionary branching times.''<ref name=Lee/> |
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}} |
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The fossil record of snakes is relatively poor because snake [[skeleton]]s are typically small and fragile, making [[fossilization]] uncommon. Fossils readily identifiable as snakes (though often retaining hind limbs) first appear in the fossil record during the [[Cretaceous]] period.<ref>Durand, J.F. (2004). "The origin of snakes". Geoscience Africa 2004. Abstract Volume, University of the Witwatersrand, Johannesburg, South Africa, pp. 187.</ref> The earliest known snake fossils come from sites in Utah and Algeria, represented by the genera ''[[Coniophis]]'' and ''[[Lapparentophis]]'', respectively. These fossil sites have been tentatively dated to the [[Albian]] or [[Cenomanian]] age of the late Cretaceous, between 112 and 94 [[Megaannum|Ma]] ago. However, an even greater age has been suggested for one of the Algerian sites, which may be as old as the [[Aptian]], 125 to 112 Ma ago.<ref name=timetree>Vidal, N., Rage, J.-C., Couloux, A. and Hedges, S.B. (2009). "Snakes (Serpentes)". Pp. 390-397 in Hedges, S. B. and Kumar, S. (eds.), ''The Timetree of Life''. Oxford University Press.</ref> |
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Based on [[comparative anatomy]], there is consensus that snakes descended from [[lizard]]s.<ref name="Meh87">Mehrtens JM. 1987. ''Living Snakes of the World in Color''. New York: Sterling Publishers. 480 pp. ISBN 0-8069-6460-X.</ref>{{Rp|11}}<ref name="Sanchez">{{cite web |last = Sanchez |first = Alejandro |title = Diapsids III: Snakes |work= Father Sanchez's Web Site of West Indian Natural History |url = http://www.kingsnake.com/westindian/metazoa12.html |accessdate = 2007-11-26 }} |
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</ref> [[Pythonidae|Python]]s and [[Boidae|boa]]s—primitive groups among modern snakes—have vestigial hind limbs: tiny, clawed digits known as [[anal spur]]s, which are used to grasp during mating.<ref name="Meh87"/>{{Rp|11}}<ref name="legs"/> The [[Leptotyphlopidae]] and [[Typhlopidae]] groups also possess remnants of the pelvic girdle, sometimes appearing as horny projections when visible. |
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Front limbs are nonexistent in all known snakes. This is caused by the evolution of [[Hox gene]]s, controlling limb [[morphogenesis]]. The axial skeleton of the snakes’ common ancestor, like most other tetrapods, had regional specializations consisting of cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvic), and caudal (tail) vertebrae. Early in snake evolution, the Hox gene expression in the axial skeleton responsible for the development of the thorax became dominant. As a result, the vertebrae anterior to the hindlimb buds (when present) all have the same thoracic-like identity (except from the [[Atlas (anatomy)|atlas]], [[Axis (anatomy)|axis]], and 1–3 neck vertebrae). In other words, most of a snake's skeleton is an extremely extended thorax. Ribs are found exclusively on the thoracic vertebrae. Neck, lumbar and pelvic vertebrae are very reduced in number (only 2–10 lumbar and pelvic vertebrae are present), while only a short tail remains of the caudal vertebrae. However, the tail is still long enough to be of important use in many species, and is modified in some aquatic and tree-dwelling species. |
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Modern snakes greatly diversified during the [[Paleocene]]. This occurred alongside the [[adaptive radiation]] of mammals, following the extinction of (non-avian) [[dinosaur]]s. The [[colubrids]], one of the more common snake groups, became particularly diverse due to preying on [[rodents]], an especially successful mammal group. |
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===Origins=== |
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The origin of snakes remains an unresolved issue. There are two main hypotheses competing for acceptance. |
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;Burrowing lizard hypothesis |
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There is fossil evidence to suggest that snakes may have evolved from burrowing lizards, such as the [[monitor lizard|varanids]] (or a similar group) during the [[Cretaceous|Cretaceous Period]].<ref name="EB">{{Cite journal |last =Mc Dowell |first =Samuel |title =The evolution of the tongue of snakes and its bearing on snake origins |journal =Evolutionary Biology |year =1972 |volume=6 |pages = 191–273 }}</ref> An early fossil snake, ''[[Najash rionegrina]]'', was a two-legged burrowing animal with a [[sacrum]], and was fully [[Terrestrial animal|terrestrial]].<ref name=najash> |
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{{cite journal | |year = 2006 |month = April |title = A Cretaceous terrestrial snake with robust hindlimbs and a sacrum |journal = Nature |volume = 440 |issue = 7087 |pages = 1037–1040 |doi = 10.1038/nature04413 |url = http://www.nature.com/nature/journal/v440/n7087/edsumm/e060420-11.html |accessdate = 2007-11-29 |pmid = 16625194 |last1 = Apesteguía |first1 = Sebastián |last2 = Zaher |first2 = Hussam }}</ref> One [[extant taxon|extant]] analog of these putative ancestors is the earless monitor ''[[Lanthanotidae|Lanthanotus]]'' of [[Borneo]] (though it also is semi[[Aquatic animal|aquatic]]).<ref name="M2">{{Cite journal |last =Mertens | first =Robert |title =Lanthanotus: an important lizard in evolution |journal =Sarawak Museum Journal |year =1961 |volume=10 |pages = 320–322 }}</ref> [[wikt:subterranean|Subterranean]] species evolved bodies streamlined for burrowing, and eventually lost their limbs.<ref name="M2"/> According to this hypothesis, features such as the [[Transparency (optics)|transparent]], fused eyelids ([[brille]]) and loss of external ears evolved to cope with [[fossorial]] difficulties, such as scratched [[cornea]]s and dirt in the ears.<ref name="EB"/><ref name="M2"/> Some primitive snakes are known to have possessed hindlimbs, but their pelvic bones lacked a direct connection to the vertebrae. These include fossil species like ''[[Haasiophis]]'', ''[[Pachyrhachis]]'' and ''[[Eupodophis]]'', which are slightly older than ''[[Najash]]''.<ref name="legs">{{cite web |title = New Fossil Snake With Legs |work = UNEP WCMC Database | publisher =American Association For The Advancement Of Science |location = Washington, D.C. |url =http://www.wildlifenews.co.uk/articles2000/march/march2500a.htm |accessdate =2007-11-29}} |
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</ref> |
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[[File:Naturkundemuseum Berlin - Archaeophis proavus Massalongo - Monte Bolca.jpg|thumb|left|Fossil of ''Archaeophis proavus''.]] |
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;Aquatic mosasaur hypothesis |
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An alternative hypothesis, based on [[Morphology (biology)|morphology]], suggests the ancestors of snakes were related to [[mosasaur]]s—extinct [[aquatic animal|aquatic]] reptiles from the [[Cretaceous]]—which in turn are thought to have derived from varanid lizards.<ref name="Sanchez"/> According to this hypothesis, the fused, transparent eyelids of snakes are thought to have evolved to combat marine conditions (corneal water loss through osmosis), and the external ears were lost through disuse in an aquatic environment. This ultimately lead to an animal similar to today's [[sea snake]]s. In the Late [[Cretaceous]], snakes recolonized land, and continued to diversify into today's snakes. Fossilized snake remains are known from early Late Cretaceous marine sediments, which is consistent with this hypothesis; particularly so, as they are older than the terrestrial ''Najash rionegrina''. Similar skull structure, reduced or absent limbs, and other anatomical features found in both mosasaurs and snakes lead to a positive [[Cladistics|cladistical]] correlation, although some of these features are shared with varanids. |
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Genetic studies in recent years have indicated snakes are not as closely related to monitor lizards as was once believed—and therefore not to mosasaurs, the proposed ancestor in the aquatic scenario of their evolution. However, more evidence links mosasaurs to snakes than to varanids. Fragmented remains found from the [[Jurassic]] and Early Cretaceous indicate deeper fossil records for these groups, which may potentially refute either hypothesis. |
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== Distribution == |
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[[File:World distribution of snakes.svg|thumb|Approximate world distribution of snakes.]] |
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There are over 2,900 species of snakes ranging as far northward as the Arctic Circle in Scandinavia and southward through Australia.<ref name="Sanchez"/> Snakes can be found on every continent except Antarctica, in the sea, and as high as 16,000 feet (4,900 m) in the [[Himalayan Mountains]] of Asia.<ref name="Sanchez"/><ref name="Con91">Conant R, Collins JT. 1991. ''A Field Guide to Reptiles and Amphibians: Eastern and Central North America''. Houghton Mifflin, Boston. 450 pp. 48 plates. ISBN 0-395-37022-1.</ref>{{Rp|143}} There are numerous islands from which snakes are absent, such as Ireland, [[Iceland]], and New Zealand<ref name=Bauchot/><ref name="Con91"/> (although New Zealand's waters are infrequently visited by the [[Pelamis platura|yellow-bellied sea snake]] and the [[Laticauda colubrina|banded sea krait]]).<ref name="AucklandMuseum">{{cite web |url=http://www.aucklandmuseum.com/349/natural-history-questions##2 |title=Natural History Questions |author=Natural History Information Centre, Auckland War Memorial Museum |work=Auckland War Memorial Museum {{pipe}} Tamaki Paenga Hira |publisher=[[Auckland War Memorial Museum]] |location=[[Auckland]], New Zealand |at=Q. Are there any snakes in New Zealand? |accessdate=26 April 2012}}</ref> |
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==Taxonomy== |
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All modern snakes are grouped within the [[Class (biology)|suborder]] '''Serpentes''' in [[Linnean taxonomy]], part of the [[class (biology)|order]] [[Squamata]], though their precise placement within squamates is controversial.<ref name="ITIS">{{ITIS |id=174118 |taxon=Serpentes |accessdate=20 August 2007}}</ref> |
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The two [[infraorder]]s of Serpentes are: [[Alethinophidia]] and [[Scolecophidia]].<ref name="ITIS"/> This separation is based on [[comparative anatomy|morphological]] characteristics and [[mitochondrial DNA]] sequence similarity. Alethinophidia is sometimes split into [[Henophidia]] and [[Caenophidia]], with the latter consisting of "colubroid" snakes (colubrids, vipers, elapids, hydrophiids, and attractaspids) and acrochordids, while the other alethinophidian families comprise Henophidia.<ref name="Pou92">{{cite book | author=Pough ''et al.'' |origyear=1992 |title= Herpetology: Third Edition |publisher= Pearson Prentice Hall |year=2002 |isbn=0-13-100849-8 }}</ref> While not extant today, the [[Madtsoiidae]], a family of giant, primitive, python-like snakes, was around until 50,000 years ago in Australia, represented by genera such as ''[[Wonambi]]''. |
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There are numerous debates in the systematics within the group. For instance, many sources classify [[Boidae]] and [[Pythonidae]] as one family, while some keep the [[Elapidae]] and [[Hydrophiidae]] (sea snakes) separate for practical reasons despite their extremely close relation. |
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Recent molecular studies support the [[monophyly]] of the clades of modern snakes, scolecophidians, typhlopids + anomalepidids, alethinophidians, core alethinophidians, uropeltids (''Cylindrophis'', ''Anomochilus'', uropeltines), macrostomatans, booids, boids, pythonids and caenophidians.<ref name=Lee>{{cite journal |first=Michael S. Y. |last=Lee |coauthors=Andrew F. Hugall, Robin Lawson & John D. Scanlon|title=Phylogeny of snakes (Serpentes): combining morphological and molecular data in likelihood, Bayesian and parsimony analyses |journal=Systematics and Biodiversity |volume=5 |issue=4 |pages=371–389 |doi=10.1017/S1477200007002290 |url=http://hdl.handle.net/2440/44258 |year=2007}}</ref> |
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===Families=== |
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{|cellspacing=0 cellpadding=2 border=1 style="border-collapse: collapse;" |
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|- |
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|colspan="100%" align="center" {{bgcolor-blue}}|Infraorder '''[[Alethinophidia]]''' 15 families |
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|- |
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! style="background:#f0f0f0;"|Family<ref name="ITIS"/> |
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! style="background:#f0f0f0;"|Taxon author<ref name="ITIS"/> |
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! style="background:#f0f0f0;"|Genera<ref name="ITIS"/> |
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! style="background:#f0f0f0;"|Species<ref name="ITIS"/> |
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! style="background:#f0f0f0;"|Common name |
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! style="background:#f0f0f0;"|Geographic range<ref name="McD99">McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).</ref> |
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|- |
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|[[Acrochordidae]] |
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|[[Charles Lucien Bonaparte|Bonaparte]], 1831 |
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| style="text-align:center;"|1 |
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| style="text-align:center;"|3 |
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|Wart snakes |
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|style="width:40%"|Western India and Sri Lanka through tropical Southeast Asia to the Philippines, south through the Indonesian/Malaysian island group to Timor, east through New Guinea to the northern coast of Australia to [[Mussau Island]], the [[Bismarck Archipelago]] and [[Guadalcanal Island]] in the Solomon Islands. |
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|- |
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|[[Aniliidae]] |
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|[[Leonhard Hess Stejneger|Stejneger]], 1907 |
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| style="text-align:center;"|1 |
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| style="text-align:center;"|1 |
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|False coral snake |
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|Tropical South America. |
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|- |
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|[[Anomochilidae]] |
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|Cundall, Wallach, 1993 |
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| style="text-align:center;"|1 |
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| style="text-align:center;"|2 |
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|Dwarf pipe snakes |
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|West Malaysia and on the Indonesian island of [[Sumatra]]. |
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|- |
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|[[Atractaspididae]] |
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|[[Albert C. L. G. Günther|Günther]], 1858 |
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| style="text-align:center;"|12 |
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| style="text-align:center;"|64 |
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|Burrowing asps |
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|Africa and the Middle East.<ref name="Meh87"/><ref name="SB95">Spawls S, Branch B. 1995. The Dangerous Snakes of Africa. Ralph Curtis Books. Dubai: Oriental Press. 192 pp. ISBN 0-88359-029-8.</ref><ref name="P&G77">Parker HW, Grandison AGC. 1977. Snakes -- a natural history. Second Edition. British Museum (Natural History) and Cornell University Press. 108 pp. 16 plates. LCCCN 76-54625. ISBN 0-8014-1095-9 (cloth), ISBN 0-8014-9164-9 (paper).</ref> |
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|- |
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|[[Boidae]] |
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|[[John Edward Gray|Gray]], 1825 |
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| style="text-align:center;"|8 |
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| style="text-align:center;"|43 |
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|Boas |
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|Northern, Central and South America, the Caribbean, southeastern Europe and Asia Minor, Northern, Central and East Africa, Madagascar and [[Reunion Island]], the Arabian Peninsula, Central and southwestern Asia, India and Sri Lanka, the [[Maluku Islands|Moluccas]] and New Guinea through to Melanesia and Samoa. |
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|- |
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|[[Bolyeriidae]] |
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|[[Robert Hoffstetter|Hoffstetter]], 1946 |
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| style="text-align:center;"|2 |
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| style="text-align:center;"|2 |
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|Splitjaw snakes |
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|[[Mauritius]]. |
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|- |
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|[[Colubridae]] |
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|[[Nicolaus Michael Oppel|Oppel]], 1811 |
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| style="text-align:center;"|304<ref name="NRDB-Cs"/> |
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| style="text-align:center;"|1938<ref name="NRDB-Cs"/> |
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|Typical snakes |
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|Widespread on all continents, except Antarctica.<ref name="Spa04">Spawls S, Howell K, Drewes R, Ashe J. 2004. A Field Guide To The Reptiles Of East Africa. London: A & C Black Publishers Ltd. 543 pp. ISBN 0-7136-6817-2.</ref> |
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|- |
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|[[Cylindrophiidae]] |
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|[[Leopold Fitzinger|Fitzinger]], 1843 |
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| style="text-align:center;"|1 |
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| style="text-align:center;"|8 |
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|Asian pipe snakes |
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|Sri Lanka east through Myanmar, Thailand, Cambodia, Vietnam and the Malay Archipelago to as far east as [[Aru Islands]] off the southwestern coast of New Guinea. Also found in southern China (Fujian, Hong Kong and on Hainan Island) and in Laos. |
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|- |
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|[[Elapidae]] |
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|[[Friedrich Boie|Boie]], 1827 |
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| style="text-align:center;"|61 |
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| style="text-align:center;"|235 |
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|Elapids |
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|On land, worldwide in tropical and subtropical regions, except in Europe. Sea snakes occur in the Indian Ocean and the Pacific.<ref name="NRDB-E">{{NRDB family |page=elapidae.php |family=Elapidae |date=3 December |year=2008}}</ref> |
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|- |
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|[[Loxocemidae]] |
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|[[Edward Drinker Cope|Cope]], 1861 |
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| style="text-align:center;"|1 |
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| style="text-align:center;"|1 |
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|Mexican burrowing snake |
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|Along the Pacific versant from Mexico south to Costa Rica. |
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|- |
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|[[Pythonidae]] |
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|[[Leopold Fitzinger|Fitzinger]], 1826 |
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| style="text-align:center;"|8 |
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| style="text-align:center;"|26 |
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|Pythons |
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|Subsaharan Africa, India, Myanmar, southern China, Southeast Asia and from the Philippines southeast through Indonesia to New Guinea and Australia. |
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|- |
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|[[Tropidophiidae]] |
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|[[L.D. Brongersma|Brongersma]], 1951 |
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| style="text-align:center;"|4 |
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| style="text-align:center;"|22 |
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|Dwarf boas |
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|From southern Mexico and Central America, south to northwestern South America in Colombia, ([[Amazon Basin|Amazonian]]) Ecuador and Peru, as well as in northwestern and southeastern Brazil. Also found in the West Indies. |
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|- |
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|[[Uropeltidae]] |
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|[[Johannes Peter Müller|Müller]], 1832 |
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| style="text-align:center;"|8 |
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| style="text-align:center;"|47 |
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|Shield-tailed snakes |
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|Southern India and Sri Lanka. |
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|- |
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|[[Viperidae]] |
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|[[Nicolaus Michael Oppel|Oppel]], 1811 |
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| style="text-align:center;"|32 |
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| style="text-align:center;"|224 |
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|Vipers |
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|The Americas, Africa and Eurasia. |
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|- |
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|[[Xenopeltidae]] |
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|[[Charles Lucien Bonaparte|Bonaparte]], 1845 |
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| style="text-align:center;"|1 |
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| style="text-align:center;"|2 |
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|Sunbeam snakes |
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|Southeast Asia from the [[Andaman Islands|Andaman]] and [[Nicobar Islands]], east through Myanmar to southern China, Thailand, Laos, Cambodia, Vietnam, the Malay Peninsula and the East Indies to [[Sulawesi]], as well as the Philippines. |
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|} |
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<br /> |
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{|cellspacing=0 cellpadding=2 border=1 style="border-collapse: collapse;" |
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|- |
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|colspan="100%" align="center" {{bgcolor-blue}}|Infraorder '''[[Scolecophidia]]''' 3 families |
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|- |
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! style="background:#f0f0f0;"|Family<ref name="ITIS"/> |
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! style="background:#f0f0f0;"|Taxon author<ref name="ITIS"/> |
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! style="background:#f0f0f0;"|Genera<ref name="ITIS"/> |
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! style="background:#f0f0f0;"|Species<ref name="ITIS"/> |
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! style="background:#f0f0f0;"|Common name |
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! style="background:#f0f0f0;"|Geographic range<ref name="McD99"/> |
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|- |
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|[[Anomalepidae]] |
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|[[Edward Harrison Taylor|Taylor]], 1939 |
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| style="text-align:center;"|4 |
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| style="text-align:center;"|15 |
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|Primitive blind snakes |
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|style="width:40%"|From southern Central America to northwestern South America. Disjunct populations in northeastern and southeastern South America. |
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|- |
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|[[Leptotyphlopidae]] |
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|[[Leonhard Hess Stejneger|Stejneger]], 1892 |
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| style="text-align:center;"|2 |
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| style="text-align:center;"|87 |
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|Slender blind snakes |
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|Africa, western Asia from Turkey to northwestern India, on [[Socotra Island]], from the southwestern United States south through Mexico and Central to South America, though not in the high [[Andes]]. In Pacific South America they occur as far south as southern coastal Peru, and on the Atlantic side as far as Uruguay and Argentina. In the Caribbean they are found on the Bahamas, [[Hispaniola]] and the [[Lesser Antilles]]. |
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|- |
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|[[Typhlopidae]] |
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|[[Blasius Merrem|Merrem]], 1820 |
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| style="text-align:center;"|6 |
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| style="text-align:center;"|203 |
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|Typical blind snakes |
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|Most tropical and many subtropical regions around the world, particularly in Africa, Madagascar, Asia, islands in the Pacific, tropical America and in southeastern Europe. |
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|} |
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==Biology== |
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[[File:Leptotyphlops carlae.jpg|thumb|right|An adult Barbados threadsnake, ''[[Leptotyphlops carlae]]'', on an [[Quarter (United States coin)|American quarter dollar]].]] |
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===Size=== |
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The now [[extinct]] ''[[Titanoboa|Titanoboa cerrejonensis]]'' snakes found were {{convert|12|–|15|m|ft|abbr=on}} in length. By comparison, the largest [[Extant taxon|extant]] snakes are the [[Python reticulatus|reticulated python]], which measures about {{convert|9|m|0|abbr=on}} long, and the [[Eunectes murinus|anaconda]], which measures about {{convert|7.5|m|0|abbr=on}} long<ref name="CTV">{{cite web|url=http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/20090204/snake_biggest_090204/20090204?hub=SciTech |title=CTV: Ancient, gargantuan snakes ate crocs for breakfast |publisher=Ctv.ca |date= |accessdate=2013-03-08}}</ref> and is considered the heaviest snake on Earth. |
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At the other end of the scale, the smallest [[Extant taxon|extant]] snake is ''[[Leptotyphlops carlae]]'', with a length of about {{convert|10|cm|in|0|abbr=on}}.<ref>{{cite journal |url=http://www.mapress.com/zootaxa/2008/f/zt01841p030.pdf |title=At the lower size limit in snakes: two new species of threadsnakes (Squamata: Leptotyphlopidae: Leptotyphlops) from the Lesser Antilles |author=S. Blair Hedges |journal=[[Zootaxa]] |volume=1841 |pages=1–30 |date=August 4, 2008 |accessdate=2008-08-04 |format=PDF}}</ref> Most snakes are fairly small animals, approximately 1 m (3 ft) in length.<ref>{{cite doi|10.1554/0014-3820(2003)057[0345:EEFAOB]2.0.CO;2}}</ref> |
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===Perception=== |
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;Smell |
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: Snakes use smell to track their prey. They smell by using their [[forked tongue]]s to collect airborne particles, then passing them to the [[vomeronasal organ]] or ''Jacobson's organ'' in the mouth for examination.<ref name="Cogger91_180">Cogger(1991), p. 180.</ref> The fork in the tongue gives snakes a sort of directional sense of smell and taste simultaneously.<ref name="Cogger91_180"/> They keep their tongues constantly in motion, sampling particles from the air, ground, and water, analyzing the chemicals found, and determining the presence of prey or predators in the local environment. In water-dwelling snakes, such as the [[Anaconda]], the tongue functions efficiently under water.<ref name="Cogger91_180"/> |
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;Eyesight |
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: Snake vision varies greatly, from only being able to distinguish light from dark to keen eyesight, but the main trend is that their vision is adequate although not sharp, and allows them to track movements.<ref>[http://www.petplace.com/reptiles/reptile-senses-understanding-their-world/page1.aspx "Reptile Senses: Understanding Their World"].</ref> Generally, vision is best in arboreal snakes and weakest in burrowing snakes. Some snakes, such as the Asian vine snake (genus ''[[Ahaetulla]]''), have [[binocular vision]], with both eyes capable of focusing on the same point. Most snakes focus by moving the [[Lens (anatomy)|lens]] back and forth in relation to the [[retina]], while in the other [[amniote]] groups, the lens is stretched.<br />[[File:wiki snake eats mouse.jpg|thumb|right|Thermographic image of a snake eating a mouse]] |
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;Infrared sensitivity |
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: Pit vipers, pythons, and some boas have [[infrared sensing in snakes|infrared-sensitive receptors]] in deep grooves on the snout, which allow them to "see" the radiated heat of warm-blooded prey mammals. In pit vipers the grooves are located between the nostril and the eye, in a large "pit" on each side of the head. Other infrared-sensitive snakes have multiple, smaller labial pits lining the upper lip, just below the nostrils.<ref name="Cogger91_180"/> |
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;Vibration sensitivity |
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: The part of the body in direct contact with the ground is very sensitive to vibration; thus, a snake can sense other animals approaching by detecting faint vibrations in the air and on the ground.<ref name="Cogger91_180"/> |
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[[File:Ptyas gab fbi.png|thumb|right|A line diagram from [[G.A. Boulenger]]'s [[Fauna of British India]] (1890) illustrating the terminology of shields on the head of a snake.]] |
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===Skin=== |
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{{main|Snake scales}} |
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The skin of a snake is covered in [[Snake scales|scales]]. Contrary to the popular notion of snakes being slimy because of possible confusion of snakes with [[worm]]s, snakeskin has a smooth, dry texture. Most snakes use specialized belly scales to travel, gripping surfaces. The body scales may be smooth, [[keeled scales|keeled]], or granular. The eyelids of a snake are transparent "spectacle" scales, which remain permanently closed, also known as [[brille]]. |
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The shedding of scales is called ''[[ecdysis]]'' (or in normal usage, ''[[molt]]ing'' or ''sloughing''). In the case of snakes, the complete outer layer of skin is shed in one layer.<ref name = "Smith1_30">Smith, Malcolm A. ''[[The Fauna of British India, Including Ceylon and Burma]]''. Vol I, Loricata and Testudines. p. 30.</ref> Snake scales are not discrete, but extensions of the epidermis—hence they are not shed separately but as a complete outer layer during each [[molt]], akin to a sock being turned inside out.<ref name="RSSlimy">[http://www.szgdocent.org/resource/rr/c-slimy.htm Are snakes slimy?] at [http://www.szgdocent.org/ Singapore Zoological Garden's Docent]. Accessed 14 August 2006.</ref> |
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The shape and number of scales on the head, back, and belly are often characteristic and used for taxonomic purposes. Scales are named mainly according to their positions on the body. In "advanced" ([[Caenophidia]]n) snakes, the broad belly scales and rows of [[dorsal scale]]s correspond to the [[vertebra]]e, allowing scientists to count the vertebrae without [[dissection]]. |
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[[File:Diamond-python moult eye-scales.JPG|thumb|right|Eye scales visible during the [[molt]] of a [[Diamond Python]].]] |
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Snakes' eyes are covered by their clear scales (the brille) rather than movable [[eyelids]]. Their eyes are always open, and for sleeping, the [[retina]] can be closed or the face buried among the folds of the body. |
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====Moulting==== |
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[[Moulting]] serves a number of functions. Firstly, the old and worn skin is replaced; secondly, it helps get rid of parasites such as mites and ticks. Renewal of the skin by moulting is supposed to allow growth in some animals such as insects; however, this has been disputed in the case of snakes.<ref name="RSSlimy"/><ref name="ZooPax3">[http://whozoo.org/ZooPax/ZPScales_3.htm Part III: Scales of Lizards and Snakes] at [http://whozoo.org/ WhoZoo]. Accessed 4 December 2008.</ref> |
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[[File:Nerodia sipedon shedding.JPG|thumb|left|A snake shedding its skin.]] |
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Molting occurs periodically throughout the snake's life. Before a molt, the snake stops eating and often hides or moves to a safe place. Just before shedding, the skin becomes dull and dry looking and the eyes become cloudy or blue-colored. The inner surface of the old skin liquefies. This causes the old skin to separate from the new skin beneath it. After a few days, the eyes clear and the snake "crawls" out of its old skin. The old skin breaks near the mouth and the snake wriggles out, aided by rubbing against rough surfaces. In many cases, the cast skin peels backward over the body from head to tail in one piece, like pulling a sock off inside-out. A new, larger, brighter layer of skin has formed underneath.<ref name="RSSlimy"/><ref name="GenSnakeInfo">[http://www.sdgfp.info/Wildlife/Snakes/SnakeInfo.htm General Snake Information] at [http://www.sdgfp.info/ South Dakota Game, Fish and Parks]. Accessed 4 December 2008.</ref> |
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An older snake may shed its skin only once or twice a year. But a younger snake, still growing, may shed up to four times a year.<ref name = "GenSnakeInfo"/> The discarded skin gives a perfect imprint of the scale pattern, and it is usually possible to identify the snake if the discarded skin is reasonably intact.<ref name="RSSlimy"/> This periodic renewal has led to the snake being a symbol of [[healing]] and [[medicine]], as pictured in the [[Rod of Asclepius]].<ref name=AIM>{{cite journal|last=Wilcox|first=Robert A|last2=Whitham|first2= Emma M|title=The symbol of modern medicine: why one snake is more than two|date=15 April 2003|pages=673–7|issue=8|volume=138 |
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|url=http://www.annals.org/cgi/content/full/138/8/673|journal=Annals of Internal Medicine|accessdate=2007-11-26 | pmid = 12693891}}</ref> |
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<!-- |
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Scale counts can sometimes be used to tell the sex of a snake when the species is not distinctly sexually dimorphic. A probe is inserted into the [[cloaca]] until it can go no further. The probe is marked at the point where it stops, removed, and compared to the subcaudal depth by laying it alongside the scales.<ref name="Rosenfeld_11"> Rosenfeld (1989), p. 11.</ref> The scalation count determines whether the snake is a male or female as hemipenes of a male will probe to a different depth (usually longer) than the cloaca of a female.<ref name="Rosenfeld_11"/>!!-- can this be clarified, is it really scale counts or are the scales merely used to measure the probe penetration ? |
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--> |
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===Skeleton=== |
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[[File:Snake Skeletons.jpg|thumb|left|When compared, the skeletons of snakes are radically different from those of most other reptiles (such as the [[turtle]], right), being made up almost entirely of an extended ribcage.]] |
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The [[snake skeleton|skeleton]] of most snakes consists solely of the skull, hyoid, vertebral column, and ribs, though henophidian snakes retain vestiges of the pelvis and rear limbs. |
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The [[snake skull|skull of the snake]] consists of a solid and complete braincase, to which many of the other bones are only loosely attached, particularly the highly mobile jaw bones, which facilitate manipulation and ingestion of large prey items. The left and right sides of the lower jaw are joined only by a flexible ligament at the anterior tips, allowing them to separate widely, while the posterior end of the lower jaw bones articulate with a quadrate bone, allowing further mobility. The bones of the mandible and quadrate bones can also pick up ground borne vibrations.<ref>{{cite journal | last1 = Harline | first1 = P H | year = 1971 | title = Physiological basis for detection of sound and vibration in snakes | url = http://jeb.biologists.org/cgi/reprint/54/2/349.pdf | format = PDF | journal = J. Exp. Biol. | volume = 54 | issue = 2| pages = 349–371 }}</ref> Because the sides of the jaw can move independently of one another, snakes resting their jaws on a surface have sensitive stereo hearing which can detect the position of prey. The jaw-quadrate-stapes pathway is capable of detecting vibrations on the [[angstrom]] scale, despite the absence of an outer ear and the [[ossicle]] mechanism of [[impedance matching]] used in other vertebrates to receive vibrations from the air.<ref>{{cite journal|url=http://prl.aps.org/abstract/PRL/v100/i4/e048701|title=Auditory Localization of Ground-Borne Vibrations in Snakes|journal=Phys. Rev. Lett.|volume=100|page=048701|year=2008}}</ref><ref>{{cite web|url=http://www.physorg.com/news122123444.html|title=Desert Snake Hears Mouse Footsteps with its Jaw|date=2008-02-13|author=Lisa Zyga|publisher=PhysOrg}}</ref> |
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The hyoid is a small bone located posterior and ventral to the skull, in the 'neck' region, which serves as an attachment for muscles of the snake's tongue, as it does in all other [[tetrapod]]s. |
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The vertebral column consists of anywhere between 200 to 400 (or more) vertebrae. Tail vertebrae are comparatively few in number (often less than 20% of the total) and lack ribs, while body vertebrae each have two ribs articulating with them. The vertebrae have projections that allow for strong muscle attachment enabling locomotion without limbs. |
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[[Autotomy]] of the tail, a feature found in some lizards is absent in most snakes.<ref>Cogger, H 1993 Fauna of Australia. Vol. 2A Amphibia and Reptilia. Australian Biological Resources Studies, Canberra.</ref> Caudal autotomy in snakes is rare and is intervertebral, unlike that in lizards, which is intravertebral—that is, the break happens along a predefined fracture plane present on a vertebra.<ref>{{cite journal | last1=Arnold | first1=E.N. | doi=10.1080/00222938400770131 | title=Evolutionary aspects of tail shedding in lizards and their relatives | journal=Journal of Natural History | year=1984 | volume=18 | issue=1 | pages=127–169 }}</ref><ref>N. B. Ananjeva and N. L. Orlov (1994) Caudal autotomy in Colubrid snake ''[[Xenochrophis piscator]]'' from Vietnam. Russian Journal of Herpetology 1(2)</ref> |
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In some snakes, most notably [[Boidae|boa]]s and [[Pythonidae|python]]s, there are vestiges of the hindlimbs in the form of a pair of [[pelvic spur]]s. These small, claw-like protrusions on each side of the [[cloaca]] are the external portion of the vestigial hindlimb skeleton, which includes the remains of an ilium and femur. |
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===Internal organs=== |
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{{snake anatomy imagemap}} |
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The snake's heart is encased in a sac, called the ''[[pericardium]]'', located at the [[:wiktionary:bifurcation|bifurcation]] of the [[bronchi]]. The heart is able to move around, however, owing to the lack of a diaphragm. This adjustment protects the heart from potential damage when large ingested prey is passed through the esophagus. The [[spleen]] is attached to the [[gall bladder]] and [[pancreas]] and filters the blood. The [[thymus gland]] is located in fatty tissue above the heart and is responsible for the generation of immune cells in the blood. The cardiovascular system of snakes is also unique for the presence of a renal portal system in which the blood from the snake's tail passes through the kidneys before returning to the heart.<ref name="Mader"/> |
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The [[vestige|vestigial]] left [[lung]] is often small or sometimes even absent, as snakes' tubular bodies require all of their organs to be long and thin.<ref name="Mader">{{Cite journal |
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| last = Mader |
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| first = Douglas |
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| title = Reptilian Anatomy |
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| journal = Reptiles |
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| volume =3 |
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| issue =2 |
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| pages =84–93 |
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| date = June 1995 |
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}}</ref> In the majority of species, only one [[lung]] is functional. This lung contains a vascularized anterior portion and a posterior portion that does not function in gas exchange.<ref name="Mader"/> This 'saccular lung' is used for [[hydrostatic]] purposes to adjust buoyancy in some aquatic snakes and its function remains unknown in terrestrial species.<ref name="Mader"/> Many organs that are paired, such as [[kidneys]] or [[reproductive organs]], are staggered within the body, with one located ahead of the other.<ref name="Mader"/> |
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Snakes have no [[lymph node]]s.<ref name="Mader"/> |
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===Venom=== |
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{{see also|Snake venom|Venomous snake|#Bite}} |
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[[File:Red milk snake.JPG|thumb|[[Milk snake]]s are often mistaken for [[coral snake]]s, whose venom is deadly to humans.]] |
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Cobras, vipers, and closely related species use [[venom]] to immobilize or kill their prey. The venom is modified [[saliva]], delivered through [[snake venom|fangs]].<ref name="Meh87"/>{{Rp|243}} The fangs of 'advanced' venomous snakes like viperids and elapids are hollow to inject venom more effectively, while the fangs of [[Snake skeleton#Opisthoglyph|rear-fanged]] snakes such as the [[boomslang]] merely have a groove on the posterior edge to channel venom into the wound. Snake venoms are often prey specific—their role in self-defense is secondary.<ref name="Meh87"/>{{Rp|243}} |
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Venom, like all salivary secretions, is a predigestant that initiates the breakdown of food into soluble compounds, facilitating proper digestion. Even nonvenomous snake bites (like any animal bite) will cause tissue damage.<ref name="Meh87"/>{{Rp|209}} |
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Certain birds, mammals, and other snakes (such as [[kingsnake]]s) that prey on venomous snakes have developed resistance and even immunity to certain venoms.<ref name="Meh87"/>{{Rp|243}} Venomous snakes include three [[family (biology)|families]] of snakes, and do not constitute a formal [[taxonomic classification|classification]] group used in [[Taxonomy (biology)|taxonomy]]. |
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The term '''poisonous snake''' is mostly incorrect. Poison is inhaled or ingested, whereas venom is injected.<ref name="Freiberg84_125"/> There are, however, two exceptions: ''[[Rhabdophis]]'' sequesters toxins from the toads it eats, then secretes them from nuchal glands to ward off predators, and a small population of [[garter snakes]] in Oregon retains enough toxin in their liver from the newts they eat to be effectively poisonous to small local predators (such as crows and foxes).<ref name="Freiberg84_123">Freiberg (1984), p. 123.</ref> |
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Snake venoms are complex mixtures of [[protein]]s, and are stored in poison glands at the back of the head.<ref name="Freiberg84_123"/> In all venomous snakes, these glands open through ducts into grooved or hollow teeth in the upper jaw.<ref name="Meh87"/>{{Rp|243}}<ref name="Freiberg84_125">Freiberg (1984), p. 125.</ref> These proteins can potentially be a mix of [[neurotoxin]]s (which attack the nervous system), [[hemotoxin]]s (which attack the circulatory system), [[cytotoxin]]s, [[bungarotoxin]]s and many other toxins that affect the body in different ways.<ref name="Freiberg84_125"/> Almost all snake venom contains ''[[hyaluronidase]]'', an enzyme that ensures rapid diffusion of the venom.<ref name="Meh87"/>{{Rp|243}} |
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Venomous snakes that use hemotoxins usually have fangs in the front of their mouths, making it easier for them to inject the venom into their victims.<ref name="Freiberg84_125"/> Some snakes that use neurotoxins (such as the [[Boiga dendrophila|mangrove snake]]) have fangs in the back of their mouths, with the fangs curled backwards.<ref name="Freiberg84_126">Freiberg (1984), p. 126.</ref> This makes it difficult both for the snake to use its venom and for scientists to milk them.<ref name="Freiberg84_125"/> ''[[Elapid]]s'', however, such as [[cobra]]s and [[krait]]s are ''[[proteroglyphous]]''—they possess hollow fangs that cannot be erected toward the front of their mouths, and cannot "stab" like a viper. They must actually bite the victim.<ref name="Meh87"/>{{Rp|242}} |
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It has recently been suggested that all snakes may be venomous to a certain degree, with harmless snakes having weak venom and no fangs.<ref name="Fry_2006_earlyevolution">{{Cite journal |last1 = Fry |first1 = Brian G |last2 = Vidal |first2 = Nicholas |last3 = Norman |first3 = Janette A. |last4 = Vonk |first4 = Freek J. |last5 = Scheib |first5 = Holger |last6 = Ramjan |first6 = Ryan |last7 = Kuruppu |first7 = Sanjaya |title = Early evolution of the venom system in lizards and snakes |journal = Nature (Letters) |volume = 439 |pages = 584–588 |year = 2006 |doi = 10.1038/nature04328 |pmid = 16292255 |last8 = Fung |first8 = K |last9 = Hedges |first9 = SB |issue = 7076 }}</ref> Most snakes currently labelled "nonvenomous" would still be considered harmless according to this theory, as they either lack a venom delivery method or are incapable of delivering enough to endanger a human. This theory postulates that snakes may have evolved from a common lizard ancestor that was venomous—and that venomous lizards like the [[gila monster]], [[beaded lizard]], [[monitor lizards]], and the now-extinct [[mosasaurs]] may also have derived. They share this [[venom clade]] with various other [[sauria]]n species. |
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Venomous snakes are classified in two [[Taxonomy (biology)|taxonomic]] [[family (biology)|families]]: |
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*'''[[Elapid]]s''' – [[cobra]]s including [[king cobra]]s, [[Bungarus|kraits]], [[mamba]]s, [[Austrelaps|Australian copperheads]], [[sea snake]]s, and [[coral snake]]s.<ref name="Freiberg84_126"/> |
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*'''[[Viperidae|Viperids]]''' – [[Viperidae|vipers]], [[rattlesnake]]s, [[Agkistrodon contortrix|copperheads]]/[[Agkistrodon piscivorus|cottonmouths]], and [[Lachesis (genus)|bushmasters]].<ref name="Freiberg84_126"/> |
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There is a third family containing the ''opistoglyphous'' (rear-fanged) snakes (as well as the majority of other snake species): |
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*'''[[Colubrid]]s''' – [[boomslang]]s, tree snakes, [[Ahaetulla|vine snakes]], [[boiga|mangrove snakes]], although not all [[colubrid]]s are [[venomous]].<ref name="Meh87"/>{{Rp|209}}<ref name="Freiberg84_126"/> |
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===Reproduction=== |
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Although a wide range of reproductive modes are used by snakes, all snakes employ [[internal fertilization]]. This is accomplished by means of paired, forked [[hemipenis|hemipenes]], which are stored, inverted, in the male's tail.<ref name="Capula89_117">Capula (1989), p. 117.</ref> The hemipenes are often grooved, hooked, or spined in order to grip the walls of the female's [[cloaca]].<ref name="Capula89_117"/> |
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Most species of snakes lay [[egg (biology)|eggs]], but most snakes abandon the eggs shortly after laying. However, a few species (such as the [[king cobra]]) actually construct nests and stay in the vicinity of the hatchlings after incubation.<ref name="Capula89_117"/> Most [[Pythonidae|python]]s coil around their egg-clutches and remain with them until they hatch.<ref name="Cogger91_186">Cogger (1991), p. 186.</ref> A female python will not leave the eggs, except to occasionally bask in the sun or drink water. She will even "shiver" to generate heat to incubate the eggs.<ref name="Cogger91_186"/> |
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Some species of snake are [[Ovoviviparity|ovoviviparous]] and retain the eggs within their bodies until they are almost ready to hatch.<ref name="Capula89_118">Capula (1989), p. 118.</ref><ref name="Cogger91_182">Cogger (1991), p. 182.</ref> Recently, it has been confirmed that several species of snake are fully [[Vivipary|viviparous]], such as the [[boa constrictor]] and [[Eunectes murinus|green anaconda]], nourishing their young through a [[placenta]] as well as a [[yolk sac]], which is highly unusual among reptiles, or anything else outside of [[requiem sharks]] or [[placental mammals]].<ref name="Capula89_118"/><ref name="Cogger91_182"/> Retention of eggs and live birth are most often associated with colder environments.<ref name="Capula89_117"/><ref name="Cogger91_182"/> |
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==Behavior== |
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===Winter dormancy=== |
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In regions where winters are colder than snakes can tolerate while remaining active, local species will [[Dormancy|brumate]]. Unlike hibernation, in which mammals are actually asleep, brumating reptiles are awake but inactive. Individual snakes may brumate in burrows, under rock piles, or inside fallen trees, or snakes may aggregate in large numbers at hibernacula, large dens which are used year after year for brumation. |
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===Feeding and diet=== |
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[[File:Snake eating mouse.jpg|thumb|left|Snake eating a [[rodent]].]] |
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[[File:Carpet snake.jpg|thumb|upright|[[Carpet python]] constricting and consuming a [[chicken]].]] |
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[[File:Eierschlange frisst Zwergwachtelei.jpg|thumb|upright|[[Dasypeltis|African egg-eating snake]].]] |
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All snakes are [[hypercarnivore|strictly carnivorous]], eating small animals including lizards, other snakes, small mammals, birds, [[egg (biology)|eggs]], fish, snails or insects.<ref name="Meh87"/>{{Ref|81}}<ref name="Sanchez"/><ref name="Bebler79_581">Behler (1979) p. 581.</ref> Because snakes cannot bite or tear their food to pieces, they must swallow prey whole. The body size of a snake has a major influence on its eating habits. Smaller snakes eat smaller prey. Juvenile pythons might start out feeding on lizards or mice and graduate to small deer or antelope as an adult, for example. |
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The snake's [[jaw]] is a complex structure. Contrary to the popular belief that snakes can dislocate their jaws, snakes have a very flexible [[mandible|lower jaw]], the two halves of which are not rigidly attached, and numerous other joints in their [[skull]] (see [[snake skull]]), allowing them to open their mouths wide enough to swallow their prey whole, even if it is larger in diameter than the snake itself.<ref name="Bebler79_581">Bebler (1979) p. 581.</ref> For example, the [[Dasypeltis|African egg-eating snake]] has flexible jaws adapted for eating eggs much larger than the diameter of its head.<ref name="Meh87"/>{{Rp|81}} This snake has no teeth, but does have bony protrusions on the inside edge of its [[Vertebral column|spine]], which it uses to break shells when it eats eggs.<ref name="Meh87"/>{{Rp|81}} |
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While the majority of snakes eat a variety of prey animals, there is some specialization by some species. [[King cobra]]s and the Australian [[Vermicella annulata|bandy-bandy]] consume other snakes. ''Pareas iwesakii'' and other [[snail]]-eating [[colubrid]]s of subfamily [[Pareatinae]] have more teeth on the right side of their mouths than on the left, as the shells of their prey usually spiral clockwise<ref name="Meh87"/>{{Rp|184}}<ref>{{cite journal | last1 = Hori | first1 = Michio | last2 = Asami | first2 = Takahiro | last3 = Hoso | first3 = Masaki | title = Right-handed snakes: convergent evolution of asymmetry for functional specialization | doi = 10.1098/rsbl.2006.0600 | pmc = 2375934 | pmid = 17307721 | journal = Biology Letters | year = 2007 | volume = 3 | issue = 2 | pages=169–72 }}</ref> |
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Some snakes have a venomous bite, which they use to kill their prey before eating it.<ref name="Bebler79_581"/><ref>Freiberg (1984), pp. 125–127.</ref> Other snakes kill their prey by [[constriction]].<ref name="Bebler79_581"/> Still others swallow their prey whole and alive.<ref name="Meh87"/>{{Rp|81}}<ref name="Bebler79_581"/> |
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After eating, snakes become dormant while the process of [[digestion]] takes place.<ref name="Rosenfeld_11">Rosenfeld (1989), p. 11.</ref> Digestion is an intense activity, especially after consumption of large prey. In species that feed only sporadically, the entire [[intestine]] enters a reduced state between meals to conserve energy. The digestive system is then 'up-regulated' to full capacity within 48 hours of prey consumption. Being [[ectothermic]] ("cold-blooded"), the surrounding temperature plays a large role in snake digestion. The ideal temperature for snakes to digest is {{convert|30|°C|°F}}. So much [[metabolism|metabolic]] energy is involved in a snake's digestion that in the Mexican rattlesnake (''[[Crotalus durissus]]''), surface body temperature increases by as much as {{convert|1.2|C-change|sigfig=2}} during the digestive process.<ref>{{cite journal |
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| year = 2004 |
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| last1 = Tattersall |
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| url =http://jeb.biologists.org/cgi/content/abstract/207/4/579 |
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| first1 = GJ |
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| last2 = Milsom |
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| first2 = WK |
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| last3 = Abe |
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| first3 = AS |
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| last4 = Brito |
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| first4 = SP |
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| last5 = Andrade |
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| first5 = DV |
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| title =The thermogenesis of digestion in rattlesnakes |
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| journal =Journal of Experimental Biology |
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| volume=207 |
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| pmid = 14718501 |
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| issue = Pt 4 |
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| pages =579–585 |
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| publisher =The Company of Biologists |
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| accessdate =2006-05-26 |
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| doi = 10.1242/jeb.00790 |
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}}</ref> Because of this, a snake disturbed after having eaten recently will often [[vomiting|regurgitate]] its prey to be able to escape the perceived threat. When undisturbed, the digestive process is highly efficient, with the snake's digestive [[enzymes]] dissolving and absorbing everything but the prey's hair (or [[feather]]s) and [[claws]], which are excreted along with [[uric acid|waste]]. |
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===Locomotion=== |
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The lack of limbs does not impede the movement of snakes. They have developed several different modes of locomotion to deal with particular environments. Unlike the gaits of limbed animals, which form a continuum, each mode of snake locomotion is discrete and distinct from the others; transitions between modes are abrupt.<ref name="Cogger91_175">Cogger(1991), p. 175.</ref><ref name = "Gray">{{Cite journal |
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| last = Gray |
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| first = J. |
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| title = The mechanism of locomotion in snakes |
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| journal = Journal of experimental biology |
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| year = 1946 |
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| volume = 23 |
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| issue = 2 |
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| pages= 101–120 |
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| pmid = 20281580 }}</ref> |
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====Lateral undulation==== |
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{{main|Undulatory locomotion}} |
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Lateral undulation is the sole mode of aquatic locomotion, and the most common mode of terrestrial locomotion.<ref name = "Gray"/> In this mode, the body of the snake alternately flexes to the left and right, resulting in a series of rearward-moving "waves".<ref name="Cogger91_175"/> While this movement appears rapid, snakes have rarely been documented moving faster than two body-lengths per second, often much less.<ref name = "Hekrotte">{{Cite journal |
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| last = Hekrotte |
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| first = Carlton |
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| title = Relations of Body Temperature, Size, and Crawling Speed of the Common Garter Snake, Thamnophis s. sirtalis |
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| journal = Copeia |
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| year = 1967 |
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| volume = 23 |
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| issue = 4 |
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| pages= 759–763 |
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| doi = 10.2307/1441886 |
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| jstor = 1441886 |
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}}</ref> This mode of movement has the same net cost of transport (calories burned per meter moved) as running in lizards of the same mass.<ref name = "Walton">{{Cite journal |
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| last1 = Walton |
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| first1 = M. |
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| last2 = Jayne |
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| first2 = B. C. |
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| last3 = Bennett |
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| first3 = A. F. |
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| title = The energetic cost of limbless locomotion |
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| journal = Science |
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| year = 1967 |
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| volume = 249 |
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| issue = 4968 |
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| pages= 524–527 |
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| doi = 10.1126/science.249.4968.524 |
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| pmid = 17735283 }}</ref> |
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=====Terrestrial===== |
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Terrestrial lateral undulation is the most common mode of terrestrial locomotion for most snake species.<ref name="Cogger91_175"/> In this mode, the posteriorly moving waves push against contact points in the environment, such as rocks, twigs, irregularities in the soil, etc.<ref name="Cogger91_175"/> Each of these environmental objects, in turn, generates a reaction force directed forward and towards the midline of the snake, resulting in forward thrust while the lateral components cancel out.<ref name = "Gray_lissman"/> The speed of this movement depends upon the density of push-points in the environment, with a medium density of about 8 along the snake's length being ideal.<ref name = "Hekrotte"/> The wave speed is precisely the same as the snake speed, and as a result, every point on the snake's body follows the path of the point ahead of it, allowing snakes to move through very dense vegetation and small openings.<ref name = "Gray_lissman">{{Cite journal |
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| last = Gray |
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| first = J |
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| last2 = H.W. |
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| first2 = H |
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| title = Kinetics of locomotion of the grass snake |
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| journal = Journal of Experimental Biology |
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| year = 1950 |
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| volume = 26 |
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| issue = 4 |
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| pages= 354–367 |
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| url = http://jeb.biologists.org/cgi/content/abstract/26/4/354}}</ref> |
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=====Aquatic===== |
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{{main|Sea snake}} |
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[[File:Banded Sea Snake-jonhanson.jpg|thumb|Banded sea krait, ''[[Laticauda|Laticauda sp]]''.]] |
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When swimming, the waves become larger as they move down the snake's body, and the wave travels backwards faster than the snake moves forwards.<ref name = "Gray2">{{Cite journal |
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| last = Gray |
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| first = J |
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| last2 = Lissman |
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| title = Undulatory propulsion |
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| journal = [[Quarterly Journal of Microscopical Science]] |
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| year = 1953 |
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| volume = 94 |
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| pages= 551–578 }}</ref> Thrust is generated by pushing their body against the water, resulting in the observed slip. In spite of overall similarities, studies show that the pattern of muscle activation is different in aquatic versus terrestrial lateral undulation, which justifies calling them separate modes.<ref name = "Jayne1">{{Cite journal |
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| last = Jayne |
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| first = B. C. |
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| title = Muscular mechanisms of snake locomotion: an electromyographic study of lateral undulation of the Florida banded water snake (Nerodia fasciata) and the yellow rat snake (Elaphe obsoleta) |
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| journal = Journal of Morphology |
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| year = 1988 |
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| volume = 197 |
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| pages= 159–181 |
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| doi = 10.1002/jmor.1051970204 |
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| pmid = 3184194 |
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| issue = 2 }}</ref> All snakes can laterally undulate forward (with backward-moving waves), but only sea snakes have been observed reversing the motion (moving backwards with forward-moving waves).<ref name="Cogger91_175"/> |
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====Sidewinding==== |
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{{see also|Sidewinding}} |
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[[File:Crotalus scutulatus 03.jpg|thumb|left|A Mojave rattlesnake ([[Crotalus scutulatus]]) sidewinding.]] |
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Most often employed by colubroid snakes ([[colubrids]], [[elapids]], and [[Viperidae|vipers]]) when the snake must move in an environment that lacks irregularities to push against (rendering lateral undulation impossible), such as a slick mud flat, or a sand dune. Sidewinding is a modified form of lateral undulation in which all of the body segments oriented in one direction remain in contact with the ground, while the other segments are lifted up, resulting in a peculiar "rolling" motion.<ref name="Cogger91_177">Cogger(1991), p. 177.</ref><ref name = "Jayne2">{{Cite journal |
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| last = Jayne |
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| first = B.C. |
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| title = Kinematics of terrestrial snake locomotion |
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| journal = Copeia |
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| year = 1986 |
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| pages= 915–927 |
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| doi = 10.2307/1445288 |
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| volume = 1986 |
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| issue = 4 |
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| jstor = 1445288 }}</ref> This mode of locomotion overcomes the slippery nature of sand or mud by pushing off with only static portions on the body, thereby minimizing slipping.<ref name="Cogger91_177"/> The static nature of the contact points can be shown from the tracks of a sidewinding snake, which show each belly scale imprint, without any smearing. This mode of locomotion has very low caloric cost, less than ⅓ of the cost for a lizard or snake to move the same distance.<ref name="Walton"/> Contrary to popular belief, there is no evidence that sidewinding is associated with the sand being hot.<ref name="Cogger91_177"/> |
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====Concertina==== |
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{{main|Concertina movement}} |
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When push-points are absent, but there is not enough space to use sidewinding because of lateral constraints, such as in tunnels, snakes rely on concertina locomotion.<ref name="Cogger91_175"/><ref name = "Jayne2"/> In this mode, the snake braces the posterior portion of its body against the tunnel wall while the front of the snake extends and straightens.<ref name="Cogger91_177"/> The front portion then flexes and forms an anchor point, and the posterior is straightened and pulled forwards. This mode of locomotion is slow and very demanding, up to seven times the cost of laterally undulating over the same distance.<ref name="Walton"/> This high cost is due to the repeated stops and starts of portions of the body as well as the necessity of using active muscular effort to brace against the tunnel walls. |
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====Rectilinear==== |
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{{main|Rectilinear locomotion}} |
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The slowest mode of snake locomotion is rectilinear locomotion, which is also the only one where the snake does not need to bend its body laterally, though it may do so when turning.<ref name="Cogger91_176">Cogger (1991), p. 176.</ref> In this mode, the belly scales are lifted and pulled forward before being placed down and the body pulled over them. Waves of movement and stasis pass posteriorly, resulting in a series of ripples in the skin.<ref name="Cogger91_176"/> The ribs of the snake do not move in this mode of locomotion and this method is most often used by large [[Pythonidae|python]]s, [[Boidae|boa]]s, and [[Viperidae|viper]]s when stalking prey across open ground as the snake's movements are subtle and harder to detect by their prey in this manner.<ref name="Cogger91_177"/> |
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====Other==== |
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The movement of snakes in arboreal habitats has only recently been studied.<ref name = "Astley">{{Cite journal |
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|last = Astley |
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|first =H.C. |
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|last2 = Jayne |
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|first2 = B.C. |
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|title = Effects of perch diameter and incline on the kinematics, performance and modes of arboreal locomotion of corn snakes (Elaphe guttata) |
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|year = 2007 |
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|journal = Journal of Experimental Biology |
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|volume = 210 |
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|pages = 3862–3872 |
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|doi = 10.1242/jeb.009050 |
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|pmid = 17951427 |
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|issue = Pt 21}}</ref> While on tree branches, snakes use several modes of locomotion depending on species and bark texture.<ref name="Astley"/> In general, snakes will use a modified form of concertina locomotion on smooth branches, but will laterally undulate if contact points are available.<ref name="Astley"/> Snakes move faster on small branches and when contact points are present, in contrast to limbed animals, which do better on large branches with little 'clutter'.<ref name="Astley"/> |
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Gliding snakes (''[[Chrysopelea]]'') of Southeast Asia launch themselves from branch tips, spreading their ribs and laterally undulating as they glide between trees.<ref name="Cogger91_177"/><ref name="Freiberg84_135">Freiberg (1984), p. 135.</ref><ref>{{cite journal | doi= 10.1038/418603a | last1= Socha | first1= JJ | title= Gliding flight in the paradise tree snake | journal=Nature | volume= 418 | issue= 6898 |pages= 603–604 | year= 2002 |pmid = 12167849 }}</ref> These snakes can perform a controlled glide for hundreds of feet depending upon launch altitude and can even turn in midair.<ref name="Cogger91_177"/><ref name="Freiberg84_135"/> |
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==Interactions with humans== |
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[[File:Snake bite symptoms.png|thumb|Most common symptoms of any kind of snake bite poisoning.<ref name=MedlinePlus/><ref>[http://www.health-care-clinic.org/diseases/snakebite.html Health-care-clinic.org > Snake Bite First Aid - Snakebite]. Retrieved 2010-03-09.</ref><ref>Snake bite image example at [http://www.mdconsult.com/das/patient/body/127551351-2/0/10041/8928_en.jpg MDconsult > Patient Education > Wounds, Cuts and Punctures, First Aid for].{{Dead link|date=March 2010}}</ref> Furthermore, there is vast variation in symptoms between bites from different types of snakes.<ref name=MedlinePlus>[http://www.nlm.nih.gov/medlineplus/ency/article/000031.htm MedlinePlus > Snake bites] from Tintinalli JE, Kelen GD, Stapcynski JS, eds. ''Emergency Medicine: A Comprehensive Study Guide''. 6th ed. New York, NY: McGraw Hill; 2004. Update Date: 2/27/2008. Updated by: Stephen C. Acosta, MD, Department of Emergency Medicine, Portland VA Medical Center, Portland, OR. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. Retrieved 2010-03-09.</ref>]] |
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===Bite=== |
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{{main|Snakebite}} |
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[[File:ViperaBerusFang.JPG|thumb|left|[[Vipera berus]], one fang in glove with a small venom stain, the other still in place.]] |
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Snakes do not ordinarily prey on humans. Unless startled or injured, most snakes prefer to avoid contact and will not attack humans. With the exception of large constrictors, nonvenomous snakes are not a threat to humans. The bite of a nonvenomous snake is usually harmless; their teeth are not designed for tearing or inflicting a deep puncture wound, but rather grabbing and holding. Although the possibility of infection and tissue damage is present in the bite of a nonvenomous snake, venomous snakes present far greater hazard to humans.<ref name="Meh87"/>{{Rp|209}} |
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Documented deaths resulting from snake bites are uncommon. Nonfatal bites from venomous snakes may result in the need for amputation of a limb or part thereof. Of the roughly 725 species of venomous snakes worldwide, only 250 are able to kill a human with one bite. Australia averages only one fatal snake bite per year. In India, 250,000 snakebites are recorded in a single year, with as many as 50,000 recorded initial deaths.<ref name="Sinha">{{Cite news |
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| last =Sinha |
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| first =Kounteya |
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| author-link = |
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| title = No more the land of snake charmers... |
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| newspaper = The Times of India |
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| pages = |
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| date =25 July 2006 |
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| url =http://timesofindia.indiatimes.com/articleshow/1803026.cms }}</ref> |
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The treatment for a snakebite is as variable as the bite itself. The most common and effective method is through [[antivenom]] (or antivenin), a serum made from the venom of the snake. Some antivenom is species specific (monovalent) while some is made for use with multiple species in mind (polyvalent). In the United States for example, all species of venomous snakes are [[pit viper]]s, with the exception of the [[coral snake]]. To produce antivenom, a mixture of the venoms of the different species of [[rattlesnake]]s, copperheads, and cottonmouths is injected into the body of a horse in ever-increasing dosages until the horse is immunized. Blood is then extracted from the immunized horse. The serum is separated and further purified and freeze-dried. It is reconstituted with sterile water and becomes antivenom. For this reason, people who are allergic to horses are more likely to suffer an allergic reaction to antivenom.<ref>{{cite web|url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2146932/pdf/canfamphys00081-0113.pdf |title=NCBI.nlm.nih.gov |format=PDF |date= |accessdate=2013-03-08}}</ref> Antivenom for the more dangerous species (such as [[mamba]]s, [[taipan]]s, and [[cobra]]s) is made in a similar manner in India, South Africa, and Australia, although these antivenoms are species-specific. |
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===Snake charmers=== |
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{{main|Snake charming}} |
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[[File:Snake in basket.jpg|thumb|upright|left|An [[Indian cobra]] in a basket with a snake charmer. These snakes are perhaps the most common subjects of snake charmings.]] |
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In some parts of the world, especially in India, [[snake charming]] is a roadside show performed by a charmer. In such a show, the snake charmer carries a basket that contains a snake that he seemingly charms by playing tunes from his flutelike musical instrument, to which the snake responds.<ref name="Bagla"/> Snakes lack external ears, though they do have internal ears, and respond to the movement of the flute, not the actual noise.<ref name="Bagla"> |
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{{cite news |
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| last=Bagla |
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| first=Pallava |
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| title=India's Snake Charmers Fade, Blaming Eco-Laws, TV |
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| date=April 23, 2002 |
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| work=National Geographic News |
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| url=http://news.nationalgeographic.com/news/2002/04/0417_020423_snakecharm_2.html |
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| accessdate = 2007-11-26}}</ref><ref>[http://books.google.com/books?id=BumyQJ14n8sC&pg=PA482&dq=snake+charmer+bluff&hl=nl&ei=yDw0TYGxGsKfOs3qzLYC&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCkQ6AEwAA#v=onepage&q=snake%20charmer%20bluff&f=false "Snake charmer's bluff"] ''International Wildlife Encyclopedia'', 3rd edition, page 482</ref> |
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The [[Wildlife Protection Act of 1972]] in India technically proscribes snake charming on grounds of reducing animal cruelty. Other snake charmers also have a snake and [[mongoose]] show, where both the animals have a mock fight; however, this is not very common, as the snakes, as well as the mongooses, may be seriously injured or killed. Snake charming as a profession is dying out in India because of competition from modern forms of entertainment and environment laws proscribing the practice.<ref name="Bagla"/> |
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===Trapping=== |
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The ''Irulas'' tribe of [[Andhra Pradesh]] and [[Tamil Nadu]] in India have been hunter-gatherers in the hot, dry plains forests, and have practiced the art of snake catching for generations. They have a vast knowledge of snakes in the field. They generally catch the snakes with the help of a simple stick. Earlier, the ''Irulas'' caught thousands of snakes for the snake-skin industry. After the complete ban of the snake-skin industry in India and protection of all snakes under the [[Wildlife Protection Act of 1972|Indian Wildlife (Protection) Act 1972]], they formed the Irula Snake Catcher's Cooperative and switched to catching snakes for removal of venom, releasing them in the wild after four extractions. The venom so collected is used for producing life-saving antivenom, biomedical research and for other medicinal products.<ref name="Whitaker et al.">Whitaker, Romulus & Captain, Ashok. ''Snakes of India: The Field Guide''.(2004) pp 11 to 13.</ref> The ''Irulas'' are also known to eat some of the snakes they catch and are very useful in rat extermination in the villages. |
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Despite the existence of snake charmers, there have also been professional snake catchers or wranglers. Modern-day snake trapping involves a [[herpetologist]] using a long stick with a V- shaped end. Some television show hosts, like [[Bill Haast]], [[Austin Stevens]], [[Steve Irwin]], and [[Jeff Corwin]], prefer to catch them using bare hands. |
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<!-- NOTE: Austin Stevens only catches nonvenomous snakes with his bare hands. He uses snake tongs otherwise. --> |
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<!-- |
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At least one tribe uses a specialized form of snake catching as a rite of passage to manhood.{{Citation needed|date=February 2007}} The young man of interest will wrap his leg heavily in some type of cloth all the way to the inseam. He will then stick his leg in a burrow containing a large python, typically a [[Python reticulatus|reticulated python]]. After the snake swallows most of his leg, several other members of the tribe will pull him out of the hole along with the snake. The snake is then killed and the man's leg removed from the snake. These snakes can be over 7 meters (20 ft) long, and it is possible for the man to have his leg dislocated. The scent of a prey animal may be used to help convince the snake to swallow the leg. Snakes have a single-tract digestive system, but the digestion process is actually much slower. |
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Commented this paragraph out till the tribe is identified and a reference given. |
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--> |
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===Consumption=== |
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[[File:Guangzhou-snakes-at-restaurant-0457.jpg|thumb|A "海豹蛇" ("sea-leopard snake", supposedly ''[[Enhydris]] bocourti'') occupies a place of honor among the live delicacies waiting to meet their consumers outside of a [[Guangzhou]] restaurant.]] |
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[[File:Snake meat.jpg|thumb|left|Snake meat, in a Taipei restaurant]] |
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While not commonly thought of as food in most cultures, in some cultures, the consumption of snakes is acceptable, or even considered a delicacy, prized for its alleged pharmaceutical effect of warming the heart. Snake soup of [[Cantonese cuisine]] is consumed by local people in autumn, to warm up their body. Western cultures document the consumption of snakes under extreme circumstances of hunger.<ref>{{cite journal|last=Irvine|first=F. R.|year=1954|title=Snakes as food for man|journal=British Journal of Herpetology|volume=1|issue=10| pages=183–189 }}</ref> Cooked [[rattlesnake]] meat is an exception, which is commonly consumed in parts of the Midwestern United States. In Asian countries such as China, Taiwan, Thailand, Indonesia, Vietnam and Cambodia, drinking the blood of snakes—particularly the [[cobra]]—is believed to increase sexual virility.<ref name="Flynn"> |
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{{cite news |
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|last=Flynn |
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|first=Eugene |
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|title=Flynn Of The Orient Meets The Cobra |
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|date=April 23, 2002 |
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|publisher=Fabulous Travel |
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|url=http://www.fabuloustravel.com/gourmet/travel/cobrasblood/cobra.html |
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|accessdate=2007-11-26}}</ref> The blood is drained while the cobra is still alive when possible, and is usually mixed with some form of liquor to improve the taste.<ref name="Flynn"/> |
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In some Asian countries, the use of snakes in alcohol is also accepted. In such cases, the body of a snake or several snakes is left to steep in a jar or container of liquor. It is claimed that this makes the liquor stronger (as well as more expensive). One example of this is the [[Trimeresurus flavoviridis|Habu]] snake sometimes placed in the [[Okinawa]]n liquor [[Awamori]] also known as "Habu Sake".<ref name="Allen"> |
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{{cite news |
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|last=Allen |
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|first=David |
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|title=Okinawa’s potent habu sake packs healthy punch, poisonous snake |
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|date=July 22, 2001 |
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|work=[[Stars and Stripes (newspaper)|Stars and Stripes]] |
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|url=http://ww2.pstripes.osd.mil/01/mag/sm072201c.html |
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|accessdate=2007-11-26}}</ref> |
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[[Special Forces (United States Army)|U.S. Army Special Forces]] trainees are taught to catch, kill, and eat snakes during their survival course; this has earned them the nickname "snake eaters", which the video game ''[[Metal Gear Solid 3: Snake Eater]]'' may be inferred to draw from. |
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[[Snake wine]] (蛇酒) is an alcoholic beverage produced by infusing whole snakes in [[Chinese alcoholic beverages|rice wine]] or [[grain alcohol]]. The drink was first recorded to have been consumed in China during the [[Western Zhou dynasty]] and considered an important curative and believed to reinvigorate a person according to [[Traditional Chinese medicine]].<ref name=sw1>{{cite web|title=蛇酒的泡制与药用(The production and medicinal qualities of snake wine)|date=2007-04-09 |url=http://www.cn939.com/tcm-article-read-4694.html}}</ref> |
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===Pets=== |
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In the Western world, some snakes (especially docile species such as the [[Python regius|ball python]] and [[corn snake]]) are kept as pets. To meet this demand a [[herpetoculture|captive breeding]] industry has developed. Snakes bred in captivity tend to make better pets and are considered preferable to wild caught specimens.<ref>{{cite book |last = Ernest |first = Carl |coauthors =George R. Zug, Molly Dwyer Griffin |title = Snakes in Question: The Smithsonian Answer Book | publisher = Smithsonian Books |year =1996 |location =Washington, D.C. |page = 203 |isbn =1-56098-648-4 }}</ref> Snakes can be very low maintenance pets, especially compared to more traditional species. They require minimal space, as most common species do not exceed five feet (1.5 m) in length. Pet snakes can be fed relatively infrequently, usually once every 5 to 14 days. Certain snakes have a lifespan of more than 40 years if given proper care. |
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===Symbolism=== |
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{{main|Serpent (symbolism)}} |
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In [[History of Egypt|Egyptian history]], the snake occupies a primary role with the Nile cobra adorning the crown of the pharaoh in ancient times. It was [[snake worship|worshipped]] as one of the gods and was also used for sinister purposes: murder of an adversary and ritual suicide ([[Cleopatra VII of Egypt|Cleopatra]]). |
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[[File:Golden Uraes Cobra Tutankhamun's Throne.jpg|thumb|left|The reverse side of the throne of Pharaoh [[Tutankhamun]] with four golden uraeus cobra figures. Gold with [[lapis lazuli]]; [[Valley of the Kings]], Thebes(1347-37 BCE).]] |
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[[File:Medusa by Carvaggio.jpg|thumb|upright|[[Medusa]] by 16th Century Italian artist [[Caravaggio]].]] |
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In [[Greek mythology]] snakes are often associated with deadly and dangerous antagonists, but this is not to say that snakes are symbolic of evil; in fact, snakes are a [[chthonic]] symbol, roughly translated as 'earthbound'. The nine-headed [[Lernaean Hydra]] that [[Hercules]] defeated and the three [[Gorgon]] sisters are children of [[Gaia (mythology)|Gaia]], the earth.<ref name="BF85">Bullfinch (2000) p. 85.</ref> [[Medusa]] was one of the three Gorgon sisters who [[Perseus]] defeated.<ref name="BF85"/> Medusa is described as a hideous mortal, with snakes instead of hair and the power to turn men to stone with her gaze.<ref name="BF85"/> After killing her, Perseus gave her head to [[Athena]] who fixed it to her shield called the [[Aegis]].<ref name="BF85"/> The [[Titan (mythology)|Titans]] are also depicted in art with snakes instead of legs and feet for the same reason—they are children of Gaia and [[Uranus (mythology)|Uranus]], so they are bound to the earth. |
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[[File:PuckCartoon-TeddyRoosevelt-05-23-1906.jpg|thumb|right|U.S. President [[Theodore Roosevelt]] depicted as the infant [[Hercules]] grappling with a giant snake representing the [[Standard Oil]] Company]] |
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The legendary account of the foundation of [[Ancient Thebes (Boeotia)|Thebes]] mentioned a monster snake |
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guarding the spring from which the new settlement was to draw its water. In fighting and killing the snake, the companions of the founder [[Cadmus]] all perished - leading to the term "[[Cadmean victory]]" (i.e. a victory involving one's own ruin). |
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Three medical symbols involving snakes that are still used today are [[Bowl of Hygieia]], symbolizing pharmacy, and the [[Caduceus]] and [[Rod of Asclepius]], which are symbols denoting medicine in general.<ref name=AIM/> |
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India is often called the land of snakes and is steeped in tradition regarding snakes.<ref name="Deane_61"/> Snakes are worshipped as gods even today with many women pouring milk on snake pits (despite snakes' aversion for milk).<ref name="Deane_61">Deane (1833). p. 61.</ref> The cobra is seen on the neck of [[Shiva]] and [[Vishnu]] is depicted often as sleeping on a seven-headed snake or within the coils of a serpent.<ref>Deane (1833). pp. 62–64.</ref> There are also several temples in India solely for cobras sometimes called ''Nagraj'' (King of Snakes) and it is believed that snakes are symbols of fertility. There is a Hindu festival called [[Nag Panchami]] each year on which day snakes are venerated and prayed to. See also ''[[Nāga]]''. |
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In India there is another mythology about snakes. Commonly known in [[Hindi]] as "[[Ichchhadhari Nag|Ichchhadhari]]" snakes. Such snakes can take the form of any living creature, but prefer human form. These mythical snakes possess a valuable gem called "Mani", which is more brilliant than diamond. There are many stories in India about greedy people trying to possess this gem and ending up getting killed. |
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The [[ouroboros]] is a symbol associated with many different religions and customs, and is claimed to be related to [[alchemy]]. The ouroboros or oroboros is a snake eating its own tail in a clock-wise direction (from the head to the tail) in the shape of a circle, representing the cycle of [[Dying god|life, death and rebirth]], leading to immortality. |
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The [[Snake (zodiac)|snake]] is one of the 12 celestial animals of [[Chinese Zodiac]], in the [[Chinese calendar]]. |
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Many ancient Peruvian cultures worshipped nature.<ref>{{cite book | last=Benson |first= Elizabeth | title= The Mochica: A Culture of Peru |location=London | publisher=Thames and Hudson |year= 1972 | isbn= 0-500-72001-0 }}</ref> They emphasized animals and often depicted snakes in their art.<ref>{{cite book | last1=Berrin |first1= Katherine |last2= Larco Museum |title=The Spirit of Ancient Peru: Treasures from the [[Larco Museum|Museo Arqueológico Rafael Larco Herrera]] | location= New York |publisher= Thames and Hudson |year= 1997 |isbn=978-0-500-01802-6 }}</ref> |
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===Religion=== |
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{{main| Snake worship}} |
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[[File:Simeon Stylite Louvre.jpg|thumb|upright|left|A snake associated with Saint [[Simeon Stylites]]]] |
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[[File:Rod of asclepius.jpg|thumb|upright|Rod of Asclepius, in which the snake, through [[ecdysis]], symbolize healing.]] |
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Snakes are a part of Hindu worship. A festival, [[Nag Panchami]], in which participants worship either images of or live [[Nāga]]s (cobras) is celebrated every year. Most images of Lord [[Shiva]] depict snake around his neck. Puranas have various stories associated with snakes. In the Puranas, [[Shesha]] is said to hold all the planets of the Universe on his hoods and to constantly sing the glories of Vishnu from all his mouths. He is sometimes referred to as "Ananta-Shesha", which means "Endless Shesha". Other notable snakes in Hinduism are [[Shesha|Ananta]], [[Vasuki]], [[Taxak]], [[Karkotaka]] and [[Pingala]]. The term [[Nāga]] is used to refer to entities that take the form of large snakes in Hinduism and Buddhism. |
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Snakes have also been widely revered, such as in [[ancient Greece]], where the serpent was seen as a healer. [[Asclepius]] carried a serpent wound around his wand, a symbol seen today on many ambulances. |
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In religious terms, the snake and [[jaguar]] are arguably the most important animals in ancient [[Mesoamerica]]. "In states of ecstasy, lords dance a serpent dance; great descending snakes adorn and support buildings from [[Chichen Itza]] to [[Tenochtitlan]], and the [[Nahuatl]] word ''coatl'' meaning serpent or twin, forms part of primary deities such as [[Mixcoatl]], [[Quetzalcoatl]], and [[Coatlicue]]."<ref>''The Gods and Symbols of Ancient Mexico and the Maya''. Miller, Mary 1993 Thames & Hudson. London ISBN 978-0-500-27928-1</ref> In both [[Maya calendar|Maya]] and [[Aztec calendar]]s, the fifth day of the week was known as Snake Day. |
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In [[Judaism]], the snake of brass is also a symbol of healing, of one's life being saved from imminent death ([[Book of Numbers]] 21:6–9). |
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In some parts of Christianity, [[Christ]]'s redemptive work is compared to saving one's life through beholding the [[Nehushtan]] (serpent of [[brass]]) ([[Gospel of John]] 3:14). [[Snake handling|Snake handlers]] use snakes as an integral part of church worship in order to exhibit their faith in divine protection. However, more commonly in Christianity, the serpent has been seen as a representative of [[evil]] and sly plotting, which can be seen in the description in [[Book of Genesis|Genesis]] chapter 3 of a snake in the [[Garden of Eden]] tempting [[Eve]]. [[Saint Patrick]] is reputed to have expelled all snakes from Ireland while Christianising the country in the 5th century, thus explaining the absence of snakes there. |
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In Christianity and Judaism, the snake makes its infamous appearance in the first book (Genesis 3:1) of the Bible when a serpent appears before the first couple [[Adam and Eve]] and tempts them with the [[forbidden fruit]] from the [[Tree of Knowledge of Good and Evil|Tree of Knowledge]]. The snake returns in [[Book of Exodus|Exodus]] when [[Moses]], as a sign of God's power, turns his staff into a snake and when Moses made the [[Nehushtan]], a bronze snake on a pole that when looked at cured the people of bites from the snakes that plagued them in the desert. The serpent makes its final appearance symbolizing [[Satan]] in the [[Book of Revelation]]: "And he laid hold on the dragon the old serpent, which is the devil and Satan, and bound him for a thousand years." (Revelation 20:2) |
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In [[Neo-Paganism]] and [[Wicca]], the snake is seen as a symbol of wisdom and knowledge. |
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[[File:Mixco Viejo ballcourt marker.jpg|thumb|upright|[[Mesoamerican ballcourt|Ballcourt]] marker from the Postclassic site of [[Mixco Viejo]] in Guatemala. This sculpture depicts [[Kukulkan]], jaws agape, with the head of a human warrior emerging from his maw.<ref>{{cite book |author={{aut|Sharer, Robert J.}} |authorlink=Robert Sharer|coauthors=with {{aut|Loa P. Traxler}} |year=2006 |title=The Ancient Maya |edition=6th (fully revised) |location=Stanford, California |publisher=Stanford University Press |isbn=0-8047-4817-9|page=619 |oclc=57577446}}</ref>]] |
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===Medicine=== |
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The cyto-toxic effect of snake venom is being researched as a potential treatment for cancers. <ref> {{cite web|url=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3627178/ | journal=Asian Pacific Journal of Tropical Medicine|title=Theraputic potential of snake venom in cancer therapy: current perspective|date=Feb 2012|Author=Vivek Kumar Vyas, Keyur Brahmbahtt, Ustav Parmar}} </ref> |
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==See also== |
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{{Portal|Amphibians and reptiles}} |
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* [[Legend of the White Snake]] |
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* [[Limbless vertebrates]] |
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* [[List of Serpentes families]] |
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* [[List of snakes]] |
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* [[Ophiology]] |
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* [[Snake skeleton]] |
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* [[Spinal osteoarthropathy]] (reptile disease) |
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* ''[[The New Encyclopedia of Snakes]]'' |
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* [[Venomous snake]] |
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{{-}} |
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==References== |
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{{reflist|30em}} |
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==Further reading== |
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{{Refbegin|30em}} |
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*{{cite book |last = Behler |first = John L. |last2 = King |first2 = F. Wayne |title = The Audubon Society Field Guide to Reptiles and Amphibians of North America |publisher = Alfred A. Knopf |location= New York |page = 581 |year= 1979 |isbn = 0-394-50824-6}} |
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*{{cite book |last =Bullfinch |first =Thomas |authorlink =Thomas Bullfinch |title =Bullfinch's Complete Mythology |publisher =Chancellor Press |year =2000 | location =London |page =679 |url =http://etext.library.adelaide.edu.au/b/bulfinch/thomas/ |
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|isbn =0-7537-0381-5 }} |
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*{{cite book |last= Capula |first= Massimo |coauthors =Behler |title= Simon & Schuster's Guide to Reptiles and Amphibians of the World |year= 1989 |publisher= Simon & Schuster |location= New York |isbn= 0-671-69098-1}} |
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*{{cite book |last= Coborn |first= John |title=The Atlas of Snakes of the World |year= 1991 |location=New Jersey |publisher = TFH Publications |isbn= 978-0-86622-749-0}} |
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*{{cite book |last = Cogger |first = Harold |authorlink = Harold Cogger |last2 = Zweifel |first2 = Richard |title = Reptiles & Amphibians |publisher = Weldon Owen |location = Sydney |year = 1992 |isbn = 0-8317-2786-1}} |
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*{{cite book |last =Conant |first =Roger |last2 =Collins |first2 =Joseph |authorlink=Roger Conant (herpetologist) |title =A Field Guide to Reptiles and Amphibians Eastern/Central North America |publisher =Houghton Mifflin Company |year= 1991 |location =Boston |isbn = 0-395-58389-6 }} |
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*{{cite book |last =Deane |first =John |authorlink =The Worship of the Serpent |title =The Worship of the Serpent |publisher =Kessinger Publishing |year =1833 |location =Whitefish, Montana |page =412 |url =http://www.sacred-texts.com/etc/wos/index.htm |isbn =1-56459-898-5}} |
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*{{cite book |last =Ditmars |first =Raymond L |authorlink =Raymond Ditmars |title = Poisonous Snakes of the United States: How to Distinguish Them |publisher =E. R. Sanborn |year =1906 |location =New York |page =11}} |
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*{{cite book |last =Ditmars |first =Raymond L |authorlink =Raymond Ditmars |title = Snakes of the World |publisher =Macmillan |year =1931 |location =New York |page =11 |isbn = 978-0-02-531730-7 }} |
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*{{cite book |last =Ditmars |first =Raymond L |authorlink =Raymond Ditmars |title = Reptiles of the World: The Crocodilians, Lizards, Snakes, Turtles and Tortoises of the Eastern and Western Hemispheres |publisher =Macmillan |year =1933 |location =New York |page =321}} |
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*{{cite book |last =Ditmars |first =Raymond L |coauthor = W. Bridges |authorlink =Raymond Ditmars |title = Snake-Hunters' Holiday |publisher =D. Appleton and Company |year =1935 |location =New York |page =309}} |
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*{{cite book |last =Ditmars |first =Raymond L |authorlink =Raymond Ditmars |title = A Field Book of North American Snakes |publisher =Doubleday, Doran & Co |year =1939 |location =Garden City, New York |page =305}} |
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*{{cite book |last= Freiberg |first= Dr. Marcos |last2= Walls |first2=Jerry |title= The World of Venomous Animals |year= 1984 |publisher= TFH Publications|location=New Jersey |isbn= 0-87666-567-9}} |
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*{{cite book |last =Gibbons |first =J. Whitfield |last2 =Gibbons |first2 =Whit |title =Their Blood Runs Cold: Adventures With Reptiles and Amphibians |publisher =University of Alabama Press |year =1983 |location =Alabama |page =164 |isbn=978-0-8173-0135-4 }} |
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*{{cite book |last =Mattison |first =Chris |title =The New Encyclopedia of Snakes |publisher =Princeton University Press |year =2007 |location =New Jersey |page =272 |isbn=978-0-691-13295-2 }} |
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*{{cite book |last=McDiarmid |first=RW |last2= Campbell |first2=JA |last3=Touré |first3=T |year= 1999 |title= Snake Species of the World: A Taxonomic and Geographic Reference |volume= 1 |publisher= Herpetologists' League |page=511 |isbn= 1-893777-00-6 }} |
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*{{cite book |last= Mehrtens |first= John |title= Living Snakes of the World in Color |year= 1987 |publisher= Sterling |location= New York |isbn= 0-8069-6461-8}} |
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* {{cite journal | last1= Nóbrega Alves | first1= RôMulo Romeu | last2= Silva Vieira | first2= Washington Luiz | last3= Santana | first3= Gindomar Gomes | title= Reptiles used in traditional folk medicine: conservation implications | journal= Biodiversity and Conservation |volume= 17 |issue=8 |pages= 2037–2049 |url=http://www.springerlink.com/content/j3558j2n828x35w3/?p=2b29f0e29e064961ad47b479f780adb2&pi=15 | year= 2008 |accessdate= 22 January 2009 | doi = 10.1007/s10531-007-9305-0 }} |
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*{{cite book |author=[[Romulus Whitaker]] (English edition); Tamil translation by O.Henry Francis |title=நம்மை சுட்ரியுள்ள பாம்புகள் (Snakes around us, Tamil) |publisher=National Book Trust |year=1996 |isbn=81-237-1905-1 }} |
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*{{cite book |last = Rosenfeld |first = Arthur |title = Exotic Pets |publisher = Simon & Schuster |location= New York |year= 1989 |page=293 |isbn = 978-0-671-47654-0}} |
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*{{cite book |last =Spawls |first=Steven |last2 =Branch |first2= Bill |year= 1995 |title= The Dangerous Snakes of Africa |publisher=Ralph Curtis Publishing |location=Sanibel Island, Florida |page= 192 |isbn = 0-88359-029-8}} |
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{{Refend}} |
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==External links== |
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{{commons and category|Serpentes}} |
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{{Americana Poster|Serpents}} |
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* {{cite web |url=http://www.snaketracks.com/species.html |title=Worldwide Snake Species List |publisher=Snake Track.com }} |
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* {{cite web |url=http://www.biodiversitylibrary.org/name/Serpentes |title=Bibliography for "Serpentes" |publisher=Biodiversity Heritage Library }} |
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* {{ITIS |id=174118 |taxon=Serpentes}} |
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* {{cite web |url=http://enature.com/fieldguides/view_default.asp?curGroupID=7&shapeID=1060 |title=US Snakes |publisher=eNature}} |
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* {{cite web |url=http://www.naturemagics.com/stock-photo/thumbnails.php?album=7 |title=Snakes of the Indian Subcontinent |publisher=Naturemagics Kerala Photo Gallery }} |
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* {{cite web |url=http://www.snakecell.org/snake-cell.html |title=About Snake Cell |publisher=Snake Cell}} (INDIA) |
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* {{cite web |url=http://www.reptilesweb.com/reptiles-section/snake-world.html |title=Snake World |publisher=ReptilesWeb.com}} |
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* {{cite web |url=http://www.oplin.org/snake |title=What's That Snake? |publisher=OPLIN}} |
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* {{cite web |url=http://artedi.nrm.se/nrmherps/qbrowse.php?FormData=scientificName |title=Herpetology Database |publisher=Swedish Museum of Natural History}} |
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*[http://www.bbc.co.uk/nature/life/Snake BBC Nature:] Snake news, and video clips from BBC programmes past and present. |
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*[http://snakesarelong.blogspot.com/2013/05/basics-of-snake-taxonomy.html Basics of snake taxonomy] at Life is Short but Snakes are Long |
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{{Snake families}} |
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[[Category:Snakes| ]] |
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{{Link FA|nl}} |
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{{Link FA|zh}} |
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{{Link GA|no}} |
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{{Link FA|ms}} |
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Revision as of 07:54, 29 October 2013
Snakes are space aliens who eat underpants. Their favourite colour is brown and their eyes are made of jam.