All language subtitles for Natural Curiosities S01E05 - Natural Powers CC HDTV x264 AC3 1080p

The natural world is
full of extraordinary animals with

amazing life histories.

Yet certain stories are more
intriguing than most.

The mysteries of a butterfly's
life cycle,

or the strange
biology of the emperor penguin.

Some of these creatures were
surrounded by myth

and misunderstandings for a very
long time.

And some have only recently
revealed their secrets.

These are the animals that stand
out from the crowd,

the curiosities I find most
fascinating of all.

Some of our most familiar animals
puzzled scientific

minds for a surprisingly long time.

The mysterious comings

and goings of barn swallows led to
some far-fetched ideas.

While the life cycle of the painted
lady butterfly took centuries

to unravel.

But the abilities of some plants

and animals are so remarkable that
they seem to be almost supernatural.

In this programme, I investigate
the shocking power of a fish that

advanced our understanding
of electricity,

and plants with senses
that are surprising modern science.

How do these extraordinary powers
help the organisms that

produced them?

The freshwater eel is
surrounded by legends.

The first Europeans to explore
the New World heard amazing

stories about it.

And when, in the 18th century,
specimens of this strange fish

reached Europe,
they created a sensation.

In 1776, Captain George Baker,

an American mariner and whaler,

made the long and difficult journey
from South America across a

raging Atlantic Ocean to bring five
live electric eels to London.

These are two of his actual eels.

Captain Baker and his five electric
eels, or gymnotas as they were
known,

set up shop in the Haymarket
and offered two shillings

and sixpence for a shock,
or five shillings for a spark.

Baker's eels had come all
the way from the lower

reaches of the Amazon
and Orinoco rivers,

where he had heard tales from the
locals about their astonishing
powers.

They called these fish
"trembladores".

Humboldt, the famous naturalist
and explorer, had described how he

had witnessed horses being killed by
the repeated shocks from these fish.

And he himself accidentally
stepped on one

and vividly described the effect.

"With each stroke, you feel
an internal vibration that lasts

"two or three seconds,
followed by a painful numbness.

"All day I felt strong pain in my
knees and in all my joints."

I encountered this remarkable
fish in its natural environment

when I filmed at the same rivers
that Humboldt explored.

There was talk of me swimming
with the eel,

but thankfully we had some technical
difficulties with the diving

equipment that
I was supposed to wear,

and so I stayed safely in a canoe
and was able to demonstrate

another subtler, but equally
remarkable, side to this fish.

The eels were constantly producing
electric discharges.

Somehow they were generating a
small, nonstop flowing current.

ELECTRIC DRONE

They were also able to sense
electricity and were

attracted to electrical pulses
emitted from my underwater detector,

suggesting that electricity plays
a key role in their lives.

But at the time of their discovery,

no-one knew the full functions of
their extraordinary abilities.

We now know that the shock was
caused by electricity,

and I can demonstrate it by touching
the animal with an electrode.

Watch.

There. You see?

The scope and the
lights are flashing up and down.

Extraordinary.

But this is only a small indication
of the real power of this fish.

If I were to try and pick it up,
I could get

a jolt of an astonishing 600 volts,
which is quite enough to kill me.

This 1960s educational film
illustrated the shock,

even though the equipment
used prevented

the volunteers from getting
its full power.

They were to join hands
and then connected to a live eel.

WOMAN SCREAMS

Firm believers in electric eels.
Thank you very much.

You can imagine how startling
Baker's electric eels

were 200 years ago.

In the 18th century,

electricity was becoming
one of the most fashionable areas

of scientific investigation, but it
was still very poorly understood.

Very few advances had been made
since its discovery 150 years

earlier by Elizabeth I's personal
physician, William Gilbert.

Gilbert repeated a trick that had
been known about since Greek times.

Rubbing a piece of amber with
cat fur, that allowed the amber

to attract a small object
like a feather. Let's give it a try.

Here is a bit of amber.

There.

It had always been assumed that
this amber effect was caused

by magnetism but Gilbert showed
that it was something different.

He named this new force
after the Greek word for amber,

electron,
and so electricity was born.

Londoners of the time developed a
fascination for this magical force.

Showmen staged bizarre spectacles
to demonstrate its properties.

In one, a young boy attached to
a friction generator

attracted small pieces of paper
to his hands.

In another, a gentleman kissed
a lady and was repulsed

by the charge carried through
her whalebone corset.

No-one knew what to do
with electricity

but a better understanding of
its nature was slowly emerging.

More and more ingenious ways
were developed

to create what we now call
static electricity.

And soon it became something more
than just a quirk of rubbing amber,

it became visible as a spark.

The ability to produce this
characteristic blue spark

along with its invigorating
smell became the signature

of this new force
and it prompted scientists to make

obvious comparisons
with other natural phenomena.

THUNDER

In the American colonies,
Benjamin Franklin bravely,

or perhaps foolishly, flew kites
into thunderstorms and proved that

Iightning and the electric spark
were one and the same.

But there's another common property
of lightning and static electricity.

That is the ability to shock.

It wasn't long before a comparison
was made between the shock from

the early generators and the shock
that could be delivered by a fish.

The electric eel wasn't
the only kind of fish

known to give humans
a powerful jolt.

The ancient Egyptians knew that
the electric catfish could also

give shocks and they called it
the "Thunderer of the Nile".

And in the nearby Mediterranean
lives the torpedo ray.

Its muscle batteries
make it so bulky

it can't undulate its body
like other rays

but has to propel itself
by waving its tail.

Like the electric eel,

it uses its discharge to stun
the other fish on which it prays.

Sadly, the pressure of celebrity
and having to produce shocks

and sparks to order exhausted
Baker's long-suffering eels

and they didn't last the winter.

But two were preserved and expertly
dissected by John Hunter,

a very distinguished
Scottish surgeon of the time

and he found a great number
of striped muscular layers

that proved to be where
the electricity was generated.

They are now referred to
as Hunter's organs.

He found these muscles along
the tail and sides of the eels

arranged in stacks.

One scientist called Galvani
believed that animals

had their own natural electricity
even without these electric organs

and he tried to prove this
by connecting wires to frogs' legs

and making them twitch.

He called this phenomenon
animal electricity.

But another scientist called Volta
had other ideas.

He proved that the frog was merely
a conductor for electricity

with a simple experiment.

Volta replaced Galvani's frog
with discs of cloth

soaked in saltwater or acid

and sandwiched them
between two different metals.

I can do the same thing
with filter paper,

copper two pence pieces and these
simple galvanised zinc washers.

Watch.

Tuppenny piece.

Filter.

And washer.

There, nearly 0.6 of a volt.

But the amount of electricity
generated was tiny.

Certainly not enough to make
the sparks seen from eels.

Unlike Galvani,
Volta saw no distinction

between animal electricity
and his new electricity from metals

so he now looked at animals to see
how he might amplify his new device.

Was it significant that the muscles

producing the electric power in
the eels were arranged in stacks?

Volta decided to add more stacks
to his electric pile.

We call this way of connecting
electric cells together

"in series", and we now know
that it increases the voltage.

But Volta was about to find this out
for the first time.

He piled up his tiny cells
like the bands of muscle

in an electric fish.

Here I've got ten pairs.

And just watch.

Nearly six volts.

Wonderful.

Volta could now produce heat,
shocks and even sparks

from electricity in a continuous
never-ending stream.

He had made the first battery,
partly inspired by the electric eel.

The pieces of the puzzle had come
together and the eel's example

had helped to advance
our understanding of electricity.

Eels, in fact,
contain natural batteries.

Stacks of special muscles.

It's amazing to think
when electricity is so much

a part of our lives today
that before Volta

the only source of electricity
was lightning,

a few static generators

and fish like this incredible
electric eel.

Understanding how electric eels
managed to find their way around

revealed a hitherto
unknown animal sense.

But it's not just animals
that have surprised us.

We're now discovering
that plants too

have intriguing abilities
that are still mysterious.

We think of plants as passive,
still and silent.

But they may have more in common
with animals than you might think.

New research suggests that
they have surprising abilities.

It depends on how you look at them.

I first started seeing plants
in a different light

when making a series called
The Private Life of Plants.

We used time-lapse photography
to reveal the way they move.

The bramble spreads aggressively -
seemingly unstoppable.

Other plants pulsed
to the rhythms of day and night.

And flower buds explode
like fireworks.

So, with speeded up film,
we had been able to translate

their time into ours

and to realise that
they're constantly on the move.

200 years ago, one plant
that moved very quickly indeed

attracted the attention
of a great scientific mind.

It appeared to behave like an animal

and could move fast enough
to catch its own food.

Charles Darwin was fascinated
by the Venus flytrap.

He called it one of the most
wonderful plants in the world.

He recognised that it could
move in a very different way

to that of plant growth.

This movement was not only fast
but also repeatable.

Darwin experimented
and found that the traps

are not triggered by raindrops

but only by a very particular
stimulation of the leaf hairs,

such as an insect might make.

But what intrigued him most
was the speed of the reaction.

He sent one of these flytraps to
a friend, Dr Burdon-Sanderson,

who was performing groundbreaking
work on muscles and electricity.

His tests confirmed that
the tiny electrical discharge

caused by an animal muscle cell
contracting was almost identical

to those signals obtained by
attaching electrodes to the flytrap

when it was shutting.

Although plants have no muscles,

electrical stimulation enables them
to move in a similar way to animals.

Electrical signals cause cells
to change the pressure of sap

in their leaves,
so creating movement.

As a result, some plants,
like animals,

can actively catch their prey.

Recently it's been discovered that
other plants use electricity too

but for a very different purpose.

Plants are rooted to the ground
and have a small negative charge.

The higher up the plant you go,
the greater the electric charge.

This creates an electric field
around the flower.

We can't see it but these
electrodes are picking up the energy

of this tiny field and converting
it into the sound that we can hear.

Bees, on the other hand, have a
positive charge.

Friction whilst flying causes them

to lose electrons, leaving them
electrically charged.

As a bee approaches a flower,
the charge fields around the flower

and the bee interact,
and the sound changes...

FALTERING ELECTRONIC BUZZ

..there.

And when it lands, the positive

and negative fields immediately
cancel each other out.

As this happens, there are two very
surprising consequences.

Firstly, the plant's negatively
charged pollen actually

jumps across onto
the positively charged bee.

Secondly, the plant has a changed
electrical field

and when another bee comes along,
it detects this altered

electrical signature
and avoids the flower.

The plant is, in effect, telling
the bee that it has no nectar

and to come back later.

When the flower has refilled
its stores of nectar, it creates

a new electric charge which
attracts another passing bee.

This simple on/off signal benefits
both the bee and the flower,

but it does have its limitations.

The electrical field is tiny,

so insects can only detect
it at close quarters.

But flowers can also draw attention
to themselves over much

greater distances and they do this
by floating messages in the air.

The perfume of a flower is not
just a pleasant smell,

it's also the primary way in which
plants communicate with insects.

A rose can contain over 400
chemical compounds and a bee

can recognise a particular
combination from over a mile away.

The very latest research has
discovered

that 90% of the chemicals
made by plants, are also

produced by insects
and that is no coincidence.

Most flowers produce scent to
persuade insects to visit them,

but others use it in a more
sophisticated way...

for protection.

Cabbages communicate
with each other using smell.

When the leaves of one plant are
being attacked by caterpillars,

it releases a scent which
warns its neighbours.

They then produce chemicals in
their leaves that caterpillars

don't like and so they avoid
being eaten.

And scent also serves to
call in the cavalry.

Leaves that are under attack give
off a chemical alarm signal that

attracts wasps which obligingly
pick off the caterpillar attackers.

So, vegetables, fruits,
leaves and flowers are constantly

communicating with each other using
touch, vision and smell.

They seem to exploit all the senses,
apart, that is, from hearing.

But there are old stories that one
particular plant is able to

produce a very strange sound.

Hundreds of years ago, a plant with
a root that was thought to

resemble a human body was said to
emit a sound that could kill.

The root was known to have
strong anaesthetic

and hallucinogenic properties.
And in the first century AD,

it was called a mandragora or
mandrake as it's now known.

It was associated with magic
and the supernatural

and was thought to derive power from
a demon that emitted a dreadful

and fatal shriek
if the plant was uprooted.

Fortunately, there were creative
ways of avoiding

death from the killer sound.

One account advised
plugging one's ears

and then tying a starving dog
to the mandrake plant.

And then, as the dog lunged for
food, the plant would be uprooted.

The dog would tragically die
from the mandrake's shriek

but the man would survive.

This particular story may have
arisen because drinks made with

the mandrake root can produce
hallucinations.

But we're just beginning to realise
that the sensory abilities

of a root could be as sophisticated
as the rest of the plant.

Latest research suggests that roots
are communicating underground.

And we now have the technology to
eavesdrop on the roots' world.

Believe it or not, the roots of
these corn seedlings can make

and sense sound.

The noise is very quiet but we can
hear it with this equipment,

if I place a corn seedling in front
of a laser beam Like this.

Now the sound vibration
can be detected

and we can hear it through
a speaker...

CRACKLING

..there.

That strange crackling is
the sound of corn roots growing.

It can be seen as pulses
on the screen.

It's been shown, too, that the
corn roots respond to the sound

when it's played back to them.

Time-lapse footage shot over just
a few hours clearly shows

the roots growing towards the tiny
speakers that emit the sound.

There is much speculation

about the purpose of this
curious phenomenon.

Perhaps it helps roots avoid growing
into hard objects or being too

close to competing plants.

It could act like simple
echolocation,

we just don't know but it's
the first clear evidence that

plants have a rudimentary
form of hearing

and might even be communicating
underground using sound.

Sensitive equipment is creating
a new window into the plant world

and it seems that, like animals,
they have a sophisticated

sense of their environment
and possess abilities that not

so long ago, we would have
thought of as supernatural.

BIRDSONG

Swallows have successfully nested

and raised their young in this
barn for several years.

These chicks will soon leave the
nest and make their first

exploratory flights around the farm

but in a few weeks' time they will
suddenly vanish.

Where do they go to?

In the past, that gave rise to
some extraordinary speculations.

In fact, in the 18th century,
it became a very long-running

debate, headed by some well-known
Church figures.

And swallows are not the only
birds that appear

and disappear with
the changing seasons.

For centuries, people speculated
about where such birds go.

One explanation was that some birds
changed into others by growing

different adult plumage.

Perhaps the redstart turned into
a robin...

..or the garden warbler
into a blackcap.

Since these species where seldom
present at the same time

the explanation seemed
entirely plausible.

The barnacle goose was
another mystery.

Each winter, huge,
noisy flocks of them

appear on European shores,
apparently from out of nowhere.

No-one had ever seen them
build a nest or raise young.

The barnacle goose gave rise to some
extraordinary folklore as this

mediaeval illustration shows.

It was thought that the geese
grew on underwater trees,

starting life as small marine
creatures called goose barnacles.

Goose barnacles do, of course,
exist, they're small

shelled marine organisms with what
looks like the head,

which is in fact enclosed by a
shell, attached by a stalk, which

was thought to resemble the neck of
a bird, to a bit of wood or a rock.

The confusion about the nature
of the barnacle goose was put to

good use by some.

Since it was unclear
whether it was a bird,

a fish or some other creature,
you could surely be

allowed to eat it on days when meat
was forbidden by the church.

But the most commonly held
belief was that birds

disappear in winter because
they hibernated.

Swallows and their close relatives,
the swifts and martins,

were thought to do so in mud at the
bottom of ponds and rivers

and it's easy to see how this
idea originated

because the birds spent much of
their time near water, skimming low

over the surface, hunting for
insects or taking a drink.

It wasn't until the Middle Ages that
another theory was proposed that

some birds may migrate

and one of its strongest proponents
was an influential religious leader.

Frederick the second of Hohenstaufen
was a powerful holy

Roman Emperor
and known for his unorthodox views.

He ignored the philosophy of
the Church

and based his knowledge of natural
history on direct observation

rather than what was ordained.

Frederick was also a keen falconer
and he wrote this book,

The Art Of Falconry,

and in it, surprisingly,

there are entire
chapters on the migration of birds.

His confidence came from
the fact that,

unlike his contemporaries
and those before him,

he had actually observed
birds in the field for himself.

He had no doubt about the migration
and so,

Iittle patience for the myths
surrounding the barnacle goose.

He considered the story to be
quite ridiculous

and argued that the birds simply
breed in distant lands.

His views started a debate that
split people into two camps,

those believing in the old
hibernation theory

and those who supported the idea
that birds migrate.

This was the start of a new era
which was to sweep away myths

and focus instead on facts
and careful observation.

Across Europe, the evidence for bird
migration started to accumulate.

In Germany, a 12th century
monk is said to have taken

a swallow from its nest and attached
a parchment note to its leg

that read, "Oh, swallow,
where do you live in winter?"

The following spring the bird
returned with a note saying,

" In Asia, in the home
of Petrus, that is Israel."

The story may not have been true,
but it certainly gave the
right hint.

In the early 16th century,
a Bishop from Sweden called

Olaus Magnus reignited the debate
about swallows with this picture.

He claimed that in winter,
fishermen often drew up

swallows in their nets, hanging
together in a mass.

This astonishing assertion
provided ample fuel

for the anti-migration lobby
and, unlikely as it was,

the view that swallows spent
their winter underwater

became increasingly entrenched.

By the 18th century, the debate
about migration versus hibernation

had come to a head and across the
continent opinions were divided.

But new evidence was about to come
from an unusual source.

Edward Jenner was an English country
doctor who also had a deep

interest in natural history.

He noted that although swallows
often splash in water

as they skim across it, they never
immerse themselves.

Were they to do so, he suggested,
their wings would become

so wet that they would be
unable to fly.

To test his idea, Jenner
reportedly held a swift

underwater for two minutes.

Not surprisingly, it died.

Jenner went on to devise
another experiment to

discover where the birds go.

He took 12 swifts from their nests
and marked them

by taking off two of their claws.

The following year, some of the
birds he'd marked were caught

again in exactly the same spot.

Although Jenner could not discover
where his swifts had been

over the winter, he was the first to
show that they returned to use

the same breeding sites
in the following years.

And we now know that this is
true for swallows as well.

About the same time, across the
Channel, a German bird enthusiast

had come up with a similar idea.

Johann Frisch caught several birds
near his house and attached

to their legs woollen threads like
this which he'd dipped

in red watercolour.

He predicted that if swallows really
did spend

the winter at the bottom of lakes,
the red colour would be washed off.

The following spring, Frisch's
swallows returned

and the threads where unchanged.

It was a very simple but very
effective experiment.

Evidence against the hibernation
theory continued to mount

and eventually a new technique put
the final nail in its coffin...

systematic bird ringing.

This bird has just been fitted
with its own individual marker.

A small metal ring on its leg with
a unique code of numbers.

It's part of a national scheme
that's been running for over 100

years and provides scientists with
invaluable data on bird movements.

Early in the 20th century, the study
of migration really took off.

Birds were recovered on their
breeding and wintering grounds

and often en route, too.

600 years after Frederick von
Hohenstaufen had first started

the debate, real evidence was
beginning to accumulate.

In the summer of 1911, a metal ring
just like this one,

was clipped onto the leg of a young
swallow in Staffordshire.

The number on the ring was B830.

18 months later, the same bird was
caught by a farmer in South Africa.

Here, at last, was the indisputable
proof that swallows migrate

and spend the winter
thousands of miles away.

Off you go. There we are.

Today, of course, we know that the
swallows' migration is

one of the most impressive in all
the animal kingdom.

It takes it across the largest
desert in the world, the Sahara,

it's a gruelling
and dangerous journey

and many die on the way
from exhaustion or starvation.

They travel for nearly four months,
covering nearly 10,000km

and eventually reach
southern Africa.

And bird ringing also helped to
dispel the myth of

the barnacle goose.

In the 1960s, a Norwegian
expedition, ringed geese nesting

on the Arctic island of Spitsbergen.
That autumn, some of the same

birds were sited on the west coast
of Scotland, some 2,000km away.

Frederick von Hohenstaufen had been
proved to be absolutely correct.

It took centuries to discover
the truth behind the swallows'

seasonal movements.

But in their time, they baffled the
minds of many great naturalists and

started one of the longest-running
of all scientific debates.

But in the end, the true story
proved to be even more extraordinary

than the fantastic myths that where
invented to explain it.

Just like the swallow,

the painted lady butterfly seems to
appear magically out of nowhere

and that started some extraordinary
ideas and controversies.

The painted lady is
one of our largest butterflies

and a familiar summer visitor
to our gardens.

And yet, its appearance

and disappearance each year, has
puzzled us for centuries.

It's only now that we're beginning
to understand this extraordinary

Iife cycle and discover where it
vanishes each year.

Early naturalists were
confused by the sudden

appearance of painted ladies each
spring because they were

unaware of the connection between
butterflies and caterpillars.

For a very long time it was widely
believed that butterflies

arise from rotting material by what
was called spontaneous generation.

In the 1830s, a German scientist
named Renous was arrested for heresy

for claiming that he could change
caterpillars into butterflies.

Arresting someone for something now
known to be common knowledge

may seem rather extreme, but at the
time, many still believed that

caterpillars and butterflies were
completely different creatures,

created by the hand of God.

Needless to say, people had been
well aware of the existence of

both butterflies and caterpillars
since the earliest times.

But the thought that any two
were related,

Iet alone the same species,
seemed impossible...

and it's easy to see why.

Not only do caterpillars
and butterflies look like very

different types of animals,
but the colours and patterns

of a caterpillar don't match up with
those of its adult form.

The only way to know which lava
and which butterfly go together

is to keep caterpillars and watch
them turn into butterflies.

But it wasn't until the 17th
century that anyone left

a record of doing that.

One of the first was a remarkable
woman named Maria Sibylla Merian.

Merian was born in Germany at a time

when women still had little
formal education

and no role in the scientific world,
but she was an accomplished

artist and painted plants and
insects she saw around her.

To do that, she kept caterpillars,
fed them on leaves

and watched them
turn into butterflies.

Merian produced hundreds of
beautiful paintings of butterflies

and their stages of development

along with the plants on which
they feed.

Her drawings are so exquisite

and detailed that they still
rank among the best in the world.

Among the things she observed with
great care, were things like this.

A curious, yet strangely beautiful
object, it's a chrysalis,

the intermediate stage between
a caterpillar and a butterfly.

She was one of the first to
record the remarkable change

that takes place in the chrysalis.

It's one of nature's most
extraordinary transformations.

At the age of 52, she sailed from
Europe to South America on a

two-year expedition to study insects
in the tropical jungles of Surinam.

It was an exceptional
journey for any naturalist

at the time and particularly
for a woman.

When she returned, she produced
this beautiful book.

It turned out to be popular

because it was one of the few
to be published

not in the scientific language of
Latin but in Dutch.

Because of this,

her work was largely
dismissed by scientists of the time

but Merian was one of the first
naturalists to correctly

connect the caterpillar with its
pupa and the adult form.

Today, Merian's book is widely

recognised as a pioneering work
of scientific observation

and it put an end to the
idea of spontaneous generation.

Around the same time, further
evidence for the connection

between butterflies and caterpillars
came from a different source.

In 1669, a Dutch scientist by the
name of Jan Swammerdam published

the results of experiments which
would finally prove that the

caterpillar and butterfly are one
and the same animal.

Swammerdam was a master of the
miniature and dissected the

caterpillars and pupae
of butterflies and moths

under a microscope. With a steady
hand and endless patience,

he carefully cut into the layers
of skin with tiny scissors

and what he discovered was
truly astonishing.

He found some of the body parts
of a butterfly.

The structures were fragile and not
complete but Swammerdam had proved

that caterpillar and butterfly are,
indeed, one and the same animal.

We now know that without the
caterpillar, there can be no
butterfly.

Yet, for a very long time,

the painted lady seemed to be
an exception.

Every spring, the adult butterflies
would appear across Britain

without any sightings
of their caterpillars.

While some butterflies hibernate
in Britain, there was no sign

of painted ladies doing so.

Some speculated that they flew to
warmer climates as birds do.

But how could a tiny insect cross
the English Channel?

In the 20th century, swarms of
butterflies moving across Europe

finally provided evidence that
painted ladies do, indeed,

cross the sea.

And they were found to fly all the
way from North Africa to Britain.

But there were almost no records
of painted ladies making

the reverse trip south.

So, for years,
it was thought that Britain must be

a dead-end for the most
northerly stragglers.

And then, in 2009, the public was
asked to help solve the mystery.

Among 12,000 sightings there were
reports of painted ladies

flying out to sea in the autumn.

And a radar station detected
them flying south

at heights of 500 metres,
way beyond the sight of human eyes.

We now know that the painted ladies
migration is a round-trip

of over 12,000km. But it's
not made by any one individual.

Each only flies part of the way,

passing on the migratory baton
to the next generation.

It's like a relay race with up to
six generations of butterflies
involved.

The painted ladies epic journey
from one continent to the next

would be a truly astonishing feature
in any animal

but for a tiny creature like this,
it seems really extraordinary.

How does it battle the wind

and the weather and navigate across
vast bodies of water?

And with no single individual ever
undertaking the whole migration,

how do they find the way?

It seems that painted ladies
are pre-programmed to either fly

north or south
and this is determined whilst

they are still caterpillars,
possibly by temperature

and day length and also by the
plants they feed on but how

does this information get passed
on from caterpillar to butterfly?

The answer may be hidden
within the chrysalis.

Recently CT scanners have allowed us
to look inside a pupa.

They reveal that some organs remain
intact during the transformation.

A one-day-old pupa clearly shows
the gut and breathing tubes

which only change slightly as the
chrysalis develops.

Could it be that the
brain or nerves also remain intact

and that memories are passed on?

Recent experiments in the lab appear
to support this idea.

Scientists taught caterpillars
to avoid specific

smells by linking them with an
unpleasant reaction.

Later on, as adults, the same
individuals remembered these

smells and chose to keep
away from them.

If the experiences of a caterpillar
can be carried over

to the adult, then maybe cues for
migration can also be passed on.

Although we've unravelled much
of the painted lady's life-cycle,

many questions remain.
How far does each individual travel?

And do offspring follow similar
routes to their ancestors?

One day we may know the answers
but, for now,

they remain some of the unsolved
mysteries of nature.

The arrival each spring
of our painted lady butterflies

and our swallows never ceases
to delight us

but now we also understand
the extraordinary journeys

they undertake when they disappear
again at the end of summer.