- "Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis.
Venomous snakes use modified saliva, and snake venom, usually delivered through highly specialized teeth, such as hollow fangs, for the purpose of prey immobilization and self-defense. In contrast, nonvenomous species either constrict their prey, or 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 venom in snakes originated more than once as the result of convergent evolution. Evidence has recently been presented for the Toxicofera hypothesis, but venom was present (in small amounts) in the ancestors 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 'nonvenomous' snake lineages have either lost the ability to produce venom (but may still have lingering venom pseudogenes), or actually do produce venom in small quantities, likely sufficient enough to help capture small prey but causing no harm to humans when bitten.
Most venomous snakes
While there have been numerous studies on snake venom, potency estimates can slightly vary,
Considering the toxicity of a species based on LD50 on mice alone may not accurately estimate the danger of the species to humans. The physiological differences between the animals tested and humans is another major problem in categorizing the most venomous snakes. Mice are the common indicator used to test venom from venomous snakes in LD50 tests, so the LD50 results may not reflect the actual effects on humans due to the physiological differences between mice and humans. Many venomous snakes are specialized predators on mice, and their venom may be adapted specifically to incapacitate mice. While most mammals have a fairly similar physiology, LD50 results may or may not be directly relevant to humans.
Based on the median lethal dose value in mice, the inland taipan venoms, drop for drop, is by far the most toxic of any snake in the world – much more so than even sea snakes. And the most venomous when tested on human heart cell culture.
Toxicity of snake venom is sometimes used to gauge the extent of their danger to humans, but this is inappropriate. A number of other factors are more critical in determining the potential hazard of any given venomous snake to humans, including the distribution and behavior of each species. For example, while the inland taipan is regarded as the world's most venomous snake based on LD50, the so-called Big Four snakes cause far more snakebites because they are much more abundant in highly populated areas. Clinical mortality rate (often estimated by measured toxicity on mice) is another commonly used indicator to determine the danger of any given venomous snake, but important too are its efficiency of venom delivery, its venom yield and its behavior when it encounters humans (as reflected by clinical precedents). Black mamba and coastal taipan are considered the most aggressive snakes, who are willing many times to stand their ground and strike in all situations Other species with clinically proven high mortality rates include the common krait at 70-80%  and the Many-banded krait from 20-30%to 77-100%, etc. The timespan between envenomation and death is another measure of how dangerous a given venomous species is to humans; e.g., a black mamba or coastal taipan bites are rapidly fatal if untreated.
LD50 toxicity rankings
Subcutaneous : Venom is injected into the fatty layer beneath the skin. Intravenous : Venom is injected directly into a vein. Intramuscular : Venom is injected into a muscle. Intraperitoneal : Venom is injected into the abdominal cavity. The most commonly tested methods are subcutaneous and intravenous injections of mice. Subcutaneous is the most applicable to actual bites. Only large Bitis or extremely large Bothrops or Crotalus specimens would be able to deliver a bite that is truly intramuscular. IV injections are extremly rare in actual bites. Testing using dry venom mixed with 0.1% bovine serum albumin in saline, gives more consistent results than just saline alone.
|Snake||Region||subcutaneous injection LD50 0.1% bovine serum albumin in Saline||subcutaneous injection LD50 Saline||intravenous injection LD50||intramuscular injection LD50 N/A for listed snakes||intraperitoneal injection LD50 N/A for listed snakes|
|Inland taipan||Australia||0.01 mg/kg||0.025 mg/kg||N/A|
|Dubois' seasnake||Coral Sea, Arafura Sea, Timor Sea and Indian Ocean||N/A||0.044 mg/kg||N/A|
|Eastern brown snake||Australia, Papua New Guinea, Indonesia||0.041 mg/kg||0.053 mg/kg||0.01 mg/kg|
|Coastal Taipan||Australia||0.064 mg/kg||0.099 mg/kg||0.013 mg/kg|
|Yellow bellied sea snake||Tropical oceanic waters||N/A||0.067 mg/kg||N/A|
|Peron's sea snake||Gulf of Siam, Strait of Taiwan, Coral sea islands, and other places||N/A||0.079 mg/kg||N/A|
|Black Tiger snake||Australia||0.099 mg/kg||0.131 mg/kg||N/A|
|Many-banded krait||Mainland China, Taiwan, Vietnam, Laos, Burma||N/A||0.108 mg/kg||0.113 mg/kg|
|Black-banded sea krait||eastern coast of the Malay Peninsula and Brunei, and in Halmahera, Indonesia..||N/A||0.111 mg/kg||N/A|
|Mainland Tiger snake||Australia||0.118 mg/kg||0.118 mg/kg||0.014 mg/kg|
|Western Australian Tiger snake||Australia||0.124 mg/kg||0.194 mg/kg||N/A|
|Beaked sea snake||Tropical Indo-Pacific||0.164 mg/kg||0.1125 mg/kg||N/A|
Venomous snakes are often said to be poisonous, although this is not the correct term since venom and poison are different entities. Poisons are absorbed by the body, such as through skin or the digestive system, while venoms must first be introduced directly into tissues or the bloodstream (envenomated) by mechanical means. It is, for example, harmless to drink snake venom as long as there are no lacerations inside the mouth or digestive tract. The two exceptions are: the Rhabdophis keelback snakes secrete poison from glands they get from the poisonous toads they consume, and similarly, certain garter snakes from Oregon retain toxins in their livers 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.
|Atractaspididae (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 (elapids)||Sea snakes, taipans, brown snakes, mambas, coral snakes, kraits, king cobra, death adders, tiger snakes and cobras|
|Viperidae (viperids)||True vipers, including the Russell's viper, saw-scaled vipers, puff adders and pit vipers, including rattlesnakes, lanceheads and copperheads and cottonmouths.|
- Snake venom
- Big Four (Indian snakes)
- List of venomous animals
- Venomous fish
- Venomous mammals
- Poisonous amphibians
- Toxic birds
- Oldest fossil evidence of modern African venomous snakes found in Tanzania, Ohio University, March 20, 2014, doi:10.1371/journal.pone.0090415
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- "What is an LD50 and LC50".
- The Australian venom research unit (August 25, 2007). "Which snakes are the most venomous?". University of Melbourne. Retrieved October 14, 2013.
- Venom Immunochemistry, Pharmacology and Emergency Response (VIPER) Institute. Frequently Asked Questions -What is the most venomous snake?. "Many experts answer that it is the Inland Taipan of Australia, because its drop-by-drop concentration of venom has great potency when measured by its ability to kill rodents" . University of Arizona. Retrieved October 14, 2013.
- Department of Wildlife Ecology and Conservation. Frequently Asked Questions About Venomous Snakes. "A comparative study found that the snake venom that is most toxic to mice (of the species tested) is that of the Inland Taipan (Oxyuranus microlepidotus), found in Australia". University of Florida. Retrieved November 5, 2013.
- Hodgson WC, Dal Belo CA, Rowan EG (2007). "The neuromuscular activity of paradoxin: a presynaptic neurotoxin from the venom of the inland taipan (Oxyuranus microlepidotus)". Neuropharmacology 52 (5): 1229–36. doi:10.1016/j.neuropharm.2007.01.002. PMID 17313963. "The inland taipan is the world's most venomous snake"
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- Journal of Herpetology Vol.17 no.1 (1983) Ecology of Highly Venoumous Snakes: the Australian Genus Oxyuranus. "..the number of mouse LD50 doses per bite is much higher for Oxyuranus microlepidotus (218,000 mice)...than for any other snakes, including sea snakes, investigated to date (Broad, Sutherland and Coulter, 1979)." (page 1) University of Sydney. Retrieved November 8, 2013.
- LISTS . Nine of the World's Deadliest Snakes. "#1: The snake with the world's deadliest venom - Oxyuranus microlepidotus" . Encyclopædia Britannica. Retrieved November 5, 2013.
- BBC Nature Wildlife. Inland Taipan page. "Australia's inland taipan is considered to be the most venomous snake in the world". BBC. Retrieved October 15, 2013.
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- Inland Taipan Venom vs. Sea Snakes Venom (most notable Belcher's sea snake)
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- kingsnake.com September Guest Chatter (September 16, 2006).Q&A with Dr. Bryan Grieg Fry, Deputy Director, Australian Venom Research Unit, University of Melbourne. "Q: In retrospect to the LD50 charts, what do you personally feel is the hottest snake, in regards to potency, defensiveness, means of injection, etc.? A: It is the inland taipan (Oxyuranus microlepidotus). Not, as is popularised, any of the sea snakes." connectedbypets.com. Retrieved October 14, 2013.
- Garden of Eden Exotics (May 2, 2012) Dr. Bryan Grieg Fry – Interview "...The inland taipan (Oxyuranus microlepidotus') is far and away the most toxic, much more so than even sea snakes." nyexotics.blogspot.com Retrieved October 14, 2013
- Fry, Bryan (February 08, 2005) Most Venomous,"Q;I was wondering what snakes venom is the most potent to humans A:Drop for drop it is the inland taipan (Oxyuranus microlepidotus), which has a venom more toxic than any other land snake or even the sea snakes." venomdoc.com Forums, Retrieved April 17, 2014
- Seymour, Jamie, World's Worst Venom, (Min 44.33) "Among the reptiles tested, the most toxic venom belongs to inland taipan, killing over 60% of heart cells in the first 10 minutes" National Geographic Channel Retrieved April 17, 2014
- Seymour, Jamie Venom deathmatch "They have the most toxic venom towards humans then any other snake in the world" (min 1:49) National Geographic Channel, Retrieved April 17, 2014
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- "University of Adelaide Clinical Toxinology Resources". "Mortality rate:70-80%"
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- White; Meier, Julian; Jurg (1995). Handbook of clinical toxicology of animal venoms and poisons. CRC Press. pp. 493–588. ISBN 978-0-84-934489-3.
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- Venomous snakes and outdoor workers Bite-prevention and treatment information for outdoor workers.