Editing Snake (section)

=== Venom ===
{{See also|Snake venom|Venomous snake|#Bite}}
[[File:Red milk snake.JPG|thumb|Innocuous [[milk snake]]s are often mistaken for [[coral snake]]s whose venom is deadly to humans.]]

Cobras, vipers, and closely related species use [[venom]] to immobilize, injure, or kill their prey. The venom is modified [[saliva]], delivered through [[fangs]].<ref name="Meh87"/><ref name=":3">{{Cite journal |last1=Oliveira |first1=Ana L. |last2=Viegas |first2=Matilde F. |last3=da Silva |first3=Saulo L. |last4=Soares |first4=Andreimar M. |last5=Ramos |first5=Maria J. |last6=Fernandes |first6=Pedro A. |date=July 2022 |title=The chemistry of snake venom and its medicinal potential |journal=Nature Reviews Chemistry |language=en |volume=6 |issue=7 |pages=451–469 |doi=10.1038/s41570-022-00393-7 |issn=2397-3358 |pmc=9185726 |pmid=35702592}}</ref>{{Rp|243}} The fangs of 'advanced' venomous snakes like viperids and elapids are hollow, allowing venom to be injected more effectively, and the fangs of [[Snake skeleton#Opisthoglyph|rear-fanged]] snakes such as the boomslang simply have a groove on the posterior edge to channel venom into the wound. Snake venoms are often prey-specific, and their role in self-defense is secondary.<ref name="Meh87"/><ref name=":3" />{{Rp|243}}

Venom, like all salivary secretions, is a predigestant that initiates the breakdown of food into soluble compounds, facilitating proper digestion. Even nonvenomous snakebites (like any animal bite) cause tissue damage.<ref name="Meh87"/><ref name=":3" />{{Rp|209}}

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 [[Taxonomy (biology)|taxonomic classification]] group.{{Citation needed|date=November 2024}}

The [[Colloquialism|colloquial]] term "poisonous snake" is generally an incorrect label for snakes. A poison is inhaled or ingested, whereas venom produced by snakes is injected into its victim via fangs.{{sfn|Freiberg|Walls|1984|p=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 unusual population of [[garter snake]]s in the US state of [[Oregon]] retains enough toxins in their livers from ingested [[newt]]s to be effectively poisonous to small local predators (such as [[crow]]s and [[fox]]es).{{sfn|Freiberg|Walls|1984|p=123}}

Snake venoms are complex mixtures of [[protein]]s,<ref name=":3" /> and are stored in [[Venom gland|venom glands]] at the back of the head.{{sfn|Freiberg|Walls|1984|p=123}} In all venomous snakes, these glands open through ducts into grooved or hollow teeth in the upper jaw.<ref name="Meh87"/>{{Rp|243}}{{sfn|Freiberg|Walls|1984|p=125}} The proteins can potentially be a mix of [[neurotoxin]]s (which attack the nervous system), [[hemotoxin]]s (which attack the circulatory system), [[cytotoxin]]s (which attack the cells directly), [[bungarotoxin]]s (related to neurotoxins, but also directly affect muscle tissue), and many other toxins that affect the body in different ways.{{sfn|Freiberg|Walls|1984|p=125}}<ref name=":3" /> Almost all snake venom contains ''[[hyaluronidase]]'', an enzyme that ensures rapid diffusion of the venom.<ref name="Meh87"/>{{Rp|243}}

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=":3" />{{sfn|Freiberg|Walls|1984|p=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.{{sfn|Freiberg|Walls|1984|p=126}} This makes it difficult both for the snake to use its venom and for scientists to milk them.{{sfn|Freiberg|Walls|1984|p=125}} Elapids, however, such as cobras and kraits 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}}

It has 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 |vauthors=Fry BG, Vidal N, Norman JA, Vonk FJ, Scheib H, Ramjan SF, Kuruppu S, Fung K, Hedges SB, Richardson MK, Hodgson WC, Ignjatovic V, Summerhayes R, Kochva E |display-authors=6 |title=Early evolution of the venom system in lizards and snakes |journal=[[Nature (journal)|Nature]] |volume=439 |issue=7076 |pages=584–8 |date=February 2006 |pmid=16292255 |doi=10.1038/nature04328 |bibcode=2006Natur.439..584F |s2cid=4386245}}</ref> According to this theory, most snakes that are labelled "nonvenomous" would be considered harmless because they either lack a venom delivery method or are incapable of delivering enough to endanger a human. The theory postulates that snakes may have evolved from a common lizard ancestor that was venomous, and also that venomous lizards like the [[gila monster]], [[beaded lizard]], [[monitor lizard]]s, and the now-extinct [[mosasaurs]], may have derived from this same common ancestor. They share this "[[venom clade]]" with various other [[sauria]]n species.{{Citation needed|date=November 2024}}

Venomous snakes are classified in two taxonomic families:

* '''[[Elapidae|Elapid]]s''' – [[cobra]]s including [[king cobra]]s, [[Bungarus|kraits]], [[mamba]]s, [[Austrelaps|Australian copperheads]], [[Hydrophiinae|sea snake]]s, and [[coral snake]]s.{{sfn|Freiberg|Walls|1984|p=126}}
* '''[[Viperidae|Viperids]]''' – vipers, [[rattlesnake]]s, [[Agkistrodon contortrix|copperheads]]/[[Agkistrodon piscivorus|cottonmouths]], and [[Lachesis (genus)|bushmasters]].{{sfn|Freiberg|Walls|1984|p=126}}

There is a third family containing the ''opistoglyphous'' (rear-fanged) snakes (as well as the majority of other snake species):

* '''[[Colubridae|Colubrid]]s''' – [[boomslang]]s, [[tree snake]]s, [[Ahaetulla|vine snakes]], [[Boiga|cat snakes]], although not all colubrids are venomous.<ref name="Meh87"/>{{Rp|209}}{{sfn|Freiberg|Walls|1984|p=126}}