Crotalinae Totally Explained

Everything about Crotalinae totally explained

ť Common names: pit vipers, pitvipers.

The Crotalinae, or crotalines, are a subfamily of venomous vipers found in Asia and the Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on either side of the head. Currently, 18 genera and 151 species are recognized: 7 genera and 54 species in the Old World, against a greater diversity of 11 genera and 97 species in the New World. These are also the only viperids found in the Americas.

Description

These snakes range in size from the diminutive hump-nosed viper, Hypnale hypnale, that grows to an average only 30-45 cm, to the bushmaster, Lachesis muta; a species that's known to reach a maximum of 3.65 m in length -- the longest viperid in the world. What makes this group unique is that they all 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. These pits are sensitive to infrared radiation, in effect giving the snakes a sixth sense that helps them to find and perhaps even judge the size of the small warm-blooded prey on which they feed. It would seem as though the pit organs work like a primitive pair of eyes, although it isn't known whether the snake experiences this sense as a visual image or in some other fashion. Regardless, it's clear that these organs are of great value to a predator that hunts at night.
   Among vipers, these snakes are also unique in that they've a specialized muscle, called the muscularis pterigoidius glandulae, between the venom gland the head of the ectopterygoid. Contraction of this muscle, together with that of the m. compressor glandulae, forces venom out of the gland.
   Many temperate species (for example most rattlesnakes) will congregate in sheltered areas or dens to overwinter (see hibernation), the snakes benefitting from the combined heat. In cool temperatures and while pregnant vipers also bask on sunny ledges. Some species don't mass together in this way, for example the copperhead, Agkistrodon contortrix, or the Mojave rattlesnake, Crotalus scutulatus.
   Like most snakes, crotalines keep to themselves and will strike only if cornered or threatened. Smaller snakes are less likely to stand their ground than are larger specimens. Pollution and the destruction of rainforests has caused many viper populations to decline. Humans also threaten vipers, as many vipers are hunted for their skins or killed by cars when they wander onto roads.

Reproduction

With few exceptions, crotalines are ovoviviparous; that is, females give birth to live young. Among the oviparous (egg-laying) pit vipers are Lachesis, Calloselasma, and some Trimeresurus species. It is believed that all egg-laying crotalines guard their eggs.
Brood sizes range from two for very small species, to as many as 86 for the fer-de-lance, Bothrops atrox: a species 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. Used in a behavior known as caudal luring, the young snakes make worm-like movements with their tails to lure unsuspecting prey within striking distance.

Genera

Genus	Authority	Species	Subsp.*	Common name	Geographic range
Agkistrodon	Palisot de Beauvois, 1799	3	9	Moccasins	North America from the northeastern and central USA southward through peninsular Florida and southwestern Texas. In Central America on the Atlantic versant from Tamaulipas and Nuevo León southward to the Yucatan Peninsula, Belize and Guatemala. Along the Pacific coastal plane and lower foothills from Sonora south through Guatemala, El Salvador, Honduras and Nicaragua to northwestern Costa Rica.
Atropoides	Werman, 1992	3	2	Jumping pitvipers	The mountains of eastern Mexico southeastward on the Atlantic versant and lowlands though Central America to central Panama. On the Pacific versant, they occur in isolated populations in east-central and southern Mexico, Guatemala, El Salvador, Costa Rica and Panama.
Bothriechis	Peters, 1859	7	0	Palm-pitvipers	Southern Mexico (southeastern Oaxaca and the northern highlands of Chiapas), through Central America to northern South America (Colombia, western Venezuela, Ecuador and northern Peru.
Bothriopsis	Peters, 1861	7	2	Forest-pitvipers	Eastern Panama and most of northern South America, including the Pacific lowlands of Colombia and Ecuador, the Andes Mountains from Venezuela and Colombia to Bolivia, the Amazon Basin and the Atlantic forests of Brazil.
Bothrops	Wagler, 1824	32	11	Lanceheads	Northeastern Mexico (Tamaulipas) southward through Central and South America to Argentina; Saint Lucia and Martinique in the Lesser Antilles; Ilha da Queimada Grande off the coast of Brazil.
Calloselasma	Cope, 1860	1	0	Malayan pitviper	Southeast Asia from Thailand to northern Malaysia and Java, Indonesia.
Cerrophidion	Campbell & Lamar, 1992	3	0	Montane pitvipers	Southern Mexico (highlands of Guerrero and southeastern Oaxaca), southward through the highlands of Central America (Guatemala, El Salvador, Honduras, northern Nicaragua, Costa Rica) to western Panama.
Crotalus^T	Linnaeus, 1758	27	43	Rattlesnakes	The Americas, from southern Canada to northern Argentina.
Deinagkistrodon	Gloyd, 1979	1	0	Hundred-pace pitviper	Southeast Asia.
Gloydius	Hoge & Romano-Hoge, 1981	9	9		Russia, east of the Ural Mountains through Siberia, Iran, the Himalayas from Pakistan, India, Nepal and China, Korea, Japan and the Ryukyu Islands.
Hypnale	Fitzinger, 1843	3	0	Hump-nosed pit vipers	Sri Lanka and India.
Lachesis	Daudin, 1803	3	1	Bushmasters	Central and South America.
Ophryacus	Cope, 1887	2	0	Mexican horned pitvipers	Mexico.
Ovophis	Burger, 1981	3	3	Mountain pit vipers	Nepal and Seven Sisters (Assam) eastward through Myanmar, Cambodia, Thailand, Laos, Vietnam, West Malaysia, Taiwan, Japan (Okinawa) and Indonesia (Sumatra and Borneo).
Porthidium	Cope, 1871	7	3	Hognose pit vipers	Mexico (Colima, Oaxaca and Chiapas on the Pacific side, the Yucatan Peninsula on the Atlantic side) southward through Central America to northern South America (Ecuador in the Pacific lowlands, northern Venezuela in the Atlantic lowlands).
Sistrurus	Garman, 1883	3	7	Ground rattlesnakes	Southeastern Canada, eastern and northwestern USA, isolated populations in northern and central Mexico.
Trimeresurus	Lacépède, 1804	35	11	Asian lanceheads	Southest Asia from India to southern China and Japan, and the Malay Archipelago to Timor.
Tropidolaemus	Wagler, 1830	2	0	Temple vipers	Southern India and Southeast Asia.

*) Not including the nominate subspecies (typical form).
^T) Type genus.

Taxonomy

In the past, the pit vipers were usually classed as a separate family: the Crotalidae. Today, however, the monophyly of the viperines and the crotalines as a whole is undisputed, which is why they're treated here as a subfamily of the Viperidae.

Further Information

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