 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Pit viper" – news ·newspapers ·books ·scholar ·JSTOR(June 2011) (Learn how and when to remove this message) |
| Pit viper | |
|---|---|
 | |
| Timber rattlesnake (Crotalus horridus), showing thecharacteristic infrared-sensing pit below and between the eye and nostril | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Viperidae |
| Subfamily: | Crotalinae Oppel, 1811 |
| Synonyms | |
List
| |
TheCrotalinae, commonly known aspit vipers,[2][3] orpit adders, are asubfamily ofvipers found in Asia and the Americas. Like all other vipers, they arevenomous. They are distinguished by the presence of aheat-sensing pit organ located between the eye and the nostril on both sides of the head. Currently, 23genera and 155 species are recognized.[4] These are also the onlyviperids found in the Americas. The groups of snakes represented here includerattlesnakes,lanceheads, andAsian pit vipers. Thetype genus for this subfamily isCrotalus, of which thetype species is thetimber rattlesnake,C. horridus.[citation needed]
These snakes range in size from the diminutive hump-nosed viper,Hypnale hypnale, that grows to a typical total length (including tail) of only 30–45 cm (12–18 in), to the bushmaster,Lachesis muta, a species known to reach a maximum total length of 3.65 m (12.0 ft) in length.[citation needed]
This subfamily is unique in that all member species share a common characteristic – a deep pit, or fossa, in the loreal area between the eye and the nostril on either side of the head. Theseloreal pits are the external openings to a pair of extremely sensitiveinfrared-detecting organs, which in effect give the snakes a sixth sense to help them find and perhaps even judge the size of the small, warm-blooded prey on which they feed.[5]
Among vipers, these snakes are also unique in that they have a specialized muscle, called the muscularis pterigoidius glandulae, between the venom gland and the head of the ectopterygoid. Contraction of this muscle, together with that of the muscularis compressor glandulae, forces venom out of the gland.[5]
The earliest known fossil pit viper remains are from theEarly Miocene ofNebraska. As pit vipers are thought to have had an Asian origin before eventually colonizing the Americas, this suggests that they must have originated and diversified even earlier. During the Late Miocene, they reached as far west as eastern Europe, where they are no longer found; it is thought that they did not expand further into Europe.[6]
The subfamily Crotalinae is found fromCentral Asia eastward and southward toJapan,China,Indonesia, peninsularIndia,Nepal,Bangladesh andSri Lanka. In the Americas, they range from southernCanada southward to Central America to southern South America.[1]
Crotalines are a versatile subfamily, with members found inhabitats ranging from parcheddesert (e.g., the sidewinder,Crotalus cerastes) torainforests (e.g., the bushmaster,Lachesis muta). They may be eitherarboreal orterrestrial, and at least one species (the cottonmouth,Agkistrodon piscivorus) is semiaquatic. The altitude record is held jointly byCrotalus triseriatus in Mexico andGloydius strauchi in China, both of which have been found above the treeline at over 4,000 m above sea level.[5]
Although a few species of crotalines are highly active by day, such asTrimeresurus trigonocephalus, a bright green pit viperendemic to Sri Lanka, most are nocturnal, preferring to avoid high daytime temperatures and to hunt when their favored prey are also active. The snakes' heat-sensitive pits are also thought to aid in locating cooler areas in which to rest.[7]
As ambush predators, crotalines typically wait patiently somewhere for unsuspecting prey to wander by. At least one species, the arborealGloydius shedaoensis of China, is known to select a specific ambush site and return to it every year in time for the spring migration of birds. Studies have indicated these snakes learn to improve their strike accuracy over time.[8]
Many temperate species of pit vipers (e.g. most rattlesnakes) congregate in sheltered areas or "dens" to overwinter (brumate, seehibernation), the snakes benefiting from the combined heat. In cool temperatures and while pregnant, pit vipers also bask on sunny ledges. Some species do not mass together in this way, for example the copperhead,Agkistrodon contortrix, or the Mojave rattlesnake,Crotalus scutulatus.[citation needed]
Like most snakes, crotalines keep to themselves and strike only if cornered or threatened. Smaller snakes are less likely to stand their ground than larger specimens. Pollution and the destruction of rainforests have caused many pit viper populations to decline. Humans also threaten pit vipers, as many are hunted for their skins or killed by cars when they wander onto roads.[citation needed]
With few exceptions, crotalines areovoviviparous, meaning that the embryos develop within eggs that remain inside the mother's body until the offspring are ready to hatch, when the hatchlings emerge as functionally free-living young. In such species, the eggshells are reduced to soft membranes that the young shed, either within the reproductive tract, or immediately after emerging.
Among theoviparous (egg-laying) pit vipers areLachesis,Calloselasma, and someTrimeresurus species. All egg-laying crotalines are believed to guard their eggs.[citation needed]
Brood sizes range from two for very small species, to as many as 86 for the fer-de-lance,Bothrops atrox, which is among the most prolific of all live-bearing snakes.
Many young crotalines have brightly coloured tails that contrast dramatically with the rest of their bodies. These tails are known to be used by a number of species in a behavior known as caudal luring; the young snakes make worm-like movements with their tails to lure unsuspecting prey within striking distance.[9]
In the past, the pit vipers were usually classed as a separatefamily: the Crotalidae. Today, however, themonophyly of theviperines and the crotalines as a whole is undisputed, which is why they are treated here as a subfamily of theViperidae.[citation needed]
| Genus[ref 1] | Taxon author[ref 1] | Species[ref 1] | Common name | Geographic range[ref 2] |
|---|---|---|---|---|
| Agkistrodon | Palisot de Beauvois, 1799 | 6 | Moccasins | North America from the northeastern and central USA southward through peninsularFlorida and southwesternTexas. In Central America on the Atlantic versant fromTamaulipas andNuevo León southward to theYucatán Peninsula,Belize andGuatemala. Along the Pacific coastal plain and lower foothills fromSonora south through Guatemala,El Salvador,Honduras andNicaragua to northwesternCosta Rica. |
| Atropoides | Werman, 1992 | 1 | Picado's jumping pit viper | Costa Rica and western Panama |
| Bothriechis | Peters, 1859 | 19 | Palm-pit vipers | Southern Mexico (southeasternOaxaca and the northern highlands ofChiapas), through Central America to northern South America (Colombia, westernVenezuela,Ecuador and northernPeru |
| Bothrocophias | Gutberlet &Campbell, 2001 | 9 | Toadheaded pit vipers | Northern South America |
| Bothrops | Wagler, 1824 | 48 | Lanceheads | Northeastern Mexico (Tamaulipas) southward through Central and South America toArgentina;Saint Lucia andMartinique in theLesser Antilles;Ilha da Queimada Grande off the coast of Brazil |
| Calloselasma | Cope, 1860 | 1 | Malayan pit viper | Southeast Asia fromThailand to northernMalaysia andJava,Indonesia |
| Cerrophidion | Campbell & Lamar, 1992 | 5 | Montane pit vipers | Southern Mexico (highlands ofGuerrero and southeastern Oaxaca), southward through the highlands of Central America (Guatemala, El Salvador, Honduras, northern Nicaragua, Costa Rica) to western Panama |
| Craspedocephalus | Kuhl &van Hasselt, 1822 | 15 | Pit viper | India toThailand to northernMalaysia andIndonesia |
| CrotalusT | Linnaeus,1758 | 51 | Rattlesnakes | The Americas, from southern Canada to northern Argentina |
| Deinagkistrodon | Gloyd, 1979 | 1 | Hundred-pace pit viper | Southeast Asia |
| Garthius | Malhotra & Thorpe, 2004 | 1 | Mount Kinabalu pit viper, Chasen's mountain pit viper | Borneo |
| Gloydius | Hoge & Romano-Hoge, 1981 | 22 | Asian moccasins | Russia, east of theUral Mountains throughSiberia,Iran, theHimalayas from Pakistan, India,Nepal and China, Korea, Japan and theRyukyu Islands |
| Hypnale | Fitzinger, 1843 | 3 | Hump-nosed pit vipers | Sri Lanka and India |
| Lachesis | Daudin, 1803 | 4 | Bushmasters | Central and South America |
| Metlapilcoatlus | Campbell, Frost, & Castoe, 2019 | 6 | Jumping pit vipers | The mountains of eastern Mexico southeastward on the Atlantic versant and lowlands though Central America to centralPanama. On the Pacific versant, they occur in isolated populations in east-central and southern Mexico, Guatemala, El Salvador, Costa Rica, and Panama. |
| Mixcoatlus | Jadin, H.M.Smith & Campbell, 2011 | 3 | Mexican pit vipers | Mexico |
| Ophryacus | Cope, 1887 | 3 | Mexican horned pit vipers | Mexico |
| Ovophis | Burger, 1981 | 7 | Mountain pit vipers | Nepal andSeven Sisters (Assam) of India eastward throughMyanmar,Cambodia, Thailand,Laos,Vietnam,West Malaysia,Taiwan, Japan (Okinawa) and Indonesia (Sumatra) |
| Porthidium | Cope, 1871 | 9 | Hognose pit vipers | Mexico (Colima, Oaxaca and Chiapas on the Pacific side, the Yucatán Peninsula on the Atlantic side) southward through Central America to northern South America (Ecuador in the Pacific lowlands, northern Venezuela in the Atlantic lowlands) |
| Protobothrops | Hoge & Romano-Hoge, 1983 | 14 | Pit vipers | Asia |
| Sistrurus | Garman, 1883 | 3 | Ground rattlesnakes | Southeastern Canada, eastern, central and northwestern USA, isolated populations in northern and central Mexico |
| Trimeresurus | Lacépède, 1804 | 43 | Asian lanceheads | Southeast Asia from India to southern China and Japan, and theMalay Archipelago toTimor |
| Tropidolaemus | Wagler, 1830 | 5 | Temple vipers | Southern India and Southeast Asia |
*) Not including the nominate subspecies.[citation needed]
T)Type genus.[ref 2]
| International | |
|---|---|
| National | |
