All language subtitles for David.Attenboroughs.Natural.Curiosities.Series.3.1of6.Impossible.Feats.720p.HDTV.x264.AAC.MVGroup.org

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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 myths

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
particularly fascinating.

Some animals can perform
amazing physical feats.

A flea's jump is said to
be the equivalent of a man

leaping over
St.Paul's Cathedral.

And it's famously
quoted, that cheetahs

can run at speeds of
70 miles an hour.

But are these
claims really true?

Quick.
Look

This is a real,
live, flea circus,

and you can see this one,
pulling along this tiny chariot.

There are very few circuses
like this, these days.

The whole business
of performing fleas,

dates back into the 16th century,
and it was used by watchmakers.

They used them, to
demonstrate how they

themselves could work on
a near-miniature scale.

They used thin gold wires,
to harness fleas,

and then link the fleas
to tiny chains.

Early magnifying
devices like this

where actually named "flea glasses",
after these pests.

And the fleas where
excellent creatures

to demonstrate a newly
visible, microscopic world.

Fleas appear to be
extraordinarily strong,

after all, this little flea here,

pulling this chariot,

was an extraordinary thing.

That's the equivalent of me, trying
to pull a jumbo jet single-handed.

And this tiny merry-to-round, that
too, is completely powered by fleas.

The secret of the flea's strength and
ability, to move such equipment,

lies in their powerful walking
and jumping techniques.

They have the ability, to store
and then release energy,

and that enables them to leap
upwards, with great acceleration.

Fleas need to be good jumpers.

They live on the skin of mammals
and birds, sucking their blood.

So they have to be able,
to quickly leap on board

their traveling hosts,
when they get the chance.

There are more than 2,500
species worldwide,

62 or which, live in Britain.

Fortunately, only
a few feed on us.

Rat fleas were said
to be responsible,

for the spread of the
black death, in 1665,

which killed millions.

But it wasn't until the invention
of the magnifying glass,

that we were able to see these
tiny creatures, face to face.

In 1665, Robert Hooke,

an inventor and
natural philosopher

made one of the first
compound microscopes.

This is a later
reproduction of it.

And he then published
his discoveries,

that he made, using it,

in a marvelous book,
called "Micrographia ".

It became one of the first
scientific best-sellers.

Samuel Pepys mentioned
it in his diary.

And it contained magnificent,
detailed drawings,

that revealed biological structures,
that had never been seen before.

He saw that plant
tissue, was made up of

little units, that
he called cells.

The word we still use.

And he drew this
marvelously detailed flea,

showing its great,
strikingly long legs.

He also watched it
through the microscope,

and he described,
how a flea jumped.

This is what he says:

"When the flea intends to leap",

"he folds up these
6 legs together"

"then springs them all
out, at the same instant"

"and thereby exerting his whole
strength at once,"

"carries his little body, to
a considerable distance."

Indeed it does.

A flea's jump, takes just
1/1000th of a second.

So Hooke, must have had very
sharp eyesight to see it.

Many researchers have
been fascinated by fleas,

and for one particular family,
they became an obsession.

Charles Rothschild, a
banker and keen naturalist,

amassed over 30,000 specimens,

and identified more
than 500 new species.

He purchased them from
specialist traders, world wide.

and one parcel from America,
had a special surprise.

The tiny fleas were
dressed as Mexicans.

Miriam, Charles' daughter,
shared his passion for fleas,

and catalogued his
whole collection.

She looked closely
at the flea's body

and the way they jumped,

and was puzzled to find, that
they could leap far higher

then should theoretically
have been possible.

But could their reputation
for jumping 200 times

their body length, possibly be true.

Most of the natural
world's top jumpers

achieve their impressive leaps,

by using straightforward
muscle power.

Kangaroos can make single
bounds, of almost 8 meters.

And frogs are able to jump

more than 20 times
their body length.

The jumping spider's leap
is even more impressive,

100 times its own length.

It achieves this, by
exploiting hydraulics.

And scientists had
long suspected,

that fleas, and other insects,

also needed something
other than muscle,

to make their huge jumps.

In the 1960's an exciting
discovery was made

in the insect world,
that helped explain,

how bigger flying insects,
like locusts and dragonflies

were able to fly
and jump so well.

A rubbery protein was
found in the hinges

and joints of locust
wings and legs.

Using ultra-violet light,
it's possible to see it,

as in this picture of a
leg joint, of a locust.

Here, that blue, is
this new substance.

But, just like this rubber, it could bend,

and then, release energy.

But the newly discovered
material did that,

with more than 90
percent efficiency.

Remarkably too,
it repeatedly snapped

back into shape, without
any deformation.

It was named: Resilin.

This stretchy protein allows
insects, to bend their stiff

bodies and stretch their
tendons, without snapping.

It's so robust, it
lasts a lifetime,

and it's believed to be the most

efficient elastic protein known.

The discovery of Resilin, opened
up a whole new area of study.

And in 1966, Henry Bennet-Clark,

an expert in insect
bio-mechanics,

had a break-through moment.

He had the chance, to see some
exciting new footage of fleas,

shot on a newly invented
high-speed camera.

Bennet-Clark studied the new
flea footage, and build

a mechanical model,
400 times bigger than the flea.

He calculated, that the fleas
were somehow generating

much more power, than their
muscles could actually provide.

He noticed, that just before leaping,

the flea bent the closed
segment, of its hind-most legs,

towards the body, and hesitated
for about 1/10th of a second.

Carefully, he dissected fleas,
and found a pad material.

And that proved to be Resilin.

He proposed, that fleas stored some
of the energy for their jumps,

in this rubber-like tissue,
and then released it,

as they pushed off, with
their shins and feet.

So the tiny wingless fleas,
use internal Resilin springs,

like those of other bigger,
flying and jumping insects.

And the secret of
their huge leaps,

lies in the efficient
way, they combine muscle,

tendons and joints, to harness
the resilin's energy.

Only today, do we know how a flea
jumps, and how high it can jump.

Just as in Hooke's time, a
modern technology, a microscope,

enabled him to see the anatomy of
the flea, for the very first time,

so, we have a camera now, which
is recording 5,000 images a second,

which enable us to
see how it jumps.

The camera is already running.

The flea is in that
little box, there.

And we can see the image from
the camera, on this computer.

I will stop it, as soon as I
see, the flea has jumped.

There.

Its legs are already cocked
in the jumping position,

and the cuticle which
has fused the Resilin,

is bent, and ready to release its energy,

and then, it lifts itself from the ground,
and it's catapulted into the air.

Our story about fleas
started 350 years ago,

with Robert Hooke's first
microscopic study.

Today, images from
electron microscopes

reveal even more details, than
Hooke's beautiful drawings.

They show the rough hairs, on
the flea's shins and toes,

that help it grip, before
thrusting itself into the air

with a final push from its toes.

So, can fleas jump 200 times
their own body length?

It would seem not.

Nonetheless, they can leap
a respectable 38 times

the length of their
bodies, which is not bad.

Fleas are
extraordinarily strong.

And we now know how they jump.

The flea's story isn't quite over.

A new discovery has added
a twist to their lives,

and dispelled another myth.

Recently, bodies of people,
who died of the black death,

were uncovered by workers,
digging a new railway line.

This inspection revealed, that the
black death was an airborne disease,

and had nothing to do with
rats, or their fleas.

So, the flea's good
name can at last be

restored, and we can
celebrate them,

as one of the natural world's

most spectacular jumpers.

Next, meet an animal that
performs another amazing feat.

The Cheetah,

that, they say, can run
at over 70 miles an hour.

Fleas can't jump as
high as some say,

but they can make
extraordinary leaps.

Next, we investigate
another amazing claim.

The Cheetah's ability to run
at speeds of 70 miles an hour.

Is that really possible?

Cheetahs are beautiful,
athletic looking cats

They've got a streamlined
body, small head,

elongated legs, narrow shoulders

and a very long spine.

This looks like an animal,
that's build for speed.

But exactly how fast can he run?

They've been admired for their
grace and speed, since antiquity.

The Egyptians were sometimes
buried with these cats,

because they believed, that they could
hasten the journey to the after-world.

And in more recent
times, sports hunters

have used cheetahs, to
run down their prey.

So, the cheetah certainly
has an impressive sprint.

But where did the magical figure
of 70 miles an hour come from?

Back in 1957, a cheetah
hit the headlines

with news of a rather
unusual experiment.

A photographer,
called Kurt Severin

filmed and measured the running
speed of a tame cheetah

using an upturned bicycle,
rather like this.

The back wheel was modified,

so that a strong fishing line

could be wound through the rim

and pull along a
meat scented bag.

As the cheetah ran the 80
yard, or 73 meter course,

the pedals of the bike were hand-cranked
as fast as humanly possible,

to drag the bag along,
just ahead of the cheetah.

The measurements
were made manually,

using a stopwatch and a pistol.

Severin wrote, that
from a deep crouch,

the cheetah spurted to the end
of the course, in 2,25 seconds,

for an average speed
of 71 miles an hour.

So, the legend was born.

This impressive figure was
immediately accepted,

and is still often quoted today.

But how accurate is it?

The top speed of any
running mammal,

depends on the power
of its muscles,

and the strength of its
tendons and bones.

Human athletes train hard, to
reach their personal best,

but there's still a limit
to how fast they can run.

In a 100 meter sprint,
a mere 2 seconds

separates a good
amateur sprinter,

from a world class champion.

The greyhound is similar in
size and shape, to a cheetah,

so it's a good substitute animal,

to test out the cheetah's
legendary top speed

of 70 miles an hour.

Their backs flex and
extend so greatly,

that at times, none of their
feet touch the ground.

But when the greyhound's
top speed was measured,

it was found to be
45 miles an hour;

a whole 25 miles an hour

slower than the cheetah.

People argued, that the cheetah
could nonetheless achieve

a bigger stride, because of
extra flexibility in its back.

The doubts about its top speed,
were beginning to creep in.

A new, more accurate way
of testing, was needed.

Here in the Royal
Veterinary College,

they use dogs, to help them
in their studies of cheetahs.

Using a lurcher as a stand-in,

they've developed an extraordinary,
data collecting collar.

It has a GPS attachment,
that will register

position, to within a
fraction of a meter.

It has movement sensors, to show

how the animal is
in fact moving.

It can be remotely programmed,

and it has a solar
charged battery,

that will last for up to a year.

The collars were
tested and perfected,

on lurchers in Britain

to make sure that they were
small and light enough,

no to disturb their wearer.

Then the collars were put
on captured cheetahs,

to see if they could cope with
the twisting, while at the hung.

The results were excellent,

and the collars were ready
for the ultimate test:

in the wild.

Here was a chance, to see if a wild
cheetah's special adaptations to hunting,

really enabled it, to run
at 70 miles an hour.

Wild cheetahs are faster than
other larger cats, like lions,

because of their lighter bones.

An advantage in the
short, high-speed chase.

They have big nostrils, so they can
take in large amounts of oxygen,

and an enlarged heart and longs,
that increase circulation.

Their long tails act like
rudders, to help them steer,

and assist their balance
as they twist and turn.

They need to be fast and maneuverable,
because the prey they hunt

is extremely agile and able to
change direction very quickly.

A cheetah can mirror such changes
of movements in an instant.

But what would the GPS-collars
tell us, about their speed?

Data from the collars, has revealed
fascinating details about cheetahs lives,

How they hunt, and exactly
how fast they can run.

The GPS measurements collected, are
accurate to within half a meter,

and can be precisely matched to
satellite images of the area.

So, it's possible to
see exactly what kind

of terrain, the cheetahs
were hunting on.

Here, we can see an 11-hour
day in the life of a cheetah,

and there, it starts to hunt.

The cheetah ran in one
circular direction, like this.

The blue represents deceleration,
getting slower here,

and there, the red, where it
gets faster and accelerates.

And the arrows, represent
the power of the force

on the cheetah's
body, as it swirls.

And there, finally,
it made the kill.

367 hunts were studied,
and the top speed of

a chase, was calculated
to be 58 miles an hour.

For more than half
a century, we have

overestimated the
cheetah's speed.

It is nonetheless, still the
fastest animal on land,

and it's greatest feat,
is its acceleration.

Four times that, of Usain Bolt.

The cheetah's legendary,
70 miles an hour,

speed record, is just a myth.

But their true top
speed of 58 miles

an hour, is still extraordinary.

A body, that is fine
tuned for hunting

helps them run, in a
really remarkable way.

But the cheetah's real
impossible feat, so-called,

is the ability to change
speed so extremely quickly.

And that makes it one of the
most maneuverable animals alive.

Aren't you?
Aren't you.

We may have overestimated the abilities
of the flea, and the cheetah.

But both exhibit remarkable feats of
acceleration, in their quest for food.

The flea, to hop on
to a passing host,

and the cheetah, to
outmaneuver its prey.

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