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The natural world is full of
extraordinary animals
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with amazing life histories.
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Yet certain stories are
more intriguing than others.
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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
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fantastic myths
and misunderstandings.
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Others have only recently
revealed their secrets.
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These are the creatures
that stand out from the crowd,
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the curiosities that I find
particularly fascinating.
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Pigeons are so common that we tend
to take them for granted.
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But in fact,
they are superb navigators
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and can find their way home
from hundreds of miles away.
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And the dung beetle will roll
a dung ball in a straight line
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even though it's head down
and walking backwards.
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How on earth do these creatures
manage to find their way?
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Pigeon fanciers know
that if they take homing pigeons
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to somewhere
where they've never been before,
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even if it's tens, even hundreds of
miles away, and then release them,
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they will, after circling
in the sky, head for home.
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These come from over there.
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Let's see what happens.
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Well, they certainly seem to be
heading in the right direction.
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But how do pigeons
find their way back home
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over totally unfamiliar territory?
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It seems the more mysterious to us
because it's something we can't do
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unless we have all kinds of
special equipment.
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But science is now beginning to find
some of the answers.
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The homing pigeon is a domesticated
descendant of the wild rock pigeon
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which lives on cliffs and ledges
along our coasts.
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When humans started to domesticate
them, they inevitably selected
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those birds that were particularly
good at returning to their roosts.
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Pigeons are thought to be
the very first birds
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to be domesticated by mankind,
many thousands of years ago.
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Since then, they've been bred
into many different varieties,
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including homing pigeons.
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And the varied appearance
of this flock around me
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is evidence of
that domesticated past.
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Since then, of course, they've come
to live alongside us in our cities
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and giving many of us
a lot of pleasure.
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Come on.
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It was not only their homing ability
that made pigeons
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so popular with breeders,
they are also superb flyers.
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Their powerful wing muscles make up
nearly half their body weight
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and enable them to fly
at speeds of 60mph.
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They're among the greatest
long-distance athletes
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in the bird world.
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And pigeon fanciers have
delighted in breeding them
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in order to race them
competitively.
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Mankind has also used pigeons
for a very practical purpose...
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..as messengers.
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It was during the two World Wars
that pigeons played a crucial role
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in carrying messages home
from the front line.
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Nearly a quarter of a million birds
served in the wars
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and helped save thousands of lives.
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One such bird was Cher Ami,
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a female donated by
a British pigeon fancier
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for use by the United States Army
during World War I.
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During one battle in France in 1918,
more than 500 soldiers
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from the US infantry became trapped
behind enemy lines.
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Worse, they were then fired upon
by their own troops
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who didn't know they were there.
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Within 24 hours, more than
half of them had been killed.
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With no other options,
the commander, Major Whittlesey,
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desperately tried
to send messages back by pigeon.
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The first two birds were shot down
and only Cher Ami was left.
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For several moments, she flew with
bullets zipping all around her,
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and eventually she was brought down.
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She'd been shot through the breast,
blinded in one eye
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and her leg was left
hanging by a tendon.
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Astonishingly, the injured bird
managed to take flight again
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and arrived back at her loft
at the division headquarters
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in just 25 minutes.
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Cher Ami's message helped save
the lives of 194 soldiers.
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Her name in French, of course,
means Dear Friend.
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When the Second World War broke out,
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Britain's pigeon fanciers once again
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gave their pigeons
to the war effort
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to provide what was called
the National Pigeon Service.
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This elite squad of birds was
extremely valuable and successful.
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98% of their messages got through.
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The Germans, realising how important
the pigeons had become,
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fought back with specially trained
pigeon snipers.
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They also retaliated in another way,
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by using the pigeon's natural
enemies - peregrine falcons.
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Pigeons played such a vital role
in the war
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that many were celebrated as heroes.
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In 1943, this medal,
the Dickin Medal,
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was founded to honour these animals.
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It was awarded to individuals
that appeared,
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if you'll allow
a little anthropomorphism,
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to have displayed
particular bravery.
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And it's sometimes referred to
as the Victoria Cross for animals.
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Of the 54 medals presented
during World War II,
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32 were given to pigeons.
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We may have prized pigeons
for centuries
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for their skills in finding
their way through the skies,
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but for a long time
we had no idea how the birds did it.
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Some suggested that
pigeons used the sun.
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Others that they were guided
by the Earth's magnetic field.
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But proving either was
surprisingly difficult.
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A breakthrough came
from an American scientist
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at Cornell University
in the 1960s.
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William Keeton attached magnets
to the backs of some pigeons,
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but not to others,
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and found that when the sun was out,
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both groups were able
to make their way home.
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But when the sun was hidden
behind clouds,
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the birds carrying magnets got lost.
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Keeton deduced that this was because
the signals from their magnets
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swamped the much weaker ones
coming from the Earth.
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So he established that pigeons
can use either the sun
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or the Earth's magnetism
to find their way around,
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according to conditions.
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00:08:40,840 --> 00:08:45,000
But how do the birds detect
the Earth's magnetism?
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This compass has
a magnetised needle,
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which is sensitive to the Earth's
magnetic field.
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It will always point north,
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allowing you to check the direction
that you're travelling in.
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But what about pigeons?
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What could they be using
to detect magnetic fields?
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Scientists were puzzled
because they couldn't find
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any cells or organs in birds
that were sensitive to magnetism.
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Then, in 2007, microscopic clusters
of iron-rich cells
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were found in the beaks
of homing pigeons,
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and it was thought that these might
help them to detect magnetic forces.
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But only five years later,
new research shattered that idea.
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It seems that the cells in fact
are a defence against infection
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and have nothing whatsoever
to do with magnetism.
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So the search for the pigeon's
magnetic compass still continues.
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But we are now beginning
to understand the other aspects
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of their navigational skills.
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A compass is just one of the tools
we need for navigation.
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But it's not much help
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unless you know in which direction
your destination lies.
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And to know that,
you need a map of some kind.
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One way of creating
a map in your mind
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is to memorise the prominent
features of a landscape.
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Scientists at Oxford University
are now using GPS technology
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to discover if pigeons do this.
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This bird has a GPS transmitting
device strapped to its back
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in a specially designed backpack
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which causes it
very little discomfort.
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And that will record the progress
of the bird, second by second,
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once I let it go.
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It comes from a loft over there
about six miles away in Oxford.
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Let's see whether or not she heads
in that direction.
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Off you go.
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Birds, like this,
that are released in a new place
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still ahead confidently
in the direction of their home loft.
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How do they do it?
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Data from GPS trackers
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and cameras attached
to the backs of pigeons
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have helped to answer that question.
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At first, a bird released
in an unfamiliar place
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will use the sun or the Earth's
magnetic field to get its bearings.
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But if you plot its movements
on a map,
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you can see that at first it doesn't
find the shortest route home.
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Then something changes.
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After repeated releases, the bird
is able to use its experience
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to take a more direct way back.
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So it appears that pigeons learn to
recognise features of the landscape
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such as hedgerows and trees,
or even roads and buildings.
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They then memorise these to create
a mental map of the area
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and by following familiar landmarks,
they find their way back home.
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It seems that
pigeons are creatures of habit.
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They like to stick to the routes
they know well.
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Here are some tracks of a pigeon
that lives in its home loft up here
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and was taken repeatedly
to this point here.
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Watch what happens.
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It consistently makes a beeline
for the major A road
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that conveniently runs past
its home loft.
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And even when released some distance
from this road,
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it will cut across to it
and then follow it all the way home,
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as shown by the red lines.
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Some birds even fly
around roundabouts
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before choosing the exit
that will lead them back.
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So it seems that pigeons use
methods of navigation
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more like ours
than we might have imagined.
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We now know that pigeons have
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a whole range of navigational
techniques at their disposal
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and can call on them as needed.
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It's a remarkably sophisticated
system
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that enables them to find their way
in nearly any situation.
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We've learned a lot
about the pigeon's homing skills,
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but some mysteries still remain.
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In 1997, over 60,000 British birds
were released
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during a pigeon race
in southern France.
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Most of them didn't make it
and were never seen again.
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In pigeon racing terms, the loss
of so many birds was unheard of.
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A disaster.
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One bird might get lost,
but tens of thousands?
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To get back to their lofts
nearly 500 miles away,
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the pigeons had to cross
the English Channel.
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00:14:14,645 --> 00:14:17,400
It was not an unusually long
or difficult journey
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for a racing pigeon,
so why did the birds not make it?
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Well, there was
a strange coincidence.
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At the very same time the racing
pigeons were crossing the Channel,
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00:14:30,965 --> 00:14:35,360
a Concorde supersonic airliner
was flying along the Channel
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00:14:35,485 --> 00:14:38,680
on its morning flight
from Paris to New York.
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The Concorde generates a shock wave
almost 100 miles wide.
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The pigeons flying below
could not have escaped it.
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00:14:49,125 --> 00:14:53,600
Could it be that this enormous
wave of sound blotted out
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all other acoustic information?
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00:14:58,480 --> 00:15:02,880
We know that pigeons can hear
low-frequency infra-sounds
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such as those generated
by ocean waves.
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00:15:06,920 --> 00:15:12,120
And these might provide them with an
acoustic map of their surroundings.
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The jury is still out as to
whether pigeons really do use
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infra-sound to navigate
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00:15:19,405 --> 00:15:23,200
and whether that explains the case
of the disappearing pigeons.
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00:15:24,360 --> 00:15:27,480
But it's an intriguing possibility.
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The familiar pigeon continues
to surprise us.
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00:15:34,325 --> 00:15:37,960
And even today, we're a long way off
from understanding
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00:15:38,085 --> 00:15:40,000
all its route-finding techniques.
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00:15:42,840 --> 00:15:47,600
The small dung beetle has a brain
no larger than a grain of rice.
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00:15:47,725 --> 00:15:53,240
But, like the pigeon, it is capable
of astonishing navigational feats.
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00:15:57,200 --> 00:16:00,640
Moving large loads by walking
head down and backwards
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00:16:00,765 --> 00:16:03,280
must surely be one of
the most bizarre ways
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00:16:03,405 --> 00:16:04,960
of collecting your food.
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00:16:07,240 --> 00:16:08,920
Dung beetles are well known
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for rolling their balls of dung
in this way.
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00:16:11,725 --> 00:16:13,720
But why do they do so?
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00:16:13,845 --> 00:16:16,440
And how can they see
where they are going?
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Ball rolling by dung beetles
is probably
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00:16:22,525 --> 00:16:26,280
one of the oldest recorded accounts
of animal behaviour,
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00:16:26,405 --> 00:16:29,000
dating back nearly 2,000 years.
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00:16:29,125 --> 00:16:32,920
These insects were held sacred
by the ancient Egyptians,
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00:16:33,045 --> 00:16:37,000
and in the fifth century,
an Egyptian scholar called Horapollo
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00:16:37,125 --> 00:16:42,440
described the dung beetle as
rolling its ball from east to west.
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00:16:42,565 --> 00:16:45,760
It seems that he was suggesting
that the beetles always
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00:16:45,885 --> 00:16:48,760
moved their dung
in a particular direction.
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00:16:48,885 --> 00:16:50,760
But how true is that?
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00:16:50,885 --> 00:16:55,200
In the following 2,000 years, little
was done to examine the question.
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00:16:57,360 --> 00:17:01,040
Dung beetles feed on what is,
to the animals that produce it,
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00:17:01,165 --> 00:17:04,280
a waste product - dung.
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00:17:04,405 --> 00:17:08,320
But in fact, there's more than
enough nourishment in one dropping
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00:17:08,445 --> 00:17:10,880
to sustain a great number
of beetles.
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00:17:12,280 --> 00:17:16,520
They locate a newly dropped pile
using their sense of smell.
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00:17:17,600 --> 00:17:20,280
Their strong and powerful legs
enable them
240
00:17:20,405 --> 00:17:21,840
to break up the dropping
241
00:17:21,965 --> 00:17:24,520
and their mouthparts
are specially shaped
242
00:17:24,645 --> 00:17:27,920
to extract the nutrients
and moisture that they need.
243
00:17:29,680 --> 00:17:33,400
They are, in fact, one of
our planet's great recyclers.
244
00:17:38,680 --> 00:17:41,840
Dung beetles are found
all over the world.
245
00:17:42,960 --> 00:17:47,520
There are over 6,000 species and
they come in all shapes and colours.
246
00:17:49,200 --> 00:17:51,560
But they have one thing in common -
247
00:17:51,685 --> 00:17:54,480
they all feed on dung.
248
00:17:57,080 --> 00:17:59,840
Some of them,
like this scarab beetle...
249
00:18:01,000 --> 00:18:04,360
..have rows of projections
on the head,
250
00:18:04,485 --> 00:18:07,600
which were likened
by the ancient Egyptians
251
00:18:07,725 --> 00:18:10,400
to the rays of the rising sun.
252
00:18:10,525 --> 00:18:13,960
The broad front legs
also carry spines.
253
00:18:14,085 --> 00:18:18,360
These are adaptations for digging
and shaping dung balls,
254
00:18:18,485 --> 00:18:21,000
while the back legs are flattened
255
00:18:21,125 --> 00:18:24,400
and have tiny hairs
for controlling the ball.
256
00:18:26,120 --> 00:18:30,000
But most dung beetles
don't roll balls.
257
00:18:30,125 --> 00:18:32,400
They live either in the dung itself
258
00:18:32,525 --> 00:18:36,200
or tunnel directly into the soil
beneath the dropping.
259
00:18:36,325 --> 00:18:39,960
Only 10% transport dung
above ground.
260
00:18:40,085 --> 00:18:43,320
And they do so because
competition near a pile of dung
261
00:18:43,445 --> 00:18:45,080
can be very fierce.
262
00:18:47,720 --> 00:18:51,280
The first ones at the scene
are usually the rollers.
263
00:18:54,120 --> 00:18:59,000
They take a little lump, mould it
into a ball and then start rolling.
264
00:19:04,840 --> 00:19:07,560
But that's easier said than done.
265
00:19:09,120 --> 00:19:11,760
Rivals are on the lookout
for an easy meal
266
00:19:11,885 --> 00:19:15,480
and will only too quickly
steal a ball if they can.
267
00:19:28,400 --> 00:19:32,480
With competition so intense,
some species roll their ball away
268
00:19:32,605 --> 00:19:35,080
as quickly as possible
and then bury it.
269
00:19:37,440 --> 00:19:39,040
They can then eat it later
270
00:19:39,165 --> 00:19:42,160
without the risk of another
stealing their meal.
271
00:19:45,680 --> 00:19:50,640
Dung beetles appear to roll their
balls of dung with great purpose.
272
00:19:50,765 --> 00:19:54,800
But it's only recently been
discovered just how determined
273
00:19:54,925 --> 00:19:58,240
they can be to do so
in one particular direction.
274
00:19:58,365 --> 00:20:02,080
Watch what happens
if I put this dung beetle
275
00:20:02,205 --> 00:20:03,520
on this board here.
276
00:20:05,400 --> 00:20:09,080
And then put an obstacle in its way.
277
00:20:11,240 --> 00:20:13,080
And what does it do?
278
00:20:14,160 --> 00:20:16,080
It's going to go around.
279
00:20:16,205 --> 00:20:17,880
Excellent.
280
00:20:18,840 --> 00:20:22,000
And it resumes
its previous direction.
281
00:20:24,240 --> 00:20:26,600
It's clear that the beetle knows
exactly
282
00:20:26,725 --> 00:20:29,280
in which direction
it wants to travel
283
00:20:29,405 --> 00:20:33,560
and will continue to do so even
when it's deflected by obstacles.
284
00:20:35,480 --> 00:20:38,520
Now, let's make things
even more difficult
285
00:20:38,645 --> 00:20:39,960
using this turntable.
286
00:20:41,040 --> 00:20:43,240
Let's see which direction
287
00:20:43,365 --> 00:20:44,560
he wants to go.
288
00:20:46,360 --> 00:20:48,680
He's going to come towards my hand.
289
00:20:48,805 --> 00:20:52,840
Now I'll turn the world
through 90 degrees beneath his feet
290
00:20:52,965 --> 00:20:55,160
and yet he maintains
291
00:20:55,285 --> 00:20:57,000
the same direction.
292
00:20:57,125 --> 00:20:59,880
Why should it want to do that?
293
00:21:00,005 --> 00:21:02,360
It's quite extraordinary.
294
00:21:02,485 --> 00:21:05,680
He corrects his course
instantaneously.
295
00:21:05,805 --> 00:21:07,880
How does he know how to do this,
296
00:21:08,005 --> 00:21:11,720
and why is he so determined
to travel in a set direction?
297
00:21:15,280 --> 00:21:17,800
The answer is, in fact,
quite simple.
298
00:21:18,880 --> 00:21:21,040
The fastest way to make a getaway
299
00:21:21,165 --> 00:21:23,880
is to roll your ball
in a straight line.
300
00:21:26,200 --> 00:21:29,280
And that is exactly
what the beetles try to do.
301
00:21:34,320 --> 00:21:36,600
Using only its front legs,
302
00:21:36,725 --> 00:21:40,800
a beetle can move a dung ball that
is up to 60 times its own weight.
303
00:21:43,320 --> 00:21:48,080
But walking head down and backwards
has its own problems.
304
00:21:48,205 --> 00:21:50,440
You can't see where you're going...
305
00:21:53,040 --> 00:21:55,240
..or watch out for danger.
306
00:22:10,080 --> 00:22:13,560
With competition around
the pile of dung so intense,
307
00:22:13,685 --> 00:22:17,920
it's obviously a good thing to get
away from it as quickly as possible.
308
00:22:18,045 --> 00:22:21,440
But how do the beetles decide
in which direction to go?
309
00:22:21,565 --> 00:22:25,480
Well, it seems it's all to do with
a little dance that they perform
310
00:22:25,605 --> 00:22:27,040
on top of their dung balls.
311
00:22:27,165 --> 00:22:29,280
Let me see
if I can persuade this one to do it.
312
00:22:32,960 --> 00:22:35,400
I'll try to get it
to walk up this ramp
313
00:22:35,525 --> 00:22:37,280
until it falls off the end
314
00:22:37,405 --> 00:22:39,720
and is separated from its ball.
315
00:22:42,080 --> 00:22:44,200
Watch what it does then.
316
00:22:48,280 --> 00:22:50,080
This little dance was once
317
00:22:50,205 --> 00:22:52,640
regarded as being
a sign of happiness,
318
00:22:52,765 --> 00:22:55,600
that the beetle was delighted
to have found a dung ball.
319
00:22:55,725 --> 00:22:58,200
But actually,
it's much more than that.
320
00:22:58,325 --> 00:23:02,440
It's a way of deciding
which direction it should go.
321
00:23:02,565 --> 00:23:06,400
And what does it use as a cue
to make that decision?
322
00:23:06,525 --> 00:23:10,840
Well, recent research is beginning
to produce the answer.
323
00:23:13,800 --> 00:23:16,440
What appears to be a dance
is actually
324
00:23:16,565 --> 00:23:19,400
a way of looking around
to get its bearings.
325
00:23:22,960 --> 00:23:24,880
But what exactly is it looking for?
326
00:23:29,080 --> 00:23:32,480
We can test what the beetles
are using for a cue
327
00:23:32,605 --> 00:23:34,520
by fitting them with caps.
328
00:23:34,645 --> 00:23:38,200
This cap allows the beetle
to see the ground beneath,
329
00:23:38,325 --> 00:23:40,120
but not the sky above.
330
00:23:40,245 --> 00:23:43,960
Compare that with this one
without a cap.
331
00:23:46,320 --> 00:23:47,760
Making up its mind.
332
00:23:47,885 --> 00:23:49,400
And away it goes.
333
00:23:50,400 --> 00:23:52,880
This one is still baffled.
334
00:23:55,000 --> 00:23:57,760
The beetle with the cap
clearly can't decide
335
00:23:57,885 --> 00:23:59,360
in which direction to go.
336
00:24:05,320 --> 00:24:07,200
Such experiments show
337
00:24:07,325 --> 00:24:11,680
that dung beetles have to see
the sky in order to orientate.
338
00:24:14,560 --> 00:24:19,440
Their eyes are split in two halves
by shovel-like extensions
339
00:24:19,565 --> 00:24:21,280
on the sides of the head.
340
00:24:22,480 --> 00:24:25,080
So, as they roll
their balls of dung,
341
00:24:25,205 --> 00:24:29,080
the upward-facing half
can watch the sky above
342
00:24:29,205 --> 00:24:32,400
and use the sun
as a celestial compass.
343
00:24:34,920 --> 00:24:38,920
But, contrary to what that
ancient Egyptian scholar claimed,
344
00:24:39,045 --> 00:24:41,960
they don't always travel
from east to west.
345
00:24:44,600 --> 00:24:47,360
Each beetle seems to choose
a particular direction
346
00:24:47,485 --> 00:24:50,920
away from the dung heap
and then keeps to that course.
347
00:24:56,840 --> 00:24:58,800
But why should anyone suppose
348
00:24:58,925 --> 00:25:02,760
that the dung beetle always
rolls its dung from east to west?
349
00:25:02,885 --> 00:25:07,120
Well, the ancient Egyptians believed
that their sun god, Khepri,
350
00:25:07,245 --> 00:25:11,600
was responsible for rolling the sun
across the sky every day
351
00:25:11,725 --> 00:25:13,240
in just that direction.
352
00:25:14,880 --> 00:25:17,640
The scarab,
the Egyptian dung beetle,
353
00:25:17,765 --> 00:25:21,000
similarly rolls its dung ball
from dawn to dusk
354
00:25:21,125 --> 00:25:23,440
and came to symbolise the sun god.
355
00:25:26,000 --> 00:25:31,680
And so the god Khepri was often
depicted with a scarab for a head.
356
00:25:34,280 --> 00:25:37,120
The Egyptians also saw the scarab
357
00:25:37,245 --> 00:25:40,160
as a symbol of life
and resurrection.
358
00:25:40,285 --> 00:25:44,160
The adult beetle would disappear
underground with the ball of dung,
359
00:25:44,285 --> 00:25:47,720
and when the eggs hatched,
shiny, new scarab beetles
360
00:25:47,845 --> 00:25:50,880
would seem to appear magically
out of nowhere.
361
00:25:51,005 --> 00:25:55,080
So the scarab came to symbolise
creation, life
362
00:25:55,205 --> 00:25:57,000
and even rebirth.
363
00:25:59,240 --> 00:26:02,640
It's easy to see how the sun helps
dung beetles
364
00:26:02,765 --> 00:26:04,760
to navigate during the day.
365
00:26:06,240 --> 00:26:08,880
But some beetles are nocturnal.
366
00:26:10,080 --> 00:26:12,680
How do they keep
on a straight course?
367
00:26:19,160 --> 00:26:20,760
On a clear night,
368
00:26:20,885 --> 00:26:24,360
the moon and millions of stars
illuminate the sky,
369
00:26:24,485 --> 00:26:27,640
just as they appear to do
in this planetarium.
370
00:26:27,765 --> 00:26:31,080
This is a nocturnal scarab beetle.
371
00:26:31,205 --> 00:26:34,760
And scientists have recently
discovered that it can use
372
00:26:34,885 --> 00:26:38,000
the light from the sky to navigate.
373
00:26:39,160 --> 00:26:41,080
But there is a puzzle.
374
00:26:41,205 --> 00:26:45,160
The scarab beetle has
very, very small eyes.
375
00:26:45,285 --> 00:26:48,240
And whereas it can
certainly see the moon,
376
00:26:48,365 --> 00:26:51,240
it can't distinguish
individual stars.
377
00:26:51,365 --> 00:26:53,960
So how then does it navigate
378
00:26:54,085 --> 00:26:56,440
on a moonless night?
379
00:27:00,080 --> 00:27:02,600
The brightest light in the night sky
380
00:27:02,725 --> 00:27:06,600
comes from the great band of stars
known as the Milky Way.
381
00:27:07,760 --> 00:27:11,000
And in the southern hemisphere,
where these beetles live,
382
00:27:11,125 --> 00:27:14,160
the Milky Way is particularly vivid.
383
00:27:17,040 --> 00:27:20,600
Researchers have discovered that,
as long as the Milky Way is in view,
384
00:27:20,725 --> 00:27:24,920
the beetle and its ball can
roll along and stay on course.
385
00:27:26,400 --> 00:27:28,680
Without this bright band of light,
386
00:27:28,805 --> 00:27:32,320
the beetle has no reference point
and is lost.
387
00:27:34,440 --> 00:27:38,720
The revelation that the beetles used
starlight to navigate
388
00:27:38,845 --> 00:27:41,240
astonished the scientific world.
389
00:27:41,365 --> 00:27:44,960
How extraordinary that
a tiny insect could use
390
00:27:45,085 --> 00:27:48,520
the edge of our galaxy
to find its way around.
391
00:27:48,645 --> 00:27:52,480
Had the ancient Egyptians known
that, surely they would have
392
00:27:52,605 --> 00:27:57,760
felt vindicated in giving the scarab
the status of a god.
393
00:28:00,160 --> 00:28:05,160
So, the dung beetle and the pigeon
are both ordinary creatures
394
00:28:05,285 --> 00:28:08,480
that have found
extraordinary solutions
395
00:28:08,605 --> 00:28:11,440
to the problem that faces us all -
396
00:28:11,565 --> 00:28:14,000
how to find the way.
33735
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