Given the way they slither along the ground – silent predators seeking out their prey – snakes are creepy enough under the best of circumstances. Their unblinking stare sets many people’s nerves jangling, and that's without even considering how dangerous they can be. While some snakes may be harmless, here we take a look at the snakes we really do have reason to be frightened of due to their highly toxic venom.
There are numerous lists on this subject by different experts who have different ways of measuring the toxicity of snake venom, and who therefore offer differing results. The most common, and probably easiest, way to measure quantities of venom is using the median lethal dose, or LD50 – the amount of venom it takes to kill half the mice tested on in a lab. The lower the number, the more venomous the snake! However, depending on the type of bite inflicted – for example, subcutaneous or intravenous – different results are produced. To complicate matters further, even among those lists of the most venomous snakes that seem to measure in the same way, there is little consistency. We're basing this article on a list compiled by Ernst and Zug (1996). Enjoy!
12. Puff Adder
The puff adder isn't the most venomous snake in Africa but it is considered to be the snake that causes the most human deaths there. This is due to the venomous viper's common occurrence in heavily populated areas and its habit of sunbathing on or near footpaths. Then of course there's its highly toxic venom, which has an LD50 of 0.14 and is delivered in large doses through long fangs.
An average-sized puff adder packs enough venom to kill four to five men! Bite symptoms include swelling, blood blisters, nausea and, if not treated, necrosis – which can lead to gangrene. This snake isn't going to stay out of your way, so you best steer clear.
11. Forest Cobra
Fast, agile and preferring woodland habitats, the forest cobra climbs trees with ease. Like other cobras, it will extend special ribs in its neck to make a hood when agitated. Oh, and did we mention that it's deadly poisonous?
The venom of the forest cobra has an LD50 of 0.12. What's more, not only is the venom extremely potent, with deadly paralyzing effects; it's also delivered in high quantities, and when this snake bites it will hang on and not release its grip. Interestingly, the forest cobra's venom contains neurotoxins that may have some use in treating Alzheimer's disease.
10. Tiger Snake
Striped like its feline namesake, the tiger snake is found in Australia, although there are several different and widely distributed varieties. It prefers wet habitats such as creeks and coastal areas and is definitely a snake to keep away from if you're looking for somewhere to cool off on a hot summer's day.
Untreated tiger snake bites – which rapidly cause breathing problems and paralysis – result in death to humans 60% of the time. The venom toxicity of this scaly serpent is said to range from an LD50 of around 0.4 for the Chappell Island tiger snake to 0.12 for the peninsular tiger snake. Beastly.
9. Desert Horned Viper
The desert horned viper is found in the Middle East and North Africa. It has little horns over each eye which makes it easily recognizable. This is a case where the snake's toxicity varies according to which scientists you believe; its LD50 ranges from 0.4 to 0.1, though Ernst and Zug state the latter figure. The desert horned viper is known for sidewinding, a form of movement whereby it presses its weight into the sand to move across the loose surface. We're tempted to say this is one diabolically venomous snake.
8. Common Krait
Next, the common krait, which is found in India, where it is one of the 'big four' – the species that cause the most snake bite cases in South Asia. This highly venomous specimen typically feeds on other snakes as well as lizards and small mammals. Alarmingly, many people who are bitten by the krait don't even realize it because the bite is practically painless. Krait bites can occur when people are asleep – feeling like that of an ant or mosquito – and there have been instances where the victim never wakes up. Even though the venom is slow-acting – it can take several hours for its effects to take hold – it has an LD50 of 0.09, with death often arriving by respiratory failure.
Beautiful but deadly, the brightly colored boomslang is found in Africa and is unique to its family (Colubridae) in that it has highly potent venom. It releases its venom through fangs at the rear of its jaw rather than at the front. Given its small size, the toxicity of its bite is perhaps surprising; its LD50 is 0.07.
Symptoms from the boomslang's bite kick in after several hours, and generally consist of external and internal bleeding brought about by blood clotting processes being disabled. That said, the boomslang is not an aggressive snake and prefers to retreat rather than attack, meaning fatalities are relatively rare. Still, we'd rather not try our luck.
6. Tiger Rattlesnake
There is huge variation among different lists regarding the strength of the venom of the tiger rattlesnake, which is found in the southwestern United States and northwestern Mexico. One source puts its venom's LD50 at 0.06 while others have it much higher – and therefore less toxic. What does seem certain, however, is that this species has the highest toxicity of all rattlesnakes, and while the venom it yields is comparatively low, being bitten by one of these snakes should be deemed a critical emergency. Let its stripes be a warning to you if you ever see one.
5. Black Mamba
The black mamba is both the world's second longest venomous snake and the fastest snake on Earth. It averages 8.2 feet in length and can move at speeds of 14 miles per hour. If black is the shade of death, this snake is well colored; its bite is deadly to say the least. The black mamba's venom has an LD50 of 0.05, meaning death – usually by respiratory failure or heart attack – typically occurs in humans in 30 minutes to one hour. Luckily, an antivenom has now brought the morality rate of those bitten down from where it once stood before the treatment became available – at nearly 100%. Big, quick and deadly, the black mamba is surely one of the world's deadliest snakes.
4. Eastern Brown Snake
The eastern brown snake is another Australian species with venom that can kill. Depending on which source you read, its venom is said to have an LD50 ranging from 0.05 to 0.03 (Ernst and Zug state the former), making it one of the most venomous snakes on land. The venom contains both neurotoxins and blood coagulants – two entirely different ways in which it can act on the system – and two people died as a result of being bitten as recently as 2007. You've been warned.
3. Russell's Viper
The Russell's viper – another of India's 'big four' – is without doubt one of the most dangerous snakes in the world. It not only has one of the most lethal types of venom, with an LD50 of 0.03; it is also commonly found in places where people live, because it is attracted by rodents. Outdoor workers are among the most in jeopardy as it likes fields and open, bushy areas.
In Burma, the Russell's viper is responsible for 90% of snakebite fatalities. Its painful bite produces venom that causes swelling, extensive bleeding, vomiting and necrosis, among other symptoms, while death may occur as a result of kidney, respiratory or cardiac failure.
Also, there is no single antivenom for treating the Russell's viper's bite, as the venom has different properties depending on the area in which the snake is found. For example, in India the venom has neurotoxic effects while in Thailand it hampers the blood's ability to clot.
2. Taipan (Inland Taipan)
Also known as the fierce snake, the inland taipan – another deadly snake found in Australia – is considered the world's most venomous land snake. Its alternate name is a reference to its venom rather than to its behavior, as it is shy and reclusive. Even when it kills prey, it retreats until the prey has died from the bite before returning to feed. Even so.
All taipans have highly toxic venom – not least the coastal taipan, which is also regarded as one of the five most venomous land snakes and is sometimes placed in the top three. The inland taipan's venom has an LD50 of 0.03 – though some sources have it as low as 0.01 – but in other taipan species it may be closer to 0.1. As well as being highly neurotoxic, the venom clots the victim's blood, blocking blood vessels. Before an antivenom was developed, it is said there were few if any survivors of taipan bites, and even with antivenom, the recovery period can be slow and painful.
1. Sea Snakes
The hook-nosed sea snake is at the top of the most venomous list with a bite containing venom that has an LD50 of 0.02. Almost all sea snakes are venomous, however, and the Belcher's sea snake is sometimes reported to have and even lower LD50, below 0.01. Ernst and Zug also give the venoms of the Dubois's reef sea snake an LD50 0.04, which would place it at number four on this list. If you see a sea snake while swimming or diving, move away.
The hook-nosed sea snake has been called “cantankerous and savage” by some herpetologists, and toxicity and aggression aren't a good mix. Only a very small amount of venom is needed – 1.5 mg is lethal in many cases – and it is said to be as much as eight times more toxic than cobra venom. Do not approach.