Editing Viper (section)

==Venom==
Viperid venoms typically contain an abundance of [[protein]]-degrading enzymes, called [[Protease|proteases]], that produce symptoms such as pain, strong local swelling and [[necrosis]], blood loss from cardiovascular damage complicated by [[coagulopathy]], and disruption of the blood-clotting system. Also being vasculotoxic in nature, viperine venom causes vascular [[Endothelium|endothelial]] damage and [[hemolysis]]. Death is usually caused by collapse in blood pressure. This is in contrast to [[elapid]] venoms, which generally contain [[neurotoxin]]s that disable muscle contraction and cause paralysis. Death from elapid bites usually results from [[Asphyxia|asphyxiation]] because the diaphragm can no longer contract, but this rule does not always apply; some elapid bites include [[proteolytic]] symptoms typical of viperid bites, while some viperid bites produce [[Neurotoxicity|neurotoxic]] symptoms.<ref name="snakesuntamed"/>

Proteolytic venom is also dual-purpose: first, it is used for defense and to immobilize prey, as with neurotoxic venoms; second, many of the venom's enzymes have a digestive function, breaking down molecules such as [[lipid]]s, [[nucleic acid]]s, and proteins.<ref name="Slo00">{{cite journal|author=Slowinski, Joe|date=2000|url=http://www.calacademy.org/calwild/2000spring/stories/venoms.html|title=Striking Beauties: Venomous Snakes|journal=California Wild|volume=53|issue=2 |archive-url=https://web.archive.org/web/20041013052652/http://www.calacademy.org/calwild/2000spring/stories/venoms.html |archive-date=13 October 2004}}</ref> This is an important adaptation, as many vipers have inefficient digestive systems.<ref name="Smi04">{{cite web|author=Smith, SA|date=2004|url=http://www.dnr.state.md.us/wildlife/ssss_snakes.asp|title=Did Someone Say... SSSSnakes?|publisher=Maryland Dept. of Natural Resources|access-date=2 December 2006|archive-date=21 July 2006|archive-url=https://web.archive.org/web/20060721184723/http://www.dnr.state.md.us/wildlife/ssss_snakes.asp|url-status=dead}}</ref>

Due to the nature of proteolytic venom, a viperid bite is often a very painful experience and should always be taken seriously, though it may not necessarily prove fatal. Even with prompt and proper treatment, a bite can still result in a permanent [[scar]], and in the worst cases, the affected limb may even have to be [[amputation|amputated]]. A victim's fate is impossible to predict, as this depends on many factors, including the species and size of the snake involved, how much venom was injected (if any), and the size and condition of the patient before being bitten. Viper bite victims may also be [[allergy|allergic]] to the venom or the [[antivenom]].

===Behavior===
These snakes can decide how much venom to inject depending on the circumstances. The most important determinant of venom expenditure is generally the size of the snake; larger specimens can deliver much more venom. The species is also important, since some are likely to inject more venom than others, may have more venom available, strike more accurately, or deliver a number of bites in a short time. In predatory bites, factors that influence the amount of venom injected include the size of the prey, the species of prey, and whether the prey item is held or released. The need to label prey for chemosensory relocation after a bite and release may also play a role. In defensive bites, the amount of venom injected may be determined by the size or species of the predator (or antagonist), as well as the assessed level of threat, although larger assailants and higher threat levels may not necessarily lead to larger amounts of venom being injected.<ref name="Hay02">Hayes WK, Herbert SS, Rehling GC, Gennaro JF. 2002. Factors that influence venom expenditure in viperids and other snake species during predatory and defensive contexts. ''In'' Schuett GW, Höggren M, Douglas ME, Greene HW. 2002. Biology of the Vipers. Eagle Mountain Publishing, LC. 580 pp. 16 plates. {{ISBN|0-9720154-0-X}}.</ref>

===Prey tracking===
[[File:(Westliche Diamantklapperschlange) Crotalus atrox.jpg|thumb|right|The western diamondback rattlesnake ''[[Crotalus atrox]]'', the venom of which contains proteins allowing the snake to track down bitten prey]]
[[Hemotoxin|Hemotoxic]] venom takes more time than neurotoxic venom to immobilize prey, so viperid snakes need to track down prey animals after they have been bitten,<ref name="Hay02"/> in a process known as "prey relocalization". Vipers are able to do this via certain proteins contained in their venom. This important adaptation allowed [[Rattlesnake|rattlesnakes]] to evolve the strike-and-release bite mechanism, which provided a huge benefit to snakes by minimizing contact with potentially dangerous prey animals.<ref name=Saviolaetal2013/> This adaptation, then, requires the snake to track down the bitten animal to eat it, in an environment full of other animals of the same species. [[Western diamondback rattlesnake|Western diamondback rattlesnakes]] respond more actively to mouse carcasses that have been injected with crude rattlesnake venom. When the various components of the venom were separated out, the snakes responded to mice injected with two kinds of [[disintegrin]]s, which are responsible for allowing the snakes to track down their prey.<ref name=Saviolaetal2013>{{cite journal| last1 = Saviola| first1 = A.J.| last2 = Chiszar | first2 = D.| last3 = Busch| first3 = C. | last4 = Mackessy| first4 = S.P.| year = 2013| title = Molecular basis for prey relocation in viperid snakes| journal = BMC Biology| volume = 11 | pages = 20| doi =10.1186/1741-7007-11-20| pmid = 23452837| pmc = 3635877| doi-access = free}}</ref>