Venomous snake
Encyclopedia
"Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis
.
Venomous snakes are snakes which have venom glands and specialized teeth for the injection of venom. Members of the families Elapidae
, Viperidae
, Hydrophiidae, and Atractaspididae
(and some from Colubridae as well) are major venomous snakes.
, usually delivered through highly specialized teeth such as hollow fangs, for the purpose of prey immobilization and self-defense. In contrast, non-venomous species either constrict
their prey, or simply overpower it with their jaws.
Venomous snakes include several families
of snakes and do not form a single taxonomic group. This has been interpreted to mean that venom in snakes originated more than once as the result of convergent evolution
. Evidence has recently been presented for the Toxicofera
hypothesis however; venom was present (in small amounts) in the ancestor of all snakes (as well as several lizard families) as 'toxic saliva' and evolved to extremes in those snake families normally classified as venomous by parallel evolution
. The Toxicofera hypothesis further implies that 'non venomous' snake lineages have either lost the ability to produce venom (but may still have lingering venom pseudogene
s), or actually do produce venom in small quantities, likely sufficient to assist in small prey capture, but cause no harm to humans if bitten.
Lists or rankings of the world's "most venomous snakes" are tentative and differ greatly due to numerous factors, including the recentness and reliability of the data, the number of species analyzed, and the testing methods used.
In addition, since mice are the common indicator used to test venom
from venomous snakes in LD50
tests, the LD50 results may not reflect the actual effects on humans due to the physiological differences between mice and humans. For example, many venomous snakes are specialized predators on mice, and their venom may be adapted specifically to incapacitate mice. While most mammals have a very similar physiology, LD50 results may or may not be directly relevant to humans. Sometimes, results from different tests may cause confusion as different toxicity scales are in use.
While there have been numerous studies on snake venom, potency estimates can vary, creating overlap and greatly complicating the task. Further, may be measured through intramuscular, intraperitoneal, intravenous or subcutaneous injection
s on small rodents, although the latter is the most applicable to actual bites. It should also be considered that mice, the most commonly used animals in determining LD50, may react to some snake venoms differently than humans do, this may be why some species of snake show high toxicity when tested on mice, but have surprisingly low mortality rates in untreated human bites (for example, the Eastern coral snake
, Philippine cobra
, and even the Eastern brown snake
). Based on medical literature dating back from the early 1900's to the present, the most venomous or deadliest snake to humans has been the Black mamba
. The species has the most rapid-acting venom of any snake and it carries a 100% mortality rate in untreated cases of human envenomation. Another snake with a similar reputation is the Coastal taipan
, which has an untreated mortality rate of 95-99% in humans, second only to the black mamba. The Eastern brown snake's venom is nearly 3 times more potent than the Coastal taipan's, yet to humans the untreated mortality rate for the Eastern brown snake is somewhere between 10-20%, far lower than both the Black mamba and Coastal taipan.
Many of these lists only take into account of terrestrial and arboreal snakes and neglect to list the of venom of the sea snakes. Species of sea snakes have been listed to have more toxic venom than even that of the Inland taipan and further investigations of some species' venom are needed.
s and poison
s are different. Poisons can be absorbed by the body, such as through the skin or digestive system, while venoms must first be introduced directly into tissues or the blood stream (envenomated
) through mechanical means. It is, for example, therefore harmless to drink snake venom as long as there are no lacerations inside the mouth or digestive tract. There are however two exceptions: the Rhabdophis
snakes (keelback snakes) secrete poison from glands that it gets from the poisonous toads that it preys on; similarly certain garter snake
s from Oregon
retain toxins in their liver from the newts they eat.
Rhabdophis
Rhabdophis is a genus of snakes, generally called keelback snakes, found primarily in southeast Asia.- Species of Rhabdophis :* Rhabdophis adleri* Rhabdophis angeli* Rhabdophis auriculata...
.
Elapidae
Elapidae is a family of venomous snakes found in tropical and subtropical regions around the world, terrestrially in Asia, Australia, Africa, North America and South America and aquatically in the Pacific and Indian Oceans...
, Viperidae
Viperidae
The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four...
, Hydrophiidae, and Atractaspididae
Atractaspididae
The Atractaspididae are a family of snakes found in Africa and the Middle East. Currently, 12 genera are recognized.-Description:This family includes many genera formerly classed in other families, on the basis of fang type. It includes fangless , rear-fanged , fixed-fanged , and viper-like species...
(and some from Colubridae as well) are major venomous snakes.
Description
Venomous snakes use modified saliva, snake venomSnake venom
Snake venom is highly modified saliva that is produced by special glands of certain species of snakes. The glands which secrete the zootoxin are a modification of the parotid salivary gland of other vertebrates, and are usually situated on each side of the head below and behind the eye,...
, usually delivered through highly specialized teeth such as hollow fangs, for the purpose of prey immobilization and self-defense. In contrast, non-venomous species either constrict
Constriction
Constriction is a method used by various snake species to kill their prey. Although some species of venomous and mildly-venomous snakes do use constriction to subdue their prey, most snakes which use constriction lack venom. The snake initially strikes at its prey and holds on, pulling the prey...
their prey, or simply overpower it with their jaws.
Venomous snakes include several families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of snakes and do not form a single taxonomic group. This has been interpreted to mean that venom in snakes originated more than once as the result of convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
. Evidence has recently been presented for the Toxicofera
Toxicofera
Toxicofera , is a hypothetical clade which represents about 4600 species of extant squamates It encompasses all venomous reptile species, as well as numerous related non-venomous species....
hypothesis however; venom was present (in small amounts) in the ancestor of all snakes (as well as several lizard families) as 'toxic saliva' and evolved to extremes in those snake families normally classified as venomous by parallel evolution
Parallel evolution
Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades.-Parallel vs...
. The Toxicofera hypothesis further implies that 'non venomous' snake lineages have either lost the ability to produce venom (but may still have lingering venom pseudogene
Pseudogene
Pseudogenes are dysfunctional relatives of known genes that have lost their protein-coding ability or are otherwise no longer expressed in the cell...
s), or actually do produce venom in small quantities, likely sufficient to assist in small prey capture, but cause no harm to humans if bitten.
Most venomous snake
| Snake | Region | SC Subcutaneous injection A subcutaneous injection is administered as a bolus into the subcutis, the layer of skin directly below the dermis and epidermis, collectively referred to as the... |
| Inland taipan | Australia | 0.025 mg/kg |
| Eastern brown snake | Australia | 0.0365 mg/kg |
| Coastal taipan Coastal Taipan The Coastal Taipan , or common taipan, is a large, highly venomous snake of the family Elapidae. It is native to the coastal regions of northern and eastern Australia and the island of New Guinea. According to most studies, this species is the third most venomous land snake in the world.-Physical... |
Australia, New Guinea | 0.106 mg/kg |
| Many banded krait Bungarus multicinctus The Many-banded krait , also known as the Taiwanese krait or the Chinese krait, is a species of the genus Bungarus found predominantly in mainland China and Taiwan.-Geographic range and habitat:... |
China, Taiwan, Burma, Laos, Vietnam | 0.108 mg/kg |
| Peninsula tiger snake | Australia | 0.131 mg/kg |
| Saw-scaled viper Echis carinatus Echis carinatus is a venomous viper species found in parts of the Middle East and Central Asia, and especially the Indian subcontinent. It is the smallest member of the Big Four snakes... |
Asia; Indian subcontinent | 0.151 mg/kg |
| Black Mamba Black mamba The black mamba , also called the common black mamba or black-mouthed mamba, is the longest venomous snake in Africa, averaging around in length, and sometimes growing to lengths of... |
Sub Saharan Africa | 0.185 mg/kg |
| Western tiger snake | Australia | 0.194 mg/kg |
| Eastern coral snake Micrurus fulvius Micrurus fulvius is a venomous elapid snake that is found in the southeastern United States and northeastern Mexico. It should not be confused with the scarlet snake or scarlet kingsnake , which are harmless mimics... |
Northeast Mexico, Southeast U.S. | 0.196 mg/kg |
| Philippine cobra Philippine Cobra The Philippine Cobra is a stocky, highly venomous spitting cobra native to the Philippines. The Philippine Cobra is called "ulupong" in Tagalog and "Agwason" in Cebuano-Bisaya.-Description:... |
Philippines | 0.21 mg/kg |
Lists or rankings of the world's "most venomous snakes" are tentative and differ greatly due to numerous factors, including the recentness and reliability of the data, the number of species analyzed, and the testing methods used.
In addition, since mice are the common indicator used to test venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
from venomous snakes in LD50
LD50
In toxicology, the median lethal dose, LD50 , LC50 or LCt50 of a toxin, radiation, or pathogen is the dose required to kill half the members of a tested population after a specified test duration...
tests, the LD50 results may not reflect the actual effects on humans due to the physiological differences between mice and humans. For example, many venomous snakes are specialized predators on mice, and their venom may be adapted specifically to incapacitate mice. While most mammals have a very similar physiology, LD50 results may or may not be directly relevant to humans. Sometimes, results from different tests may cause confusion as different toxicity scales are in use.
While there have been numerous studies on snake venom, potency estimates can vary, creating overlap and greatly complicating the task. Further, may be measured through intramuscular, intraperitoneal, intravenous or subcutaneous injection
Subcutaneous injection
A subcutaneous injection is administered as a bolus into the subcutis, the layer of skin directly below the dermis and epidermis, collectively referred to as the...
s on small rodents, although the latter is the most applicable to actual bites. It should also be considered that mice, the most commonly used animals in determining LD50, may react to some snake venoms differently than humans do, this may be why some species of snake show high toxicity when tested on mice, but have surprisingly low mortality rates in untreated human bites (for example, the Eastern coral snake
Micrurus fulvius
Micrurus fulvius is a venomous elapid snake that is found in the southeastern United States and northeastern Mexico. It should not be confused with the scarlet snake or scarlet kingsnake , which are harmless mimics...
, Philippine cobra
Philippine Cobra
The Philippine Cobra is a stocky, highly venomous spitting cobra native to the Philippines. The Philippine Cobra is called "ulupong" in Tagalog and "Agwason" in Cebuano-Bisaya.-Description:...
, and even the Eastern brown snake
Eastern brown snake
The eastern brown snake , often referred to as the common brown snake, is a species of genus Pseudonaja. This snake is considered the second most venomous land snake based on its value in mice. It is native to Australia, New Guinea and Indonesia.-Description:Adult eastern brown snakes are highly...
). Based on medical literature dating back from the early 1900's to the present, the most venomous or deadliest snake to humans has been the Black mamba
Black mamba
The black mamba , also called the common black mamba or black-mouthed mamba, is the longest venomous snake in Africa, averaging around in length, and sometimes growing to lengths of...
. The species has the most rapid-acting venom of any snake and it carries a 100% mortality rate in untreated cases of human envenomation. Another snake with a similar reputation is the Coastal taipan
Coastal Taipan
The Coastal Taipan , or common taipan, is a large, highly venomous snake of the family Elapidae. It is native to the coastal regions of northern and eastern Australia and the island of New Guinea. According to most studies, this species is the third most venomous land snake in the world.-Physical...
, which has an untreated mortality rate of 95-99% in humans, second only to the black mamba. The Eastern brown snake's venom is nearly 3 times more potent than the Coastal taipan's, yet to humans the untreated mortality rate for the Eastern brown snake is somewhere between 10-20%, far lower than both the Black mamba and Coastal taipan.
Many of these lists only take into account of terrestrial and arboreal snakes and neglect to list the of venom of the sea snakes. Species of sea snakes have been listed to have more toxic venom than even that of the Inland taipan and further investigations of some species' venom are needed.
Other information
Venomous snakes are often said to be poisonous, although this is not the correct term, as venomVenom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
s and poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....
s are different. Poisons can be absorbed by the body, such as through the skin or digestive system, while venoms must first be introduced directly into tissues or the blood stream (envenomated
Envenomation
Envenomation is the process by which venom is injected into some animal by the bite of a venomous animal. Many kinds of animals, including mammals , reptiles , spiders , insects , employ venom for hunting and for self defense...
) through mechanical means. It is, for example, therefore harmless to drink snake venom as long as there are no lacerations inside the mouth or digestive tract. There are however two exceptions: the Rhabdophis
Rhabdophis
Rhabdophis is a genus of snakes, generally called keelback snakes, found primarily in southeast Asia.- Species of Rhabdophis :* Rhabdophis adleri* Rhabdophis angeli* Rhabdophis auriculata...
snakes (keelback snakes) secrete poison from glands that it gets from the poisonous toads that it preys on; similarly certain garter snake
Garter snake
The Garter snake is a Colubrid snake genus common across North America, ranging from Alaska and Canada to Central America. It is the single most widely distributed genus of reptile in North America. The garter snake is also the Massachusettsstate reptile.There is no real consensus on the...
s from Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
retain toxins in their liver from the newts they eat.
Families of venomous snakes
Over 600 species are known to be venomous—about a quarter of all snake species. The following table lists some major species.| Family | Description |
|---|---|
| Atractaspididae Atractaspididae The Atractaspididae are a family of snakes found in Africa and the Middle East. Currently, 12 genera are recognized.-Description:This family includes many genera formerly classed in other families, on the basis of fang type. It includes fangless , rear-fanged , fixed-fanged , and viper-like species... (atractaspidids) |
Burrowing asps, mole vipers, stiletto snakes. |
| Colubridae (colubrids) | Most are harmless, but others have toxic saliva and at least five species, including the boomslang (Dispholidus typus), have caused human fatalities. |
| Elapidae Elapidae Elapidae is a family of venomous snakes found in tropical and subtropical regions around the world, terrestrially in Asia, Australia, Africa, North America and South America and aquatically in the Pacific and Indian Oceans... (elapids) |
Sea snakes, Taipans, Brown snakes Pseudonaja Pseudonaja is a genus of venomous elapid snakes native to Australia. Members are known commonly as brown snakes and are considered to be one of the most dangerous snakes in the country; even young snakes are capable of delivering a fatal envenomation to a human.- Species :* Dugite or Spotted... , Mambas, Coral snakes, Kraits Bungarus Bungarus, commonly referred to as kraits , is a genus of venomous elapid snakes found in South and South-East Asia. There are 12 species and 5 subspecies recognized.- Distribution :... , King Cobra, Death adders Acanthophis Acanthophis is a genus of elapid snakes. Commonly called death adders, they are native to Australia, New Guinea and nearby islands, and are among the most venomous snakes in the world... , Tiger Snakes Notechis Tiger snakes are a type of venomous serpent found in southern regions of Australia, including its coastal islands and Tasmania. These snakes are highly variable in their colour, often banded like those on a tiger, and forms in their regional occurrences... , Cobras Naja Naja is a genus of venomous elapid snakes. Although there are several other genera that share the common name, Naja are the most recognized and most widespread group of snakes commonly known as cobras. The genus Naja consists of 20 to 22 species, but has undergone several taxonomic revisions in... . |
| Viperidae Viperidae The Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four... (viperids) |
True vipers Viperinae The Viperinae, or viperines, are a subfamily of venomous vipers found in Europe, Asia and Africa. They are distinguished by their lack of the heat-sensing pit organs that characterize their sister group, the Crotalinae. Currently, 12 genera and 66 species are recognized... , including the russell's viper Daboia Daboia is a monotypic genus of venomous Old World viper. The single species, D. russelii, is found in Asia throughout the Indian subcontinent, much of Southeast Asia, southern China and Taiwan... , saw-scaled vipers Echis Echis is a genus of venomous vipers found in the dry regions of Africa, the Middle East, Pakistan, India and Sri Lanka. They have a characteristic threat display, rubbing sections of their body together to produce a "sizzling" warning sound... , and puff adders Bitis Bitis is a genus of venomous vipers found in Africa and the southern Arabian Peninsula. It includes the largest and the smallest vipers in the world. Members are known for their characteristic threat displays that involves inflating and deflating their bodies while hissing and puffing loudly. The... and Pit vipers Crotalinae The Crotalinae, commonly known as "pit vipers" or crotaline snakes, 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... , including rattlesnakes Crotalus Crotalus is a genus of venomous pit vipers found only in the Americas from southern Canada to northern Argentina. The name is derived from the Greek word krotalon, which means "rattle" or "castanet", and refers to the rattle on the end of the tail which makes this group so distinctive... , lanceheads Bothrops Bothrops is a genus of venomous pitvipers found in Central and South America. The generic name is derived from the Greek words bothros and ops that mean "pit" and "eye" or "face"; an allusion to the heat-sensitive loreal pit organs. Members of this genus are responsible for more human deaths in the... , and copperheads and cottonmouths Agkistrodon Agkistrodon is a genus of venomous pit vipers found in North America from the United States south to northern Costa Rica. The name is derived from the Greek words ἄγκιστρον 'fishhook' and ὁδοὐς 'tooth', and is likely a reference to the fangs... . |
See also
- SnakebiteSnakebiteA snakebite is an injury caused by a bite from a snake, often resulting in puncture wounds inflicted by the animal's fangs and sometimes resulting in envenomation. Although the majority of snake species are non-venomous and typically kill their prey with constriction rather than venom, venomous...
- Snake venomSnake venomSnake venom is highly modified saliva that is produced by special glands of certain species of snakes. The glands which secrete the zootoxin are a modification of the parotid salivary gland of other vertebrates, and are usually situated on each side of the head below and behind the eye,...
- Big Four (Indian snakes)Big Four (Indian snakes)The Big Four are the four venomous snake species responsible for causing the most snake bite cases in South Asia .The Big Four:* Indian cobra, Naja naja, probably the most famous of all Indian snakes....
- List of venomous animals
- venomous fishVenomous fishVenomous fish are fish that produce venom. There are at least 1200 species of venomous fish, and they include the Stonefish, Lionfish, Scorpion Fish, Stargazer, and Toadfish .-See also:* Hallucinogenic fish...
- Venomous mammalsVenomous mammalsVenomous mammals are animals of the class Mammalia that produce venom, which they use to kill or disable prey, or to defend themselves from predators. In modern nature, venomous mammals are quite rare. Venom is much more common among other vertebrates; there are many more species of venomous...
- Poisonous AmphibiansPoisonous amphibiansPoisonous Amphibians are amphibians that produce toxins to defend themselves from predators.Except certain salamandrid salamanders that can extrude sharp venom-tipped ribs, amphibians are not known to actively inject venom, most toxic amphibians are instead known to be poisonous to touch or eat...
- Toxic BirdsToxic birdsToxic birds are birds that produce toxins to defend themselves from predators. No species of bird is known to actively inject venom, but some birds are known to be poisonous to touch or eat...
External links
- Venomous Snake Community Pictures, forums, Classifieds and Venomous snake species listings
- Overview of the world's venomous snakes
- For goodness snakes Treating and Preventing Venomous Bites.
- Venomous snakes and outdoor workers Bite-prevention and treatment information for outdoor workers.