Arriving The Trials of Life

The savage, rocky shores of Christmas Island, 200 miles south of Java in the Indian Ocean.

It's November, the moon is in its third quarter and the sun is just setting.

A few hours from now, on this very shore, a thousand million lives will be launched.

These crabs are all females and of a kind ONLY found here.

As darkness falls, more and more of them appear, clambering resolutely down to the sea.

Now, it's nearing midnight.

Their number can only be guessed, but on the island as a whole there are probably 120 million.

And nearly all the adult females have chosen this time for their annual spawning.

A crab like this is carrying about 100,000 eggs.

She has to shed them directly into the sea if they are to hatch.

But that's hazardous for her,

because, although her ancestors came from the sea, she's a land crab and can't swim.

A wave could sweep her away and drown her.

But her compulsion to launch the next generation is irresistible

and when she does reach the sea, her triumph is, apparently, ecstatic.

The crabs have picked the moment when the tide is at its highest,

so they have the shortest distance to travel across the beach.

The astronomical number of eggs turns the water into a black soup.

As dawn approaches and the tide recedes,

the eggs are swept out to sea.

Since life began, the sea has been full of eggs.

The planet's most ancient animals still live and breed there.

Some, such as sea-urchins, may be male or female.

Both sexes discharge their sex cells during the same short period,

so that they unite in the water and form fertile eggs.

The sea keeps them at the stable temperature necessary to develop

and transports them hundreds of miles to new environments.

This perpetually-renewed soup provides a vast banquet for other floating creatures.

Small, complex globes of jelly drive themselves through the water with lines of beating hairs

and filter out the majority of the eggs.

Many fish also scatter their eggs in the water and abandon them in a similar way.

The most stupendous egg-producer of all lies beneath,

nearly buried in the reef.

The giant clam discharges sperm.

Then, half an hour later, because it's both male and female, eggs.

In each annual spasm it discharges a thousand million.

In the north-eastern Pacific, vast shoals of herring are moving towards the coast of Alaska.

These must be the densest concentrations of animal bodies in the world.

They move in huge assemblies, millions strong, sieving floating food from the ocean waters.

Now, even more tightly packed together, they start to spawn.

Their eggs are sticky and they cover the leaves of the sea plants.

As the waves stir the waters, some of the vast deposit floats up to the surface.

These milky slicks, miles long, stretching around the coast,

may look like mud, washed into the sea by a great river,

but they are made up of nothing but eggs and milt,

the annual legacy of the departed herring shoals.

Many of the eggs are washed ashore,

and the receding tide leaves them stranded on the rocks like drifts of snow.

This provides a feast for birds.

Gulls gorge on them.

Thousand upon thousand of turnstones, sandpipers and other small waders also come.

For them, this could not be better timed. They're about to set off on their spring migration

and they need to stock up on fuel before starting their long flight.

It is effective to lay vast numbers of eggs when water can distribute them.

On land, such numbers would be less practical. Even so, some land animals produce them in hundreds.

These are young mantis.

Their mother surrounded her eggs with a liquid froth which hardened.

The young developed within and now are ready for independent life.

They are covered with a thin membrane

and each hangs suspended by a thread of silk, while slowly disentangling itself.

One egg-mass from a single female may release as many as 400 young.

Latecomers continue to emerge,

while the first-born clamber up over them and prepare themselves for adult life.

Frogs produce young that swim and breathe through gills tadpoles.

Most frogs lay their eggs in ponds and streams, but not all.

This Trinidad tree frog creates a watery nursery up in a tree,

where no predatory fish can worry them or their babies.

The female pulls 2 leaves together with her hind legs and extrudes her eggs into the space between.

The eggs are surrounded by a sticky jelly, which holds the leaves together.

As they emerge from her body, the male on her back discharges his sperm and fertilises them.

Over the next 8 days, the eggs slowly turn into tadpoles.

Once the first eggs hatch, the jelly begins to dissolve.

The leaves separate and the liquid within starts to trickle out.

And with it come the tadpoles.

This is no disaster. The tadpoles drop into a new existence.

Their parents always build the nurseries overhanging water.

Here, in a bigger world, they can find something to eat and start to build their adult bodies.

This South American rain frog is independent of pools and rivers.

It lays its eggs on the ground, but each globe is full of liquid.

The tadpole develops inside this capsule and stays there, swimming in its own personal pond,

until tadpole becomes frog.

When the young finally emerge, they have no need to swim.

Like their parents, they have lungs and legs.

These elegant eggs are only the size of grains of sand.

The young of the owl-butterfly.

Their beautiful shells are not just protective they are edible.

The mother butterfly built them from her bodily reserves of protein

so that her young, when they emerge, immediately have their first meal to hand.

There's another way to provide food for your developing young

getting it from someone else's body.

That involves the grisly process of body-snatching.

That's what's going on in this dried-up mud flat in the western United States.

This strange insect is a murderous and very hard-working wasp.

She is digging a tunnel to serve as her nursery.

The sun-baked ground she selects is rock-hard and digging a hole in it is not easy.

A lot of work is invested in one of these holes

and if one seems vacant, another wasp will try to claim it.

Once finished, the female performs an elaborate dance around it,

familiarising herself with its surroundings, so she knows exactly where it is.

And then she conceals it, so that none but she is likely to find it.

Her nursery must now be provisioned and for that she needs fresh meat

a caterpillar. First, she paralyses it with her sting.

Thanks to her dance, she knows exactly where her hidden hole lies.

Each burrow will have several caterpillars in it

and each addition requires the same stopping and unstopping of the tunnel entrance.

The urge to collect caterpillars is so strong that they will pick them up wherever they find them.

She has already laid a long, yellow egg on the first caterpillar.

When the tunnel is full, she seals it with special care.

She uses a grain of gravel like a pneumatic ram, vibrating it with her wing muscles.

It's one of the few instances of an insect using a tool.

In a few days, when the egg hatches, the grub will find fresh meat awaiting it.

These cabbage white caterpillars are also doomed.

Another species of wasp injects them, not with paralysing poison, but with eggs.

Day after day, the caterpillars grow and mature, apparently unaffected.

But inside them, the wasp eggs are developing.

Having fed richly on the entrails of their caterpillar host,

the wasp grubs are ready to pupate when they emerge. They start to spin their silken cocoons.

Ten days later, they have become adult wasps and are themselves searching for caterpillars.

Just where eggs are placed can be very important.

These mosquitoes in Trinidad deposit theirs on the surface of water, where they float like rafts.

The females signal with their legs,

perhaps warning other flying females that this place is already taken.

They lay in tiny pools of standing water and particularly favour nut-shells.

Heavy raindrops might sink the tiny rafts, so if there is a shower, the adults row the eggs to shelter.

When the young hatch, they drop from the bottom of the raft and swim down to start collecting food.

These fish also care for their eggs with great solicitude.

They are Midas cichlids from Nicaragua.

Once a pair has selected their territory, the male digs a small pit in the ground.

The golden-coloured female has meticulously cleaned a rock with her mouth.

Now she is moving slowly over it, laying lines of sticky eggs.

As she completes each pass, the male follows behind and discharges his sperm.

Within an hour, there may be 2,000 fertilised eggs on the rock.

Three days later, they begin to hatch.

The female gently picks off the wriggling young.

In they go, into the cradle the male dug for them even before they were spawned.

A sticky pad on their heads lets them stick to the gravel.

With no mouth, they are nourished from a speck of yolk within them that is bigger than they are.

As they wriggle, they create a current that brings them oxygen.

Their eyes are developed and much of the yolk has been used to build their bodies.

They begin to swim.

And all the time, their parents remain above them,

to defend them against anything that might make a meal of them.

Without their yolk, they must sustain themselves a different way.

After 5 days free-swimming, they graze over their parents,

who are producing a nutritious slime from their skins,

so their cloud of babies can find food without straying too far away.

Many parents put their own personal safety at risk in order to protect their eggs.

In Brazil, a sawfly crouches over her eggs for three long weeks,

threatening any intruder with an aggressive buzz,

flicking her wings, with which she can strike, and displaying her formidable jaws.

Even an assassin bug knows when it has met its match.

As a result of her dedication, 90% of her eggs survive to hatch.

Even then, she won't desert.

She stays with her caterpillars to protect them, but a single guard can't be everywhere at once.

So her young, instead of scattering to feed, remain together.

Bigger parents have similar problems.

Snow geese, in the Russian Arctic, have to be just as vigilant if they are to rear their babies.

Eggs, packed with yolk, are splendid food and tempt a lot of thieves.

For Arctic foxes, this is a time of plenty.

Hundreds of eggs are lying around on the cold tundra, but they are all defended.

Got one!

But why doesn't it eat it?

This glut of eggs won't last long.

It's better to hide the swag for later and go back for more.

In the cold, near-freezing earth, an egg will remain fresh and edible for a long time.

Those in the nest are beginning the universal process that is one of life's great mysteries.

The greater part of a bird's egg, the yolk, is food for the young.

On its surface, beneath the cushion of clear albumen, lies just one fertile cell.

In the sustained warmth, it grows, divides and grows again.

Within two days, a beating heart appears.

Blood vessels spread around the yolk, transporting nourishment to the growing embryo.

Twelve days later, the little creature has legs.

And beneath the tracery of blood vessels, the tiny head is virtually complete.

Fifteen days, and feathers are beginning to sprout.

Twenty-one days after incubation started, the moment for hatching has arrived.

Once dried, the downy feathers help the tiny body retain warmth.

The chick is ready to start a new stage in its life.

There are few more formidable mothers than this one.

The salt-water crocodile of northern Australia builds her nest on a leaf-strewn river bank.

She digs a deep hole in the peaty soil.

In it, she lays several dozen eggs.

These eggs have one strange characteristic

although they have left her body, the sex of the babies within them is not yet fixed.

It will depend on how she looks after them.

She covers them with dead leaves, which, as they decay,

produce the heat the eggs need in order to develop.

And it is this that determines the sex of the babies.

At 30 degrees Centigrade, they will all be female. 2 degrees higher and they will be all male.

In between, they will be exactly half and half.

2 degrees higher still and a third will be male, a third female and a third will die.

Their emergence is not too arduous, for reptilian shells are leathery and easily broken.

The babies are so well-formed that even before they leave the shell, they can bite.

The technique of warming eggs with rotting leaves

has been brought to a fine art by Australia's mallee fowl.

A pair build themselves a huge mound of sand. In its heart lies a layer of leaves.

Every few days, in the breeding season, the female comes to lay

and the male kicks away sand to expose that layer.

Her egg, compared to her body, is gigantic. As soon as she has produced it, the male covers it.

The temperature must be carefully monitored. The male measures it with his beak.

Even when visitors approach, he stays bravely beside the mound to keep an eye on things.

If the mound is too cold, he piles sand on top.

If it's too hot, he kicks it away.

So obsessed is he with managing this mound,

that if someone interferes with it, his first instinct is to put that right.

If I flick sand off, he flicks it back.

The chick has to dig its own way up through the sand.

It can do so, because that huge egg contained enough yolk for the chick to stay inside for 49 days.

It will be able to fly within 24 hours.

In the trees above, there are chicks having a much harder, hungrier time.

The crested hawk laid 3 eggs, each a day apart, but they started incubation when the first arrived.

The first laid was the first to hatch and that chick was first fed.

It's already bigger than the two younger ones. The parents work hard bringing food.

But the eldest chick nearly always gets it. To him that hath, it shall be given.

The youngest stands little chance as long as either of the bigger ones are in the least hungry.

Once again, the youngest gets nothing.

And now it's dead.

This was a gamble by the adults.

Had it been a specially good year, they would have been ready to rear three chicks,

but this year, as in most years, the gamble didn't pay off.

The little body is not totally wasted.

Some of its flesh is fed to the survivors.

Animals care for their eggs and young in many different ways,

but Peripatus half-worm and half-centipede provides the ultimate parental protection.

The eggs develop inside the female and she keeps them there

until they are so advanced that they can survive without the protection of a shell.

So the young Peripatus gets a good start in life.

No waiting around defenceless, imprisoned in an egg.

It's able to feed and hide itself just as soon as it leaves mother.

All kinds of creatures have, independently, taken this strategy.

The tsetse fly the bigger the young, the fewer a female can produce

and the tsetse fly's baby is a whopper!

In the whole of her six-month life, she can only give birth to a dozen of these plump grubs.

It crawls away to turn into a pupa, from which the adult fly will quickly emerge.

These baby beetles are also long past the egg stage.

Their transformation into an adult will also be in a protective pupa,

but meanwhile they work as small eating machines,

gathering the food necessary to construct an adult body.

These gnat grubs avoid the pupal stage altogether.

They eat mushrooms, which disappear after a few days, so they must eat all they can, while they can.

To do that, they reproduce even before they become adult.

The female grub's unfertilised eggs develop inside her.

They feed from the mother's internal organs,

so that she is reduced by her young to a sausage skin,

through which 30 or so grubs force their way, coming out at both ends.

Each is a clone, genetically identical with its single parent,

and each able to repeat this trick in six days' time.

In six weeks, there could be 20,000 million all identical.

A mother sea-louse a kind of crustacean

also commits suicide to launch the next generation.

The mass of babies in her tiny shell consume so much of her energy

that, as the last leaves, she, exhausted, will die.

Not only females can give birth a few exceptional males also get pregnant.

The male pipe-fish develops a sticky underside on which the female deposits her eggs.

Flaps of skin grow round them and, when the time comes, the young wriggle out

to take their chances in a dangerous world.

Once they leave the protection of their father, they are easily picked off by sticklebacks.

But the babies who remain within their mother's body for the longest time

and who are cared for most comprehensively are mammals.

These female sea-lions mated a year ago.

The fertilised egg fixed itself to the womb wall, tapped the mother's blood supply and grew for months.

Now, that long development is over and the labour of entering the outside world has begun.

The membranes that held fluid, within which the infant swam in its mother's body,

still partially enclose it.

For all mammal babies, the shock of leaving the warm, protective haven of a mother's body

and entering the harsh, cold, danger-filled world outside, is inevitably traumatic.

Baby antelopes, whose parents have to travel continuously to find food,

must be as fully-developed as possible, for they must walk within hours, even though groggy.

Chinchillas are born in the high Andes.

Their world is a very cold one. Their mothers make no nest, so they are born fully-furred.

Were they not, they might freeze to death.

Hyena babies are not so advanced as they are born in a den, where their mother defends them.

She can get rid of their bulk at an early stage of development.

As soon as they emerge, like all young mammals, they find their mother's teat and suckle.

Perhaps the trickiest mammal birth of all is that of the bat,

for it, after all, has to arrive in this world while its mother hangs upside down from the ceiling.

Whatever happens, the baby mustn't fall.

While mother hangs from one leg, she stretches out the other,

so that the web connecting it to the tail forms a cradle in which to catch her new-born babe.

One infant is all that a mother bat of this species produces at once.

Her nature makes her keep it in her body until well-developed and even one is a heavy load.

Now she feeds it from her own body with that special food, milk, which is all the baby can digest.

The arrival of this single baby, tenderly nurtured by its mother,

could hardly be more different from that of so many creatures that live in the sea.

Birth for the Christmas Island crabs is a protracted affair.

For 28 days they float helplessly in the sea, increasing the size and complexity of their body

until they are just recognisable as miniature crabs. But very few live as long as that.

Fish eat them in huge quantities, currents sweep them into the ocean.

Most years, the entire spawning of billions is totally lost.

But, almost miraculously, about one year in five,

a few hundred thousand appear off the coast where they fell into the water as eggs.

Then the little, ant-size creatures valiantly struggle ashore.

A female crab may produce a million eggs.

If just one survives, she may be as successful as a bat, sea-lion or any other creature

that each year lavishes its care on a single baby.

In a multitude of different ways, new lives appear on earth,

and each starts its own odyssey.

They've survived their first trial, but will have to face many more

before, in turn, they too will have a chance to give birth.