All language subtitles for David Attenboroughs Natural Curiosities - 04x02 - Finding the Way Eng

The natural world is full of
extraordinary animals

with amazing life histories.

Yet certain stories are
more intriguing than others.

The mysteries
of a butterfly's life cycle.

Or the strange biology
of the Emperor Penguin.

Some of these creatures
were surrounded by

fantastic myths
and misunderstandings.

Others have only recently
revealed their secrets.

These are the creatures
that stand out from the crowd,

the curiosities that I find
particularly fascinating.

Pigeons are so common that we tend
to take them for granted.

But in fact,
they are superb navigators

and can find their way home
from hundreds of miles away.

And the dung beetle will roll
a dung ball in a straight line

even though it's head down
and walking backwards.

How on earth do these creatures
manage to find their way?

Pigeon fanciers know
that if they take homing pigeons

to somewhere
where they've never been before,

even if it's tens, even hundreds of
miles away, and then release them,

they will, after circling
in the sky, head for home.

These come from over there.

Let's see what happens.

Well, they certainly seem to be
heading in the right direction.

But how do pigeons
find their way back home

over totally unfamiliar territory?

It seems the more mysterious to us
because it's something we can't do

unless we have all kinds of
special equipment.

But science is now beginning to find
some of the answers.

The homing pigeon is a domesticated
descendant of the wild rock pigeon

which lives on cliffs and ledges
along our coasts.

When humans started to domesticate
them, they inevitably selected

those birds that were particularly
good at returning to their roosts.

Pigeons are thought to be
the very first birds

to be domesticated by mankind,
many thousands of years ago.

Since then, they've been bred
into many different varieties,

including homing pigeons.

And the varied appearance
of this flock around me

is evidence of
that domesticated past.

Since then, of course, they've come
to live alongside us in our cities

and giving many of us
a lot of pleasure.

Come on.

It was not only their homing ability
that made pigeons

so popular with breeders,
they are also superb flyers.

Their powerful wing muscles make up
nearly half their body weight

and enable them to fly
at speeds of 60mph.

They're among the greatest
long-distance athletes

in the bird world.

And pigeon fanciers have
delighted in breeding them

in order to race them
competitively.

Mankind has also used pigeons
for a very practical purpose...

..as messengers.

It was during the two World Wars
that pigeons played a crucial role

in carrying messages home
from the front line.

Nearly a quarter of a million birds
served in the wars

and helped save thousands of lives.

One such bird was Cher Ami,

a female donated by
a British pigeon fancier

for use by the United States Army
during World War I.

During one battle in France in 1918,
more than 500 soldiers

from the US infantry became trapped
behind enemy lines.

Worse, they were then fired upon
by their own troops

who didn't know they were there.

Within 24 hours, more than
half of them had been killed.

With no other options,
the commander, Major Whittlesey,

desperately tried
to send messages back by pigeon.

The first two birds were shot down
and only Cher Ami was left.

For several moments, she flew with
bullets zipping all around her,

and eventually she was brought down.

She'd been shot through the breast,
blinded in one eye

and her leg was left
hanging by a tendon.

Astonishingly, the injured bird
managed to take flight again

and arrived back at her loft
at the division headquarters

in just 25 minutes.

Cher Ami's message helped save
the lives of 194 soldiers.

Her name in French, of course,
means Dear Friend.

When the Second World War broke out,

Britain's pigeon fanciers once again

gave their pigeons
to the war effort

to provide what was called
the National Pigeon Service.

This elite squad of birds was
extremely valuable and successful.

98% of their messages got through.

The Germans, realising how important
the pigeons had become,

fought back with specially trained
pigeon snipers.

They also retaliated in another way,

by using the pigeon's natural
enemies - peregrine falcons.

Pigeons played such a vital role
in the war

that many were celebrated as heroes.

In 1943, this medal,
the Dickin Medal,

was founded to honour these animals.

It was awarded to individuals
that appeared,

if you'll allow
a little anthropomorphism,

to have displayed
particular bravery.

And it's sometimes referred to
as the Victoria Cross for animals.

Of the 54 medals presented
during World War II,

32 were given to pigeons.

We may have prized pigeons
for centuries

for their skills in finding
their way through the skies,

but for a long time
we had no idea how the birds did it.

Some suggested that
pigeons used the sun.

Others that they were guided
by the Earth's magnetic field.

But proving either was
surprisingly difficult.

A breakthrough came
from an American scientist

at Cornell University
in the 1960s.

William Keeton attached magnets
to the backs of some pigeons,

but not to others,

and found that when the sun was out,

both groups were able
to make their way home.

But when the sun was hidden
behind clouds,

the birds carrying magnets got lost.

Keeton deduced that this was because
the signals from their magnets

swamped the much weaker ones
coming from the Earth.

So he established that pigeons
can use either the sun

or the Earth's magnetism
to find their way around,

according to conditions.

But how do the birds detect
the Earth's magnetism?

This compass has
a magnetised needle,

which is sensitive to the Earth's
magnetic field.

It will always point north,

allowing you to check the direction
that you're travelling in.

But what about pigeons?

What could they be using
to detect magnetic fields?

Scientists were puzzled
because they couldn't find

any cells or organs in birds
that were sensitive to magnetism.

Then, in 2007, microscopic clusters
of iron-rich cells

were found in the beaks
of homing pigeons,

and it was thought that these might
help them to detect magnetic forces.

But only five years later,
new research shattered that idea.

It seems that the cells in fact
are a defence against infection

and have nothing whatsoever
to do with magnetism.

So the search for the pigeon's
magnetic compass still continues.

But we are now beginning
to understand the other aspects

of their navigational skills.

A compass is just one of the tools
we need for navigation.

But it's not much help

unless you know in which direction
your destination lies.

And to know that,
you need a map of some kind.

One way of creating
a map in your mind

is to memorise the prominent
features of a landscape.

Scientists at Oxford University
are now using GPS technology

to discover if pigeons do this.

This bird has a GPS transmitting
device strapped to its back

in a specially designed backpack

which causes it
very little discomfort.

And that will record the progress
of the bird, second by second,

once I let it go.

It comes from a loft over there
about six miles away in Oxford.

Let's see whether or not she heads
in that direction.

Off you go.

Birds, like this,
that are released in a new place

still ahead confidently
in the direction of their home loft.

How do they do it?

Data from GPS trackers

and cameras attached
to the backs of pigeons

have helped to answer that question.

At first, a bird released
in an unfamiliar place

will use the sun or the Earth's
magnetic field to get its bearings.

But if you plot its movements
on a map,

you can see that at first it doesn't
find the shortest route home.

Then something changes.

After repeated releases, the bird
is able to use its experience

to take a more direct way back.

So it appears that pigeons learn to
recognise features of the landscape

such as hedgerows and trees,
or even roads and buildings.

They then memorise these to create
a mental map of the area

and by following familiar landmarks,
they find their way back home.

It seems that
pigeons are creatures of habit.

They like to stick to the routes
they know well.

Here are some tracks of a pigeon
that lives in its home loft up here

and was taken repeatedly
to this point here.

Watch what happens.

It consistently makes a beeline
for the major A road

that conveniently runs past
its home loft.

And even when released some distance
from this road,

it will cut across to it
and then follow it all the way home,

as shown by the red lines.

Some birds even fly
around roundabouts

before choosing the exit
that will lead them back.

So it seems that pigeons use
methods of navigation

more like ours
than we might have imagined.

We now know that pigeons have

a whole range of navigational
techniques at their disposal

and can call on them as needed.

It's a remarkably sophisticated
system

that enables them to find their way
in nearly any situation.

We've learned a lot
about the pigeon's homing skills,

but some mysteries still remain.

In 1997, over 60,000 British birds
were released

during a pigeon race
in southern France.

Most of them didn't make it
and were never seen again.

In pigeon racing terms, the loss
of so many birds was unheard of.

A disaster.

One bird might get lost,
but tens of thousands?

To get back to their lofts
nearly 500 miles away,

the pigeons had to cross
the English Channel.

It was not an unusually long
or difficult journey

for a racing pigeon,
so why did the birds not make it?

Well, there was
a strange coincidence.

At the very same time the racing
pigeons were crossing the Channel,

a Concorde supersonic airliner
was flying along the Channel

on its morning flight
from Paris to New York.

The Concorde generates a shock wave
almost 100 miles wide.

The pigeons flying below
could not have escaped it.

Could it be that this enormous
wave of sound blotted out

all other acoustic information?

We know that pigeons can hear
low-frequency infra-sounds

such as those generated
by ocean waves.

And these might provide them with an
acoustic map of their surroundings.

The jury is still out as to
whether pigeons really do use

infra-sound to navigate

and whether that explains the case
of the disappearing pigeons.

But it's an intriguing possibility.

The familiar pigeon continues
to surprise us.

And even today, we're a long way off
from understanding

all its route-finding techniques.

The small dung beetle has a brain
no larger than a grain of rice.

But, like the pigeon, it is capable
of astonishing navigational feats.

Moving large loads by walking
head down and backwards

must surely be one of
the most bizarre ways

of collecting your food.

Dung beetles are well known

for rolling their balls of dung
in this way.

But why do they do so?

And how can they see
where they are going?

Ball rolling by dung beetles
is probably

one of the oldest recorded accounts
of animal behaviour,

dating back nearly 2,000 years.

These insects were held sacred
by the ancient Egyptians,

and in the fifth century,
an Egyptian scholar called Horapollo

described the dung beetle as
rolling its ball from east to west.

It seems that he was suggesting
that the beetles always

moved their dung
in a particular direction.

But how true is that?

In the following 2,000 years, little
was done to examine the question.

Dung beetles feed on what is,
to the animals that produce it,

a waste product - dung.

But in fact, there's more than
enough nourishment in one dropping

to sustain a great number
of beetles.

They locate a newly dropped pile
using their sense of smell.

Their strong and powerful legs
enable them

to break up the dropping

and their mouthparts
are specially shaped

to extract the nutrients
and moisture that they need.

They are, in fact, one of
our planet's great recyclers.

Dung beetles are found
all over the world.

There are over 6,000 species and
they come in all shapes and colours.

But they have one thing in common -

they all feed on dung.

Some of them,
like this scarab beetle...

..have rows of projections
on the head,

which were likened
by the ancient Egyptians

to the rays of the rising sun.

The broad front legs
also carry spines.

These are adaptations for digging
and shaping dung balls,

while the back legs are flattened

and have tiny hairs
for controlling the ball.

But most dung beetles
don't roll balls.

They live either in the dung itself

or tunnel directly into the soil
beneath the dropping.

Only 10% transport dung
above ground.

And they do so because
competition near a pile of dung

can be very fierce.

The first ones at the scene
are usually the rollers.

They take a little lump, mould it
into a ball and then start rolling.

But that's easier said than done.

Rivals are on the lookout
for an easy meal

and will only too quickly
steal a ball if they can.

With competition so intense,
some species roll their ball away

as quickly as possible
and then bury it.

They can then eat it later

without the risk of another
stealing their meal.

Dung beetles appear to roll their
balls of dung with great purpose.

But it's only recently been
discovered just how determined

they can be to do so
in one particular direction.

Watch what happens
if I put this dung beetle

on this board here.

And then put an obstacle in its way.

And what does it do?

It's going to go around.

Excellent.

And it resumes
its previous direction.

It's clear that the beetle knows
exactly

in which direction
it wants to travel

and will continue to do so even
when it's deflected by obstacles.

Now, let's make things
even more difficult

using this turntable.

Let's see which direction

he wants to go.

He's going to come towards my hand.

Now I'll turn the world
through 90 degrees beneath his feet

and yet he maintains

the same direction.

Why should it want to do that?

It's quite extraordinary.

He corrects his course
instantaneously.

How does he know how to do this,

and why is he so determined
to travel in a set direction?

The answer is, in fact,
quite simple.

The fastest way to make a getaway

is to roll your ball
in a straight line.

And that is exactly
what the beetles try to do.

Using only its front legs,

a beetle can move a dung ball that
is up to 60 times its own weight.

But walking head down and backwards
has its own problems.

You can't see where you're going...

..or watch out for danger.

With competition around
the pile of dung so intense,

it's obviously a good thing to get
away from it as quickly as possible.

But how do the beetles decide
in which direction to go?

Well, it seems it's all to do with
a little dance that they perform

on top of their dung balls.

Let me see
if I can persuade this one to do it.

I'll try to get it
to walk up this ramp

until it falls off the end

and is separated from its ball.

Watch what it does then.

This little dance was once

regarded as being
a sign of happiness,

that the beetle was delighted
to have found a dung ball.

But actually,
it's much more than that.

It's a way of deciding
which direction it should go.

And what does it use as a cue
to make that decision?

Well, recent research is beginning
to produce the answer.

What appears to be a dance
is actually

a way of looking around
to get its bearings.

But what exactly is it looking for?

We can test what the beetles
are using for a cue

by fitting them with caps.

This cap allows the beetle
to see the ground beneath,

but not the sky above.

Compare that with this one
without a cap.

Making up its mind.

And away it goes.

This one is still baffled.

The beetle with the cap
clearly can't decide

in which direction to go.

Such experiments show

that dung beetles have to see
the sky in order to orientate.

Their eyes are split in two halves
by shovel-like extensions

on the sides of the head.

So, as they roll
their balls of dung,

the upward-facing half
can watch the sky above

and use the sun
as a celestial compass.

But, contrary to what that
ancient Egyptian scholar claimed,

they don't always travel
from east to west.

Each beetle seems to choose
a particular direction

away from the dung heap
and then keeps to that course.

But why should anyone suppose

that the dung beetle always
rolls its dung from east to west?

Well, the ancient Egyptians believed
that their sun god, Khepri,

was responsible for rolling the sun
across the sky every day

in just that direction.

The scarab,
the Egyptian dung beetle,

similarly rolls its dung ball
from dawn to dusk

and came to symbolise the sun god.

And so the god Khepri was often
depicted with a scarab for a head.

The Egyptians also saw the scarab

as a symbol of life
and resurrection.

The adult beetle would disappear
underground with the ball of dung,

and when the eggs hatched,
shiny, new scarab beetles

would seem to appear magically
out of nowhere.

So the scarab came to symbolise
creation, life

and even rebirth.

It's easy to see how the sun helps
dung beetles

to navigate during the day.

But some beetles are nocturnal.

How do they keep
on a straight course?

On a clear night,

the moon and millions of stars
illuminate the sky,

just as they appear to do
in this planetarium.

This is a nocturnal scarab beetle.

And scientists have recently
discovered that it can use

the light from the sky to navigate.

But there is a puzzle.

The scarab beetle has
very, very small eyes.

And whereas it can
certainly see the moon,

it can't distinguish
individual stars.

So how then does it navigate

on a moonless night?

The brightest light in the night sky

comes from the great band of stars
known as the Milky Way.

And in the southern hemisphere,
where these beetles live,

the Milky Way is particularly vivid.

Researchers have discovered that,
as long as the Milky Way is in view,

the beetle and its ball can
roll along and stay on course.

Without this bright band of light,

the beetle has no reference point
and is lost.

The revelation that the beetles used
starlight to navigate

astonished the scientific world.

How extraordinary that
a tiny insect could use

the edge of our galaxy
to find its way around.

Had the ancient Egyptians known
that, surely they would have

felt vindicated in giving the scarab
the status of a god.

So, the dung beetle and the pigeon
are both ordinary creatures

that have found
extraordinary solutions

to the problem that faces us all -

how to find the way.