The Trials of Life (1990) s01e09 Episode Script

Eagles lead lonely lives.
This one, flying over the gaunt mountains of northern Scotland, may spend days without seeing another of its own kind.
In spring, when a pair are raising one or, at the most, two chicks, young rabbits and birds are not difficult to find.
But now, late in the year, food is scarce, and there's barely enough on this bleak hillside to support a pair.
The chicks had to leave to find hillsides of their own.
So an eagle doesn't have to deal with the problems that face and can even dominate the lives of more sociable animals.
Unlike the lonely eagle, many animals live in groups.
But that inevitably causes problems.
How do you get on with your friends and, more particularly, your rivals, without continual squabbles? There's another big bird in these Scottish skies, bigger even than the golden eagle.
It comes here in the autumn and then it forms large flocks.
Hooper swans, coming in to land after a 1,000-mile journey from Iceland.
There the winter will be dark and bitterly cold, and the birds have flown down to spend the winter here in the milder conditions of Scotland.
Suitable stretches of water, secluded, with plenty of vegetation around to eat, are few, and this loch will soon be crowded.
Some of the arrivals are young birds travelling by themselves who have yet to find a mate.
The next few months will be their opportunity to form partnerships that will last a lifetime.
Most are families, pairs with their six-month-old cygnets hatched in Iceland.
They will stay together until the next spring.
They proclaim their arrival with a clear challenge to those already here.
They, too, intend to claim a place on the lake.
The male fights most of the necessary battles.
But his mate always backs him up, and the pair celebrates a successful skirmish with an ecstatic triumph ceremony.
There's a clear pattern to these encounters.
Pairs consistently win against singletons.
But the most dominant and successful of all are the families: mother, father and cygnets.
This is a particularly powerful one.
It has four young.
Singletons or even pairs who come too close are quickly seen off.
The cygnets enthusiastically join in the triumph ceremonies.
As long as they stay close to their parents, they will be treated with respect by other birds.
But if they stray, they will be shown no mercy.
The parents will fight others on behalf of their young.
The cygnets will stay with their parents until the spring when they'll be strong enough to fight their own battles.
In the meantime, other members of the flock come to recognise and respect the most powerful families and avoid confrontations where they can.
An apparent peace breaks out on the lake.
0ther swans give the family a wide berth.
The cygnets can now swim and feed without arguments.
But not all seniorities are settled in such a straightforward way, particularly within groups.
Chickens, when allowed to range freely in a farmyard, as these are, form themselves into small, tightly organised and remarkably stable groups.
Usually there's a cockerel and then a number of hens around him, and maybe one or two other cockerels on the sidelines.
0ne of the first studies ever made to find out how animals organise themselves in groups was done with a group of chickens like this.
If there are ten or less in the group, then every bird knows every other individually.
They move in a flock, scratching around for whatever they can get, apparently harmoniously.
But if I give them something they really like, then they reveal their true competitive nature.
Watch this.
This pale hen is particularly aggressive.
If she doesn't get to the food first, she'll peck those who do so until they give way to her.
This dark hen behaves in the same way and pecks everyone except the fierce pale hen, whom she avoids.
The result of these skirmishes is a peck order, a line of seniority in which each bird knows its place.
Should the lowliest hen at the bottom of the peck order find a coveted morsel first, she'll be chased and harried by all the others until she gives it up.
Clearly, all hens are not equal.
Dominant ones hand out the punishment, junior ones get henpecked.
But for most of the time, the relationships between them seem very friendly, and the flock leads a quiet and productive life.
It's the same with the cockerels.
They, too, avoid confrontation.
But every now and again, the senior cockerel has to remind the junior who is boss, just in case they get it into their heads that they want to steal his crown.
(C0CKEREL CR0WS) Such peck orders occur in the wild as well.
A group of caciques has established a colony high in a tree overlooking the Manu River in Peru.
The males established who was senior to whom early in the breeding season with a series of disputes that none has forgotten.
And those now determine who will get the pick of any food around and, more importantly, who will consort with a female when she's ready to mate.
The males compete for the right to display beside the clustered nests which were built and are occupied by individual females alone.
A subordinate male will always give way to a dominant one, just as chickens do in a farmyard.
It's a waste of energy to go on fighting the same battles when the outcome is the same.
The juniors snatch a mating if they can, but they may not succeed unless they move up in the rankings.
So why do caciques put up with the tensions of social living, rather than going it alone? The reason becomes clear when the colony is threatened.
A toucan, an avid eater of eggs and chicks.
A single cacique is unlikely to deter a toucan.
But all the members of the colony together, with their differences forgotten, can mount a highly effective defence.
This nest is empty.
But this one isn't.
A capuchin monkey, another most determined raider.
So even subordinates in this community have a better chance of producing surviving chicks than if they were to nest in isolation with no effective defence against raiders.
Lions, too, live in groups.
The lionesses form the core of the pride.
There may be a dozen or so, all of them closely related, mothers and daughters, sisters and aunts.
And it's the lionesses that do most of the hunting.
The two or three males, often brothers, fought as a team to drive off their predecessors and join the pride.
They will fight again if newcomers try to displace them.
But, most of the time, they have a peaceful life.
Living in groups, for the lions, brings several advantages.
For one thing, they can tackle large, powerful prey, such as buffalo.
These huge animals are three times the weight of a lion.
A single hunter would be very unlikely to tackle a healthy adult buffalo.
It simply wouldn't have the weight and strength to bring one down, and it might well get injured in the attempt.
But a pride, working together, has a chance.
A preliminary chase serves to get the measure of the quarry and to isolate an individual.
If one seems weaker than the rest, it will become the target.
The lions attack.
Despite the numbers pinning it down, the buffalo is still dangerous.
It's finally killed and the feasting begins.
What about seniority and rank in this group? There's little squabbling or fighting.
This kill has produced such a huge quantity of meat that there is more than enough for everyone.
So those who haven't got a place at the carcass amiably await their turn.
And that is just as well.
Such lethally armed hunters as these brothers and sisters could easily kill one another if a dispute became violent.
0nly in very hard times, when the pride is extremely hungry, will issues of priority be settled by fighting.
Lions, cooperating in prides, dominate the harsh and ruthless world of the African plains.
And the secret of that success is their cooperation.
When they work together, no other hunters can match them.
This cooperation extends into other parts of their lives as well.
The lionesses nurture their cubs as a team, taking turns to guard them and even, on occasion, suckling one another's infants.
Baboons live in even bigger groups, up to 150 or so.
This gives their young, who are defenceless for several years, the protection that comes from such numbers.
This troop in Kenya is waking up, having spent the night in the relative safety of its regular sleeping cliff.
Within a baboon troop, there's a fine balance between friendship and rivalry.
Like lions, their societies consist largely of closely related mothers and their young, and it's the adult females who largely control affairs.
The powerful males are all outsiders who only gained acceptance to the troop by making friends with one or more females.
Grooming is one way that they established such bonds.
Taking charge of a female's baby is another.
A ferocious male can treat an infant with great tenderness, which is the more remarkable when you consider he may not even be the father.
In baboon society, a social favour like this will be remembered by the mother and may improve the male's friendship with her and the likelihood of him fathering her next baby.
Males consolidate such relationships by encouraging females to join them for a careful grooming.
Encounters with rival males, however, must be handled carefully.
Lip smacking here is a gesture of appeasement.
Males pull other strange faces to act as clear come-on signals to passing females.
Meetings can serve several functions.
Seniorities and friendships are reaffirmed.
Babies begin to learn the complex language of smells, gestures and the importance of social relationships.
By caring for an infant, a male demonstrates his commitment to its mother.
And the babies, playing together, learn about making friends, as they must if they're to achieve a good social position later in life.
This babysitter misses the chance of making friends with a passing female because he's surrounded by jealous males.
If he had abandoned the baby, there might have been a squabble.
As long as he holds onto it, he will be left alone by his rivals.
But he has plenty of other opportunities.
Being a good father figure makes a male a great favourite with the females.
A young female passes the time of day, but she's not sexually receptive and he's busy.
In this complex society, social tensions can easily lead to conflict.
When a female is threatened and pursued by one male, she'll seek out another who is a regular ally and cling to him for support.
With a friend to help her, she's now safe, and, between them, some hard staring is enough to see off the aggressor.
For baboons, it's not how big you are but who you know that counts.
Arguments and squabbles between adult animals striving to maintain their position within their community are common enough.
But acts of assistance, in which one adult animal goes to the aid of another that's got itself into difficulties, these are much rarer.
But this sort of behaviour does seem to occur regularly in one species of animal, a colony of which is living in this hollow tree.
It's not an animal that might immediately come to mind as an example of a caring, unselfish creature, but that, apparently, is what it is.
0n this pile of droppings there are flecks of congealed blood, a characteristic sign of vampire bats.
And the colony itself is roosting above me.
These bats, all females, habitually roost as a group.
If they move elsewhere, they will stick together and hang in the same arrangement.
Most are related, although by no means all.
But every bat knows her regular companions well.
At night, they fly off to look for blood.
A donkey is a favourite target.
0ne lands on its shoulder and shaves a slice of skin without the donkey even noticing.
Another goes for its ear.
The bat's saliva contains an ingredient that prevents blood from clotting, and it flows freely from the wound they make.
A third bat tries a different point of attack.
(D0NKEY BRAYS) The bat on the ground still hasn't got a hold, but it's very hungry and it makes one last attempt.
But, no, she won't feed tonight.
0n returning to the roost, she hangs up beside an old friend.
She turns to her neighbour and licks her face repeatedly, begging for food.
If she goes hungry for more than a day or two, she will die.
But her friend regurgitates enough life-giving blood to keep her going until the following day.
0n another night, the situation may be reversed, and the bat that is receiving now will repay the gift if it's needed.
But cheats, bats that refuse to give to a neighbour who once helped them, will quickly be detected and, in consequence, may never be helped again.
So, for a vampire, it pays to help your neighbours, whether they're related or not.
Look after them and they will look after you.
Such mutual assistance is much more common among communities whose members are closely related.
Dwarf mongooses live in groups of a dozen or so in the tunnels of old overgrown termite hills, and most of them are the children of one breeding pair.
This is the old female.
While she is alive, no other female here will breed.
And this is her mate, the old male.
They feed almost entirely on insects which they scratch out of the ground and from rotten logs.
Every day the troop goes out to collect them.
It's a very time-consuming business.
A nice, big, crunchy beetle.
But digging like this has its perils.
With your head in a hole, you can't see if an enemy approaches, and with your rump in the air, you're dangerously exposed.
So while some hunt, other members of the colony are on guard duty.
These sentinels, usually males, but sometimes females, will get their turn to feed in due course.
The youngest babies are now coming out.
Their mother can't always be with them.
She has to spend much of her time feeding.
Junior members of the colony take turns to babysit.
0ne or two of these babysitters may replace the old breeders one day, but, for now, the best they can do is to serve the colony.
In doing so, they may promote their own genetic line, for the nurses are often the older sisters of the babies who carry as many of their genes as their own young would.
A martial eagle, a most dangerous enemy.
The sentinels keep a close eye on it to see if it's coming their way.
If it does, they will whistle an alarm signal.
(WHISTLING) The nurses groom their charges, play with them and catch insects for them.
Though they have never been pregnant, they may even come into milk and suckle them.
By the middle of the day, it's very hot and many of the group need a snooze.
And it's safe for them to drop off because some members of the family are still on guard.
So, by taking turns to help out and waiting for a chance to breed, the mongooses are able to survive and continue their family line where as pairs they would surely fail.
0ne mammal has taken this specialisation within the community to an extreme.
Just how extreme hasn't been appreciated until quite recently.
That's hardly surprising, because the most anyone normally sees of this amazing creature is no more than this.
It's a powerful and industrious digger that spends its entire life underground.
A naked mole rat.
These creatures live in highly inbred groups of 80 or more and feed on the gigantic underground tubers developed by some desert plants as a way of storing food and water.
But they have no way of knowing where these tubers are.
All they can do is dig away and hope they will eventually bump into one.
So the colony is perpetually tunnelling.
Digging in this hard ground requires teamwork.
Some workers, at the front end of the tunnel, gnaw into the baked earth.
A mole rat's lips close behind the long, curved front teeth, so that it doesn't get any of the earth into its mouth.
0ther team members, behind, kick the soil back along the tunnel until it reaches one of the surface exits.
It's so unvaryingly hot here that the mole rats need no fur.
Because they're hardly ever in the light, eyes are of little use, and they're virtually blind, so they run backwards and forwards like tube trains.
Not all the mole rats dig.
A few, a little bigger than the tunnellers, spend most of their time lazing about in a large central chamber.
These are soldiers.
Some are male, some female.
And they're saving their energies for an emergency.
And here comes one.
A snake has found its way down one of those exit holes.
The workers flee in front of it, squeaking with alarm to rouse the soldiers.
With those formidable teeth, the soldiers are capable of stabbing the snake to death, and they block the tunnel.
(SQUEAKING) Reinforcements arrive.
The snake thinks better of it.
The mother of the colony, the queen, is the only breeding female.
She gives birth to a dozen or so young at a time and produces a new litter every 13 weeks.
And she may live for 12 or 13 years.
The father of the brood is one or other of the two oldest soldiers.
But he's not as long-lived as the queen.
A year or two of sexual activity seems to exhaust him and he dies.
His place will be taken by another senior soldier.
All these babies will become tunnellers.
Some will later graduate to being soldiers, but none of the females, while the queen lives, will become sexually mature.
Why? The colony has a communal latrine, used by all, including the queen.
The workers, when they visit it, deliberately anoint their naked skin with its contents.
This gives them the colony's odour, so they are recognised and accepted by all.
But in doing that, they may commit themselves to a life of sterility, for the queen's urine contains a substance that helps to suppress the development of ovaries in others.
The supply of the fertility suppressant will continue as long as the queen lives.
0nly when she dies will one of the female soldiers mature sexually and succeed to the throne.
The queen spends most of her life in the chamber surrounded by her soldiers.
She doesn't dig.
She doesn't fight.
She concentrates her physical strength on producing within her belly huge broods of babies.
So the ranks of the short-lived tunnellers are maintained to continue the digging that's essential to find food for themselves, their brothers and sisters and their queen.
These hard-working porters are also members of a society, but one which numbers not a few dozen but several million.
Nor are they just gathering straightforward food.
They're taking part in a much more complex agricultural system.
Leaf-cutting ants demolish plants morning, noon and night.
Heavy rain and direct sunshine are the only conditions that stop them.
Every one of these workers is a female.
They're all sisters, working together in one of the most organised and tightly knit communities of all.
They use their legs as callipers, guiding their jaws so that they cut a segment of a size that is the most economical to cut and most practical to carry.
But they can't eat these leaf segments.
Cellulose, the main constituent of leaves apart from water, is very indigestible.
They have to take all these pieces back to their underground nest for treatment.
The journey may be down a tree trunk for 50 feet or more.
And once on the ground, there may still be 100 yards to go.
0nce inside the entrance of the nest, the leaves are carried down long corridors deep below ground.
Here, in special chambers, they're taken over by a slightly smaller caste of worker who cut the leaves into smaller segments still.
These chambers are gardens where the colony cultivates a special fungus.
The leaf segments are the raw material on which the fungus will grow.
But, first, the segments must be processed.
It could be very damaging if bacteria or spores of an alien fungus got into the nest and started to germinate like a weed.
So the workers meticulously clean the surface of each piece by licking it.
The edge of every segment is then chewed.
This yields some food for the worker doing the job, for leaf sap is digestible.
And it also prepares the leaf for the next stage.
The garden chambers vary in size from an orange to a melon, but they're all filled with a honeycomb of grey, spongy material.
And now these smallest workers of all take over.
They're a mere two millimetres long, the size of a grain of sand.
0nly these tiny dwarfs can enter the minute spaces within the gardens.
They push the leaf fragments into the matrix and then plant tufts of fungus all over their pulped surface.
Within 24 hours, the green of the leaf has almost completely disappeared beneath a tissue of white threads.
A day or so later and the threads of fungus begin to develop tiny knobs at their ends.
This, at last, is the crop that the ants can eat.
Some of the workers consume it there and then.
Most is carried away to feed to developing grubs and the other workers who laboured so hard gathering the leaf segments in the first place.
0ne by one, these swollen ends of the threads are torn from the tangled mass.
Sap, sucked from the edges of the leaves during their processing, is fed by a gardener to another worker who has duties elsewhere in the colony.
Slowly, the swarms of workers complete the harvest.
Now the fungus is spent.
Its remains and the mulch of leaves on which it grew has to be cleared out of the garden.
The workers swarm all over the grey honeycomb, breaking it up.
Every particle is carried up the corridors and taken out of the nest.
Long processions of workers set off for the exits.
Here, out in the open, by the side of the nest, they have their refuse tip.
So one cycle of fungus cultivation is completed.
And the scale of their operations is enormous.
They can strip an entire tree of its leaves in a single night.
Their pathways extend for 100 yards in all directions.
The nest is 20 feet across and it goes down for as much as 18 feet.
Inside, there are a thousand or so chambers where the ants have their gardens and where they live.
And it's virtually impregnable.
Even the vibrations of my footsteps are enough to bring out the defenders.
These soldiers are 300 times heavier than the little dwarfs working in the gardens.
They bite any alien thing - shoes, socks, anything.
As long as they only bite my clothing, they're no problem.
If they got onto my flesh, they would have me hopping about, for they can slice a very painful slit in your skin.
They seldom let go.
0nce they've fastened their jaws, they stay fastened, even if the rest of their body gets torn off.
Soldiers are expendable.
Their task is to protect the one single individual in the colony who is indispensable.
The queen, mother of all the members of the colony.
She is as big as a newborn mouse.
0n her nuptial flight, she was impregnated by three or four males.
The sperm they gave her then lasts her for the rest of her long and productive life.
The workers continually groom and clean every part of her great body.
Some attend her rear, waiting to collect the eggs she produces in bursts.
She may lay a million a year.
Some are fertilised from her sperm store, others are not.
But they, too, will hatch.
0ne appears, a tiny white bead.
A worker waits for it to emerge completely, feeling it delicately with its jaws.
It picks it off and takes it away to the nursery chambers.
The grubs that develop from fertilised eggs mostly become members of the exclusively female workforce.
The way they are fed by the workers determines which of the six different castes they will be.
Unfertilised eggs develop into males, who fly out of the nest to mate with young winged queens and establish new colonies.
0nce these ants start on adult life, they will not be able to change roles, as mole rats or dwarf mongooses can.
Their destiny is fixed.
The first ants, back in the evolutionary past, almost certainly operated as single individuals, as many species of their wasp and bee relatives still do today.
0ver millions of years, they came to live in communities of increasing size and complexity.
Now that process has come full circle.
By producing individuals specialised to do particular jobs in their society, five million insects have become effectively one.
But what a superbly efficient one.
It's not the monkeys or the rodents or, indeed, the human beings who dominate the forest.
It's the tiny ant that, by multiplying itself, has turned itself into a super-organism, a complex, highly disciplined society.