Does Australia really have the deadliest snakes? We debunk 6 common myths

A red-bellied black snake
Damian Michael, Author provided

Damian R. Michael, Charles Sturt University; Dale Nimmo, Charles Sturt University, and Skye Wassens, Charles Sturt University

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.

Read more:
I’ve always wondered: who would win in a fight between the Black Mamba and the Inland Taipan?

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.

A snake warning sign
With snakes on the move this season, people and pets are more likely to spot them.

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.

Read more:
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.

A black and red garter snake.
The toxins from the rough-skinned newt can stay in a garter snake’s liver for up to a month.
Steve Jurvetson/Wikimedia, CC BY

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?

It depends on how you define “deadly”. Death by snake bite in Australia is very uncommon, with just two per year, on average, compared to 81,000-138,000 deaths from snakes annually worldwide.

Read more:
Yes, Australian snakes will definitely kill you – if you’re a mouse

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.

An Indian cobra upright on a log
Indian cobra’s are one of the deadliest snakes in the world.

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.

A sea snake dives underwater
An olive sea snake can actually detect light through their tail.

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.

Read more:
Explainer: what should you do if you’re bitten by a snake?

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.

But it’s not just age — venom toxicity can vary among individuals of the same population, or among populations of the same species.

A black snake with white stripes on a rock.
Bandy Bandy (Vermicella annulata). Defensive behaviours are often misinterpreted as aggression.
Damian Michael, Author provided

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.

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New research reveals these 20 Australian reptiles are set to disappear by 2040

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.The Conversation

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

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Are Australian snakes the deadliest in the world? Not even close

David Williams, University of Melbourne

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.

The Eastern Brown Snake (Pseudonaja textilis) and its relatives cause most of the bites and fatalities in Australia.
David Williams, Author provided

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.

West African carpet viper (Echis ocellatus) from Togo – member of a genus of small vipers that are the world’s most dangerous snakes.
David Williams, Author provided

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.

Russell’s viper

In Pakistan, India and Sri Lanka, carpet vipers give way to the larger Russell’s viper (Daboia russelii).

A Russell’s viper (Daboia russelii) arguably the most dangerous snake in Asia with a potent cocktail of destructive toxins in its venom.
David Williams, Author provided

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.

Venezuelan lancehead (Bothrops venezuelensis) one of a large, widely distributed genus of dangerous pit vipers that cause enormous misery in Latin America.
David Williams, Author provided

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.

The Conversation

David Williams, Head, Charles Campbell Toxinology Centre at the University of Papua New Guinea & Australian Venom Research Unit, University of Melbourne

This article was originally published on The Conversation. Read the original article.