The link below is to an article that addresses 6 myths concerning Australian snakes.
As we settle into spring and temperatures rise, snakes are emerging from their winter hideouts to bask in the sun. But don’t be alarmed if you spot one, it’s hard to imagine a more misunderstood group of animals than snakes.
Our interactions with snakes are conversation starters, with yarns told and retold. But knowing what’s fact and fiction gets harder with each retelling.
As is so often the case with wildlife, the myths pale in comparison to what science has shown us about these incredible creatures. So let’s debunk six misconceptions we, as wildlife ecologists, often hear.
1. Black snakes and blue tongue lizards keep brown snakes away
This is a common old wives’ tale in southern Australia. The myth goes that if you see a red-bellied black snake or a blue-tongue lizard on your property, you’re unlikely to see the highly venomous brown snake, because black snakes keep brown snakes at bay.
This myth probably originates from observations of black snakes eating brown snakes (which they do).
But it’s not one-way traffic. There are many reported examples of brown snakes killing black snakes, too. Overall, no scientific evidence suggests one suppresses the other.
There is also no evidence blue-tongue lizards prey upon or scare brown snakes. In fact, many snakes feed on lizards, including brown snakes which, despite a preference for mammal prey as adults, won’t hesitate to have a blue tongue for lunch.
2. Snakes are poisonous
While the term poisonous and venomous are often used interchangeably, they mean quite different things. If you eat or ingest a toxic plant or animal, it’s said to be poisonous, whereas if an animal stings or bites you and you get sick, it’s venomous.
Why are some snakes so venomous?
Venom is a specialised type of poison that has evolved for a specific purpose. For venom to work, it needs a wound to enter the body and into the bloodstream. Snakes, therefore, are generally venomous, not poisonous.
But there are exceptions. For example, the American garter snake preys on the rough-skinned newt which contains a powerful toxin.
The newt’s toxin accumulates in the snake’s liver, and effectively makes this non-venomous snake species poisonous if another animal or human eats it. Remarkably, these snakes can also assess whether a given newt is too toxic for them to handle, and so will avoid it.
3. Australia has the deadliest snakes in the world
Approximately 20% of the world’s 3,800-plus snake species are venomous. Based on the median lethal dose — the standard measurement for how deadly a toxin is — the Australian inland taipan is ranked number one in the world. Several other Australian snakes feature in the top 10. But does that make them the deadliest?
If we define “deadly snakes” as those responsible for killing many people, then the list would be topped by snakes such as the Indian cobra, common krait, Russell’s viper and the saw-scaled viper, which occur in densely populated parts of India and Asia.
A lack of access to antivenoms and health care contribute substantially to deaths from snake bites.
4. Snakes have poor eyesight
Compared to other reptiles, such as monitor lizards, most snakes have poor eyesight, especially species that are active at night or burrow in soil.
However, snakes that are active by day and feed on fast-moving prey have relatively good vision.
One study in 1999 showed people are less likely to encounter eastern brown snakes when wearing clothing that contrasted with the colour of the sky, such as dark clothing on a bright day. This suggests they can see you well before you see them.
Some snakes such as the American coachwhip can even improve their eyesight when presented with a threat by constricting blood vessels in the transparent scale covering the eye.
And then there’s the olive sea snake, whose “phototactic tails” can sense light, allowing them to retract their tails under shelter to avoid predation.
5. Young snakes are more dangerous than adults
This myth is based on the idea juvenile snakes can’t control the amount of venom they inject. No evidence suggests this is true.
However, research shows the venom of young and old snakes can differ. A 2017 study showed the venom of young brown snakes is different to adults, probably to facilitate the capture of different types of prey: young brown snakes feed on reptiles, whereas adult brown snakes predominantly feed on mammals.
6. Snake are aggressive
Perhaps the most pervasive myth about snakes is they’re aggressive, probably because defensive behaviours are often misinterpreted.
But snakes don’t attack unprovoked. Stories of snakes chasing people are more likely cases where a snake was attempting to reach a retreat site behind the observer.
When threatened, many snakes give a postural warning such as neck flaring, raising their head off the ground, and opening their mouths, providing clear signals they feel threatened.
It’s fair to say this approach to dissuade an approaching person, or other animal, works pretty well.
Rhesus macaques display more fearful behaviour when confronted with snakes in a striking pose compared to a coiled or elongated posture. And showing Japanese macaques images of snakes in a striking posture sets of a flurry of brain activity that isn’t evoked when they’re shown images of snakes in nonthreatening postures.
The same is true for humans. Children and adults detect images of snakes in a striking posture more rapidly than a resting posture. And a study from earlier this year found human infants (aged seven to 10 months) have an innate ability to detect snakes.
Snakes are amazing, but shouldn’t be feared. If you encounter one on a sunny day, don’t make sudden movements, just back away slowly. Never pick them up (or attempt to kill them), as this is often when people are bitten.
Damian R. Michael, Senior research fellow, Charles Sturt University; Dale Nimmo, Associate Professor in Ecology, Charles Sturt University, and Skye Wassens, Associate Professor in Ecology, Charles Sturt University
Snakes are a diverse lineage of reptiles that are found on every continent except Antarctica. Despite differences in appearance, habitat preference, defence tactics and underlying biology, one thing is common to all 3,800 species of snakes — every last one is a predator.
As predators, snakes are likely to fulfil important roles in ecosystems. Knowing what snakes eat can help scientists better understand ecological connections among snakes and other species. This will lead to a better understanding of how ecosystems function and how ecological communities might be affected by changes in habitat or climate.
Some snake species have also evolved potent venoms which aid in subduing prey. Mounting evidence suggests venom composition is adaptive and linked to what snakes eat. Although snake venoms have evolved primarily for feeding, venomous snakes also bite defensively.
Incidents of snake bites on people prompted the World Health Organisation to declare snakebite a neglected tropical disease in 2017. Given the link between venom biochemistry and feeding, a detailed understanding of a species’ diet can inform research dedicated to mitigating the effects of snakebite.
Unfortunately, the details of many African snake diets remain a mystery. Historically, information on snake diets has come from dissecting preserved museum specimens or fortuitous observations of snake feeding that are published as brief notes in journals or newsletters.
More recently, methods for studying snake feeding habits have embraced technology. These include fixed videography studies of ambush predators like puff adders and timber rattlesnakes, as well as DNA analysis of faecal material from smooth snakes. But these approaches cannot be used for many snake species, and they require a significant amount of time, effort, and resources.
Snake diets can be difficult to study, so, in 2015 we realised that photographs and videos of snakes feeding were being shared regularly on Facebook. We set out to gather these observations using a dedicated Facebook group – Predation Records – Reptiles and Frogs (Sub-Saharan Africa) – and to record the shared observations systematically. Our findings showcase how the network of active users on Facebook can help us to collect ecological data quickly and cheaply.
After several years of community participation in our study, we turned more than 1,900 observations of reptiles or amphibians eating or being eaten into scientific data. Our database includes 83 families of predators and 129 families of prey.
For snakes, we gathered more than 1,100 feeding records. We soon saw that social media had helped gather these feeding records faster than ever before. The data collected from Facebook represent 27% of scientifically documented snake feeding records in southern Africa. More than 70% of all feeding records had not been recorded previously in the scientific literature.
To find out how data from social media compared to data collected using other platforms, we used iNaturalist (a popular citizen science platform) and Google Images to find observations of feeding snakes. Facebook outperformed both platforms in terms of the overall number of observations collected.
Finally, we noticed that observations collected from the different platforms produced different prey profiles, suggesting that certain prey may be over – or underrepresented in studies depending on the source of the observation.
Nearly all methods used for studying snake diets have biases. This may be why there are striking difference between what social media and the existing scientific literature revealed.
Facebook also let us identify prey more precisely. Most of the prey was photographed while being eaten or after regurgitation. On the other hand, prey collected from the stomachs of museum specimens are often partially digested, making the identification process difficult.
Our findings highlight the remarkable power of citizen science to reveal undocumented details about the natural world. In the case of snake diets, specifically, it is the harnessing of thousands of social media users that facilitated the data collection.
This is mainly because snakes feed secretively and relatively infrequently in the wild. But social media and the widespread use of smartphones with cameras means that even difficult to observe events can now be recorded in large numbers and across different geographic areas.
The continued detection of new feeding interactions shows how there is much to be learned about these remarkable animals. As more observations are made, the full picture of a species’ diet will be revealed. By using a community of observers, more data and information can be gathered for little to no cost.
While our study was restricted to southern Africa, expanding data collection efforts like this into the rest of Africa is necessary. Given that Africa experiences some of the world’s heaviest snakebite burden, details on the biology of its snakes will prove useful. If ever there was an opportunity to gather novel, important ecological information about snakes in Africa, this is it.
Globally, there are hundreds of groups on Facebook – some of which have close to 200,000 members – dedicated to sharing original photographs and observations of snakes. More generally, Facebook groups exist for most classes of animals and plants, and these communities have unprecedented observational power for researchers asking appropriate questions of the natural world.
Bryan Maritz, Senior Lecturer, Biodiversity and Conservation Biology, University of the Western Cape and Robin Maritz, Research fellow, Biodiversity and Conservation Biology, University of the Western Cape
We are all familiar with the concept of “fake news”: stories that are factually incorrect, but succeed because their message fits well with the recipient’s prior beliefs.
We and our colleagues in conservation science warn that a form of this misinformation – so-called “feelgood conservation” – is threatening approaches for wild animal management that have been developed by decades of research.
The issue came to a head in February when major UK-based retailer Selfridges announced it would no longer sell “exotic” skins – those of reptile species such as crocodiles, lizards and snakes – in order to protect wild populations from over-exploitation.
But this decision is not supported by evidence.
Banning the use of animal skins in the fashion industry sounds straightforward and may seem commendable – wild reptiles will be left in peace, instead of being killed for the luxury leather trade.
But decades of research show that by walking away from the commercial trade in reptile skins, Selfridges may well achieve the opposite to what it intends. Curtailing commercial trade will be a disaster for some wild populations of reptiles.
How can that be true? Surely commercial harvesting is a threat to the tropical reptiles that are collected and killed for their skins?
Actually, no. You have to look past the fate of the individual animal and consider the future of the species. Commercial harvesting gives local people – often very poor people – a direct financial incentive to conserve reptile populations and the habitats upon which they depend.
If lizards, snakes and (especially) crocodiles aren’t worth money to you, why would you want to keep them around, or to protect the forests and swamps that house them?
Biggest man-eaters in the billabong
The iconic case study that supports this principle involves saltwater crocodiles in tropical Australia – the biggest, meanest man-eaters in the billabong.
Overharvested to the point of near-extinction, the giant reptiles were finally protected in the Northern Territory in 1971. The populations started to recover, but by 1979-80, when attacks on people started to occur again, the public and politicians wanted the crocodiles culled again. It’s difficult to blame them for that. Who wants a hungry croc in the pond where your children would like to swim?
But fast-forward to now and that situation has changed completely. Saltwater crocs are back to their original abundance. Their populations bounced back. These massive reptiles are now in every river and creek – even around the city of Darwin, capital of the Northern Territory.
This spectacular conservation success story was achieved not by protecting crocs, but by making crocs a financial asset to local people.
Eggs are collected from the wild every year, landowners get paid for them, and the resulting hatchlings go to crocodile farms where they are raised, then killed to provide luxury leather items, meat and other products. Landowners have a financial interest in conserving crocodiles and their habitats because they profit from it.
The key to the success was buy-in by the community. There are undeniable negatives in having large crocodiles as neighbours – but if those crocs can contribute to the family budget, you may want to keep them around. In Australia, it has worked.
The trade in giant pythons in Indonesia, Australia’s northern neighbour, has been examined in the same way, and the conclusion is the same. The harvest is sustainable because it provides cash to local people, in a society where cash is difficult to come by.
Decisions without evidence
So the evidence says commercial exploitation can conserve populations, not annihilate them.
Why then do companies make decisions that could imperil wild animals? Probably because they don’t know any better.
Media campaigns by animal-rights activists aim to convince kind-hearted urbanites that the best way to conserve animals is to stop people from harming them. This might work for some animals, but it fails miserably for wild reptiles.
We argue that if we want to keep wild populations of giant snakes and crocodiles around for our grandchildren to see (hopefully, at a safe distance), we need to abandon simplistic “feelgood conservation” and look towards evidence-based scientific management.
We need to move beyond “let’s not harm that beautiful animal” and get serious about looking at the hard evidence. And when it comes to giant reptiles, the answer is clear.
The ban announced by Selfridges is a disastrous move that could imperil some of the world’s most spectacular wild animals and alienate the people living with them.
Daniel Natusch, Honorary Research Fellow, Macquarie University; Grahame Webb, Adjunct Professor, Environment & Livelihoods, Charles Darwin University, and Rick Shine, Professor in Evolutionary Biology, University of Sydney
Few sights and sounds are as emblematic of the North American southwest as a defensive rattlesnake, reared up, buzzing, and ready to strike. The message is loud and clear, “Back off! If you don’t hurt me, I won’t hurt you.” Any intruders who fail to heed the warning can expect to fall victim to a venomous bite.
But the consequences of that bite are surprisingly unpredictable. Snake venoms are complex cocktails made up of dozens of individual toxins that attack different parts of the target’s body. The composition of these cocktails is highly variable, even within single species. Biologists have come to assume that most of this variation reflects adaptation to what prey the snakes eat in the wild. But our study of the Mohave rattlesnake (Crotalus scutulatus, also known as the Mojave rattlesnake) has uncovered an intriguing exception to this rule.
A 20-minute drive can take you from a population of this rattlesnake species with a highly lethal neurotoxic venom, causing paralysis and shock, to one with a haemotoxic venom, causing swelling, bruising, blistering and bleeding. The neurotoxic venom (known as venom A) can be more than ten times as lethal as the haemotoxic venom (venom B), at least to lab mice.
The Mohave rattlesnake is not alone in having different venoms like this – several other rattlesnake species display the same variation. But why do we see these differences? Snake venom evolved to subdue and kill prey. One venom may be better at killing one prey species, while another may be more toxic to different prey. Natural selection should favour different venoms in snakes eating different prey – it’s a classic example of evolution through natural selection.
This idea that snake venom varies due to adaptation to eating different prey has become widely accepted among herpetologists and toxinologists. Some have found correlations between venom and prey. Others have shown prey-specific lethality of venoms, or identified toxins fine-tuned for killing the snakes’ natural prey. The venom of some snakes even changes along with their diet as they grow.
We expected the Mohave rattlesnake to be a prime example of this phenomenon. The extreme differences in venom composition, toxicity and mode of action (whether it is neurotoxic or haemotoxic) seem an obvious target for natural selection for different prey. And yet, when we correlated differences in venom composition with regional diet, we were shocked to find there is no link.
In the absence of adaptation to local diet, we expected to see a connection between gene flow (transfer of genetic material between populations) and venom composition. Populations with ample gene flow would be expected to have more similar venoms than populations that are genetically less connected. But once again, we drew a blank – there is no link between gene flow and venom. This finding, together with the geographic segregation of the two populations with different venoms, suggests that instead there is strong local selection for venom type.
The next step in our research was to test for links between venom and the physical environment. Finally, we found some associations. The haemotoxic venom is found in rattlesnakes which live in an area which experiences warmer temperatures and more consistently low rainfall compared to where the rattlesnakes with the neurotoxic venom are found. But even this finding is deeply puzzling.
It has been suggested that, as well as killing prey, venom may also help digestion. Rattlesnakes eat large prey in one piece, and then have to digest it in a race against decay. A venom that starts predigesting the prey from the inside could help, especially in cooler climates where digestion is more difficult.
But the rattlesnakes with haemotoxic venom B, which better aids digestion, are found in warmer places, while snakes from cooler upland deserts invariably produce the non-digestive, neurotoxic venom A. Yet again, none of the conventional explanations make sense.
Clearly, the selective forces behind the extreme venom variation in the Mohave rattlesnake are complex and subtle. A link to diet may yet be found, perhaps through different kinds of venom resistance in key prey species, or prey dynamics affected by local climate. In any case, our results reopen the discussion on the drivers of venom composition, and caution against the simplistic assumption that all venom variation is driven by the species composition of regional diets.
From a human perspective, variation in venom composition is the bane of anyone working on snakebite treatments, or antidote development. It can lead to unexpected symptoms, and antivenoms may not work against some populations of a species they supposedly cover. Anyone living within the range of the Mohave rattlesnake can rest easy though – the available antivenoms cover both main venom types.
Globally, however, our study underlines the unpredictability of venom variation, and shows again that there are no shortcuts to understanding it. Those developing antivenoms need to identify regional venom variants and carry out extensive testing to ensure that their products are effective against all intended venoms.
Australia is renowned worldwide for our venomous and poisonous creatures, from snakes, spiders and ticks on land, to lethal jellyfish, stingrays and stonefish in our waters. Even the shy platypus can inflict excruciating pain if handled without due care.
Yet while injuries and deaths caused by venomous snakes and jellyfish are often sensationalised in the media, and feared by international visitors, a recent review found that very few “deadly” Australian animals actually cause deaths. Between 2000 and 2013, there were two fatalities per year from snake bites across Australia, while the average for bee stings was 2.2 and for jellyfish 0.25, or one death every four years. For spiders – including our notorious redbacks and Sydney funnel-webs – the average was zero.
Snakes nevertheless strike fear into many people who live in or visit Australia. When we have a higher risk of injury or death from burns, horses, bee stings, drownings and car accidents, why don’t we fear these hazards as we do the sight of a snake?
Snakes and statistics through history
When settlers arrived in Australia in the late 18th century, they believed that Australian snakes were harmless. By 1805 it was accepted that local serpents might kill humans, but they were hardly feared in the same way as the American rattlesnake or Indian cobra.
Until the 1820s, less than one human death from snake bite was recorded each year; in 1827 visiting surgeon Peter Cunningham remarked that:
…comparatively few deaths [have] taken place from this cause since the foundation of the colony.
Similar observations were made into the 1840s. What the colonists did note, however, was the significant death toll among their “exotic” imported animals, from cats and sheep to highly valuable horses and oxen.
By the 1850s, living experiments in domestic creatures – especially chickens and dogs – were standard fare for travelling antidote sellers. Given the popularity of these public snake bite demonstrations, from the 1860s, doctors and naturalists also took to experimenting with captive animals. It was during this period that official statistics on deaths began to be collated across the Australian colonies.
One sample from 1864–74, for instance, reported an average of four snake bite deaths per year across Victoria, or one death per 175,000 colonists. In contrast, during the same period one in 6,000 Indians died from snake bites each year; little wonder that around the world, Australian snakes were considered trifling.
The 1890s represented a dramatic period of divergence, though. On one hand, statistical studies in 1882–92 suggested that on average, 11 people died annually from snake bite across Australia. Similar data compiled in Victoria led physician James Barrett to declare in 1892 that snakes posed “one of the most insignificant causes of death in our midst”. On the other hand, by 1895 standardised laboratory studies, aimed especially at producing an effective antivenom, saw a global recognition that Australian snake venoms were among the most potent in the world.
In Sydney, physiologist Charles Martin claimed that Australian tiger snake venom was as powerful as that of the cobra. In 1902, his collaborator Frank Tidswell ranked local tiger snake, brown snake and death adder venoms at the top of the global toxicity table.
Over the ensuing century, this paradox has remained: why do so few Australians die from snake bites when our serpents have the world’s most potent venoms? Why aren’t they more deadly?
Scientific research has delivered ever-expanding knowledge about venoms, what they do, how they work, how they affect us clinically, and their comparative “potency” based on animal studies. In response we have introduced first aid measures, guidelines, effective clinical management and treatment, which in Australia forms one of the world’s best emergency health care systems.
In contrast, countries where snakebites cause far more deaths generally face challenges in accessing affordable essential medicines, prevention and education options.
Snakes form an essential part of their ecosystems. They do not “attack” humans, mostly being shy animals, but are defensive and prefer to escape.
It would seem that venom potency is not a good measure of deadliness, and it may be a combination of our history, behaviour and belief that creates a cultural fear.
Without understating the potential danger posed by venomous snakes, what we offer instead is reassurance. As nearly two centuries of statistics and clinical experience suggest, most snake bites in Australia are survivable, if managed quickly, calmly and effectively. In fact, encounters with humans all too often prove deadly to the snakes themselves – a paradox that is within our power to change.
The authors are presenting on this topic at the upcoming Emerging Issues in Science and Society event at Deakin University’s Downtown campus on 6 July 2017. Sponsored by the Australian Academy of Science and Deakin University’s Science and Society Network.
The event brings together scientists with humanities and social science scholars to discuss common questions from different angles. For more information on the event and to book tickets see the event’s website.
The idea that Australia is home to many of the most deadly snakes in the world is based on animal research from the 1970s that looked at the effect of 25 venoms on mice. While not entirely untrue, the claim is also not quite right.
A more accurate statement might be that Australian snakes are the best mouse killers in the world: they’re able to kill the most mice with the smallest amount of venom. While that’s clearly bad news for mice, how does it translate into human risk?
The occurrence and severity of a snake bite depends on a complex interaction between snake behaviour, venom toxicity and human behaviour. Significant factors include how toxic the venom is; how much of it is injected by the snake; and how humans encounter and interact with snakes.
Australian snakes have very toxic venoms but inject tiny amounts at a time because most have short fangs. The only evidence of a brown snake bite may be a small scratch, for instance, but the venom is so toxic that it quickly results in the person’s blood failing to clot, which puts them at risk of bleeding to death.
Mulga snakes (King Brown) can deliver larger amounts of venom, but have one of the less toxic venoms of dangerous Australian snakes.
Historically, tiger snakes and death adders were responsible for most deaths. They’re widely distributed throughout Australia and their bites cause paralysis.
Before the advent of modern intensive care, paralysis was – more often than not – fatal. But with the development of antivenom in the 1930s and 1950s, and machines that can breathe for people, paralysis from snakebite has become uncommon.
Taipans also cause paralysis, but are a rare cause of snakebite in Australia (in contrast to Papua New Guinea where they cause much havoc).
In modern times, brown snake bites have become more common and now cause the majority of such deaths in Australia. This group of snakes appears to have thrived despite human invasion and the destruction of natural habitats. Brown snakes are now the most common cause of severe snake envenoming in Australia, according to the Australian Snakebite Project.
They cause the majority of the one to five deaths from snakebites each year, usually from early collapse and cardiac arrest. Unfortunately, antivenom is unlikely to help these people because cardiac arrest happens within 30 minutes of the bite. Early basic life support from bystanders is most important for snake bites because this can keep someone alive until they’re transported to hospital.
Severe snake envenoming is actually quite rare in Australia, with only about 100 cases each year. After brown snakes, red-bellied black snake bites are the next most common, but they rarely cause severe envenoming and occur only in eastern Australia.
Tiger snakes, which continue to account for a significant number of bites in southern Australia, are one of three snakes found in Tasmania and account for almost all serious snake bites in Victoria. They cause all three major types of toxicity: coagulopathy (making a person’s blood unable to clot), neurotoxicity (paralysis) and myotoxicity (muscle damage).
Snake bites are treated with antivenom, which needs to be given as soon as possible after a bite to be effective. The Australian Snakebite Project has demonstrated that only one vial of antivenom is required to treat all cases of snake envenoming.
But many of the effects of snake envenoming are irreversible in the short term (muscle damage, for instance, and paralysis), so antivenom won’t help for these. Instead, treatment in intensive care will support the patient while the body repairs. This is why antivenom needs to be given early.
Using antivenom comes with the risk of an allergic reaction, so it’s important that only people with envenoming be treated. Recent research measuring snake venom enzymes in blood appears to identify envenoming early. It is hoped that development of bedside testing of these enzymes will improve early recognition.
Although the effects of venom are reasonably well understood, why they cause severe toxicity in humans remains unclear. After all, we are not prey for snakes; small reptiles (such as skinks) or small mammals (such as marsupial rats) are their primary targets.
The toxicity we see in humans, such as venom’s clotting effects that commonly occur with brown snake, tiger snake and taipan bites, is most likely a chance occurrence. This idea is supported by recent research that shows many animals, including rodents and skinks, are highly resistant to the clotting effect of snake venom. But they’re highly susceptible to the neurotoxic effects of snake venoms.
In most other parts of the world, vipers, which have much larger fangs, are much more common. They inject ten or more times as much venom as Australian snakes, but have less toxic venoms. The other major difference is that vipers can cause local skin and tissue damage and, in some cases, this can lead to amputation. Unlike the human impact of Australian snakes, viper envenoming is a huge public health issue worldwide.
This article is part of our series Deadly Australia. Stay tuned for more pieces on the topic in the coming days.
Many Australians pride themselves on the belief that, of all the countries in the world, their snakes, spiders, jellyfish, centipedes, fish, ticks, bees and ants are the worst. And it’s easy to believe they’re right.
After all, there’s a 37-year-old list that says that 21 of the 25 most toxic snakes in the world are all from Australia. And aren’t funnel-web spiders, box jellyfish, stonefish and cone snails all dead-set killers?
But is Australia really the most lethal nation on earth when it comes down to it? Actually, no, it’s not. And the reason is simple.
A matter of perspective
It’s useless to measure how dangerous something is based solely on laboratory lethality tests. Venom toxicity and the number of mice killed with a snake’s average venom yield, for instance, are interesting only from an academic perspective.
If you happen to be one of around 100,000 people who die of snake bites around the world in any given year, such facts are irrelevant. The same goes for just about any other venomous creature we might like to proudly declare as the planet’s most lethal.
While Australia has spiders, jellyfish and other animals with lethal venom, the reality is that bites and deaths are rare. In other words, despite very toxic venoms, these creatures don’t bite enough people to cause major problems. Even when they do bite, it’s rare for snakes to inject venom (or “envenom”), less than 450 of 3,000 snakebite cases a year, for example. Death is even rarer (two to three cases a year).
Animals that cause the greatest burden of human suffering and death are the ones we need to be most worried about, and from that perspective, the most dangerous are not Australian.
Consider snakes, one of the most feared groups of venomous animals in the world. If we want to know which snakes are the most dangerous, we should consider the global, rather than individual impact. That view shows three groups of vipers that collectively span almost all of the tropical developing world – and have a huge impact on human health – best deserve the title of the world’s most dangerous.
Meet the carpet viper
Perhaps the most dangerous of these three genera is a diverse group of small, seemingly innocuous vipers that range from Sri Lanka and India, across the Middle East and through a huge part of the northern half of Africa.
These snakes got their name from the patterns that adorn their bodies. They are small- to medium-sized vipers believed to injure and kill more people each year than any other species in the world. Yet they don’t make the list of most toxic snakes mentioned above at all.
In just one hospital in Nigeria’s north-eastern Gombe State, 5,367 victims of carpet viper envenoming were treated over a two-year period. But for the use of an effective antivenom, the fatality rate may have been as high as 35% to 45%. That’s more cases at one hospital in two years than all the recorded cases throughout Australia in ten.
Their huge range across a vast swathe of the rural tropics brings carpet vipers into contact with hundreds of thousands of people each year. And while nobody has a tally of just how many lives they affect, international experts all agree that when it comes to the most dangerous snake, these vipers have no competition.
In Pakistan, India and Sri Lanka, carpet vipers give way to the larger Russell’s viper (Daboia russelii).
This pugnacious viper lurks in fields, rice paddies and farmland from Pakistan through India, Nepal, Sri Lanka, Bangladesh, Myanmar, Thailand and Cambodia, as well as Taiwan and southern China. There’s a distinct, disjoined population of an equally dangerous sister species (Daboia siamensis) in eastern Java and the lesser Sundas in Indonesia.
Like the victims of carpet vipers, those bitten by these snakes bleed uncontrollably and often fatally. At the same time, local tissue destruction and necrosis, acute kidney injury, neurotoxic paralysis, shock, and cardiac arrhythmia can produce a terrifying clinical picture that can very quickly lead to death.
Lancehead pit vipers
Latin America, from Mexico to Argentina, is home to more than 40 species in the genus Bothrops, lancehead pit vipers. Collectively, this very diverse group is responsible for many of the estimated 150,000 or more cases of venomous snakebites in Central and South America each year.
Lancehead bites produce devastating local tissue injury with oedema (or fluid retention), bruising, skin and muscle necrosis and fluid-filled blisters. Permanent disability including amputation is common.
Systemic effects involving stopping the ability of blood to clot, platelet destruction, shock, acute kidney injury and thrombosis present doctors with a complex medical emergency that – even with the best care available in a modern hospital – can still ultimately prove fatal.
Since many cases occur in rural areas, away from good medical care, poor outcomes are common.
Within Australia, the low mortality from snakebite (and other types of venomous injury) is very much the product of decades of research and excellent clinical care, not to mention safe and effective antivenoms.
It’s the lack of these same attributes elsewhere in the world that renders snakebites such a potentially life-changing (if not, life-ending) public health issue.
This article is part of our series Deadly Australia. Stay tuned for more pieces on the topic in the coming days.
David will be on hand for an Author Q&A between 11am and noon AEDT on Tuesday, January 12, 2016. Post your questions in the comments section below.