The Trials of Life (1990) s01e04 Episode Script

(L0W-PITCHED CRIES) These great skuas bonxies here in Shetland, are among the most aggressive and ferocious of birds.
They're attacking me now because I'm approaching one of their nests where there are chicks, but they are pirates that will rob other birds of their food actually in the air and they are also extremely skilful hunters.
They're killers.
Their hungry chicks waiting in the nest for food make them specially determined and they seek their prey in the huge colony of seabirds nesting on the cliffs nearby.
Few creatures are not all their lives caught up in duels between hunters and hunted like these being fought out here, duels that have shaped their bodies and govern their daily behaviour.
The skua's tactic is to cruise so close to the cliff that the kittiwake parents are frightened off their nests, leaving the chicks unprotected.
The kittiwake chicks are almost full-grown and the skuas want them to feed to THEIR young.
(AGITATED SCREECHING) That bird actually caught an adult kittiwake in mid-air.
The skuas go first for the liver.
With crops stuffed full, they will be able to feed their chicks today.
Many different kinds of birds, having spent most of the year out at sea, come to these cliffs in the spring to nest.
Each has its own favoured territory.
In parts where there is turf and soil, puffins dig their nest holes.
Sitting beside them, they're relatively safe, for if danger threatens, they can duck inside their hole.
It's when they're in the air that they're really vulnerable.
Here the greater black-backed gull is on patrol.
It's a huge bird, substantially bigger than the lesser black-back.
It has a wingspan of over five feet and the manoeuvrability of a fighter aircraft.
The puffins, whose wings and feet also serve in swimming and diving, are much less agile in the air.
Flying in flocks reduces an individual's risk, but that's not always possible.
With the puffin almost swallowed, the gull has at last got a meal.
0r has it? The murdering robber has been robbed.
There are other animals which spend most of their life at sea, but come to land for a few weeks each year: seals and sea lions.
These are South American sea lions off the coast of Patagonia.
They can't give birth while they're swimming as whales and dolphins do.
Instead, they have to come ashore, and here, in dense groups, moving awkwardly between land and sea, they're a great temptation to any hunter that can reach them.
Their nursery beach seems secure.
The landward side has steep cliffs.
0n the other side the beach is protected by the sea.
But the sea itself can harbour enemies.
A killer whale, thirty feet long, eight tons in weight.
Every year the same group of a dozen of them assemble off the sea lion nursery to hunt.
For sea lions to venture into deep water here is very dangerous.
It's much safer to stay in the shallows if they can.
In one or two places, channels enable the whales to get really close to the beach.
Those are the danger spots.
To get off the beach, the killer has to thrash its body.
No other whale deliberately beaches itself like this or has perfected this method of getting back to the sea.
As long as the sea lions stay up the beach, you might think they'd be safe, but the hungry whales are very daring.
Now several of the whales are hunting in a group.
That sea lion was keeping just ahead of one of the whales, but was caught by another it probably hadn't seen.
This savage beating may be to separate hide from flesh.
But very often the successful hunter takes its victim out to sea without even killing it.
And there, it plays with its catch as if it were exalting in triumph.
To get all the food it needs, a killer whale must catch at least three sea lion pups a day.
And every day in the breeding season, this group of skilled, highly intelligent hunters do just that.
The Indian fishing cat hunts at night.
It's a little larger than a domestic cat, but it feeds on all kinds of prey from mice and rabbits to frogs and birds.
But its speciality is fish.
This pair have found an ideal opportunity, a drying river where the fish have been concentrated by the shrinking water into a pool.
Even so, it's not easy.
It requires stealth, lightning reflexes, endless patience and perfect coordination between eye and paw.
But these cats have brought such skills to perfection.
Slugs, you might think, are hardly a challenge to a hunter, but few things want to hunt them.
This, however, is one: the thirst snake.
Its hunting technique is simplicity itself.
The slug's slime, which makes it so unappetising to most predators, provides the trail which the thirst snake follows.
But swallowing such a slimy mouthful is not easy.
The snake manages it by dislocating its lower jaw and twisting it forward so that it snags the slug with its teeth.
Then a yawn puts the lower jaw back into its position.
Not all the hunted give in so easily.
Many have ways of deterring hunters that try to make a meal of them.
An American opossum may think this frog will make an easy mouthful.
It's quite wrong.
First, the frog inflates its lungs so it looks as big and formidable as possible.
Then it lets off a most surprising alarm.
(L0UD WAILING SCREECH) The whole performance is more than enough to put off the opossum.
In Australia, dingoes too can be put off by bluff.
A frilled lizard.
The frill is nothing but skin, but it disconcerts the dingo long enough to allow the lizard to make its escape.
This, however, is no bluff.
Poison is carried by all kinds of animals.
Hunters like this viper, use it to kill their prey.
And the hunted use it, too, as a deterrent.
The tomato frog, when it's threatened, exudes a milky poison from glands in its skin that would make any aggressor that swallowed it very ill indeed.
The problem about having poison as a defence is, if you're not careful, by the time you've convinced your attacker you're not worth eating, it has either mauled you or killed you.
So many animals that have poison advertise the fact long before it's necessary to use it.
Look, for example, at this little creature.
It's a spotted skunk.
Like the bigger striped skunk that also lives in the southern USA, its has glands beneath its tail which can squirt a jet of liquid with a smell so appalling that it can make you sick, so you should treat it with caution.
Now I'm going to press my luck a bit It doesn't want to waste its ammunition by squirting unnecessarily, so it gives fair warning.
It's as eloquent a display of gymnastics as you could imagine with which to back up its warning spots and stripes.
How better could you call attention to the spray gun beneath your tail? I'm not going to get any closer, because I'll get sprayed.
And I don't want to risk that! Salamanders also put on gymnastic displays to declare that they have chemical weapons.
In their case, it's in their skin.
Having jerked convulsively into an extraordinary contortion, they stay there, transfixed.
Its warning colours are on its belly only, so when danger threatens it throws itself on its back.
And this one has its poison in a line of sacs along its flanks, released by the drastic method of sticking its ribs through its skin, tearing them open.
Some poisonous bugs carry their ''keep off'' signs like banners on their legs.
And these add an additional trick.
They keep together in a swarm.
If a bird misguidedly takes one, it won't peck at the others while that nasty taste is still fresh in its mouth.
Black and yellow is a colour code for poison that is widely understood.
It's used not only by wasps, but by salamanders and snakes and caterpillars like this one.
Here the poison is in the yellow spines themselves.
These long hairs are also poisonous and the caterpillar walks around with the confidence of one who knows he's well-armed.
But some pretend to be well-armed when they're not.
This may look like an ant with a sting, but the ant body is a mask, an outgrowth from the back of a harmless and edible plant hopper.
This little creature looks like a spider and so does this.
In fact, both are fruit flies.
They have neither poison fangs nor stings and they could make a good meal for a spider.
And here is a real one.
It signals with its black and white palps and legs as it would to another spider.
And the fly responds by waving its black and white wings in a similar way.
It's mimicking the spider ''keep away'' sign.
And it works.
Instead of being conspicuous, you can protect yourself by doing the reverse, by concealing yourself.
And insects are the great masters at doing this.
A stick? No, an insect.
This is its head with the front legs stretched up beside it.
You really only have a chance of recognising it for what it is when it walks.
A band of moss, perhaps? No, another insect.
But lying so flat against the twig that it seems to be almost a part of it.
0nly its antenna, lifted above the twig, and a slight adjustment of its position, gives the game away.
Dead leaves lie all over a forest floor, so an insect mimicking them can wander undetected over a wide area.
It's a kind of bush cricket.
And this insect mimics living leaves.
Its vivid green wing covers are veined like real leaves.
Green flanges sprout from its legs.
Few of those hunted among leaves can have a better or more elaborate concealment.
Thorn bugs.
Like many bugs, they produce excretions that are collected by ants, and ants are one of the few creatures that seem to know which are thorns and which are bugs.
But two can play at that game.
What could look more innocent than this orchid, blooming in the half-light of the Malaysian rainforest? Its white flowers are bright and proclaim the sweetness of its nectar, attracting a lot of insects.
But even in such a lovely thing as this danger can lurk.
Sitting on it, exactly matching the colour and texture of the petals, is a mantis.
It's facing left, with its abdomen up on the right, and it's waiting motionless for the butterfly.
Beside the entrance of a termite hill, a pile of refuse tipped out from the nest by the termite workers, and on it, another hunter lurking in disguise.
It's an assassin bug.
It throws particles of refuse on to its spiny body not to conceal itself from its prey, termites, for they're blind, but to hide from birds and other creatures that might eat it.
Its cloak of droppings, however, may help to conceal it from the termites by giving it a protective smell.
Certainly, the industrious workers are unaware that there's an enemy there until it's too late.
Mimicry doesn't always deflect attention.
Sometimes it attracts it.
A death adder from Northern Australia.
And this could be its next meal - a skink searching for worms.
Perhaps this is what it's looking for.
In fact, it's the tip of the death adder's tail.
That was a near miss.
Lures can also be used in defence.
A blue tit hunting for food may overlook a hawk moth concealed by its camouflage.
But if it investigates, then the moth suddenly exposes its hind wings.
Eyespots don't alarm this blue tit, but they induce an attack, so the moth, instead of getting a lethal peck on its head, is struck on the hind wing and no damage is done.
Eyespots give this caterpillar an almost snake-like appearance and these tentacles which release a nasty smell heighten that resemblance.
But could this really be an imitation of a snake's forked tongue? Could the caterpillar be mistaken for a snake when it's only a couple of inches long? We don't know and can only guess.
And this is an even greater mystery.
It's a frog, and one that like most frogs is hunted by snakes.
The centres of these eyespots carry poison glands, but they could hardly have deterred the snake.
It can't see them from the front.
So just how does having a face on its bottom protect the frog? No one knows.
Big eyes undoubtedly attract attacks, and as this frog has real ones, it needs not to display them, but to conceal them.
It lives in bromeliad plants, a favourite hunting ground for small snakes.
By reversing into the heart of the plant, it conceals everything except the top of its head, which is protected by a special helmet, a bony shield.
So, many animals have developed a multitude of techniques for preventing other animals from making meals of them - high-speed sprints, jinking runs, distraction displays, near-perfect camouflage, even taking on disguises that make them look as though they are hunters themselves.
But there is one animal against which none of these techniques works, one hunter which is invariably successful.
This one.
Beneath this log is an immense ball of ants.
Its surface is a lacy veil, formed by individuals clinging to one another's legs.
There are about three quarters of a million of them.
They are army ants, and this is their bivouac.
In the morning, a raiding force of workers escorted by bigger soldiers leaves the bivouac.
They're almost blind, but they follow a scent trail laid down by scouts who are foraging ahead.
Few things are safe from them.
Not even a giant spider.
The sting of a scorpion is useless against such tiny aggressors.
They're too small to hit and too numerous.
A wasps' nest is a major prize.
The adult wasps, even though they have powerful stings, can't repel them, and they watch helplessly as their colony is pillaged.
The fat grubs are hauled from their cells, butchered and carried off.
The bigger victims are cut up for easier transport, and carried back to the queen and the workers waiting in the bivouac.
A caterpillar's camouflage didn't save it.
A ring-shaped segment from a millipede has got caught on a spike.
In some places, the soldiers form living bridges across which the porters run.
The bite of the jaws and the sting in the tail of these ants is so painful that getting close to them is almost impossible and so studying them is very difficult indeed.
So we really know very little of what goes on in the heart of a bivouac like this, but this optical probe may help us find out.
The bivouac has an internal structure, with walls made by the ants themselves clinging together.
You have to be careful.
Even though the probe has been greased, some soldiers manage to run up it.
Here is the nursery, full of young, developing grubs.
After two weeks in camp, the numerous eggs the queen has been laying are hatching.
The grubs need feeding and the entire army once more starts to march.
The workers carry the baby grubs.
Soldiers, huge jaws agape, guard the sides of the route.
The army marches across new hunting grounds, making temporary camps each night, until, after about two weeks, it bivouacs and repeats the whole cycle.
The most powerful hunters in the bird world are, of course, hawks and eagles.
The Harris hawk in the deserts of New Mexico has a particular and unusual skill.
It hunts in groups.
The team of half a dozen or so assembles in the morning and begins to search the countryside.
Their lookout posts are the great pillars of the saguaro cactus.
The cacti are certainly splendidly tall, but they don't appear to be the most comfortable of perches.
And the prickly pear is hardly any better.
A pack rat.
In this thorny tangle, it's difficult to get a clear sight for long enough to pounce.
Some of the hawks go down to try and chase the rat into the open.
Since the rat is so much quicker on the ground than they are, they will only manage to catch it if there are several of them.
They've lost the rat, but found bigger prey.
A cottontail rabbit.
The two on the ground chase it out.
Those perching can now get a clear sight.
0nce the kill is made, the entire team gathers and each bird tears off a share.
0ne bird by itself is unlikely to have made such a kill in such country as this.
Hunting together has paid off, but were the birds working in a team with a plan? Probably not.
Individual birds do not regularly play the same role.
Each simply reacted individually to the movements of the rabbit and each benefited from the fact that its companions were doing the same.
Here in the thick forests of the Ivory Coast in West Africa live animals that are our closest relatives.
Chimpanzees.
A peaceful scene of jungle harmony.
(WHISPERING) You don't normally think of them as hunters.
More as gentle vegetarians, munching fruit and picking leaves.
But if you follow them in their true home, these forests in West Africa, you discover that they are hunters.
What's more, they hunt in teams, and have a more complex strategy than any other hunting animal, except except, of courseman.
And one of the hunters, the experienced male, is sitting right there.
This is the time they hunt: the wet season.
Their regular prey are monkeys, but they're very selective.
A Diana monkey, a big species, and one they seldom tackle.
A spot-nosed monkey.
Red colobus.
They're better jumpers than chimps and can go onto thinner branches.
So in theory a chimp can't catch them.
The only way is to work as a team, and there are six experienced males in this group of about sixty who regularly do so.
This is one of them.
From his purposeful walk, it's clear the search for prey has started.
The other members of the team are not far away.
They've been following the monkeys for twenty minutes, looking for an opportunity.
The technique they'll almost certainly use is that one of them will be driving the colobus ahead of them.
Then there'll be others up on either side, the blockers, who make no attempt to catch them.
Then there are chasers, who try to grab the monkey.
Finally, there's one male who will go up ahead and ambush it, so bringing the whole trap closed.
The monkeys are now getting alarmed.
A driver's going up to prevent the group from settling and to drive them towards an area where they're more easily trapped.
That's one of the blockers that's quietly come ahead of the colobus.
He's halfway up the tree now.
He's deliberately making himself conspicuous.
Now it looks like they're all in position.
The drivers and blockers have gone up, and the one who'll make the ambush and close the ring has gone up, too.
The colobus will be very lucky if they escape now.
(DIN 0F SCREECHING) They've got one! The hunters are tearing it apart.
Everyone, the hunters in the trees and the spectators, are screaming with excitement.
Now the kill is brought down, so that the females and others can share it.
And there's the reward for that long chase, the divided body of a colobus monkey.
These bloodstained faces .
.
may well horrify us, but we might also see in them the face of our long-distant hunting ancestors.
And if we are appalled by that mob violence and bloodlust we might also see in that, too, perhaps, the origins of the teamwork that have, in the end, brought human beings many of their greatest triumphs.