All language subtitles for The Trials Of Life 12of12 Continue The Line

(DRUMMING)

(PE0PLE SINGING IN SAM0AN)

(HAND-CLAPPING)

This is Samoa, in the middle of the Pacific.

It's 0ctober, the moon has just
entered its third quarter,

and the villagers have come out onto the reef,
because this is an extraordinary moment.

0n this one day of the year,
just around dawn for about an hour,

the sea produces the most delicious food
that the people ever get from it.

The water becomes alive
with millions upon millions of worms -

palolo.

To be accurate, each of these wriggling threads
is only half a worm - the back half.

The head ends are still safe within burrows
in the stony walls of the coral reef.

But these tail ends
contain the all-important sex cells.

The yellow threads are male,
the green ones, female.

The writhing segments disintegrate
as they reach the light, releasing their contents.

Milky sperm oozes out

and meets the green eggs
spilling through the ruptured body walls.

Fertilisation is achieved

and on an astronomic scale.

So this simple animal, by a feat of timing
which we still don't understand,

manages to solve the problem that faces
all animals if they're to be a biological success -

how to pass on their genes to the next generation.

But though the problem is always the same,

the solutions are amazingly varied.

Barnacles, stuck to the rocks, groping for food,

face a particular difficulty
when it comes to mating - they can't move.

Their solution is a male organ
that, proportionately,

is the longest possessed by any animal.

And they have another aid to mating.

Each barnacle possesses
both male and female organs,

so every neighbour is a potential mate.

Eggs are only produced once a year.

As soon as a barnacle has them ready,
it advertises the fact by releasing a chemical,

and all its neighbours
reach across to try and fertilise it.

Unlike eggs, which require
a lot of energy to make,

sperm can be produced quickly
and in great quantity.

So, as a male, a barnacle can fertilise
many others. They all compete to do so.

The egg bearer, as a consequence,
is given far more sperm than necessary

and ejects most of it as a white blob.

So a barnacle manages to get the best
of both the male and the female world.

These fish, blue-headed wrasse
on the reefs of the Bahamas,

are also bisexual, but not simultaneously.

The big, blue-headed one is a male,
the smaller one, a female.

A number of females visit a spawning site
controlled by an individual male.

As each lays her eggs, he fertilises them.

So he passes on his genes to far more young
than an individual female does.

In the competition to continue the line,

it's better for a wrasse
to be a big male than a female.

And when a male dies,
the biggest female claims his throne.

Within two weeks, she develops a blue head,
produces sperm,

and becomes a parent of more babies
than if she had remained a ''she''.

But most animals don't have this option.
They're stuck with the sex they're born with.

A male octopus is always male,

and if he is to pass on his genes,
he is the one who has to take action.

0nce he's grabbed the female,
he strokes her to calm her.

He has eight arms with which to do so.

His third right arm
has a particularly sensitive tip.

While he caresses her with the other seven,
he uses it to feel for her genital opening.

He has found it.

Now, with muscular waves,
he pumps packets of sperm into her.

The male dumpling squid,
having mated in a similar way, separates.

Some of his sperm packets
still trail from his special arm.

But the majority
have successfully released their contents.

A female doesn't always have to accept
the first male to grab her.

A female tortoise in Madagascar proclaims
her readiness to mate by releasing a perfume.

But when a male turns up, she plays hard to get.

He, however, is armed.

He has a spike on his shell that is so big
that it gives the species its name,

the ploughshare tortoise.

He may not be able to force her to mate,

but he can use his spike to demonstrate
his strength in a very convincing way.

Her perfume has attracted another male.

Now the rivals must fight it out.

With his opponent overturned,
the victor can claim his prize.

The female, having righted herself, seems
to be sufficiently impressed by his strength

to accept him as the most powerful male around.

(GRUNTING)

And the vanquished can only lie by helplessly.

Female elephants have a similar way
of sorting out the men from the boys.

Producing a calf takes a female a long time,

22 months of pregnancy and then
a further four years of feeding it on milk.

So she wants to make sure
that her calf has the best father around.

She becomes sexually receptive
for just a few days every four years or so.

Mature bulls spend most of their time away
from the herd, wandering in special bull areas.

So it's usually a teenage hanger-on
who is the first to notice her availability.

But he's not yet very good at mating,

and he's not the strong and proven partner
that she wants, so she leaves him.

The male she seeks is a mature bull
like this 50-year-old.

Male elephants are only in full sexual condition
for three months of the year.

But this one is. A gland behind his eye
is discharging and his genitals are dripping.

He is in musth.

During this time, he devotes his energy
to seeking out receptive females.

He assesses their condition by smell.

If a female's smell is promising,
he tastes her urine to test it.

It's as important for her as it is for him
to make clear her reproductive state.

This female isn't quite ready,
but there is one nearby who is.

(RUMBLING)

The deep rumble is being made
by a female who's just mated.

She's declaring that she's still receptive,

and her partner defers to the big male
by walking away.

The big male starts to follow her.

She encourages him
with a special, coy, swinging walk.

Each time she is mated, she calls again,
just in case there's a bigger musth male around.

By the end of her receptive period
when her egg is released into her womb,

she will be partnered and guarded
by the biggest male in the neighbourhood,

and he will be the father of her calf.

Chinchilla females are not so welcoming.

If a male presses his suit
when she's not ready for him, there's trouble.

A quick squirt of urine in the face
makes her feelings clear.

He won't pester her again
until he has cleaned himself.

Things can be even more tricky for a male
if his mate is well armed, as spiders are.

The female tarantula has fearsome poison fangs.

The male is much smaller than she is
and approaches her with obvious trepidation.

His life at this moment depends on being able
to hold her poison fangs out of the way.

0nly now dare he reach forward with his palps.

At the end of these there's a suction bulb
which he's loaded with sperm.

He must thrust his palps into a pair of genital
pores on her underside, just beyond her head.

That's a very dangerous proceeding.

He's done it.

Male spiders are by no means always so skilful.

These few legs are all that remains
of a male Nephila spider who failed.

But another male is on the same web now,
preparing to chance his luck.

And his task is indeed formidable,

for his mate is gigantic, six inches across
and several hundred times his weight.

She's virtually blind and relies on vibrations
of her web to tell her what's going on.

If he sends the wrong vibes along the threads,
she could easily get the idea that he's a meal.

He's now within range of her strike.

He retreated just in time.

This, indeed, is a meal. A fly, a welcome
diversion as far as the male is concerned.

While she's occupied with trussing it up
in bonds of silk, he has his chance.

He clambers over her mountainous underside
and delivers his packet.

He's so small, it's hard to see him on her body,

and it seems doubtful if she notices him at all.

A male cockroach from Cuba encourages
his mate to nibble him - or bits of him.

He lifts his wings to offer her a potion
produced from special glands

which not only smells good but tastes good.

While she licks them, he must couple,
and do so before her nibble becomes a bite.

He has achieved a connection
and escaped injury.

Now he must hang on
until he has transferred his sperm.

The mountain dusky salamander has an extreme
way of persuading a female to mate with him.

It involves biting her neck, a habit that has
given him the nickname of vampire salamander.

But he doesn't do it to drink her blood.

Special glands on his chin
produce an aphrodisiac,

and he anoints her with it by rubbing her neck.

But he must do more than this
to really get it under her skin.

A quick scratch with his teeth
and he's vaccinated her.

Now she'll follow him wherever he goes.

But he has a particular problem.
Salamanders are amphibians.

Unlike all other four-legged land animals,

the male amphibian doesn't have an apparatus
with which to inject sperm into a female's body.

So he has to use another method.

He begins to walk away, and the female,
excited by her vaccination, follows him.

He deposits a blob of sperm on the ground.

As she continues to walk after him,

he leads her across it
so that her underside presses against it.

When it's level with her genital opening,
she draws it in.

Some females, no matter what the male does,
are physically inaccessible for most of their lives.

Crabs wear suits of armour,
which makes mating impossible.

But this big male has detected
a faint taste in the water

that tells him that the little female
is about to shed hers.

As soon as she slips out of her shell,
while her new one is still pliable,

she and he can become intimate.

He's going to hold onto her so that no other male
can claim her at that crucial moment.

Her moult has begun. Her shell has split along
the underside and he is helping her to disrobe.

The empty suit of armour makes it seem
as if he has two females in his embrace.

The fact that one is the ghost of her former self
is revealed only by its vacant eye sockets

and the way the current blows it about.

Now the female, with her new shell
still soft and leathery, crawls beneath him.

He fertilises her swiftly,
before her shell hardens.

She won't be able to mate again
until her next moult.

Soon he will abandon her,

but he's ensured that the eggs she will nurture
for the next few weeks will carry his genes.

A male butterfly has to be just as alert
as a crab if he is to secure a mate.

This forest in Costa Rica
is full of competitors for the females

who are appearing from pupae
hanging in the bushes.

This is a male Heliconius butterfly,

and he's settled on a pupa
which he knows contains a female.

He's waiting for that moment
when the female will emerge, a virgin,

and then in the first few seconds
of her adult life, he'll mate with her.

And so intent is he on achieving that

that he won't move
even if I touch him with my fingers.

But watch what happens if I take this,
which is an adult female which has newly mated.

What happens if I brush him lightly with her?

The reason he left is because this female,
when she was mated,

was given a particular smell
which even I can detect,

a smell that all other males find very repugnant.

If I let her fly away,
that male may return to complete his business.

And even before the newly emerged female's
wings have expanded, he mates with her,

dabbing her with his smell,
which will repel other males for weeks.

No rival will displace his sperm.

(H0WLING)

A female wolf who's just become
sexually receptive

joins her howling pack in the Canadian north.

All the males are interested in her,

but there's a ranking system in the pack
and the senior male has priority in mating.

0thers who try their luck
have to be reminded who's boss.

And he claims his rights.

But he does not now leave her.
Indeed, he couldn't even if he wanted to.

His genitals have swollen so greatly inside her
that the pair are locked together.

This is no unfortunate accident. It's an important
part of the male's breeding strategy.

Remaining tied for so long
gives his sperm time to reach her eggs

before a competitor can displace him.

It may be half an hour or so
before they're able to pull apart.

The aftermath of such a genital lock
may be slightly painful,

but the process has virtually
guaranteed him his paternity.

Animals that don't take such precautions
can't be nearly so certain.

A male bluegill sunfish
swimming in a lake in North America

seems big, strong and confident enough
to take on any rivals.

He's eight years old,
and he, too, is ready to breed.

He hollows out a shallow nest by fanning his tail.

Then he sets about persuading one of
the females in the shoals swimming nearby

to come down and join him.

He is offering both a nest
and his parental services.

0ne arrives. Although she's considerably
smaller than he is, she is full-grown.

He chivvies her into his nest to lay.

She catches his mood from his distended fins
and circling dance. Things are going well.

But lurking in the weeds
is a tiny two-year-old male.

He will never build a nest or woo a female,

but he's a serious rival nonetheless.

As soon as the female lays,
he darts in and delivers a jet of sperm.

Back he comes and adds another squirt
before he's finally chased off.

The owner of the nest continues his dance.

The more eggs that are laid in it, the better.

The little sneak retires to the weeds.

Now the big male seems to have been joined
by a second female.

Not so. The new one in the middle
is an older sneaking male

who dances so like a female
that the big male doesn't notice the difference.

The nest owner chases away other males,

leaving the female impersonator with
the real female, unhurriedly fertilising her eggs.

Eventually, the big male is left
in sole charge of the nursery.

He labours away, fanning the eggs
to keep oxygen-rich water flowing over them.

He's a devoted father, steadfastly
standing guard over the fry when they hatch.

With him hovering above them,
they're safe from most predators.

But the fact is that two thirds of them
are probably not his.

Baby lily-trotters, jacanas,
are also left in the charge of their father.

Unusually for a bird,
the female defends the territory

and mates with three or four males
who build the nests and look after the broods.

A strange female is trespassing
on this breeding territory.

There are eggs here,
so the male should be nearby.

He returns to protect them,
but he seems to be alone.

The intruder lurks in the weeds,
watching him with interest.

Finding a male alone probably means
that his mate has been killed,

and her territory and all her males
could be up for grabs.

He displays aggressively towards her,
trying to drive her away,

but female jacanas are bigger than the males
and she is not to be deterred.

He is of no use to her
while he broods another female's eggs.

She starts to smash them,
and he is unable to prevent her.

They were on the verge of hatching.

Having destroyed his brood,
she now offers herself to him.

And the bereaved male
mates with the murderer of his chicks.

Again and again, she displays
and induces him to mate with her.

So she succeeds in getting rid of all the chicks
that do not carry her genes

and replaces them with those that do.

0ne female with many mates is unusual.

In most polygamous relationships, it's the male
who has a harem of several females,

and that is the arrangement here.

A male sea louse is recruiting.

He puffs out silt from his burrow,

lacing it with a chemical taste
that a female sea louse finds irresistible.

She is bloated with the blood of a fish
which she parasitised,

but she will never feed again,
and now she's looking for a mate.

0ne by one, he assembles his harem.

Inside his tunnel,
he parks his females in a long line.

For three months he continues to collect them,
until eventually he may have two dozen or so.

As each moults, she, like the female crab,
becomes sexually available.

So he monitors their progress with great care.

When the critical time arrives,
he mates with each of them.

Polygamy gives a great advantage
to the individual who controls the harem.

The more wives a male has,
the more children will carry his genes.

It can develop wherever a female is able to raise
her young with little or no help from her mate.

So, not surprisingly, polygamy has appeared
in many different parts of the animal kingdom.

Each of these dark clusters hanging from
the many domed roof of a cave in Trinidad

is a harem of a dozen or more
greater spear-nosed bats.

The male, who controls the harem,
suspends himself in a prominent position,

keeping a sharp lookout for young males
who might try to take over.

If he's not up to the job, his reign will be brief.

A young intruder hangs around nearby.

The harem boss is not going to be caught
unawares, and threatens him.

Repulsed from one,
the young hopeful backs into another

and gets the same reception.

Controlling a harem by force
has inevitable consequences.

If it's always the strongest male in the community
who fathers the great majority of babies,

then over many generations
males will become bigger and bigger

until their size and ferocity
makes them very dangerous.

A full-grown male sea lion comes ashore
in Patagonia early in the season

to claim a patch of beach
and start assembling his harem.

The females arrive
within a few days of one another.

They're only a third his size, and he tries
to keep as many as he can close to him.

Young males come, too. They're not
big enough yet to win battles for females.

Within a day or so of arriving, the females give
birth to the pups who were conceived a year ago,

almost certainly on this very beach.

Six days after the birth of her pup,
a female becomes sexually receptive again,

and the beachmaster, who has taken her
into his harem, mates with her.

The best sites for a harem
are well above high-water mark,

but now the beach is very crowded indeed
and even the less good positions are occupied.

Around the edge of the central breeding area,

males without a harem prowl around
looking for a chance to mate.

There's an atmosphere
of suppressed violence in the colony.

A young male rushes into the breeding area.

As the harem-holders are forced to fight,

others see a chance of winning something
from the confusion.

An intruding male tries to abduct a female.

He will rape her if he can.

The violence spreads. A young male who has
not mated works off his frustration on a pup.

So the number of different ways
in which males and females

can come together and raise their young is huge.

I, because of the species to which I belong
and the society in which I have been reared,

tend to think that the monogamous pair,
one male, one female, husband and wife,

staying together long enough to share
responsibility of raising the young, is the norm.

But actually, in the animal kingdom at large,
it's very, very rare.

And one of the few creatures
that also does that is this beautiful bird...

..the royal albatross.

These two birds first mated over 20 years ago,
and they have been together ever since.

They met as five-year-olds, when they returned
to these cliffs where they had hatched.

While their elders nested, they joined with
groups of others of their own age to dance.

(C0NSTANT CALLING)

As the dance parties proceeded,

the male and the female began
to dance with one another habitually.

After a few weeks of these courtship games,
the young birds flew off back to sea.

During the year that followed, they cruised
the oceans separately, looking for fish,

but the following year they were both back.

By now they were regular companions
during their time ashore.

And then the male claimed a nest site.

At last, after four years of courtship,
their alliance was consolidated.

The permanence of their partnership
was essential,

for an albatross chick takes nearly a year
to grow big enough to fend for itself at sea.

Throughout that time, each parent must make
voyages lasting several weeks to collect food

and be so faithful that it flies back
hundreds of miles to feed its chick

and relieve its near-starving partner,
who has been its lonely guard.

If you watch animals objectively for any
length of time, you're driven to the conclusion

that their main aim in life is to pass on
their genes to the next generation.

Most do so directly, by breeding.

And the few examples that don't do so by design,

they do it indirectly, by helping a relative
with whom they share a great number of genes.

And inasmuch as the legacy that human beings
pass on to the next generation

is not only genetic but to a unique degree
cultural, we do the same.

So animals and ourselves, to continue the line,

will endure all kinds of hardship,
overcome all kinds of difficulties,

and eventually the next generation appears.

This albatross is over 30 years old.

She's already a grandmother,

and this year, once again, she's produced a chick.

She'll devote the next ten months
of her life looking after it.

She has faced the trials of life

and triumphed.

For her little two-day-old chick,
the trials are just beginning.