Instant Genius - Snakes, with Prof Mark O’Shea

Episode Date: March 3, 2023

Whether you love them or are frightened of them, you cannot deny that snakes are fascinating, adaptable creatures. They are found on every continent except Antarctica, and occupy all sorts of habitats, from deserts, to swamps, to forests, oceans and trees. In this episode, herpetologist Prof Mark O’Shea, reveals how snakes move, why we have so few species in the UK, and how venom works. Learn more about your ad choices. Visit podcastchoices.com/adchoices

Ambition comes in all shapes and sizes. At First Citizens Bank, we roll with your goals because we're built for what you're building. Fit for your ambition for Citizens Bank. This podcast is sponsored by name, audio and focal. Streaming has made music more accessible than ever, but true listening is about more than ease. It's about quality. British audio experts name audio, alongside French acoustic specialist focal, combine how to handcrafted tradition with cutting-edge innovation and high-end materials, delivering digital

precision with analogue warmth. So you can experience exceptional sound at home. Music just as the artist intended. Visit name audio.com to learn more. Hello and welcome to Instant Genius, a bite-sized masterclass in podcast form. I'm Alice Lipscomb Southwell, the managing editor at BBC Science Focus magazine. Whether you love them or are frightened of them, you cannot deny that snakes are fascinating, adaptable creatures. They're found on every continent except Antarctica and occupy all sorts of habitats from deserts to swamps to forests to oceans and trees. So to find out even more about snakes, I spoke to Mark O'Shea, a professor of herpetology at the University of Wolverhampton, who told me more about how snakes move, why we have so few species in the UK, and how venom works. I'm Mark O'Shea. I'm Professor of Herpetology at the University of Wolverhampton.

I've been doing research on reptiles for many decades. I spent 33 years as curator of reptiles at Westminster Safari Park. I had my own TV series on Animal Planet Channel 4 Discovery Channel for 5 years. I've authored, I think eight books. I think there's 9th I'm just finished. And I've worked on a lot of reptile surveys around the world. I've worked on every continent except Antarctica. And I've been involved in snake bike research as well, and that was probably the main thing for,

behind my MBA in the Queen's Birthly Honors in 2020. So I'll probably start with basic questions then. How many species of snake are there? This is obviously in flux, because taxonomy is always in a state of flux. When I was a child, I looked up some numbers for when I was a child, when I was in the 60s, And the figure that everyone bandied about there was 3,200. And it's gone up considerably since then. My count at the moment is 4,032.

But other people would have slightly different counts, whether you recognize a particular species or whether you've seen a paper that's just been published. We described three new species earlier this year and raised three from Synonymy where they'd been sunk. So we added six papers coming out, describing a couple more. And to be honest, whereas in the 80s, there were only like 11 new species of snake being described

every year. In the 70s, probably about 8, now it's money more. And in 2020, 22, 45 species of snake would describe 2021-67. And this is really down to the fact that there's now the molecular techniques, which enable you to distinguish between morphologically similar species or species that are spread over a wide area that look different at the two extremes. They may actually be the same species. So the molecular techniques sort of support or question the data you get from morphological examination or specimens. So it's an ever-increasing number, but it's never been more important to understand biodiversity because you can't conserve species unless you know what they're called because you can't draw up legislation and put them on any protected lists unless they've got a name.

So it's really important now to name and describe new species. And what's the biggest species of snake out there at the moment? The biggest. Well, I was asked this question, well, I've been asked it several times, but I was asked by a TV company back in the mid-90s. What's the largest snake? I said, well, do you mean length or weight? And they settled on weight. The longest snake in the world is a reticulated python.

and there's been stories of how big they're going to get, and people have talked about 30-odd foot. But yeah, 9, 10 metres, but they're not massively heavy. A really big female, because the females are larger. I mean, Boas and Pythons, she'd be 75 kilograms. Now, anacondas are not as long, and the female anacondas might get to 8 meters, often quite less than that,

but they could be 100 kilograms, because they're an aquatic snake, and so the water supports their weight. And when I was asked that question, they said, oh, we'd like the heaviest anacondas. And I said, okay, and they said, where did you find them? And I told them that I knew somebody with a massive ranching Venezuela. And they said, well, if we sent you out there with a film crew, could you guarantee to catch someone? I said, oh, yeah. And I went out and I caught 32.

Whoa. And the largest was 18 feet long and two stone heavier than me. I got three over 15 foot long. Big aquatic snakes, but you find those in the dry season because they're congregating the smaller watercourses. But how do you catch such a big snake like that? Do you just have a stick or a sack or what? There's pure muscle.

It's normally a two-man job, but we were finding so many. It was ending that was a one-man job. With anacondas, it's quite an interesting approach because most snakes you look for in the wet season, beginning of the rains when they start being active and they're hunting and things like that. But anacondas are much better sort in the dry season when, as I say, they're congregating in the lagoons as they shrink and they might astivate then in the mud or try and get over there and to a more permanent watercourse like a river. And what you do in the lagoons all around the literal vegetation,

or the lagoons, you've got a mat of vegetation, which is a bit like a waterbed, really. It's vegetation on the water. And the water, the open water is quite warm. It's bath warm, but the water underneath there is a bit cooler. And what you do is you walk around on there. You can do it with boots on you, you can do it barefoot, but you're feeling for the snakes and you're prodding, prodding, prodding.

And if there's an an alaconda under there, it starts to go a bit like a waterbed. And it's working out where it's going, getting up to the front end and getting hold of the head and pulling it out. And you don't know how big it's going to be until you do that, because you can't see it. But that's the approach with Anacondas. Pythons, well, you'll see them.

They'll call defensively, in the case of trying to catch them about getting constricted. And really, to be honest, it would be very foolish for an individual person to try and capture a large reticulated python because they're, you know, easily capable of killing a human. And constriction is very fast. and it's not the crushing of bones, nor is it suffocation. It actually, the coils are so tight. They stop your circulation and you die of a heart attack. And it can be very fast, surprisingly fast.

Constriction kills quickly. You don't have much time to deal with it and you won't get the coils off. So a really, really large python, it's much better to stand back and admire it unless there's a group of you capable of dealing with it. because they, and then you've got to say, well, why catch it? You've got to have a reason if you're going to catch it, if you want to find out its length and weight and so forth. But sometimes it's just nice to stand there and watch the animal and see what it's doing.

Yeah, definitely. So at the other end of the spectrum, then, what's the smallest species of snake? Well, obviously, that's quite a difficult question because you could have the smallest species, but a baby of another species as an adult is smaller, because babies are obviously smaller. But as an adult, the Barbados thread snake, and I've got a measurement of 104 millimeters.

Which country has the most species of snake then? Well, in that case, if you want a country, with a large number of snake species, you need a large country with diverse habitats, mountains as well as lowlands, etc, etc., etc. And the nearer the equator it is, obviously the potential of high diversity there. And I worked out some numbers for this because it's always changing and there are only bucket science numbers because to sit down and literally go through

everyone and determine if it's in that country or not is a huge, it's a huge thing. But figures I've managed to work up from Mexico, 47, Brazil, 437. So both neotropical countries, on opposite sides of the equator. China, 320, a very large country, a lot of it temperate, some of it quite cold, but still got a lot of habitat. Australia, 229. That's a figure that could easily be checked, that you just pick up a guide to Australia and then. And in Africa, Democratic Republic of Congo is a massive tropical country,

and I've got around about 200 species for there. So that's, that gives you an idea. the biggest countries. But at the other end of the scale, obviously New Zealand and Ireland have no snakes. There are three native snakes in Britain, the grass snake, the adder or viper, and the protected smooth snake, which is in the southern counties, plus one introduced species, the osculapian snake, a European rat snake, which is found in two colonies, one in North Wales and one on the Regents Park Canal in London. So what is it about the UK that means we have so very few species of snakes?

The British Isles are on the northwestern fringe of Europe and were at one time attached to Europe by land bridges. The land bridge between Britain and Europe was in the Southern North Sea, eastern English Channel. And that permitted a lot of species, not just reptiles, but a lot of species, mammals, etc. to spread into Britain and establish themselves. And when those land bridges were broken,

that put an end to immigration and emigration from the British Isles. It's the same way humans originally got here, early man, got here, was across the land bridges. Now, the Irish Sea, I believe that land bridge was broken earlier. And so snakes didn't get to Ireland. It hasn't nothing to do with St. Patrick. it is to do with island biogeography. And when you look at the distribution of snakes in Britain,

you see that the smooth snake, which is our most endangered and protected species, is only found in the southern counties. And it likes particular habitats like southern heathland, which are peculiar to that part of the country. And it's not a rare snake in Europe, but it's just got into Britain in that small area as the sort of western extent of its European range, which is then broken, and therefore you've got this isolated and potentially threatened population.

Grass snakes occur up as far north as southern Scotland, while our only venomous snake, the adder or viper, the northern adder is generally what it's called, that will occur right the way up to the tip of northern tip of Scotland and on some of the inhabitants. and the reason why that's distributed so widely and the grass snake stops in southern Scotland is down to their reproduction because grass snakes lay eggs. They lay them somewhere nice and warm like a compost heap or something like that and then they leave them. The eggs are then at the vagaries of the weather. And where you could get very cold climates, southern northern Scotland,

is quite possible the eggs would not survive, whereas the adder is a live bearer. She doesn't come out of its cold. comes out and moves around when it's nice and warm and she can move around with the sunspots and she's a mobile incubator and so she's much better adapted for cold climates and the northern adder is actually the northern most distributed snake in the world it's found well north of the arctic circle in norway sweden finland and the col of the interior of siberia so it is well adapted for cold weather because it's a life bearer and it's a northern species but the disadvantage of this is that it probably is going to be threatened by global warming. As Britain warms, it becomes less

suitable for the adder and would be more suitable for one of the more southern vipus species from Europe. But that's basically in a nutshell why we've only got those species and why their distribution is as it is. So snakes can occupy all kinds of habitats. Now, can you explain some of the different ways that snakes can move? Because they've got quite a good range of locomotion, haven't they? There's four or five. There's a classic way you see a snake crawling away with a serpentine motion. You'll see a grass snake swimming with its head up,

doing exactly that sort of serpentine motion, everyone's familiar with. But there are other means of locomotion. There's a concertina method whereby heavy-bodied snake. Some of the borrowers do this, like the shield tails in Sri Lanka. They will push the head forward, anchorage, draw the body up. And it's a bit like a concertina, a musical instrument, drawing themselves forward, and then on again, and drawing themselves forward. Then there's rectilinear motion, which people call caterpillar crawl.

And you can see this in really heavy-bodied snakes that are too heavy to be throwing coils to either side, like lightly built snake. If you watch them move, they're in a dead straight line, and they just wobble along. and you can see waves of contractions going down the body as the intercostal muscles move the ribs forward and then the next set and the next set and the next set. And it does look as if they're just crawling, wobbling along the ground, like a caterpillar. These modes of locomotion are only possible

because snakes don't have a sternum. I mean, that's a really important thing about a snake. And I'll come back to us in a moment because that is quite interesting. But if they've got a sternum, a breastbone, the ribs and the muscles would be attached to that. And they wouldn't have the mobility that they do have and move in their ribs independently,

which we can't do because we've got sternum. Then the sidewinding, anybody who's tried to run up a sand dune knows it's not very easy. And it's the same for snakes. And so sidewinders go across the sand diagonally. And what they're doing is lifting their body, making an anchorage, they're not bringing their body over,

lifting their body and making an anchorage. And they leave J-shaped, tracks in the sand. And you can follow these. I mean, I've followed them in North Africa, in Mauritania, in the Arabian Peninsula, and found the snake at the other end, as they've sidewined it across. And there are sidewinding snakes in most of the deserts. There's one, there's the sidewinding rattlesnakes in southwestern USA, North Mexico. There's the Namib's sidelining viper in southern Africa. There's the sand vipers in North Africa and Arabia. There's MacBohens Viper on the Pakistan-Afghan border in the deserts there.

They all use the same form of locomotion. They've all evolved it independently as a means of traversing a very difficult terrain. And then there's climbing. If you look at a lot of snakes, some snakes are in cross-section round, but others are arch-shaped in cross-section. Things like rat snakes, the common corn snake that people keep. And if you look at the underside, the big broad belly scales, have a ridge down either side of them.

So it makes them, sort of gives them a little corner, if you like, at the bottom. It's like an arch shape. And when they're climbing a tree, they can change their body shape in cross-section from an arch to a bell. They can actually push those little corners into crevices and go straight up. Some of the tree snakes can go straight up a palm tree, all the little imperfections and gripping them. And it's quite phenomenal.

Whereas a big python, climbing a tree, it uses constriction. It puts the coils round and the coils round, and it moves coils forward and goes up a tree equally as fast. And then there's leaping out of trees and gliding. And again, this is where I'll talk about the ribs. Snake has got hundreds of ribs, but no sternum, no breastbone. So that means that a snake can move its ribs independently of each other and independently of the ribs on the other side. So if they've got the intercostal muscles between the ribs, they can obviously manipulate how their ribs are.

And that's obvious you can see it in the rectilinear motion as they crawl along the ground. That's also useful for a cobra spreading a hood. So the ribs expanding. It is also useful for a snake that wants to bask, maybe a female snake, a female viper that's got embryos inside. She can spread her body flatter and provide a larger surface area to the surface. done to warm herself up. A snake that's eaten a large meal or is carrying a number of eggs, again, the ribs can expand outwards a bit to allow the body to be broader, to encompass either the eggs or a big meal, sometimes a huge meal. This is all part of the white, sternum

possibly is no great adaptation. And when you come to the gliding snakes, the five species of flying snakes, which don't fly, of course. Flight is the preserve of the bats. the birds and the insects. They glide. They come down. They don't go up again. They can't take off and go up. But what they are doing is spreading their ribs to create concavity in the belly. And so when they leap, it's like a parachute. And they can control the speed and direction of descent by changing their body shape slightly. And again, it's only possible because they don't have a sternum. This podcast is sponsored by Name, Audio and Focal. With over 100 years of combined expertise,

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It's a complex cocktails of enzymes and proteins. And it is complex because it contains many different types of proteins and enzymes. And a particular snake very often doesn't. just have one kind, it'll have a cocktail. And it is like mixing cocktails. To give you an idea, okay, neurotoxins that attack the nervous system, the cause of death is respiratory paralysis, but they cause paralysis of a lot of other things. Early signs are tois. You can't lift your eyelids, you look like you drugged, you get blephorosis, your eye, your eye can't follow a finger, can't move your eyeball, you get flashed facial paralysis that you can't smile, you find that it's difficult to swallow saliva and things like. These are all early signs of neurotoxicity,

which ultimately, if untreated and there's enough venom, lead to respiratory paralysis and death. But the two neurotoxins go about it in different ways. Well, the two families of neurotoxins, if you like, the pre-synaptics and the post-synaptics go about it in different ways. And it's quite interesting. Now, if you remember biology classes, when a message travels down a nerve,

it's a change of polarity, plus and minus, all the way down the nerve. And then it comes to what's known as a synaptic gap. And it's a junction to jump to the next nerve. And for the message to jump to the next nerve, you have to have a product called acetalcholine injected from the sites on the upstream nerve into the synapse so that the message can cross over and carry it on down the next nerve. And then something called acetalcoline goes into the synapse.

to stop the effects of the astolcone, otherwise you're just going to have spasm. You're going to the message you're going to keep travelling. Now, with a post-synaptic neurotoxin, what the venom does is it gums up the receptor sites on the downstream side of the synapse. Like sticking chewing gum in a lock. You can't put the key in and turn it and you can't open the door. That's all it does. It blocks them up.

Now, if you administer, and a lot of cobra venoms are like that, and if you administer anti-venom, it will basically undo the damage quite quickly. Even if a patient is moribund, it can really turn the patient around quickly. A normal service will be resumed and the messages will continue to pass down the nerves. But what a pre-synaptic neurotoxin does is different. That's on the transmitting. sites on the upstream side of the synapse, it doesn't block them, it destroys them, it digests them. And if it has done a significant amount of damage, no amount of antivenom is going to reverse that.

Nothing's going to reverse that until the transmitter site have regenerated, which could take several days, during which time the victim can't breathe and would need to be ventilated, either on a ventilator, intubated in a hospital or ambubagged or mouth to mouth for three to five days, that's not feasible. So that's the problem. So you've got two different neurotoxins and they actually do completely different things because they're actually not similar in their composition. Then you've got amongst the blood toxins, the hematoxins, you've got procoagulants that cause a lot of clotting. You've got anticoagulants that prevent a lot of clotting and cause bleeding. But they actually end up doing the same thing. Now, a procoagulant venom that causes clotting.

When the snake bites its prey and injects the venom, it will cause a lot of blood clots in that prey and it will die and the snake will follow it and eat it. When that venom is injected into a human, the same amount of venom, it'll cause a lot of microclots in the blood. But your body then breaks those clots down and it'll fall more and it breaks them down. And this carries on until you've got no clotting factor left in your blood, whereupon you become superhemophiliac in effect, you can't clot. So then if you cut yourself, you bleed. And when I've had bites with a venom like this,

when they've just taken blood for a blood sample from me, they've ended up holding the thumb over the puncture in for like 40 minutes because I won't stop bleeding. Now, add into that some venom's hemorrhagic. They put holes in your blood vessels so that you bleed like a sieve. You can bleed to death internally without any external. And, of course, cranially, you could have a stroke. And then you've got the hemolytic venoms that actually destroyed the red blood cells.

And all of the destroyed red blood cells end up your kidneys and blocking up your kidneys and causing you renal problems. That's blood and nerves. Now you've got cytotoxins that destroy tissue. Now, few of these cause death, but you can lose limbs and spend a lot of time having to have skin grafts for the rest of your life. So that's another, you know, puff adders can inject. That is designed. A baby puff adder feeds on lizards, and it has neurotoxinsid venom that knocks out the lizard before it gets very far, and the baby puff adder eats that finds and eats the lizard. But the adults are feeding more on rats. So they need to speed it.

up the digestive process because a snake with a big meal in its stomach is vulnerable to being killed itself. So the cytotoxins speed up the digestive process and what might take a boge constrict as non-venomous five or six days to digest maybe, I'm just pulling the numbers out of the air, puff adamite digest in three days because of the cytotoxin. So it's vulnerable for a shorter period of time. So this is all amazing stuff. And it brings me to another little thought. Venoms vary. I've just said the juveniles got slightly different venom to the adult. They vary ontogenetically like that. So if antivenom is produced from adults, then if you're bitten by juvenile,

they might not cover all bases. But there's also things like variation in geographical variation in venom, where a snake A is feeding on lizards on this side of its range, but the same species, the other side of its range is eating birds. I haven't even got onto cardiotoxins and nephro-toxins and all the rest of them. So how many people die from snake bites every year? The figure of snake by fatalities is normally put between 94 and 138,000 people a year. And we're probably up at the upper level now.

Now, it's hard to determine because we have birth, death, and marriages, and you can't just disappear very easily in the West without records. And if you die, generally there'll be a death certificate. but that's not the case obviously in the developing world. And a lot of people, bitten in villages, don't want to go to the sterile western hospital a long distance away because they want to stay with their family. I suppose in a way it's a bit like if you're terminal cancer,

you'd rather be with your family and friends in familiar surroundings because you accept you're going to die rather than in a white-coated hospital or something like that. You know, that's the preference some people will take. And somebody who is, okay, they've been bitten by a venomous snake and they really think they're going to die. Maybe they'd prefer to stay at home than not make the journey and be and die on their own in the hospital because their family can't afford to come with them. And this is a mindset that's, I think, is quite common. And so we don't always know about all the snake bites.

And also, when snake bites are recorded in hospitals in developing countries, often it's snake bite, whether it's venomous or non-venomous. and if they record poisonings, then sometimes it's a poisoning, whether it's oral poisonous berries or mushrooms, or a snake bite. So the data is only as good as what's being recorded. But we think we're at maximum around 138,000. Very few of those deaths are in Europe or the United States or in Australia. I mean, Australia is always, oh, the land with more highly venomous snakes than anywhere else. top 10 venomous snake. It's argumentative where they've got the top 10, but the point is that there are a lot of highly venomous snakes there, very few deaths because of their excellent healthcare

system and the flying doctor service and the reduction of anti-venoms and all the rest of this, that Australia might lose two, three people a year. In 1985, I think it was, they lost, they had a, I think they lost eight because they were starting to use. It was a different therapy they were using, and it turned out to be a bad idea with brown snake. But it's very rare to dive a snake. If you dive a snakebite in Australia, you'll probably be on the front page of the Australian newspaper. Now, looking at figures for developing countries, Latin America is probably about 5,000 deaths a year. Africa, sub-Saharan Africa is somewhere around about 15,000, 20,000. The Middle East and North Africa, 100, 200, Asia. 100,000 deaths a year. It's massive. Now, these figures are the deaths, and those people die

and they're mourned, they're buried and they're mourned. But that's not all of snake bite. A lot of people are bitten by snakes that, say, the cytotoxins that lead to amputation of a limb, or they may have had anoxia, they may have been unconscious for a while and not breathing and then being resuscitated and have suffered brain damage. These are survivors, but they're not really surviving. They're living with a living death then because of the fact that what the snake has done to them has taken away what they did before. Very often the breadwinner in the family, imagine there's a really, really important

film called Minutes to Die, which emphasizes all of this. But imagine if you're a poor family and you've got five goats and a member of the family, the breadwinner or one of the children, is bitten by a snake and you sell the goats to get the money to get them to hospital to possibly save, they may not survive, but if they do survive, they may not have, they may lose a limb or something and that will also their chances have been able to work or marry and things like this, which a knock-on effect and now the family doesn't have five goats and actually has a mouth to feed that it can't afford. So there's, it's snake,

that can happen. It's been estimated that 400,000 people a year are permanently disabled by a snakebite. So add that to 138, and you're over half a million people a year. And for a long time, this was a neglected tropical disease. And it is a disease because there is a cure, anti-venom. And a lot of the big Western biopharmac companies have pulled out to producing anti-venom. There are still companies producing anti-venom around the world. And in my opinion, the heroes are the Institute. to Claudemira Piccardo at the University of San Jose in Costa Rica. That's not a biopharmac company. That's a university research department. And they produce anti-venom, not just for Costa Rica, not just for Latin America, but for

some countries in Africa, for some countries in Asia, and also they produce a typan anti-venom for us in New Guinea. So they're the heroes, in my opinion. But snake bite is a massive thing. But equally, while snakes are busy killing people, they're also saving people because of the fact that they are the best rodent traps you can get. And if you've been in Asia and seen the amount of rat damage to the rice crop, it's like crop circles.

It's massive. A lot is lost to rodents in the rice paddies. And then in the mills afterwards, you've got rats urinating on grain that's going to go for human consumption. So you've got the problems of things like wheels disease or, you know, transmittable diseases to humans. It's snakes that are actually the best rodent catchers. They are the best.

And living in paddy fields, they're eating a lot of them. So it's weighing up the number of people snakes kill, with the number of people snakes potentially save as vermin exterminators. You said there about snakes have this important role as eating rats. But what other role do snakes play in the environment? Nobody wants a jigsaw with a piece missing. And the snake is part of the food web, the food check. It is a predator. It's also prey itself. Quite a few things eat snakes. It fulfills a part in

the ecology, just the same as anything else would. If you were to remove, well, in parts of Southeast Asia, where they've collected lots and lots of snakes for the snake restaurants, they do have big rodent problems because the main predator of the rodents has gone. And if you remove the predator, something as fast-breeding as rodents, are just going to, the population's going to explode exponentially. So they're a really important part of the ecology, like anything else. So if you've got all these snakes eating rodents and pets and things like that, are there any vegetarian snakes? There's a piece of video somewhere on the internet, I've seen it, of identified the snake as an Australian whip snake, which is a venomous snake that feeds on rodent.

and lizards. And it's going over, there's a load of brush that's been pulled to one's side as they've cleared somewhere. And there's what look like olives or grapes. I think they're olives, actually, on this bush. And the snake's mooching around, it flicking its tongue, and it's jerking around, it's clearly interested in something. And that tells me it's, it's either following the trail of prey or a female. And then it starts tugging and it eats, manages to pull one of these olives or whatever it is off, and swallows it. And people are, I'm a vegetarian snake. No, No, no, no. It thinks it's eating something else. I would say that there's been a rodent on there, running around, scampering around, urinating, and the snake has tracked that down,

and it finds something with a lot of rodent urine in, and it smells like rodent, therefore it is a rodent. When we maintain snakes in captivity, we sometimes trick them into eating something we want them to eat by sending it with something they'd rather have. And so they've, they've, they've, they've very chemo sensory and that's that's their primary sense and so if it smells like a rodent it is a rodent there was um and i'm a celebrity many years ago the lead singer from happy mondays he had to put his hand into several holes and the one hole he put his hand in there was some rats and he's feeling around for stars and he pulled his hand out and then the next hole he got a stick his hand in and got carpet pythons in oh i knew it was going to he got bitten

do it the other way round. His hand had been on the rat. It smells like a rat. It is a rat. I'm speaking of the senses there as well, because we know they use their forked tongues, and I'll use that to taste the air and pick up where the prey is. But there was also some news research that came out recently

where they've now found that snakes appear to be able to hear sound through the air, whereas previously we thought they detected it through their jaw on the floor. Yes, we did, because the three bones in your ear that give you, hearing are actually part of the lower jaw in a snake. And because it's on the ground, we do think they detect vibrations. But certain airborne sounds may well create vibrations.

And we don't really know enough about snake hearing. We've always said snakes have poor eyesight and they're deaf to airborne sounds. But those are sort of statements that were made decades ago. And as we learn more, we determine that's not true. Some snakes have got excellent vision. Binocular vision tree snakes are able to sneak up and camouflaged lizards that I can't see. They're just very, very good at it.

And again, hearing will have evolved to suit the lifestyle of a particular snake. And some may have decent hearing, but it's not hearing as we know it, Jim. There's also another sense we should touch on, which is the ability to sense infrared heat. We're warm-blooded, so it's no good us having those receptors because all we go, oh, no, it's me. But with us, there are three families of snakes that have evolved heat receptors independently because they are not warm-blooded animals, cold-blooded, but of course a snake's blood could be warmer than hours if it's sitting in the sun and cooking.

So, so cold-blooded, warm-blooded aren't great terms, but you know what I mean. In pythons and boas, these, they're called pits and they're arranged a series of little slashes along the lip scales, both the upper and lower jaw. if you look at a photograph of a reticulated python, they're very obvious. They've even got them on the rostral scale at the front. Very, very obvious. Whereas in, so the pythons and boas, they're unrelated families that evolved in different parts of the world. The other group are the pit vipers, rattlesnakes and their kin, and they have a couple of

large, round, forward-facing orifices in front of the eye, but behind the nostril and down a little bit. And they face forward. And when you look at a rattlesnake from the front, you might think, a nostrils, they're not. The nostrils are further forward, and they face sideways, backwards, if anything, slightly. But these are forward-facing because it's picking up, it's picking up heat on both of them,

and where they overlap, it's able to work out distance. And so it makes a rattlesnake or any other pit viper remarkably accurate in the total dark, as I know to my cost. They are very, very accurate. accurate for locating prey. So being a cold-blooded animal feeding on warm-blooded animals, this is an obvious, wonderful adaptation. So what are some of the biggest threats to snakes? Biggest threats to snakes, there are many. Let's leave out natural threats like natural predators,

because that's the law of the jungle. That's what's supposed to happen. Snakes are prey just as their predators. Obviously, the skin trade is a big threat. Over collection and so forth. Habitat destruction, fragmentation, and alteration, those are three different things. You either destroy a habitat or you fragment it so that the species are living in the fragments, the individuals can't get together, or you alter it in some way, changing primary rainforest to plantation or something like that. Collection for medicines of suspicious value. such as drinking a gallbladder of a snake in a glass of whiskey or red wine every day for 30 days for lowered libido. Snakes got the same number of gallbladders as we have, one.

And they won't survive without it. There was some time ago there were snakes being sold into the pet trade in UK from Asia, and they were dying soon after people had purchased them. and a vet did an autopsy and found he didn't have a gallbladder and the guy who was shipping them was he knew under which scale to make a little slit to take out the gallbladder to sell separately then he sold a snake on I mean yeah I don't need to say any more about that I don't think but there are an awful lot of of threats to snakes in snake populations

and especially island snakes they're very threatened because if you if you if you change the habitat on an island to the detriment of the snake species or any other island species is very much harder for the population to re-establish, especially if it's some distance from the mainland. And I'm quite concerned about a very little snake called Ogmodon Vitianus. It's an elapid. It's a venomous snake, but it's harmless to humans. It's very tiny. It eats earthworms, we think. And it's only found on Viti Levo in Fiji. It's the only island is on. And it's under great threat from pigs rooting it up and eating it and habitat destruction and so forth.

That snake is not closely related to anything until you get to the Solomon Islands. I mean, that's a big distance. So that's a particular one. Active persecution, people are just killing snakes because they're snakes and some religions, you know, the snakes are seen as evil in Christiano-Judeism, possibly snakes are not seen as beneficial.

In other religions, in Buddhism, they are. But some people just kill snakes, because they're snakes, and that is as if it's a crime. The illegal pet trade, the rare as something is, the more valuable it is, and therefore potentially more people that are going to risk getting caught to catch them and smuggle them and make a profit. The trouble with the illegal pet trade is that the fines do not fit the crime. People who make a living out of this, if they get caught,

they get let off with quite a small fine, whereas, you know, and it's almost worth it because they'll make that money back. Rattlesnake Roundups in the United States, why those are still going on in the 21st century is beyond me because they catch the rattlesnakes, they do an enormous amount of damage collecting them to the animals that are still living in those habitats, like pulling gasoline down, boroughs,

and driving everything out. And it's seen as entertainment, and you can go and somebody will see how many rattlesnakes it and stuff into a sack, in 30 seconds or they'll get into a sleeping bag with suddenly rattle snakes and all these really silly things and then there's the killing of the rattlesnakes and the eating of the rattlesnakes and it just I find difficulty understanding how in the 21st century as a civilised people we can do something so barbarous because there's absolutely no need to do that.

Thank you for listening to this episode of Instant Genius. That was Herpetologist Professor Mark Jose talking about snakes. His fascinating new book, Snakes of the World, a guide to every family, is out now. The latest issue of BBC Science Focus magazine is now available. Pick up a copy in store or visit sciencefocus.com. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name audio believes you can have digital precision with analog warmth. Alongside French acoustic specialist vocal, Name creates high-end audio systems,

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