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??
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The natural world is full of extraordinary
animals, with amazing life histories.
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Yet, certain stories are
more intriguing than most.
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00:00:15,769 --> 00:00:18,558
The mysteries of a
butterfly's life cycle,
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or the strange biology
of the emperor penguin.
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Some of these creatures
were surrounded by myths
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and misunderstandings
for a very long time.
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And some have only recently
revealed their secrets.
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These are the animals, that
stand out from the crowd.
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The curiosities I find
particularly fascinating.
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Some animals can perform
amazing physical feats.
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A flea's jump is said to
be the equivalent of a man
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leaping over
St.Paul's Cathedral.
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And it's famously
quoted, that cheetahs
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can run at speeds of
70 miles an hour.
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But are these
claims really true?
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Quick.
Look
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This is a real,
live, flea circus,
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and you can see this one,
pulling along this tiny chariot.
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There are very few circuses
like this, these days.
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The whole business
of performing fleas,
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dates back into the 16th century,
and it was used by watchmakers.
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They used them, to
demonstrate how they
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themselves could work on
a near-miniature scale.
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They used thin gold wires,
to harness fleas,
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and then link the fleas
to tiny chains.
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Early magnifying
devices like this
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where actually named "flea glasses",
after these pests.
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And the fleas where
excellent creatures
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to demonstrate a newly
visible, microscopic world.
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Fleas appear to be
extraordinarily strong,
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after all, this little flea here,
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pulling this chariot,
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was an extraordinary thing.
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That's the equivalent of me, trying
to pull a jumbo jet single-handed.
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And this tiny merry-to-round, that
too, is completely powered by fleas.
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The secret of the flea's strength and
ability, to move such equipment,
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lies in their powerful walking
and jumping techniques.
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They have the ability, to store
and then release energy,
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and that enables them to leap
upwards, with great acceleration.
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Fleas need to be good jumpers.
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They live on the skin of mammals
and birds, sucking their blood.
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So they have to be able,
to quickly leap on board
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their traveling hosts,
when they get the chance.
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There are more than 2,500
species worldwide,
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62 or which, live in Britain.
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Fortunately, only
a few feed on us.
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Rat fleas were said
to be responsible,
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for the spread of the
black death, in 1665,
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which killed millions.
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But it wasn't until the invention
of the magnifying glass,
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that we were able to see these
tiny creatures, face to face.
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In 1665, Robert Hooke,
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00:03:53,201 --> 00:03:55,560
an inventor and
natural philosopher
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00:03:55,560 --> 00:03:58,389
made one of the first
compound microscopes.
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This is a later
reproduction of it.
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00:04:01,072 --> 00:04:02,736
And he then published
his discoveries,
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that he made, using it,
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00:04:04,861 --> 00:04:08,048
in a marvelous book,
called "Micrographia ".
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00:04:08,455 --> 00:04:12,220
It became one of the first
scientific best-sellers.
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00:04:12,447 --> 00:04:15,100
Samuel Pepys mentioned
it in his diary.
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00:04:15,166 --> 00:04:18,431
And it contained magnificent,
detailed drawings,
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00:04:18,491 --> 00:04:22,229
that revealed biological structures,
that had never been seen before.
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He saw that plant
tissue, was made up of
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little units, that
he called cells.
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The word we still use.
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00:04:30,531 --> 00:04:34,132
And he drew this
marvelously detailed flea,
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showing its great,
strikingly long legs.
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He also watched it
through the microscope,
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and he described,
how a flea jumped.
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This is what he says:
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"When the flea intends to leap",
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"he folds up these
6 legs together"
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"then springs them all
out, at the same instant"
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"and thereby exerting his whole
strength at once,"
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"carries his little body, to
a considerable distance."
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Indeed it does.
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A flea's jump, takes just
1/1000th of a second.
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So Hooke, must have had very
sharp eyesight to see it.
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Many researchers have
been fascinated by fleas,
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00:05:27,045 --> 00:05:30,474
and for one particular family,
they became an obsession.
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Charles Rothschild, a
banker and keen naturalist,
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amassed over 30,000 specimens,
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and identified more
than 500 new species.
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He purchased them from
specialist traders, world wide.
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00:05:49,224 --> 00:05:53,075
and one parcel from America,
had a special surprise.
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The tiny fleas were
dressed as Mexicans.
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Miriam, Charles' daughter,
shared his passion for fleas,
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and catalogued his
whole collection.
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She looked closely
at the flea's body
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and the way they jumped,
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and was puzzled to find, that
they could leap far higher
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then should theoretically
have been possible.
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00:06:21,677 --> 00:06:24,699
But could their reputation
for jumping 200 times
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their body length, possibly be true.
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00:06:32,193 --> 00:06:34,630
Most of the natural
world's top jumpers
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achieve their impressive leaps,
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by using straightforward
muscle power.
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Kangaroos can make single
bounds, of almost 8 meters.
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00:06:45,025 --> 00:06:47,158
And frogs are able to jump
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more than 20 times
their body length.
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The jumping spider's leap
is even more impressive,
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100 times its own length.
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00:07:02,602 --> 00:07:05,828
It achieves this, by
exploiting hydraulics.
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00:07:06,657 --> 00:07:08,820
And scientists had
long suspected,
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00:07:08,829 --> 00:07:10,602
that fleas, and other insects,
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00:07:10,626 --> 00:07:13,352
also needed something
other than muscle,
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to make their huge jumps.
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In the 1960's an exciting
discovery was made
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in the insect world,
that helped explain,
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00:07:26,479 --> 00:07:29,932
how bigger flying insects,
like locusts and dragonflies
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00:07:29,958 --> 00:07:32,485
were able to fly
and jump so well.
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A rubbery protein was
found in the hinges
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00:07:35,941 --> 00:07:39,150
and joints of locust
wings and legs.
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00:07:39,293 --> 00:07:42,694
Using ultra-violet light,
it's possible to see it,
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00:07:42,720 --> 00:07:46,503
as in this picture of a
leg joint, of a locust.
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Here, that blue, is
this new substance.
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But, just like this rubber, it could bend,
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00:07:53,662 --> 00:07:56,407
and then, release energy.
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00:07:56,618 --> 00:07:59,439
But the newly discovered
material did that,
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with more than 90
percent efficiency.
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00:08:02,454 --> 00:08:04,954
Remarkably too,
it repeatedly snapped
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00:08:04,980 --> 00:08:07,328
back into shape, without
any deformation.
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00:08:07,423 --> 00:08:09,520
It was named: Resilin.
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00:08:11,481 --> 00:08:15,391
This stretchy protein allows
insects, to bend their stiff
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00:08:15,417 --> 00:08:18,989
bodies and stretch their
tendons, without snapping.
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00:08:20,464 --> 00:08:23,604
It's so robust, it
lasts a lifetime,
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00:08:23,616 --> 00:08:25,101
and it's believed to be the most
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00:08:25,127 --> 00:08:27,746
efficient elastic protein known.
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00:08:30,850 --> 00:08:35,178
The discovery of Resilin, opened
up a whole new area of study.
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00:08:35,397 --> 00:08:39,269
And in 1966, Henry Bennet-Clark,
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00:08:39,693 --> 00:08:42,169
an expert in insect
bio-mechanics,
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00:08:42,514 --> 00:08:44,545
had a break-through moment.
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00:08:46,050 --> 00:08:49,628
He had the chance, to see some
exciting new footage of fleas,
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00:08:49,652 --> 00:08:53,042
shot on a newly invented
high-speed camera.
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00:08:54,970 --> 00:08:58,279
Bennet-Clark studied the new
flea footage, and build
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00:08:58,305 --> 00:09:02,026
a mechanical model,
400 times bigger than the flea.
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He calculated, that the fleas
were somehow generating
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00:09:05,540 --> 00:09:09,220
much more power, than their
muscles could actually provide.
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00:09:09,832 --> 00:09:12,097
He noticed, that just before leaping,
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00:09:12,106 --> 00:09:15,915
the flea bent the closed
segment, of its hind-most legs,
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00:09:15,965 --> 00:09:20,476
towards the body, and hesitated
for about 1/10th of a second.
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Carefully, he dissected fleas,
and found a pad material.
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00:09:25,450 --> 00:09:27,910
And that proved to be Resilin.
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He proposed, that fleas stored some
of the energy for their jumps,
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00:09:31,826 --> 00:09:34,802
in this rubber-like tissue,
and then released it,
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00:09:34,819 --> 00:09:37,252
as they pushed off, with
their shins and feet.
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So the tiny wingless fleas,
use internal Resilin springs,
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like those of other bigger,
flying and jumping insects.
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00:09:50,358 --> 00:09:52,521
And the secret of
their huge leaps,
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lies in the efficient
way, they combine muscle,
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tendons and joints, to harness
the resilin's energy.
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Only today, do we know how a flea
jumps, and how high it can jump.
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Just as in Hooke's time, a
modern technology, a microscope,
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enabled him to see the anatomy of
the flea, for the very first time,
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so, we have a camera now, which
is recording 5,000 images a second,
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which enable us to
see how it jumps.
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The camera is already running.
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00:10:27,744 --> 00:10:30,919
The flea is in that
little box, there.
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00:10:31,353 --> 00:10:35,231
And we can see the image from
the camera, on this computer.
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I will stop it, as soon as I
see, the flea has jumped.
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There.
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Its legs are already cocked
in the jumping position,
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and the cuticle which
has fused the Resilin,
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is bent, and ready to release its energy,
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and then, it lifts itself from the ground,
and it's catapulted into the air.
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00:11:04,827 --> 00:11:08,957
Our story about fleas
started 350 years ago,
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00:11:08,983 --> 00:11:12,155
with Robert Hooke's first
microscopic study.
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Today, images from
electron microscopes
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reveal even more details, than
Hooke's beautiful drawings.
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00:11:19,830 --> 00:11:23,072
They show the rough hairs, on
the flea's shins and toes,
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that help it grip, before
thrusting itself into the air
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00:11:26,419 --> 00:11:28,808
with a final push from its toes.
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00:11:29,644 --> 00:11:34,284
So, can fleas jump 200 times
their own body length?
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00:11:34,925 --> 00:11:36,229
It would seem not.
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00:11:36,941 --> 00:11:40,460
Nonetheless, they can leap
a respectable 38 times
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00:11:40,486 --> 00:11:43,723
the length of their
bodies, which is not bad.
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Fleas are
extraordinarily strong.
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00:11:49,096 --> 00:11:51,908
And we now know how they jump.
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00:11:52,588 --> 00:11:54,658
The flea's story isn't quite over.
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A new discovery has added
a twist to their lives,
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and dispelled another myth.
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00:12:01,697 --> 00:12:05,166
Recently, bodies of people,
who died of the black death,
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were uncovered by workers,
digging a new railway line.
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00:12:09,345 --> 00:12:13,811
This inspection revealed, that the
black death was an airborne disease,
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00:12:13,837 --> 00:12:17,650
and had nothing to do with
rats, or their fleas.
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00:12:18,132 --> 00:12:20,527
So, the flea's good
name can at last be
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00:12:20,553 --> 00:12:23,520
restored, and we can
celebrate them,
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00:12:23,546 --> 00:12:25,104
as one of the natural world's
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00:12:25,130 --> 00:12:27,737
most spectacular jumpers.
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00:12:32,987 --> 00:12:37,463
Next, meet an animal that
performs another amazing feat.
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00:12:37,659 --> 00:12:38,409
The Cheetah,
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00:12:38,435 --> 00:12:42,692
that, they say, can run
at over 70 miles an hour.
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00:12:53,374 --> 00:12:55,936
Fleas can't jump as
high as some say,
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00:12:55,944 --> 00:12:58,748
but they can make
extraordinary leaps.
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00:12:59,311 --> 00:13:02,619
Next, we investigate
another amazing claim.
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00:13:02,651 --> 00:13:06,651
The Cheetah's ability to run
at speeds of 70 miles an hour.
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00:13:07,641 --> 00:13:09,695
Is that really possible?
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00:13:13,077 --> 00:13:17,741
Cheetahs are beautiful,
athletic looking cats
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00:13:17,777 --> 00:13:20,971
They've got a streamlined
body, small head,
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00:13:21,042 --> 00:13:24,772
elongated legs, narrow shoulders
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00:13:24,788 --> 00:13:27,007
and a very long spine.
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00:13:28,562 --> 00:13:31,280
This looks like an animal,
that's build for speed.
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00:13:31,554 --> 00:13:34,413
But exactly how fast can he run?
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00:13:37,714 --> 00:13:42,068
They've been admired for their
grace and speed, since antiquity.
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00:13:42,691 --> 00:13:45,698
The Egyptians were sometimes
buried with these cats,
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00:13:45,704 --> 00:13:49,961
because they believed, that they could
hasten the journey to the after-world.
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00:13:50,774 --> 00:13:53,985
And in more recent
times, sports hunters
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00:13:53,997 --> 00:13:57,039
have used cheetahs, to
run down their prey.
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00:14:00,974 --> 00:14:04,443
So, the cheetah certainly
has an impressive sprint.
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00:14:05,950 --> 00:14:10,082
But where did the magical figure
of 70 miles an hour come from?
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00:14:14,643 --> 00:14:17,924
Back in 1957, a cheetah
hit the headlines
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00:14:17,950 --> 00:14:20,986
with news of a rather
unusual experiment.
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00:14:28,864 --> 00:14:31,245
A photographer,
called Kurt Severin
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00:14:31,419 --> 00:14:34,965
filmed and measured the running
speed of a tame cheetah
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00:14:35,212 --> 00:14:38,301
using an upturned bicycle,
rather like this.
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00:14:38,915 --> 00:14:40,845
The back wheel was modified,
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00:14:40,871 --> 00:14:42,895
so that a strong fishing line
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00:14:42,921 --> 00:14:44,601
could be wound through the rim
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00:14:44,627 --> 00:14:47,490
and pull along a
meat scented bag.
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00:14:47,923 --> 00:14:52,056
As the cheetah ran the 80
yard, or 73 meter course,
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00:14:52,080 --> 00:14:55,747
the pedals of the bike were hand-cranked
as fast as humanly possible,
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00:14:55,771 --> 00:14:59,104
to drag the bag along,
just ahead of the cheetah.
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00:14:59,457 --> 00:15:01,652
The measurements
were made manually,
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00:15:01,678 --> 00:15:04,108
using a stopwatch and a pistol.
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00:15:05,301 --> 00:15:08,294
Severin wrote, that
from a deep crouch,
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00:15:08,312 --> 00:15:12,632
the cheetah spurted to the end
of the course, in 2,25 seconds,
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00:15:12,672 --> 00:15:16,281
for an average speed
of 71 miles an hour.
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00:15:16,380 --> 00:15:18,372
So, the legend was born.
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00:15:20,887 --> 00:15:23,933
This impressive figure was
immediately accepted,
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00:15:23,948 --> 00:15:26,230
and is still often quoted today.
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00:15:26,715 --> 00:15:28,280
But how accurate is it?
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00:15:29,422 --> 00:15:31,315
The top speed of any
running mammal,
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00:15:31,341 --> 00:15:33,408
depends on the power
of its muscles,
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00:15:33,427 --> 00:15:36,284
and the strength of its
tendons and bones.
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00:15:38,242 --> 00:15:42,052
Human athletes train hard, to
reach their personal best,
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00:15:42,188 --> 00:15:45,657
but there's still a limit
to how fast they can run.
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00:15:47,355 --> 00:15:50,257
In a 100 meter sprint,
a mere 2 seconds
239
00:15:50,263 --> 00:15:52,772
separates a good
amateur sprinter,
240
00:15:52,798 --> 00:15:55,195
from a world class champion.
241
00:15:56,917 --> 00:16:00,477
The greyhound is similar in
size and shape, to a cheetah,
242
00:16:00,682 --> 00:16:02,807
so it's a good substitute animal,
243
00:16:02,833 --> 00:16:05,505
to test out the cheetah's
legendary top speed
244
00:16:05,531 --> 00:16:07,314
of 70 miles an hour.
245
00:16:10,746 --> 00:16:13,605
Their backs flex and
extend so greatly,
246
00:16:14,167 --> 00:16:17,276
that at times, none of their
feet touch the ground.
247
00:16:21,205 --> 00:16:23,736
But when the greyhound's
top speed was measured,
248
00:16:23,753 --> 00:16:26,853
it was found to be
45 miles an hour;
249
00:16:26,862 --> 00:16:28,901
a whole 25 miles an hour
250
00:16:28,927 --> 00:16:31,307
slower than the cheetah.
251
00:16:35,038 --> 00:16:38,439
People argued, that the cheetah
could nonetheless achieve
252
00:16:38,465 --> 00:16:42,800
a bigger stride, because of
extra flexibility in its back.
253
00:16:45,760 --> 00:16:49,345
The doubts about its top speed,
were beginning to creep in.
254
00:16:49,401 --> 00:16:52,439
A new, more accurate way
of testing, was needed.
255
00:16:55,536 --> 00:16:58,053
Here in the Royal
Veterinary College,
256
00:16:58,067 --> 00:17:01,481
they use dogs, to help them
in their studies of cheetahs.
257
00:17:01,822 --> 00:17:04,239
Using a lurcher as a stand-in,
258
00:17:04,298 --> 00:17:07,962
they've developed an extraordinary,
data collecting collar.
259
00:17:08,533 --> 00:17:11,526
It has a GPS attachment,
that will register
260
00:17:11,552 --> 00:17:14,408
position, to within a
fraction of a meter.
261
00:17:14,834 --> 00:17:16,802
It has movement sensors, to show
262
00:17:16,810 --> 00:17:19,075
how the animal is
in fact moving.
263
00:17:19,115 --> 00:17:21,154
It can be remotely programmed,
264
00:17:21,180 --> 00:17:23,488
and it has a solar
charged battery,
265
00:17:23,514 --> 00:17:25,623
that will last for up to a year.
266
00:17:27,244 --> 00:17:29,275
The collars were
tested and perfected,
267
00:17:29,294 --> 00:17:31,033
on lurchers in Britain
268
00:17:31,135 --> 00:17:33,260
to make sure that they were
small and light enough,
269
00:17:33,276 --> 00:17:35,113
no to disturb their wearer.
270
00:17:37,570 --> 00:17:39,921
Then the collars were put
on captured cheetahs,
271
00:17:39,932 --> 00:17:43,069
to see if they could cope with
the twisting, while at the hung.
272
00:17:47,889 --> 00:17:49,726
The results were excellent,
273
00:17:49,740 --> 00:17:52,436
and the collars were ready
for the ultimate test:
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00:17:52,570 --> 00:17:53,787
in the wild.
275
00:17:58,278 --> 00:18:03,176
Here was a chance, to see if a wild
cheetah's special adaptations to hunting,
276
00:18:03,211 --> 00:18:07,164
really enabled it, to run
at 70 miles an hour.
277
00:18:09,313 --> 00:18:12,883
Wild cheetahs are faster than
other larger cats, like lions,
278
00:18:12,907 --> 00:18:15,016
because of their lighter bones.
279
00:18:15,129 --> 00:18:18,054
An advantage in the
short, high-speed chase.
280
00:18:20,084 --> 00:18:24,357
They have big nostrils, so they can
take in large amounts of oxygen,
281
00:18:25,634 --> 00:18:29,517
and an enlarged heart and longs,
that increase circulation.
282
00:18:31,927 --> 00:18:35,416
Their long tails act like
rudders, to help them steer,
283
00:18:35,442 --> 00:18:38,192
and assist their balance
as they twist and turn.
284
00:18:39,614 --> 00:18:43,574
They need to be fast and maneuverable,
because the prey they hunt
285
00:18:43,583 --> 00:18:48,277
is extremely agile and able to
change direction very quickly.
286
00:18:48,303 --> 00:18:52,615
A cheetah can mirror such changes
of movements in an instant.
287
00:18:55,310 --> 00:18:59,256
But what would the GPS-collars
tell us, about their speed?
288
00:19:02,365 --> 00:19:07,025
Data from the collars, has revealed
fascinating details about cheetahs lives,
289
00:19:07,217 --> 00:19:10,550
How they hunt, and exactly
how fast they can run.
290
00:19:11,162 --> 00:19:15,263
The GPS measurements collected, are
accurate to within half a meter,
291
00:19:15,283 --> 00:19:18,786
and can be precisely matched to
satellite images of the area.
292
00:19:18,928 --> 00:19:21,777
So, it's possible to
see exactly what kind
293
00:19:21,803 --> 00:19:24,132
of terrain, the cheetahs
were hunting on.
294
00:19:24,549 --> 00:19:28,314
Here, we can see an 11-hour
day in the life of a cheetah,
295
00:19:28,338 --> 00:19:31,251
and there, it starts to hunt.
296
00:19:32,485 --> 00:19:38,055
The cheetah ran in one
circular direction, like this.
297
00:19:38,657 --> 00:19:42,672
The blue represents deceleration,
getting slower here,
298
00:19:42,720 --> 00:19:46,597
and there, the red, where it
gets faster and accelerates.
299
00:19:47,004 --> 00:19:50,246
And the arrows, represent
the power of the force
300
00:19:50,262 --> 00:19:53,098
on the cheetah's
body, as it swirls.
301
00:19:53,192 --> 00:19:56,012
And there, finally,
it made the kill.
302
00:19:56,957 --> 00:20:00,886
367 hunts were studied,
and the top speed of
303
00:20:00,912 --> 00:20:05,719
a chase, was calculated
to be 58 miles an hour.
304
00:20:12,239 --> 00:20:14,510
For more than half
a century, we have
305
00:20:14,536 --> 00:20:17,162
overestimated the
cheetah's speed.
306
00:20:19,396 --> 00:20:22,997
It is nonetheless, still the
fastest animal on land,
307
00:20:23,603 --> 00:20:27,017
and it's greatest feat,
is its acceleration.
308
00:20:27,587 --> 00:20:30,665
Four times that, of Usain Bolt.
309
00:21:01,962 --> 00:21:04,188
The cheetah's legendary,
70 miles an hour,
310
00:21:04,214 --> 00:21:06,612
speed record, is just a myth.
311
00:21:07,120 --> 00:21:09,655
But their true top
speed of 58 miles
312
00:21:09,681 --> 00:21:11,839
an hour, is still extraordinary.
313
00:21:12,073 --> 00:21:14,658
A body, that is fine
tuned for hunting
314
00:21:14,741 --> 00:21:17,666
helps them run, in a
really remarkable way.
315
00:21:18,065 --> 00:21:22,018
But the cheetah's real
impossible feat, so-called,
316
00:21:27,379 --> 00:21:30,886
is the ability to change
speed so extremely quickly.
317
00:21:31,136 --> 00:21:35,286
And that makes it one of the
most maneuverable animals alive.
318
00:21:35,539 --> 00:21:37,765
Aren't you?
Aren't you.
319
00:21:41,013 --> 00:21:45,639
We may have overestimated the abilities
of the flea, and the cheetah.
320
00:21:45,688 --> 00:21:51,265
But both exhibit remarkable feats of
acceleration, in their quest for food.
321
00:21:51,618 --> 00:21:54,500
The flea, to hop on
to a passing host,
322
00:21:54,875 --> 00:21:57,797
and the cheetah, to
outmaneuver its prey.
323
00:22:00,039 --> 00:22:02,039
***
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00:22:02,089 --> 00:22:06,639
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