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Life in Cold Blood Sophisticated Serpents Snakes

where whatever your feelings, you cant deny that they have an extraordinary beauty Their lack of limbs compels them to deal with life's problems in ways that are utterly different from ours. But nonetheless the techniques they have developed are spectacularly successful. Snakes have one of the simplest of body shapes. Essentially just a long thin tube. But they have some remarkably effective ways of getting around. They can climb a tree simply by embracing its trunk. Some can flatten their bodies so that they catch the air beneath them and glide. By hitching up their undersides they can inch themselves forward in a straight line. A sinuous wriggle enables them to skate across loose sand. And the same action works equally well in water. There some swim close to the surface. Others explore the depths and can stay underwater for hours on end. One believe it or not can jump. So leglessness hardly seems such a handicap. But how did snakes get that way? Well their remote ancestors 100 million years ago at the time of the dinosaurs did have legs rather like today's lizards. Doubtless they were very effective runners. But some also started to burrow in search of prey. Below ground legs are a hindrance and over generations they became smaller. Today burrowing lizards such as skinks seem to be going through the same process. Many have tiny but recognizable legs. In others the limbs have become nothing more than functionless flaps. In this burrowing lizard the process has gone even further. The animal still has the face of a lizard but its legs have disappeared totally. It seems that the ancestral snakes went through just such a process way back in geological history some 92 million years ago. So what did these very first snakes look like? Well the answer can be found in Asian jungles in American woodlands and gardens and even in flowerpots like this. It may look like an earthworm but actually it's a flowerpot snake and it's completely blind. It doesn't need to see because it spends all its life underground. Ill put it back in its flowerpot and put a flower on top and it will live perfectly happily there in this flowerpot all by itself providing it has enough food. And there's a surprising amount for a small snake to eat underground. Ant larvae for example. These early legless reptiles flourished and remained underground for a long time. Then around 20 million years ago some of them returned to the surface. Why? Well by this time the dinosaurs had disappeared and the early mammals had arrived. They were more nutritious than beetles and worms so the snakes began to catch them instead and became so good at doing so that today they are among the most skilful hunters on Earth. Here in North America there is a snake that combines its great speed and extraordinary senses in a remarkable hunting strategy we are only just beginning to understand. A timber rattlesnake. There's a mouse just along that log. That obviously came to nothing but the cameras have started recording again and the snake is moving. He's checking out the trail with his tongue. See that's exactly where that mouse was running. Its pitch dark and the mouse clearly have no idea that the snake is there. But the snake is well aware of the mouse. Thanks no doubt to those heat-detecting pits. A snake strikes by suddenly straightening the curve in its neck. But at the moment the mouse is not within range. He's worked out that that is the path along which the mice run and has getting himself properly adjusted so he can strike it when he next gets a chance. Now once again waiting. That's what snakes are so good at. Oh my goodness. That's a dead mouse all right. Slow down that shot and you can see that the snake stabs the mouse just once. After three convulsive kicks the mouse is dead. The snake is moving again. He's going back now to look for the one that he knows is dead back there. Where is it? Ah. Now it looks as though has really got it. That's his dinner and that can last him for three weeks four weeks if necessary. Rattlesnakes are among the least obtrusive inhabitants of the forests of North America and they are probably far more numerous than many people realize. Like many other animals snakes use their nostrils to detect smells. But the most sensitive and accurate information about the world around them comes from that constantly flickering tongue. With this a snake gathers molecules from the air and carries them back for evaluation to a pair of extremely sensitive organs in the roof of its mouth. To see of just how important scent can be to a snake I've come here to Carnac Island just off the coast of Western Australia. Its home to a large population of highly venomous tiger snakes. Snakes have been established here for many years but there's something odd about this particular population. Many of them have damaged heads and some of them are actually blind like this one. And yet puzzlingly in spite of the fact that they're blind they all appear to be very well fed. So how do their heads get damaged? And how in that condition when they cant sees anything can they catch all the prey they need? The snakes of course are not the only inhabitants of the island. It's also home for a large colony of silver gulls. The gulls breed throughout the year so their chicks are a source of food for the snakes that never ends. In fact the snakes eat pretty well nothing else. But the snakes don't get it all their own way. The gulls are valiant defenders of their nests and their chicks. Their stabbing beaks are powerful sharp and strong. And the gulls always go for the snakes head. One in 10 of the snakes are totally blinded. Tiger snakes don't have those heat-sensitive pits that rattlesnakes have so these blinded hunters must be guided entirely by their forked tongue. It's a superb direction-finding device. The snake can measure the strength of a smell separately on each of the two forks of its tongue. And if it wishes to follow up a smell then it simply detects the one that has the stronger smell and goes in that direction. Gull chicks are an ideal prey for a blinded snake because they are programmed to stay on their nests. Once a snake has located it a chick is doomed. Snakes it must be admitted have had a bad reputation ever since one appeared in the Garden of Eden. But in reality even the most aggressive venomous snake will avoid biting a human being if it can. Why waste venom and risk violent retribution by biting something you're not going to eat? To prevent misunderstanding most venomous snakes warn other animals including human beings to keep out of their way. Some snakes do that with sound. Others such as cobras give a visual signal by expanding the skin around their heads to form a conspicuous hood. The threat of a bite is far better defense for a snake than the bite itself. However there are some snakes that not only use their venom to kill their prey but have also found a way of using it to deter their enemies without even biting them. This Mozambique cobra has a very special way of doing that. To demonstrate this with some degree of safety I'm going to wear this visor which has been coated with a substance that turns pink in contact with venom. Let's see what happens. It's watching me waiting to see if I get too close for its liking. Venom spurts from its fangs. As it spits it turns its head from side to side so that the jets have the best chance of hitting my eyes. Well I was well and truly sprayed. Every one of those pink dots is a bead of venom. And if any one of them had gone in my eye I would be now blind and in extreme pain. So it's a fair warning from that snake to me not to get any closer. And I dare say if I did I would deserve what I would get which would be a bite. I have no intention of doing that. On the other hand some snakes which may appear to be venomous are in reality quite harmless. These two snakes look very similar and they both occur here in the southern United States so you are quite likely to meet one or the other here. One of them however is harmless. It's called a king snake. The other one is a coral snake and highly venomous. One bites certain death. The question is which is which. Well the key lays in the order of the colour rings. People here have a local saying Red and black venom lack. Red and yellow can kill a fellow. And this one has red and black so I guess that's a kingsnake. Well see. So far so good. Yeah this is a king snake. And what a beautiful snake it is. A really lovely reptile. The king snake pretends to be venomous when its not. And there's another snake that pretends to be dead when it isn't. Snakes being cold-blooded seem to relish the warmth of sun-baked roads and often bask on them. And as a result of course many get run over. But things aren't always exactly what they seem. He looks kind of dead but in fact this hog-nosed snake is perfectly all right. He was just feigning death so that things that might have been interested in a living snake are not. And what's more he has produced rather a remarkable smell. In fact the smell as it was of rotting flesh. So maybe he was pretending too that he was not only dead but decomposing. Very convincing. Off you go. The lack of limbs that might seem to us to be such a huge handicap has not stopped snakes from getting around in all kinds of ways and neither does it prevent them from tackling all kinds of meals. This South African snake has become a specialist in swallowing a particularly awkward mouthful. It's as accomplished a tree climber as you'll find among snakes. The trees it frequents also hold colonies of masked weaverbirds that suspend their nests from the very tip of the branches. But the snake is a skilled enough climber to reach them. The weaverbirds know it well and recognize it as a threat. It's well accustomed to these attacks. These defenders however are just too determined and it retreats. But it doesn't give up altogether. This nest is unguarded. And this is what the snake is after the eggs. Each is several times bigger than the snakes head but its jaws are linked by ligaments that are amazingly elastic. Once the egg is engulfed by the snake's jaws powerful throat muscles push it down its gullet. Moving X-rays enable us to see exactly what's happening. Soon the egg reaches a part of the backbone that has downward pointing spines on it. The snake arches its backbone and then squeezes. The shell cracks and the spines on the backbone slit the membrane. The shell is crushed and rich nutritious yolk flows into the snakes gut. Then what's left of the shell is regurgitated. But that of course was a small meal. Some snakes can tackle much bigger meals than that. An African rock python one of the biggest of all snakes that can grow over seven metres 20 feet long. And it is eating an antelope. It too has an elastic ligament connecting its jaws. It killed the antelope not with venom but by squeezing it so tightly that it was unable to breathe. Python's teeth can't cut or rip. It has to swallow its prey whole or not at all. And that may take a day or more. Without limbs the python can't push the antelope down its throat. Instead it hitches its jaws diagonally back and forth so that they as it were walk along and over the prey. Its tube-like body has to stretch so extremely to accommodate such a gigantic meal that its flanks have torn. But such injuries heal very quickly. The last of the antelope its hooves are about to disappear. Gone. The python will now hide itself away and begin the long process of digestion. Everything will be dissolved skin hair hooves even horns. This python will not need to eat again for a year or more. Wherever it's warm and there are animals of some kind there will be snakes to hunt them no matter how difficult the conditions and how awkward the mouthful. Crabs are in plentiful supply in this mangrove swamp. There must be 20 on any one of these trees around me. They're all up there waiting for the tide to go out so that they can feed in the mud below. So there is a meal for a snake here but crabs are not easy to tackle. They're strong armour-plated and covered in spines. For a snake to tackle one of these would be like me trying to eat a lobster twice the size of my head with my hands tied behind my back. But there is a snake that knows how to do so. The crabs cling to the arching struts of the mangroves to keep out of the way of predatory fish but as the tide retreats it becomes safe for them to climb down and start looking for such edible bits as the tide has left behind on the mud. For the moment they're safe but soon the sun will set. Then the snakes will come out of their burrows. They hunt in the darkness but well are able to follow them with our infrared cameras. It's now very dark indeed and the snake has to find its way around entirely by touch and smell. Finding crabs is not difficult. They swarm all over the mud and the snake is almost bound to encounter one sooner rather than later. The snake is armed with venom and has short strong fangs which can pierce a crabs shell and stun it. But that is only half the problem. It's what it does after it has caught its crab that sets it apart from all other snakes. It has it. Now what? The crab is so large that the snake can't swallow it whole. Slowly and deliberately the snake dismembers the crab. Each leg contains nutritious muscle. But the crab's armoured body is simply discarded. Too difficult. There are hard-shelled creatures in fresh waters as well as in salt. Not nearly as many but sufficient number for some snakes to specialize in eating them. And in the eastern United States many rivers contain crayfish. Like crabs they have a hard protective shell and they have particularly powerful pincers as well. The queen snake however eats crayfish and nothing else. But not just any crayfish. It's very selective. Crayfish as they grow shed their armour. Every three to four weeks a split appears across the back of its shell. The old shell hinges away and the crayfish hauls itself out and expands its body which is soft. It's now that the snake has its chance. A newly molted crayfish looks much the same but it gives off different chemicals that the snake can detect in the water with its tongue and from some distance away. It can swallow this crayfish because since it is newly molted it's as soft as a boiled egg. On occasion snakes have to grapple not only with their prey but with one another in disputes over mates and territory. This is one of the most formidable the king cobra. Highly venomous and about four metres 14 feet long. Disputes between rival male king cobras are potentially very dangerous indeed for this species specializes in eating other kinds of snakes. So they observe strict rules in their fights which prohibit the use of their lethal bite. Slowed down it's a performance full of grace as each contestant strives not to kill his opponent but simply to slam him to the ground. The defeated male leaves the arena and no harm has been done. Snakes must also find a way of preventing their courtship from becoming lethal. This is a Californian king snake a male. He has detected the scent of a female ready to mate. Like all snakes his eyesight is not good but he can tell from the taste of the air that she is close by. In fact she is within inches. For some time the two follow one another nose to tail. The male begins to caress her sensually jerking and rocking his body as he holds her close. He has a pair of sexual organs one of which can project to the left and the other to the right. So no matter which side of him she happens to lie he can reach her. At last union is achieved. They may remain together for several hours. In a few weeks time the female will lay a clutch of eggs. It may take six or seven weeks for them to hatch but the regions where most snakes live are warm enough for them to develop without any help from the parents. Cobras lay them on the ground in the leaf litter. Their soft parchment-like shell is easily split when pushed from within. The front end of a cobra hatchling is quite capable of giving a bite even while the back end is still within the shell. Their fangs may be small but since it only takes a tiny drop of cobra venom to kill an animal these youngsters can be as lethal as their parents. They already have that characteristic warning signal the hood. Not all snakes lay their eggs. In some species the female retains them within her body until they're ready to hatch so she gives birth to live young. The marshes of northern Argentina home to one of the largest of live-bearing snakes the anaconda. This is a female and she's heavily pregnant. Its morning and she's chilly so she moves out of the water and onto the swamp to warm herself in the sun. Slowly the day begins to warm up. Now it's getting a little too hot for her so she moves back to the water to cool off. In this way she manages to keep her body close to 29 degrees centigrade perfect for the babies developing within her. But she won't give birth here and now. There are caiman around. At last she finds the quiet pool that she needs. And her contractions start. The first of her babies has arrived. Up it goes to the surface to take its first breath of air. But there are more babies to come. Eventually she produces 12. In fact that's quite modest for an anaconda. They can produce up to 40. Right from the beginning of their lives they're totally independent and get no care or protection from their mother. The anaconda spends so much of its time in water and is such a powerful swimmer that it can be properly considered aquatic. Snakes have become adapted to almost every environment including even the sea as this one has. It doesn't often bite but it does have extremely powerful venom so I am not going to handle it. But I will help it a little with this stick. As you can see it has a much flattened paddle at the end of its tail. But on land it's pretty helpless. However if I assist it in getting into the sea and now it's in its element. Sea snakes have had to modify many of the features that enabled their far distant ancestors to colonize the land. They still have a lung with which to breathe air like other snakes but they can also absorb oxygen from the seawater through their skin. Salt inevitably gets into a sea snakes body but the snake manages to get rid of that by excreting it from a gland under its tongue. It also needs to drink fresh water. So in calm seas it waits at the surface for rain. Sea snakes really are truly marine creatures.


 
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The rattlesnake cant move fast enough to chase and catch a little chipmunk
The rattlesnake cant move fast enough to chase and catch a little chipmunk
  Carnac Island its home to a large population of highly venomous tiger snakes
Carnac Island its home to a large population of highly venomous tiger snakes
  An African rock python one of the biggest of all snakes eating an antelope
An African rock python one of the biggest of all snakes eating an antelope
  King cobra, one of the most formidable serpents
King cobra, one of the most formidable serpents
 
They can live out here in the open ocean and the only clue you have to their link with the land is that they have to come up every quarter of an hour or so for a gulp of air. Most sea snakes like this bar-bellied species hunt fish. They have one of the most lethal venoms known which kills almost instantaneously. And that is a very important quality if you hunt fast-swimming ocean-going prey. But paradoxically the most highly specialized sea snake of all has abandoned venom altogether. It has a beak like a turtle and a wholly different way of feeding. Reef fish don't like to have it around. They mob it. It doesn't even retaliate. It's not interested in them. It's after their eggs. These the fish have stuck to the stony branches of the coral. The snake's hardened turtle-like top lip enables it to scrape them off. It's a slow-moving browser that algae and other small organisms grow on its skin as they do on the bottom of a boat. The loss of limbs could seem to be a handicap and certainly makes the snakes seem alien creatures to us. But it is that very loss that has enabled the snakes to colonize every environment from below the ground to above the ground from bushes to trees to the air and even to the sea. And it is that absence of limbs too which has enabled them to do it with such elegance and grace. Filming venomous snakes presented a lot of special problems to the Life in Cold Blood team but the toughest was trying to film rattlesnake hunting in the wild. A rattlesnake making a kill has rarely even been seen and never before filmed and for several reasons. For one thing rattlesnakes are so well camouflaged they're very difficult to find. We enlisted the help of snake expert Harry Greene and his team. They've been studying a group of timber rattlesnakes using radio telemetry which enables them to find their rattlesnakes at any time of day or night. Most of us will never find them and they're superbly camouflaged. Exactly but that's been one of the wonderful things about radio telemetry is we can have an animal that we can dial up.     To have any chance of success the crew had to be able to find the rattlesnakes on their own. So producer James Brickell had to take a course in telemetry techniques himself. Hmm point it a little bit more this way. Each snake has been implanted with a tiny transmitter. If you dial its frequency you can pick up a beeping sound. And that gets louder the nearer you get to the snake. And so its just like if you were trying to find your favourite rock-and-roll station or something but now were gonna find our favourite rattlesnake. So you just punch in its number and it's on the air. It sounds simple in theory but there's a snag. Its here somewhere. Just are really careful guys. In a forest the signal can bounce off trees and give you a false reading so that it can seem that the snake is everywhere. And you don't want to think a reading is false and then tread on your snake by mistake. He's that way there? You'll find has up there somewhere. Let's find him. James it's starting to get dark. Yeah I know. He's in there. I reckon has hunting. James is careful where you're going. And it isn't just the one snake you're tracking. There are dozens of others in the area that aren't tagged. Follow my hand. There he is. Its about 20 feet. All right good. Six metres. And so at last the crew meets a very special snake called Hank. Hank is in a perfect position for his ambush. To film the action without disturbing him or his prey cameraman Mark MacEwen has fitted his camera with motion detectors from a burglar alarm. They will turn on the camera without anyone having to be here. So for the first time they set up their gear in front of a live snake . They could now leave Hank and track another of Harris snakes. So that means you know individual snakes over a long period of time. Do they differ very much? Absolutely. Now there are species differences so certain rattlesnake species are more sort of nasty-tempered than others. But even within a population you'll have one that just never gets riled up and one that you know you just can't get too close to without it getting upset.