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ATTENBOROUGH: 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 most.

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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 myths and misunderstandings

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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 1 find
most fascinating of all.

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1n this programme, 1 examine
the remarkable lives

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of two animals that have mastered

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the problems of life in the dark.

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The giant squid,

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which lives in the deepest oceans,

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and owls,

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highly-specialised hunters
that seek their prey at night.

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When you think of animals of the night,

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owls tend to come to mind.

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In fact, not all owls are nocturnal.

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But those that are
have a very similar shaped face.

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Round and flat.

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And the most prominent facial features

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are the large forward-facing eyes.

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These give them a seemingly wise look.

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And, in fact, owls have often
been revered for their wisdom.

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But they have also been linked

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with legends of death and evil.

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They are birds of the night.

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To many, they seem eerie and mysterious.

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But how good is an owl's eyesight?

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Can they really see what we can't?

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The colour picture that forms
at the back of our eyes

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is very much like that

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that forms in the eyes of a bird.

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We have roughly the same number
of colour receptors.

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But when day changes to night,
the picture changes.

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Then different receptors
come into play called rods.

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And owls have a much higher proportion
of rods in their eyes than we do.

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So they are extremely good
at seeing at low light levels.

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Aren't you?

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The barn owl sets off
to hunt shortly after dusk.

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As the light fades, we struggle to see.

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But the owl has no such problem.

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Flying low, it keeps its eyes
trained on the ground,

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looking for any movement of the grass.

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1ts eyes now give it
the edge over its prey.

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And it can hunt at a time
when few other birds can.

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And there's another important difference

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between an owl's eye and ours.

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The pupil in front of the eye, the hole,

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is very much bigger than ours.

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Ours measures around
8 millimetres across.

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An owl's, like this
tawny owl, is around 1 3.

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That means very much more
light can get into the eyes,

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so the picture formed on the retina
is very much brighter.

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In fact, it's about
three times as bright.

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-(HOOTING)
-Oh!

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-(HOOTING)
-Oh!

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so unlike other birds, which
cannot see so well in the dark,

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the owl can remain active
throughout the night.

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But the specialist eyes create problems.

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squeezing a large eyeball
into a relatively small skull

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requires changes.

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The shape of the owl eye
is more tubular than round.

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And this may help to increase
the size of the image

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on the retina at the back.

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But the owl eye shape and size
presents certain problems.

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It doesn't fit snugly into the skull

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and there's no room in the
socket for muscles to move it.

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And there's another problem.

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A closer look at an owl's skull

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shows that its ear
openings are very big.

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so the only way for the tubular
eyes to fit into the skull

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is for them to be placed
in the middle of the face

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in a forward-looking position.

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And this limits the owl's field of view.

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But owls have a trick

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that allows them to dramatically
increase their field of view.

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They can rotate their heads
nearly all the way round.

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Folklore has it that you can kill an owl

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by walking in circles round
a tree in which one is perched

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and so make it twist its head off.

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That, of course, is not true.

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But owls can certainly turn
their heads through

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2 70 degrees in either direction.

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1f we tried to do that,

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we'd tear our arteries
and break our necks.

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so how do owls do it?

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Recently, scientists have discovered

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that it's due to a remarkable
adaptation of their bones.

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Owls' necks, as you can see
in this skeleton of an eagle owl,

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have 1 4 vertebrae.

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That's twice the number that we have.

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And this gives them greater flexibility.

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But only recently, CT scans

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have shown researchers how
the owl can rotate its head

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without passing out.

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Cavities within the neck bones
are 1 0 times larger

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in an owl's neck than in ours,

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giving more room for vital blood vessels
that run up to the owl's head.

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What's more, the carotid
arteries enter the head

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much higher up the neck

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and are centrally positioned.

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And this may help avoid
damage during twisting.

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And the owl's arteries seem
to widen below the brain,

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allowing blood to pool.

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This may create a vital blood reservoir

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that guarantees blood flow to the brain

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should the vessels below be
squeezed while the head is turning.

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So the owl can turn its head
almost all the way round

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without risk of injury.

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so owls have successfully
dealt with the problems

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created by having large eyes.

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(HOOTING)

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But are these eyes really all they seem?

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1t was long thought
that owls can see perfectly

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even on the darkest of nights.

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But that is not the case.

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On cloudy nights and beneath trees
with dense canopies,

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they can only discern
the faintest silhouettes.

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1t's nowhere near detailed
enough to hunt for prey.

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But the owl has another
sense to help it.

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Acute hearing.

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In the 1 8th century, the great French
naturalist Count de Buffon wrote,

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''Their sense of hearing seems to be
superior to that of other birds.

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''And perhaps, to that
of every other animal,

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''for the drum of the ear
is proportionately

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''larger than in quadrupeds.

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''And besides, they can open
and shut this organ at pleasure,

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''a power possessed by no other animal.''

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Well, we know today that that's true

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of some owls, though not all.

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But Buffon was quite right

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to draw our attention
to the remarkable hearing of owls.

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(HOOTING)

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The owl's large ear openings
are not visible

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because they're hidden
beneath the face feathers.

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And, unlike other birds, they have
fleshy outer ears like our own.

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1n many owls, they are positioned

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at slightly different levels
on either side of the head.

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And it's these features that help
them to accurately pinpoint their prey.

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Most owls have very similar
shaped faces, flat and round.

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It's called a facial ruff.

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And it's formed from feathers
that are particularly dense and bristly.

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And they lie flat
on either side of the face,

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just behind the opening to the ears.

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It's thought that they deflect
the sound into the ears.

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In fact, the facial ruff seems
to be a kind of sound amplifier.

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The barn owl has a distinctive
heart-shaped ruff

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and its face acts like a satellite dish,

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focusing the sounds
from below into the ears.

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1ts soft flight feathers

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enable it to move through the air
in all most complete silence,

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so that it can hear the slightest rustle

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and approach its prey undetected.

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But few have as large a facial
ruff as the great grey owl.

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Although it hunts during the day,

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its prey is hidden
under a cover of snow.

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so it has to rely entirely on its ears.

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Studies have shown
that owls' hearing is particularly acute

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for very quiet sounds.

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In fact, part of an owl's brain

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that detects sound has three
times as many neurons

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as its equivalent, in say,
a crow's brain.

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And the hairs of the inner ear,
which detect the vibrations of sound,

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are particularly abundant in an owl.

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And not only that.

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Whereas, the equivalent hairs
in my ear degrade with age,

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in an owl's, they are regrown.

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So whereas my hearing
gets worse as I get older,

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an owl's always remains very acute.

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The owl's ears may, in fact,
be more crucial

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to its nocturnal lifestyle
than its eyes.

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But by combining all its senses,

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it has solved the problems
of living in the dark.

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So it seems that the shape of the face

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helps both the owl's
sight and its hearing.

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So whether or not you
think the owl is wise,

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it certainly has a head
for life in the dark.

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Next, we journey
into the darkest of places

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to try and unravel
the life of a creature

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that has long captured our imagination.

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Here, in the Natural History Museum,
is a specimen of an animal

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that has fascinated humanity
for thousands of years.

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It's a giant squid.

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This particular one was netted
off the Falkland Islands,

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immediately put on ice
and then brought here

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to the museum in London.

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Few museums have complete,

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or as perfectly-preserved
specimen as this one.

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This one measures about eight metres,

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the length of a London bus.

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But others have been caught even bigger.

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One about twice the length,
that weighed around a tonne.

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Very few people have ever seen
one of these creatures alive.

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And that's because they live at
depths of around 1 ,000 metres.

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And down there, it's pitch black.

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So how do these animals manage
to hunt in such conditions?

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That's a question that's proved
exceedingly difficult to answer.

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sailors, a long time ago, told stories

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of having seen a gigantic
squid-like creature

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known as the kraken.

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1t was said to have huge tentacles,
strong enough to grip and sink a ship.

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The tales seemed unlikely
and far-fetched.

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But could the giant squid perhaps

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have been the source
of these extraordinary reports?

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The first clues to this creature
may, in fact, be real

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came from the tales of sailors

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on whaling ships
in the 1 8th and 1 9th centuries.

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Some of them reported
in their ships' logs

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that they often noticed

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strange circular scars on the heads
and jaws of captured sperm whales.

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The scars suggested a fierce wrestling
match with some enormous beast.

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But what creature could
take on a 70-tonne whale?

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Inside of the stomachs
of the whales were clues.

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A number of hard indigestible objects,
like this one.

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It looks a bit like a beak of a parrot.

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But, in fact, it belongs to an entirely
different kind of animal.

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To a cephalopod.

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Cephalopods are marine animals

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that include the octopus,
the squid and the cuttlefish.

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This beak is a mouth part
of one such creature,

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and is used to tear its prey
into small pieces.

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The sailors on the whaling ships
immediately recognised the beak

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as being from a cephalopod.

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But its size
suggested a creature many times bigger

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than any known species.

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Cephalopods have a ring of eight
or ten arms, or tentacles,

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which they use to push food
into their mouth

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in the centre of the ring.

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The arms are equipped with round
suckers to help hold onto their prey.

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And it's the marks from these

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that were found by sailors
on the bodies of sperm whales.

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Could a gigantic squid
have caused such injuries?

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And how massive must it be
to tackle a sperm whale,

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one of the biggest animals
on the planet?

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And then, in 1 873,

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fishermen caught what
they called a sea monster

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off the coast of Newfoundland in Canada.

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After killing it with their knives,
they lost the body.

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But they brought the head and
tentacles to the local clergyman.

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The clergyman bought it off
the fishermen for $1 0

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and displayed it in his living room

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by carefully draping it
over a bath stand

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to show off its many arms and tentacles.

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The photograph clearly proved
that here was a gigantic squid

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00:14:48,527 --> 00:14:52,759
with its beak at the top
and over seven-metre-long tentacles.

249
00:14:53,807 --> 00:14:55,559
Here, at last, was the evidence

250
00:14:55,647 --> 00:14:58,320
that the monster of the deep,
the kraken,

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00:14:58,567 --> 00:15:00,239
really does exist.

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00:15:01,767 --> 00:15:03,439
But the giant squid itself

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00:15:03,527 --> 00:15:07,156
continued to evade scientists
even after its discovery.

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00:15:07,687 --> 00:15:10,201
1t's only since the invention
of submersibles

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00:15:10,287 --> 00:15:13,757
that we've been able to follow it
down into its deep sea home.

256
00:15:14,367 --> 00:15:16,881
Even so, we seem
to have had little success

257
00:15:16,967 --> 00:15:19,162
in finding the elusive giant.

258
00:15:19,687 --> 00:15:23,236
so scientists are now trying
to piece together its biology

259
00:15:23,327 --> 00:15:26,285
by looking at other
closely-related animals.

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00:15:28,447 --> 00:15:30,563
This is an octopus.

261
00:15:30,647 --> 00:15:33,605
And it uses both its
eyes and its tentacles

262
00:15:33,687 --> 00:15:35,518
to explore its surroundings.

263
00:15:36,127 --> 00:15:38,880
The octopus's brain is distributed
throughout its body

264
00:15:38,967 --> 00:15:42,642
so that its arms can control
much of their own movement.

265
00:15:43,327 --> 00:15:45,921
It also has highly complex eyes

266
00:15:46,007 --> 00:15:48,282
and sees in much the same way as we do,

267
00:15:48,367 --> 00:15:51,837
with a lens projecting an image
onto the retina behind.

268
00:15:52,247 --> 00:15:56,479
But while our eyes focus by
squeezing the lens to change its shape,

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00:15:56,887 --> 00:15:59,845
the octopus' eyes focus like a camera,

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00:15:59,927 --> 00:16:02,202
with a lens moving in and out.

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00:16:05,207 --> 00:16:07,801
The giant squid's eyes have
much the same structure

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00:16:07,887 --> 00:16:09,240
as those of an octopus.

273
00:16:09,927 --> 00:16:11,838
But when it comes to size,

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00:16:11,927 --> 00:16:14,760
it has the biggest
eye in the animal kingdom,

275
00:16:14,847 --> 00:16:16,917
as large as a football.

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00:16:18,807 --> 00:16:22,641
For seeing in dim light,
a large eye is better than a small one.

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00:16:23,087 --> 00:16:27,000
so many animals of the deep
have exceptionally big eyes.

278
00:16:30,807 --> 00:16:33,082
But, in order to see at all,

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00:16:33,167 --> 00:16:35,203
there has to be some light.

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00:16:35,287 --> 00:16:38,802
And the giant squid lives
at depths of 1,000 metres.

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00:16:41,847 --> 00:16:45,681
Although very little sunlight
reaches the deeper parts of the ocean,

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00:16:45,767 --> 00:16:48,042
there is another kind of light there.

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00:16:48,327 --> 00:16:50,443
It's produced by the deep sea animals

284
00:16:50,527 --> 00:16:52,961
and is called bioluminescence.

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00:16:53,407 --> 00:16:55,875
The light is produced
by a chemical reaction

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00:16:55,967 --> 00:16:58,959
in the same way as that
in a glow stick does.

287
00:16:59,047 --> 00:17:01,277
When I shake and snap the stick,

288
00:17:01,367 --> 00:17:04,564
two chemicals called luciferin
and luciferase

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00:17:04,887 --> 00:17:08,084
react together to produce
a bioluminescent glow.

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00:17:08,367 --> 00:17:09,436
Like this.

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00:17:10,847 --> 00:17:11,882
There.

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00:17:12,367 --> 00:17:16,280
Some deep sea animals use their
own luciferants to produce light,

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00:17:16,527 --> 00:17:18,643
while in others it's
produced by bacteria,

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00:17:18,727 --> 00:17:20,843
living within special light organs.

295
00:17:22,687 --> 00:17:25,121
A flashing light can act as a lure,

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00:17:25,647 --> 00:17:27,877
or confuse a predator.

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00:17:28,527 --> 00:17:31,758
1t's thought that about 90%
of deep sea creatures

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00:17:31,847 --> 00:17:34,236
produce bioluminescence.

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00:17:34,327 --> 00:17:37,399
And they use it
in a number of different ways.

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00:17:40,287 --> 00:17:42,801
All these fish come from the deep sea,

301
00:17:43,007 --> 00:17:46,363
and they all produce light
in one way or another.

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00:17:46,967 --> 00:17:49,686
This is the football anglerfish.

303
00:17:49,887 --> 00:17:53,766
And it has a modified ray
from its dorsal fin

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00:17:53,847 --> 00:17:55,803
which has a lot of little
tentacles on the top.

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00:17:55,887 --> 00:17:59,436
And the tip of each tentacle
produces a little green light.

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00:17:59,527 --> 00:18:01,836
So it looks as though
there's a little shoal

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00:18:01,927 --> 00:18:05,397
of small creatures, maybe shrimps,
hovering above it

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00:18:05,487 --> 00:18:06,806
in the blackness.

309
00:18:06,887 --> 00:18:10,038
And when some other shrimp
thinks it might join some friends

310
00:18:10,127 --> 00:18:11,321
and come along that way,

311
00:18:11,407 --> 00:18:15,241
the anglerfish simply tilts up,
opens this immense jaw

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00:18:15,327 --> 00:18:16,646
and has its breakfast.

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00:18:18,167 --> 00:18:19,486
This, on the other hand,

314
00:18:19,567 --> 00:18:22,206
is a stoplight loosejaw.

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00:18:22,287 --> 00:18:25,404
And it operates in a different way.

316
00:18:26,927 --> 00:18:32,160
It produces red light from
two little organs at the front.

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00:18:32,567 --> 00:18:36,037
Hardly any other species of fish
in the sea can see red light.

318
00:18:36,127 --> 00:18:39,517
So it can hunt that way
and find its prey.

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00:18:39,807 --> 00:18:44,642
And when it does it opens this
immense loose jaw and engulfs it.

320
00:18:44,887 --> 00:18:45,956
There you are.

321
00:18:46,127 --> 00:18:47,196
Back you go.

322
00:18:50,407 --> 00:18:52,682
But what about the giant squid?

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00:18:53,127 --> 00:18:56,437
Could it also be producing
bioluminescence?

324
00:18:57,127 --> 00:18:59,960
some of its close relatives
apparently can.

325
00:19:01,487 --> 00:19:03,876
This is the vampire squid.

326
00:19:03,967 --> 00:19:07,721
1t has eight arms lined
with tooth-like projections.

327
00:19:10,367 --> 00:19:13,518
And when threatened,
it turns itself inside out,

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00:19:13,607 --> 00:19:15,882
wrapping its body in a dark cloak.

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00:19:19,967 --> 00:19:22,925
1f that doesn't work,
the squid has another trick.

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00:19:24,727 --> 00:19:27,116
small lights at the end of its arms

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00:19:27,207 --> 00:19:30,438
flash like eyes to distract
the predator.

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00:19:36,487 --> 00:19:39,479
With so many creatures
of the deep producing light,

333
00:19:39,567 --> 00:19:43,037
you might think that the giant
squid would do so as well.

334
00:19:44,727 --> 00:19:48,845
But scientists studying their carcasses
have not been able to find any evidence

335
00:19:48,927 --> 00:19:52,681
of light-producing bacteria
or pigments in their bodies.

336
00:19:54,767 --> 00:19:57,964
so it seems
that the ocean's elusive giant

337
00:19:58,047 --> 00:20:00,436
truly hides in the dark.

338
00:20:04,927 --> 00:20:07,395
Although it may not produce
its own light,

339
00:20:07,487 --> 00:20:08,556
the giant squid

340
00:20:08,647 --> 00:20:11,525
can surely see the
bioluminescence of others.

341
00:20:11,967 --> 00:20:15,039
And this may help it to locate its prey.

342
00:20:19,407 --> 00:20:23,366
With no sightings of a living giant
squid since it was first discovered,

343
00:20:23,447 --> 00:20:26,439
we seem to be no closer
to discovering the truth.

344
00:20:27,927 --> 00:20:32,921
But, in 2004,Japanese scientists
finally made a breakthrough.

345
00:20:33,887 --> 00:20:35,923
Using small squid as bait,

346
00:20:36,007 --> 00:20:40,319
they were able to attract
a live giant squid.

347
00:20:43,047 --> 00:20:45,880
These first images are tantalising.

348
00:20:45,967 --> 00:20:49,039
But they still reveal little
of the animal's true behaviour.

349
00:20:49,527 --> 00:20:51,961
Where does it live and how does it feed?

350
00:20:52,367 --> 00:20:55,643
Questions such as these
remain unanswered.

351
00:20:57,287 --> 00:20:59,243
In spite of its great size,

352
00:20:59,327 --> 00:21:02,842
the giant squid has proved
remarkably difficult to find.

353
00:21:03,407 --> 00:21:05,523
No doubt scientists will continue

354
00:21:05,607 --> 00:21:07,916
to search for it and
discover more about it.

355
00:21:08,527 --> 00:21:11,485
But my guess is that the giant squid

356
00:21:11,567 --> 00:21:14,365
is likely to remain ahead of the game.

357
00:21:14,447 --> 00:21:20,079
That this natural curiosity is
likely to see us before we see it.

358
00:21:24,807 --> 00:21:29,437
Both the owl and the giant squid
live in a world with little light

359
00:21:29,807 --> 00:21:32,116
and both have evolved large eyes,

360
00:21:32,207 --> 00:21:34,277
the better to see the world around them.

361
00:21:35,727 --> 00:21:39,720
But while we've unravelled the owl's
ways of surviving in the dark,

362
00:21:39,807 --> 00:21:44,278
much about giant squid
still remains a mystery.