BBC Life in Cold Blood E04 Sophisticated Serpents
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00:30Whatever your feelings about snakes, you can't deny that they have an extraordinary beauty.
00:47Their lack of limbs compels them to deal with life's problems in ways that are utterly different
00:52from ours.
01:01But nonetheless, the techniques they've developed are spectacularly successful.
01:22Snakes have one of the simplest of body shapes, essentially just a long, thin tube.
01:28But they have some remarkably effective ways of getting around.
01:34They can climb a tree simply by embracing its trunk.
01:44Some can flatten their bodies so that they catch the air beneath them and glide.
01:54By hitching up their undersides, they can inch themselves forward in a straight line.
02:01A sinuous wriggle enables them to skate across loose sand.
02:08And the same action works equally well in water.
02:16There, some swim close to the surface.
02:22Others explore the depths and can stay underwater for hours on end.
02:30One, believe it or not, can jump.
02:53So leglessness hardly seems such a handicap.
02:57But how did snakes get that way?
03:00Well, their remote ancestors 100 million years ago, at the time of the dinosaurs, did have
03:06legs, rather like today's lizards.
03:16Doubtless, they were very effective runners.
03:19But some also started to burrow in search of prey.
03:26On low ground, legs are a hindrance, and over generations, they became smaller.
03:32Today, burrowing lizards, such as skinks, seem to be going through the same process.
03:38Many have tiny but recognisable legs.
03:42In others, the limbs have become nothing more than functionless flaps.
03:50In this burrowing lizard, the process has gone even further.
03:54The animal still has the face of a lizard, but its legs have disappeared totally.
04:03It seems that the ancestral snakes went through just such a process way back in geological
04:09history some 95 million years ago.
04:14So what did these very first snakes look like?
04:17Well, the answer can be found in Asian jungles, in American woodlands and gardens, and even
04:25in flowerpots, like this.
04:31It may look like an earthworm, but actually, it's a flowerpot snake.
04:39And it's completely blind.
04:41It doesn't need to see, because it spends all its life underground.
04:47I'll put it back in its flowerpot, and put a flower on top, and it will live perfectly
04:54happily there in this flowerpot, all by itself, providing it has enough food.
05:00And there's a surprising amount for a small snake to eat underground.
05:05Ant larvae, for example.
05:18These early legless reptiles flourished and remained underground for a long time.
05:25Then, around 50 million years ago, some of them returned to the surface.
05:35Why?
05:36Well, by this time, the dinosaurs had disappeared, and the early mammals had arrived.
05:41They were more nutritious than beetles and worms, so the snakes began to catch them instead,
05:47and became so good at doing so, that today they are among the most skillful hunters on earth.
05:55Here in North America, there's a snake that combines its great speed and extraordinary
06:01senses in a remarkable hunting strategy we are only just beginning to understand.
06:11A timber rattlesnake.
06:15The morning sun has warmed its body, giving it energy, and it starts to move.
06:30It's searching for a place where it can conceal itself, and wait for prey to come within striking distance.
06:41A little chipmunk. It's in no danger yet.
06:44The rattlesnake can't move fast enough to chase and catch it.
06:50But small mammals tend to use the same paths as they run over the forest floor,
06:55and they leave behind a faint trail of scent.
06:59The rattlesnake can detect that scent with its tongue.
07:11It can also locate the warm-blooded chipmunk if it's nearby, with heat detectors in a pair of pits beneath its eyes.
07:22As it moves, it carefully holds its rattle above the ground, so it makes no noise.
07:34It's chosen the place to wait, at the bottom of this tree stump.
07:38Its colouration matches the ground so closely it needs no further concealment.
07:45Now it's just a matter of time.
07:49Seeing a rattlesnake actually catching its prey is a very, very difficult thing to observe.
07:56In fact, some scientists have watched rattlesnakes for years without seeing that particular crucial moment.
08:03But we have a chance, partly because rattlesnakes are ambush hunters,
08:08so we know exactly where to put up our gear,
08:11and partly because in that gear we've got the very latest in surveillance equipment.
08:19There are remotely controlled cameras and infrared lights on stands.
08:25And there are motion detectors that will switch on the cameras if anything moves,
08:29so I needn't wait alongside.
08:32If anything happens, the cameras will switch on automatically.
08:39Later, I check the replay.
08:43There's a mouse, just along that log.
08:57That obviously came to nothing.
08:59But the cameras have started recording again and the snake is moving.
09:03He's checking out the trail with his tongue.
09:09See, that's exactly where that mouse was running.
09:19It's pitch dark, and the mouse clearly has no idea that the snake is there.
09:24But the snake is well aware of the mouse, thanks no doubt to those heat-detecting pits.
09:33The snake strikes by suddenly straightening the curve in its neck,
09:37but at the moment, the mouse is not within range.
09:44The mouse is not aware that the snake is there,
09:47but the snake is aware of the mouse.
09:55He's worked out that that is the path along which the mice run.
10:02And he's getting himself properly adjusted,
10:05so he can strike when he next gets a chance.
10:25Now once again, waiting.
10:29That's what the snakes are so good at.
10:54Oh! Oh my goodness!
11:02That's a dead mouse, all right.
11:07Slow down that shot, and you can see that the snake stabs the mouse just once.
11:15After three convulsive kicks, the mouse is dead.
11:20The snake is moving again.
11:23He's going back now,
11:26to look for the one that he knows is dead, back there.
11:33Where is it?
11:38Ah, now it looks as though he's found it.
11:43Where is it?
11:47Ah, now it looks as though he's really got it.
11:55That's his dinner.
11:57And that can last him for three weeks, four weeks if necessary.
12:13Rattlesnakes are among the least obtrusive inhabitants of the forests of North America,
12:18and they're probably far more numerous than many people realise.
12:25Like many other animals, snakes use their nostrils to detect smells,
12:30but the most sensitive and accurate information about the world around them
12:34comes from that constantly flickering tongue.
12:43With this, a snake gathers molecules from the air
12:47and carries them back for evaluation
12:49to a pair of extremely sensitive organs in the roof of its mouth.
12:55To see just how important scent can be to a snake,
12:59I've come here to Karnak Island, just off the coast of Western Australia.
13:04It's home to a large population of highly venomous snakes,
13:09to a large population of highly venomous tiger snakes.
13:16Snakes have been established here for many years,
13:19but there's something odd about this particular population.
13:24Many of them have damaged heads,
13:27and some of them are actually blind, like this one.
13:31And yet, puzzlingly, in spite of the fact that they're blind,
13:36they all appear to be very well fed.
13:39So, how do their heads get damaged,
13:42and how, in that condition, when they can't see anything,
13:45can they catch all the prey they need?
13:52The snakes, of course, are not the only inhabitants of the island.
13:56It's also home for a large colony of silver gulls.
14:02The gulls breed throughout the year,
14:05so their chicks are a source of food for the snakes that never ends.
14:14In fact, the snakes eat pretty well nothing else.
14:22But the snakes don't get it all their own way.
14:25The gulls are valiant defenders of their nests and their chicks.
14:30Their stabbing beats are powerful, sharp and strong,
14:34and the gulls always go for the snake's head.
15:00One in ten of the snakes are totally blinded.
15:04Tiger snakes don't have those heat-sensitive pits that rattlesnakes have,
15:09so these blinded hunters must be guided entirely by their forked tongue.
15:14It's a superb direction-finding device.
15:18The snake can measure the strength of a snail separately on each of its legs.
15:25The snake can measure the strength of a snail separately
15:28on each of the two forks of its tongue.
15:31And if it wishes to follow up a smell,
15:34then it simply detects the one which has the strongest smell
15:38and goes in that direction.
15:44Gull chicks are an ideal prey for a blinded snake
15:48because they're programmed to stay on their nests.
15:55CHICKS SQUAWK
16:08Once a snake has located it, a chick is doomed.
16:18Snakes, it must be admitted, have had a bad reputation
16:21ever since one appeared in the Garden of Eden.
16:24But in reality, even the most aggressive venomous snake
16:28will avoid biting a human being if it can.
16:32Why waste venom and risk violent retribution
16:35by biting something you're not going to eat?
16:40To prevent misunderstanding,
16:42most venomous snakes warn other animals, including human beings,
16:46to keep out of their way.
16:51Some snakes do that with sound.
17:05Others, such as cobras, give a visual signal
17:08by expanding the skin around their heads to form a conspicuous hood.
17:15The threat of a bite is far better defence for a snake
17:19than the bite itself.
17:23However, there are some snakes
17:26that not only use their venom to kill their prey,
17:30but have also found a way of using it
17:34to deter their enemies without even biting them.
17:41This Mozambique cobra has a very special way of doing that.
17:45To demonstrate this with some degree of safety,
17:48I'm going to wear this visor,
17:50which has been coated with a substance
17:52that turns pink in contact with venom.
17:55Let's see what happens.
18:00It's watching me, waiting to see if I get too close for its liking.
18:16Venom spurts from its fangs.
18:20As it spits, it turns its head from side to side
18:23so that the jets have the best chance of hitting my eyes.
18:32Well, I was well and truly sprayed.
18:36Every one of those pink dots is a bead of venom,
18:40and if any one of them had gone in my eye,
18:43I would be now blind and in extreme pain.
18:46So it's a fair warning from that snake to me not to get any closer.
18:51And I dare say if I did, I would deserve what I would get,
18:55which would be a bite.
18:57I have no intention of doing that.
19:02On the other hand, some snakes, which may appear to be venomous,
19:06are, in reality, quite harmless.
19:10These two snakes look very, very similar,
19:14and they both occur here in the southern United States,
19:18so you're quite likely to meet one or the other here.
19:21One of them, however, is harmless.
19:24It's called a kingsnake.
19:26The other one is a coral snake and highly venomous,
19:30one bite, certain death.
19:32The question is, which is which?
19:36Well, the key lies in the order of the colourings.
19:40People here have a local saying,
19:43red and black venom lack,
19:47red and yellow can kill a fellow.
19:51And this one has red and black,
19:57so I guess that's a kingsnake.
20:02We'll see.
20:06So far, so good.
20:09Yeah, this is a kingsnake.
20:11And what a beautiful snake it is.
20:18A really lovely reptile.
20:27The kingsnake pretends to be venomous when it's not,
20:31and there's another snake that pretends to be dead when it isn't.
20:40Snakes, being cold-blooded,
20:42seem to relish the warmth of sun-baked roads
20:45and often bask on them,
20:47and as a result, of course, many get run over.
20:55But things aren't always exactly what they seem.
20:59He looks kind of dead.
21:06But, in fact, this hog-nosed snake is perfectly all right.
21:14He was just feigning death
21:18so that things that might have been interested in a little bit of fun
21:24so that things that might have been interested in a living snake are not.
21:30And what's more, he's produced a rather remarkable smell.
21:36In fact, the smell, as it were, of rotting flesh.
21:41Maybe he was pretending, too, that he was not only dead but decomposing.
21:47Very convincing.
21:49Off you go.
21:54The lack of limbs that might seem to us to be such a huge handicap
21:59has not stopped snakes from getting around in all kinds of ways,
22:03and neither does it prevent them from tackling all kinds of meals.
22:09This South African snake has become a specialist
22:12in swallowing a particularly awkward mouthful.
22:15It's as accomplished a tree-climber as you'll find among snakes.
22:31The trees it frequents also hold colonies of masked weaver birds
22:36that suspend their nests from the view of other snakes.
22:40They also hold colonies of masked weaver birds
22:43that suspend their nests from the very tip of the branches.
22:47But the snake is a skilled enough climber to reach them.
22:51The weaver birds know it well and recognise it as a threat.
23:06It's well accustomed to these attacks.
23:10It's well accustomed to these attacks.
23:31These defenders, however, are just too determined, and it retreats.
23:40But it doesn't give up altogether.
23:57This nest is unguarded.
24:05And this is what the snake is after, the eggs.
24:09Each is several times bigger than the snake's head,
24:12but its jaws are linked by ligaments that are amazingly elastic.
24:23Once the egg is engulfed by the snake's jaws,
24:26powerful throat muscles push it down its gullet.
24:31Moving X-rays enable us to see exactly what's happening.
24:39Soon, the egg reaches a part of the backbone
24:42that has downward-pointing spines on it.
24:48The snake arches its backbone and then squeezes.
24:53The shell cracks, and the spines on the backbone slit the membrane.
25:01The shell is crushed,
25:03and rich, nutritious yolk flows into the snake's gut.
25:08Then what's left of the shell is regurgitated.
25:15But that, of course, was a small number of eggs.
25:21The snake's gut is filled with eggs,
25:24and the shell is filled with eggs,
25:27and the shell is filled with eggs,
25:30and the shell is filled with eggs,
25:33and the shell is filled with eggs,
25:36and that was a small meal.
25:38Some snakes can tackle much bigger meals than that.
25:45An African rock python,
25:47one of the biggest of all snakes that can grow over 7 metres, 20 feet long.
25:52And it is eating an antelope.
25:55It, too, has an elastic ligament connecting its jaws.
26:01It killed the antelope not with venom,
26:04but by squeezing it so tightly that it was unable to breathe.
26:12A python's teeth can't cut or rip.
26:15It has to swallow its prey whole or not at all,
26:19and that may take a day or more.
26:22Without limbs, the python can't push the antelope down its throat.
26:27Instead, it hitches its jaws diagonally back and forth
26:31so that they, as it were, walk along and over the prey.
26:36Its tube-like body has to stretch so extremely
26:40to accommodate such a gigantic meal that its flanks are torn.
26:44But such injuries heal very quickly.
26:52The last of the antelope, its hooves.
26:55Just at the antelope, its hooves are about to disappear.
27:07Gone.
27:15The python will now hide itself away
27:18and begin the long process of digestion.
27:21Everything will be dissolved.
27:23Skin, hair, hooves, even horns.
27:34This python will not need to eat again for a year or more.
27:45Whenever it's warm and there are animals of some kind,
27:48there will be snakes to hunt them,
27:50no matter how difficult the conditions and how awkward the mouthful.
27:56Crabs are in plentiful supply in this mangrove swamp.
27:59There must be 50 on any one of these trees around.
28:03They're all up there waiting for the tide to go out
28:06so that they can feed in the mud below.
28:09So there is a meal for a snake here.
28:12But crabs are not easy to tackle.
28:15They're strong, armour-plated and covered in spines.
28:19For a snake to tackle one of these
28:22would be like me trying to eat a lobster twice the size of my head
28:26with my hands tied behind my back.
28:29But there is a snake that knows how to do so.
28:34The crabs cling to the arching struts of the mangroves
28:37to keep out of the way of predatory fish.
28:40But as the tide retreats, it becomes safe for them to climb down
28:44and start looking for such edible bits
28:46as the tide has left behind on the mud.
28:57For the moment, they're safe, but soon the sun will set.
29:01Then the snakes will come out of their burrows.
29:05They hunt in the darkness,
29:07but we'll be able to follow them with our infrared cameras.
29:17It's now very dark indeed,
29:20and the snake has to find its way around entirely by touch and smell.
29:34Finding crabs is not difficult.
29:37They swarm all over the mud
29:39and the snake is almost bound to encounter one sooner rather than later.
29:45The snake is armed with venom and has short, strong fangs
29:50which can pierce a crab's shell and stun it.
29:53But that's only half the problem.
29:55It's what it does after it's caught its crab
29:58that sets it apart from all other snakes.
30:06The crab is a very dangerous predator.
30:09And so are snakes.
30:36It has it.
30:39The crab is so large that the snake can't swallow it whole.
30:44Slowly and deliberately, the snake dismembers the crab.
30:53Each leg contains nutritious muscle.
30:57But the crab's armoured body is simply discarded.
31:02Too difficult.
31:07There are hard-shelled creatures in fresh waters as well as in salt.
31:11Not nearly as many, but sufficient number for some snakes
31:15to specialise in eating them.
31:17And in the eastern United States, many rivers contain crayfish.
31:26Like crabs, they have a hard, protective shell.
31:30And they have particularly powerful pincers as well.
31:39The crayfish are a very dangerous predator.
31:42And so are crabs as well.
31:51The queen snake, however, eats crayfish and nothing else.
32:13But not just any crayfish.
32:21It's very selective.
32:24Crayfish, as they grow, shed their armour.
32:31Every three to four weeks, a split appears across the back of its shell.
32:37The old shell hinges away, and the crayfish pours itself out
32:41and expands its body, which is soft.
32:46It's now that the snake has its chance.
33:00A newly-moulted crayfish looks much like a crab.
33:06It's not much the same, but it gives off different chemicals
33:10that the snake can detect in the water with its tongue
33:13and from some distance away.
33:16It can swallow this crayfish because, since it's newly-moulted,
33:21it's as soft as a boiled egg.
33:25It can swallow this crayfish because, since it's newly-moulted,
33:30it's as soft as a boiled egg.
33:55On occasion, snakes have to grapple not only with their prey,
34:00but with one another, in disputes over mates and territory.
34:06This is one of the most formidable, the king cobra,
34:09highly venomous and about four metres, 14 feet, long.
34:16The king cobra is the largest snake in the world.
34:20It's about four metres, 14 feet, long.
34:26Disputes between rival male king cobras
34:29are potentially very dangerous indeed,
34:32for this species specialises in eating other kinds of snakes.
34:39So they observe strict rules in their fights,
34:42which prohibit the use of their lethal bite.
34:46Slowed down, it's a performance full of grace,
34:50as each contestant strives not to kill his opponent,
34:54but simply to slam him to the ground.
35:15MUSIC PLAYS
35:46The defeated male leaves the arena, and no harm has been done.
36:01Snakes must also find a way of preventing their courtship
36:05from becoming lethal.
36:07This is why the king cobra is so popular.
36:10They must also find a way of preventing their courtship
36:13from becoming lethal.
36:15This is a Californian kingsnake, a male.
36:22He has detected the scent of a female, ready to mate.
36:30Like all snakes, his eyesight is not good,
36:34but he can tell from the taste of the air that she's close by.
36:41In fact, she is within inches.
36:45For some time, the two follow one another nose to tail.
36:54They are both very shy.
36:57They are both very shy.
37:00They are both very shy.
37:03And they are both very shy.
37:06And they are both very shy.
37:09And they are both very shy.
37:12Nose to tail.
37:20The male begins to caress her,
37:23sensually jerking and rocking his body as he holds her close.
37:31He has a pair of sexual organs,
37:34one of which can project to the left and the other to the right.
37:38So no matter which side of him she happens to lie,
37:42he can reach her.
37:46At last, union is achieved.
37:49They may remain together for several hours.
38:20In a few weeks' time, the female will lay a clutch of eggs.
38:25It may take six or seven weeks for them to hatch,
38:28but the regions where most snakes live
38:30are warm enough for them to develop
38:32without any help from the parents.
38:38Cobras lay them on the ground in the leaf litter.
38:43Their soft, parchment-like shell
38:46is easily split when pushed from within.
38:57The front end of a cobra's body
39:00is covered with a thick layer of skin.
39:03It's the skin of a cobra.
39:06It's the skin of a cobra.
39:10The front end of a cobra hatchling
39:13is quite capable of giving a bite,
39:15even while the back end is still within the shell.
39:35Their fangs may be small,
39:37but since it only takes a tiny drop of cobra venom
39:40to kill an animal,
39:42these youngsters can be as lethal as their parents.
40:08They already have that characteristic warning signal,
40:12the hood.
40:17Not all snakes lay their eggs.
40:20In some species, the female retains them within her body
40:24until they're ready to hatch,
40:26so she gives birth to live young.
40:31The marshes of northern Argentina,
40:34home to one of the largest of live-bearing snakes,
40:37the anaconda.
40:46This is a female, and she's heavily pregnant.
40:57It's morning, and she's chilly,
41:00so she moves out of the water and onto the swamp
41:03to warm herself in the sun.
41:19Slowly, the day begins to warm up.
41:34Now it's getting a little too hot for her,
41:38so she moves back to the water to cool off.
41:44In this way, she manages to keep her body
41:47close to 29 degrees centigrade,
41:50perfect for the babies developing within her.
41:55But she won't give birth here and now.
41:59There are caiman around.
42:07At last, she finds the quiet pool that she needs.
42:14And her contractions start.
42:17And her contractions start.
42:48The first of her babies has arrived.
42:55Up it goes to the surface to take its first breath of air.
43:06But there are more babies to come.
43:18Eventually, she produces 15.
43:21In fact, that's quite modest for an anaconda.
43:24They can produce up to 40.
43:28Right from the beginning of their lives,
43:30they're totally independent
43:32and get no care or protection from their mother.
43:39The anacondas are the first of their kind.
43:43They're going to be quite a big ones.
43:45They're going to be quite strong,
43:47and they're going to need a lot of protection from their mother.
43:52The anaconda spends so much of its time in water
43:55and is such a powerful swimmer
43:57that it can be properly considered aquatic.
44:05Snakes have become adapted to almost every environment,
44:09including even the sea, as this one has.
44:13I'm not going to handle it, but I will help it a little with this stick.
44:18As you can see, it has a very flattened paddle at the end of its tail.
44:25But on land, it's pretty helpless.
44:28However, if I assist it in getting into the sea...
44:40And now it's in its element.
44:46Sea snakes have had to modify many of the features that enabled their far distant ancestors
44:51to colonise the land.
44:53They still have a lung with which to breathe air, like other snakes, but they can also
44:58absorb oxygen from the seawater through their skin.
45:10Salt inevitably gets into a sea snake's body, but the snake manages to get rid of that by
45:16excreting it from a gland under its tongue.
45:19It also needs to drink fresh water, so in calm seas, it waits at the surface for rain.
45:28Sea snakes really are truly marine creatures.
45:32They can live out here in the open ocean, and the only clue you have to their link with
45:38the land is that they have to come up every quarter of an hour or so for a gulp of air.
45:55Most sea snakes, like this barbellid species, hunt fish.
46:00They have one of the most lethal venoms known, which kills almost instantaneously, and that
46:06is a very important quality if you hunt fast-swimming, ocean-going prey.
46:13But paradoxically, the most highly specialised sea snake of all has abandoned venom altogether.
46:21It has a beak like a turtle and a wholly different way of feeding.
46:41Reef fish don't like to have it around.
46:44They mob it.
46:56It doesn't even retaliate.
46:58It's not interested in them.
47:07It's after their eggs.
47:09These, the fish, have stuck to the stony branches of the coral.
47:19The snake's hardened, turtle-like top lip enables it to scrape them off.
47:33It's such a slow-moving browser that algae and other small organisms grow on its skin
47:39as they do on the bottom of a boat.
47:46The loss of limbs could seem to be a handicap, and it certainly makes the snakes seem alien
47:53creatures to us.
47:55But it is that very loss that has enabled the snakes to colonise every environment,
48:02from below the ground to above the ground, from bushes to trees to the air and even to
48:07the sea.
48:08And it is that absence of limbs, too, which has enabled them to do it with such elegance
48:15and grace.
48:27Killing venomous snakes presented a lot of special problems to the Life in Cold Blood
48:31team.
48:33But the toughest was trying to film a rattlesnake hunting in the wild.
48:38A rattlesnake making a kill has rarely even been seen and never before filmed, and for
48:44several reasons.
48:45For one thing, rattlesnakes are so well camouflaged they're very difficult to find.
48:51We enlisted the help of snake expert Harry Green and his team.
48:55They'd been studying a group of timber rattlesnakes using radio telemetry, which enables them
49:00to find their rattlesnakes at any time of day or night.
49:04Most of us would never find them, and they're superbly camouflaged.
49:09Exactly.
49:10But that's been one of the wonderful things about radio telemetry is we can have an animal
49:14that we can dial up.
49:15To have any chance of success, the crew had to be able to find the rattlesnakes on their
49:20own.
49:21So producer James Brickle had to take a course in telemetry techniques himself.
49:25Yeah, point it a little bit more on this one.
49:29Each snake has been implanted with a tiny transmitter.
49:32If you dial its frequency, you can pick up a beeping sound, and that gets louder the
49:36nearer you get to the snake.
49:44And so it's just like if you were trying to find your favourite rock and roll station
49:48or something, but now we're going to find our favourite rattlesnake.
49:51So you just punch in its number, and it's on the air.
49:54It sounds simple in theory, but there's a snag.
49:58It's here somewhere.
50:01Just be really careful, guys.
50:06In a forest, the signal can bounce off trees and give you a false reading so that it can
50:10seem that the snake is everywhere, and you don't want to think a reading is false and
50:15then tread on your snake by mistake.
50:17You're fine.
50:18He's up there somewhere.
50:19Let's find him.
50:20James, it's starting to get dark.
50:21He's in there.
50:22I reckon he's come to.
50:23James, be careful where you go.
50:24And it isn't just the one snake you're tracking.
50:29There are dozens of others in the area that aren't tagged.
50:33Follow my hand.
50:36There he is.
50:37He's about 20 feet.
50:38That's it.
50:39Very good spot.
50:40Six metres.
50:41And so, at last, the crew meet a very special snake called Hank.
50:53Hank is in a perfect position for his ambush.
50:56To film the action without disturbing him or his prey, cameraman Mark McEwan has fitted
51:00his camera with motion detectors from a burglar alarm.
51:04They will turn on the camera without anyone having to be there.
51:10So, for the first time, they set up their gear in front of a live snake.
51:16They could now leave Hank and track another of Harry's snakes.
51:21So that means you know individual snakes over a long period of time.
51:25Do they differ very much?
51:27Absolutely.
51:28Absolutely.
51:29Now, there are species differences.
51:30So certain rattlesnake species are more sort of nasty-tempered than others.
51:34But even within a population, you'll have one that just never gets riled up and one
51:39that you know you just can't get too close to without it getting upset.
51:43With one camera set up on Hank, James decides to track another snake.
51:48And to do so in the dark, which is when most rattlesnakes hunt.
51:52But in the pitch blackness, there was a distinct possibility that James would accidentally
51:56get so close to the snake he was looking for, he would step within striking distance.
52:02Quite unnerving, if you haven't done it before.
52:09It's actually pretty dangerous walking around in the middle of the night trying to find
52:14the rattlesnake in these conditions.
52:25I think the snake's about probably five, ten metres away.
52:29It would be easier to find a needle in a haystack than to find a reptile that looks like a load
52:36of dead leaves in a huge pile of dead leaves.
52:39Are you sounding for us?
52:42Negative, Mark.
52:43We've got to a huge pile of logs and wood.
52:47The team decide to abandon tracking the second snake and instead check on the camera they'd
52:52left on Hank in the afternoon.
52:55I think it's too dangerous, actually, to go poking around in there and anywhere you
52:58wouldn't be able to get the lights and the camera in, so we're going to wrap on it and come back.
53:03We've seen things on your videos we've never seen before, which is kind of surprising.
53:07I mean, we've watched snakes a lot, we, I mean, all the rattlesnake biologists, and
53:13we've seen things on your videos we haven't seen before, so I think it's actually kind
53:17of exciting to think about how this kind of collaboration might really be a feedback between
53:22the media and the public and science and so forth.
53:25And something very surprising had happened.
53:28At our very first attempt, and in broad daylight, a chipmunk had tripped the motion detectors
53:33and Hank makes a kill right in front of the cameras.
53:44We've got a strike already, we've got it.
53:48I thought you were winding up.
53:49James, there's something's happened here.
53:51I thought, oh, that's just a classic wind-up.
53:53First night to get that.
53:56We hadn't got the eating shot, but it's a start.
53:59And then the camera is set off again by a second chipmunk behaving very strangely.
54:04We showed the recording to Harry, and he was fascinated.
54:09Now what was that chipmunk doing?
54:10Was it perceiving something that the other chipmunk left as some kind of alarm odour
54:14or something?
54:15Was it perceiving the odour of the rattlesnake, or was it something I can't even imagine yet?
54:20But something was going on there that I didn't know to expect anyway, and it's in your film.
54:26Hank could clearly be the star of the show, so the crew decide to concentrate all their
54:30efforts on him and to track him for two weeks around the clock.
54:35They quickly learn that despite his ability to hurt one of them very seriously, he seems
54:39pretty unconcerned.
54:40In fact, he never even rattles a warning at them.
54:45The more they get to know him, the more they think they've got a good chance of filming
54:50another hunt.
54:51But then there is a serious problem.
54:53It's just been raining here non-stop for the past three days, and they say that Tuesday
54:57afternoon's hard rainstorm was the straw that broke the camel's back.
55:01Just as things are looking so promising, New York State has its worst floods for a decade,
55:06and all filming comes to a standstill.
55:09As you can see, the weather's awful.
55:12It won't affect the rattlesnake at all.
55:15He's perfectly happy.
55:16He'll be sat down in here somewhere just waiting, but it does affect the mammals.
55:20The chipmunks and the mice, they'll just be hunkered down somewhere not doing anything
55:24very much, and it affects us, but he'll be fine.
55:27It's just we can't film anything, so it's just a matter of waiting now.
55:33After tracking him in the rain for ten days, there's a break in the weather, and Hank starts
55:38hunting again.
55:40He chooses a position for an ambush in a very accessible spot.
55:44The team has another chance to use their remote cameras, this time operating in night vision.
55:50James, just be careful where you come in.
55:52Don't go that way.
55:53I think that's the direction he's headed in.
55:55You've got something, have you?
55:58Mate, we've got him hitting a mouse in the middle of frame and swallowing it.
56:04This time, they get more than the strike.
56:07This time, Hank decides to eat his dinner very obligingly right in front of the camera.
56:14Mate, that is the most incredible piece of behaviour you have ever seen.
56:18So, after two weeks and a lot of effort, they succeed in capturing a crucial and intimate
56:24moment in the life of this very special snake.
56:28People don't automatically love snakes.
56:30Most of them don't.
56:31And yet, if you can show them things about the lives of these animals that impress them
56:35with the fact these are animals with complex daily activities, these aren't things that
56:40are waiting around for an opportunity to kill people.
56:43If you tell people things like that, then they get drawn in.
56:47And hopefully, when we show them your films, they'll be drawn in.
56:50Well, you've drawn me in.
56:51Thank you very much.
56:52Pleasure.
56:54And when I get to see the footage, it's fair to say that I'm just as knocked sideways as
57:00the crew had been.
57:03There's the mouse.
57:06Oh, my goodness.
57:10Yes.
57:13That's a dead mouse, all right.
57:43Oh, my goodness.