As every snake-keeper knows, once your friends and colleagues find out your choice of pets, it’s only a matter of time before someone turns the conversation around to poisonous snakes and the dangers of snake-bite.
Despite the widely held – and entirely untrue – belief that all snakes can deal instant death, the more sober truth is that only around a third of the world’s snakes have any poison at all, and of these very few possess venom powerful enough to present any real danger to people.
Never-the-less, it’s almost impossible to like snakes and not be at least a little intrigued by the whole idea of venom – and when it comes to snakes and snake bites, there are more things to consider than simply the strength of the poison.
The Evolution of Venom
Although we tend to concentrate on the potential harm to humans that snake venom can do, it didn’t originally evolve as a weapon – although you’d have to admit, it does make a remarkably effective one! Unlike amphibian poisons, which did naturally develop as a defensive measure and with few exceptions have no mechanism to actively fire them, in snakes, poison arose as a way of helping some of these leg-less carnivores get a meal.
Snake venom is modified saliva and contains enzymes to help break down food. A number of different kinds of animals have taken the step of developing a way of injecting saliva into their prey to speed up digestion; spiders are one example – and obviously snakes are another. Back in snake history, “toxic” saliva would naturally find its way into the snake’s victim through the wounds made by the bite. As snakes gradually evolved, grooves appeared in their teeth to help the saliva to drip down into the punctures and eventually a variety of snakes developed the hypodermic-needle-like hollow fangs and poison glands – modified salivary glands – that they have today.
The hinged arrangement of fangs in a modern rattlesnake or viper represents perhaps evolution’s most perfect venom delivery system – and accounts for the remarkable success of these snakes as ambush predators.
For all its value as a way of subduing a meal, inevitably venom is of more immediate interest when we start thinking about its potential to do harm to us, and sooner or later, that leads to someone asking which snake is the “most deadly.” On the face of it, it seems a straightforward enough question – but trying to answer it can turn out to be rather more difficult than you might at first suppose.
Simply working out the venom “rankings” in terms of which type can potentially kill the highest number of people on a drop for drop basis presents no great difficulty, but that’s only a part of it.
As a group, the sea snakes can probably lay claim to the title of the world’s most potent venom – but paradoxically despite this fearsome natural armament, recorded deaths are very rare. The reasons are simple; firstly, they are some of the world’s most even tempered snakes, and seem very reluctant to bite at all and secondly, if and when they do bite humans, they rarely inject venom. The sea snakes are one of the best examples of a highly venomous reptile not wasting its valuable reserves of poison on something it cannot eat.
On the other hand, some kinds of snakes that are armed with much less potentially powerful venoms – such as the irascible Puff Adder (Bitis arietans) – can be provoked into striking far more readily and often with fatal results.
To further complicate the whole issue, the outcome of two bites from the same species of snake can be entirely different – depending on a range of factors including how much venom the snake actually injected, how old or fit the victim was, what was bitten and how quickly treatment began. In addition, there is a good deal of evidence to suggest that the mental attitude of the victim also plays a significant part; a surprisingly large number of people have died from the bite of entirely harmless snakes – simply because they thought they’d been bitten by something poisonous. When it comes to snakes and snake-bite, evidently the power of the mind can be a dangerous thing!
Although keeping highly venomous snakes is – quite rightly – highly regulated and restricted in the UK and something that few snake enthusiasts would ever wish to do, these poisonous reptiles do, never-the-less, have their own unique fascination. The reality of snakes and snake-bite is every bit as captivating as the commonly-held myths – and adds a great deal to the appeal of this remarkable and often misunderstood group of animals.