Nature

A Mangrove Pit-Viper, one of the world's deadliest snakes, deciding whether to attack

They’re Coming to Get You…

WE HAVE LOOKED AT POISONOUS PLANTS A NUMBER OF TIMES IN OUR ARTICLES. LET’S LOOK AGAIN AT SOME OF THE POISONOUS ANIMALS THAT ARE OUT THERE … WAITING …!

In fact, there aren’t really that many of them, especially in this lovely part of France. Even worldwide, the list is fairly brief. First, though, we must decide exactly what we mean by “poisonous”.

Venomous or Poisonous?

Some animals use their toxic products to enable them to catch prey more effectively. In these cases, the toxins must be introduced into the prey’s body, so a form of injection is required. This can be active injection, by means of a hollow or grooved tooth that delivers the toxin into the prey’s body directly, or passive perfusion, in which the toxin mixes with the predator’s saliva and enters a wound produced by the otherwise quite normal teeth of the predator. Animals that do this are venomous. Others use their poison defensively, either secreting it onto their bodies or storing it in certain of their body-tissues, so that if they are threatened by a potential predator, the unpleasant or harmful effect of the toxin will deter the predator and perhaps save the prey animal’s life. Such animals are poisonous. The extreme examples of this are the Poison Dart (or ‘Arrow’) frogs of South America, whose toxin, exuded onto the skin of the frog in time of danger, can kill a human, though this is not the frog’s intention. Indeed, killing the attacker is counter-productive; a poisonous animal wants the attacker to live, so it learns not to attack again, and may even pass this knowledge on to its fellows. This is complicated by the fact that venomous creatures sometimes reserve their envenomating skills for self-defence and will, if provoked, attack if they perceive a threat. Honey-bees, wasps etc. come into this category. Sometimes the envenomating system is dual-purpose. The most spectacular examples of this are the Spitting Cobras, which have hollow fangs that can envenomate normally, but also are so arranged that they can release a jet of venom into the eyes of a threatening predator from up to 2 metres distant, an action which produces intense pain and rapid blindness in the attacked animal, effectively putting it out of the fight. However, all venomous snakes will reserve

By Mike George

Mike George is our regular contributor on wildlife and the countryside in France. He is a geologist and naturalist, living in the Jurassic area of the Charente

The Red Strawberry Poison Dart Frog from Panama. The colour warns that it secretes a poison deadly to animals - including Man

The Slow Loris (above), a charming but vulnerable primate from the Phillipines. Using glands in its elbows, it coats its fur in a mild toxin (as seen here). Note - not to scale!

the right to defend themselves when provoked, and that is where the trouble arises. Believe me, no snake is going to regard a human as its potential prey (except, perhaps, for a very large Anaconda, which is not venomous) and will have no wish to waste its precious venom (it takes the average snake several months fully to refill its venom-gland if it is completely emptied). Most snakes will do their utmost to avoid conflict with such a large animal, and will only attack if they see no alternative, or if they are actually attacked (such as by being threatened or trodden on). Remove the threat, often by retreating slightly or just standing motionless, and the snake will make itself scarce.

Which animals are venomous and which are poisonous?

There is quite a list, and it grows as naturalists look ever more closely at the

This Puffer-fish tries to protect itself by inflating its body and erecting its spines. It cannot inject poison, but is poisonous if anything succeeds in eating it

natural world. Let us start with the venomous ones: Mammals: Duck-billed Platypus, Mole, Water Shrew Birds: None have so far been identified

Reptiles:

Snakes: Back-fanged Colubrids, Frontfanged Elapids, Vipers Lizards: Gila Monster, Beaded Lizard, Komodo Dragon (all back-fanged) Amphibians: None so far identified Fish: Weever Fish, Lion Fish, Scorpion Fish, Stingrays, Catfish Arachnids: Spiders, Scorpions, Insects: Ants, Bees, Wasps, Hornets Echinoderms: Sea Urchins, Starfish Coelenterates: Jellyfish can be dangerous to humans. Sea Anemones and Corals, which also fall into this category, are venomous but the venom is too weak and the dose delivered is too small to be a threat to humans. Molluscs: Cone Shells, Octopuses (especially the Blue-ringed)

NOW THE POISONOUS ONES:

Mammals: Slow Loris Birds: Two species in Borneo, the Pitohui and the Blue-capped Ifrit, infuse toxins into their plumage and flesh. Reptiles: Lizards: Many lizards exude mild toxins, even our familiar Wall Lizards. Amphibians: Salamanders, Frogs, Toads, Newts exude toxins onto the surface of their bodies, usually from the parietal glands behind the eyes. Fish: The Puffer-fish, or Fugu, is deadly poisonous. Probably many others are mildly toxic. Invertebrates: Many insects (for example, Cinnabar moths) carry toxins, but are no danger to humans as long as they don’t try to eat them! Some moth caterpillars have hairs that can cause skin irritation or aggravate asthma quite seriously.

Venomous mammals?

It comes as a surprise, but a few mammals, and even one primate, produce venom. The male Duck-billed Platypus has spurs on its hind legs that it employs during the breeding season to fight other males. The spurs can inject a toxin which causes considerable pain, but there are no reliable reports of death among humans. Platypuses are so rare and shy that few people ever see one, let alone get into a situation where they may be spiked.

The Slow Loris is a primate, about the size of a small cat, all thick fur and great big eyes. It secretes a cocktail of chemicals from glands in its arms, which it rubs over its own fur to give itself a mildly poisonous coating. The problem arises when a Loris grooms its fur with its tongue. The brachial-gland fluid mixes with the Loris’s mildly toxic saliva and produces a far more toxic fluid which can then be injected by biting. The result is a bite with longlasting pain and skin necrosis, but the only reported human death resulting from a Loris bite seems to have been the result of allergic reaction, not toxicity. Still, it is enough to put the unbearably cute Slow Loris into the “venomous animal” category! Mole venom is only effective on earthworms, to paralyse them. It has no effect on humans so far as is known. Considering the way moles are persecuted, some might feel they deserve a bit of extra weaponry! The Water Vole has only recently been shown to have toxic saliva. It is possible other voles have also, but research here is on-going. The Water Vole (or Water Rat as it is often mistakenly called) has been shown to be capable of immobilising toads and small fish by mixing a nerve toxin into its saliva to render its bite toxic, and has even been known to keep the prey in its paralysed state for later consumption. No human deaths have been reported! Incidentally, this gives an interesting reverse spin to “The Wind in the Willows”. Why were the Mole and the Water Rat so keen to be friends with Mr Toad?

Snakes: The Thing Everybody Worries about

Where we live, there really is no reason to be afraid of snakes. In this area we have only one native venomous snake, the Asp Viper. This is a small, shy snake, which will flee rather than attack, and only responds to aggression (like being stepped on!). There are four other venomous snakes found in France: the Adder in the North (Brittany, Normandie etc), the Montpellier Snake and Seoane’s Viper in the Pyrenees and Orsini’s Viper in the extreme south-east. None of them is massively venomous – very few deaths have been reported as a result of their bite – and they are not aggressive. All other native snake-like creatures in France are either constrictor snakes or legless lizards, and while a bite from any of them would be unpleasant and might be infected by bacteria, it will not be envenomated. They are not that big, either; the largest is the Aesculapian Snake, which can reach two metres in length. The thing to do if you are worried is to buy a good book which includes pictures of the snakes (Larousse Nature en Poche –Animaux sauvages, ISBN 2-03-582258-0 is very good, and Dorling Kindersley publish a similar volume but in English) and make sure of the appearance of each snake. Should you be bitten by a snake, get yourself to the nearest hospital emergency clinic. Try to have a reliable identification of the species. I do not advocate humans killing any wild animal except in an extreme case, but this might be just such a case, so catch the snake if you can do so without danger, or kill it as humanely as you can, and take it with you to the clinic. Incidentally, I recommend that if you are bitten by any wild creature you go without delay to an emergency clinic for a checkup and treatment. Even if a human bites you, you should do the same. One never knows what bacteria are present! These soothing words, however, do not apply outside Europe. There are some extremely venomous and aggressive snakes out there, and you should seek

They sit, quietly concealed in advice, if you travel abroad (remember the sand, and if you happen to step on one, you will be spiked those times?!), on what precautions to take and which animals to avoid. If anything bites you, try to get hold of it and envenomated (dead or alive) and go straight to hospital. Make sure you know where your nearest one is. Don’t forget to take the body of your aggressor, so that the correct antivenin can be used.

Venomous Fish

Don’t worry; fish are not going to rush out and give you a fatal bite. It is far more subtle than that. A few fish are able to deliver a fairly potent form of venom via the spines on their fins or their gill-covers, or in the case of the ray, via a special spine at the base of the tail. They sit, quietly concealed in the sand, and if you happen to step on one, you will be spiked and envenomated. This happens even around the coasts of France and Britain. The wound is painful, but rarely fatal. There are occasions when fish can be aggressive. The late Australian naturalist Steve Irwin was passing time during the shooting of a TV documentary with a little freelance work. He saw a beautiful Stingray and began filming it. Unfortunately, it seems his approach was similar to that of one of the few predators of Sting-rays, the Tiger Shark. The ray thrust upwards with its sting to ward him off, and actually

This Asp Viper Vipera aspis looks very like the Adder Vipera berus, but the tiptilted snout gives it away. Both are mildly venomous.

Cobra being ‘milked’ of its venom for medical research

stabbed him to the heart. He died, but the venom made no difference in that case.

What Use Is Venom?

For the animal, it is extremely useful. It enables it to tackle prey much larger than itself, and then just wait until the prey is no longer able to resist. No big struggle, no endless tracking, just a nice warm meal – and to some extent pre-digested! In vertebrates at least, venom is in fact modified saliva, and some of its components are already preparing the creature to be eaten, as well as killing it. If you are going to study Natural History, you need a strong stomach at times! Venom also gives the creature an edge in the struggle for life. Few animals will square up to a venom-dealing opponent, which is why so many of them make themselves very obvious by colours, markings, or even (in the case of the super-aggressive Rattlesnake) by shaking a warning rattle. Thus, they hope to avoid conflict. Should a fight follow, the venomous competitor has a good chance of winning. That is why in aggressive biters the bite is immediately very painful. However, the venom is never injected wholesale. Enough only is given to win the fight. No point in emptying your stock of venom; as I have said before, it can take weeks to replenish. But why do humans try to collect (at great personal risk) and study venom? The chief reason is so that anti-venoms can be prepared. The problem is that every venom is different. The venom of one species of snake can be so different from that of another that the anti-venom for one will be quite ineffective against the other. Changing a snake’s diet can alter its venom. In many cases it has been found that snakes of some species, if they live in different environments and hunt different prey, can have venoms sufficiently different in make-up as to be untreatable with anti-venom made from the same species living elsewhere. You need an antivenom made from a local specimen of that snake. There are some “universal” antivenoms, but in many cases these do not work. Each venom is a cocktail of components tailored to the requirements of the snake. What influences the makeup of the venom, and how much, if any, influence the individual snake has on its own venom, are matters of conjecture.

Are There Any Other Medical Benefits from Venom?

This is a vexed question, which is currently the subject of several studies. Folk-tales attributing healing properties to venoms have been told for centuries. Many elderly folks swore that their rheumatism was considerably eased after they had been extensively stung by bees. This may have been psychosomatic; if your body is a-fire from a swarm of beestings, your rheumatism would probably lose its importance, but whether this would last is debatable. For many years, people have been selling various preparations to which a few drops of snake-venom have been added. This culminated in the boom in “Snake-oil” in the late 19th century in America, which has become somewhat legendary in Western studies. Of course, the oil had no medicinal value at all, as you were supposed to swallow it or rub it on the skin, in neither of which situations is venom effective. Some of the components of venom are designed to seek out and block certain receptors in the body. This is how neurotoxins work. Studies of some of these have led to the development of probe chemicals to identify such receptors in living systems, which enables researchers to identify how they work. One major success is α-bungarotoxin, isolated from snake venom and widely used to identify nicotinic acetylcholine receptors, which are vital in the exchange of information between muscles and nerves, and whose malfunction can contribute to the effects of Parkinson’s Disease, schizophrenia and Alzheimer's Disease. Some of the chemicals are capable of crossing the blood/brain barrier, that very discerning filter that protects the brain from many toxins. Where medicines or markers have to be introduced into the brain, for example to locate or treat braintumours, such chemicals could provide a means of crossing that barrier. In short, there is much research in progress in many parts of the world. For those of you that would like to take this further, there is a surprisingly readable article on the subject at https://pubmed.ncbi.nlm.nih.gov/26009 701/ I hope this brief run-down of the current state of venom research has not been too traumatic. It is the season of Halloween, but as Nick Ross used to say at the end of Crimewatch - “Please don’t have nightmares”.

Folk-tales attributing healing properties to venoms have been told for centuries.