Nature's Strangest Mysteries: Solved (2019–…): Season 1, Episode 15 - Stripeless Zebra - full transcript

Narrator:
Ever wondered?

Why goats would risk
life and limb

To climb the vertical face
of a dam?

These must be some of the most
daring animals I have ever seen.

What would happen
if a zebra had no stripes?

It's this zebra that looks
totally unlike any other zebra.

Narrator: And why is this diver
surrounded by a fishy aura?

If I was the diver,
I would be very confused.

Narrator:
Nature is awe-inspiring.

But sometimes
it just doesn't make sense.

Man: I have never seen
anything like this.



Narrator:
Our team of experts investigates

The weirdest animal behavior...

That's amazing.

Narrator: ...And the
most unexpected events...

What is causing that?

Narrator:
...Ever caught on camera.

Woman: My god!

Narrator: These are...

♪

May 2017.

Cingino in the italian alps.

This 160-feet-tall wall
is a hydroelectric dam in Italy.

Narrator: Italian photographer
roberto bianchetti

Is using a drone
to film the landscape



When he spots some curious
specks moving across the dam.

♪

As he gets closer, he reveals
these specs are actually goats,

And they appear to be defying
the laws of gravity.

[ Goats bleating ]

These must be some
of the most daring animals

I have ever seen.

♪

Nelson: There is almost no place
to get a foothold,

And yet they're scaling
the edge of that cliff.

Narrator: The question is,
what could possibly possess

These anti-gravity goats
to risk life and limb like this?

These crazy goats.
What are these goats doing?

[ laughs ]

Narrator: Could they
have got there by accident?

Now, it may sound a bit silly,

But it isn't uncommon
for animals to get stuck.

So maybe these goats got stuck

Trying to cross
to the other side of the river.

[ Cat meows ]

Nelson:
A lot of animals will do things

That overestimate
their physical abilities.

I mean, everybody's familiar
with cats climbing up

And getting stuck.

Narrator:
Cats have curved claws,

Which are great for climbing up

But not so useful

For when it comes to
climbing down headfirst.

Better to descend butt-first,
which is not instinctive.

Though this cat
has got it all figured out.

The thing is, these goats don't
really look like they're stuck.

If you look at the footage,
they are perfectly at ease

On the face of this dam.

I mean, they don't seem
uncomfortable at all.

Narrator: Turns out these
are not your average goats.

[ Man yodeling ]

♪

They're alpine ibex.

Living high in the mountains,

They're used to life
on the edge.

Males have large horns which
they use to defend territories,

Compete for females,

And make for a great
back-scratcher.

These animals have evolved
in this environment,

And they're
mountain specialists.

They constantly scale cliffs
and vertical cliff faces.

♪

Narrator: But how are these
daredevil goats

Able to achieve these
incredible feats of climbing?

Daly:
Ibex have short legs.

A low center of gravity,
and strong muscles,

As well as split pincer-like
hooves which help them grip.

Nelson: These hooves
are nice and pointy.

But they're also soft
and flexible,

Enough that they
essentially grab

The edge of that cliff face.

Burke: So these split hooves
allow them to perch

And balance on tiny,
little cliff ledges.

[ Goat bleats ]

Narrator: Okay.
We know what makes these goats

Such elite mountaineers,

But this dam is really
upping the stakes.

One wrong move
on this sheer surface,

And it could be game over.

So why risk it?

[ Echoing ] time to look
into the mind of a goat.

Goats are probably one of the
most underrated animals around.

These are
really hardy creatures.

And they're not just hardy.

They'll go anywhere
where there's food.

Narrator: These moroccan goats
climb the argan tree

To feast on leaves and fruit.

Burke: It almost defies logic
and explanation

How these goats are actually
able to climb up into the trees,

But clearly they do,
and they do very well.

Narrator: So, could food be
what's inducing

This foolhardy stunt?

The real key in this mystery

Is looking at what
they're doing on the dam.

They're actually licking it.

Narrator: We all know goats
will eat practically anything.

But rocks?

Daly: It turns out

The bricks of the wall
contain mineral salts.

Narrator: As water leaches
through the face of the dam

And evaporates, it leaves
behind deposits of salt...

Vital minerals for the ibex.

A lot of animals need nutrients
from the environment to survive.

♪

Narrator:
Butterflies in the amazon

Will even drink
the tears of turtles

To meet their salt needs.

♪

Predators often get their salt
from eating other organisms,

But in this case,
they're herbivores.

They eat nothing the plants.

So if they're eating
nutrient-poor vegetation,

They need to supplement
their diet with salt.

You'd think all alpine ibex
would do this,

But it turns out it's only
females and their young.

Narrator: That's because
salts are essential

For the healthy development
of muscle and bone.

It's especially important for
ibex mums when they're feeding,

As these minerals are passed to
their young through their milk.

Narrator: So the reason
these goats risk life and limb

On this vertical dam

Is to ensure their kids
get a healthy diet.

This footage here
absolutely made my stomach turn

When I watched it.

But for them, this is just
another day at work.

♪

Narrator: July 2010.

Etosha national park, namibia.

A land of salt
and crusted dry lake beds

Where animals gather
at scattered oases.

Wildlife filmmaker pete cayless
is tracking a herd of zebra

When he notices a misfit.

Riskin:
It's zebra, zebra, zebra.

W-wait a second.
What was that one?

And it's this zebra that looks
totally unlike any other zebra.

It's black.

Burke:
So here's a real curiosity.

Why doesn't this zebra
have stripes?

Sometimes nature reveals itself
with the exceptions to the rule.

This zebra is a perfect example
of that.

Narrator: Perhaps
the case of the black zebra

Can help us solve a mystery

That's been plaguing scientists
for years.

Burke:
Why do zebras have stripes?

There's obviously some kind
of advantage that this confers,

But what exactly that is,
well, that's a mystery.

Narrator:
First, we need to tackle

A really important question.

Are zebras black
with white stripes

Or white with black stripes?

See, that part
still confused me,

And none of my zebra guys
knew that.

Narrator: It's okay.
We have zebra guys, too.

As a fetus, they are all-black,

And then, early on,
white stripes start to develop.

So they are black
with white stripes

Rather than white
with black stripes.

Narrator: Why didn't our black
zebra... let's call her lucky...

Get her stripes?

Riskin: There's a word
for this black coloration.

It's called melanism.

Which is basically
an inherited trait

That creates a dark pigment.

Narrator: Lucky isn't alone
in her bizarre coloration,

As other misfits
have been spotted,

Including squirrels, wolves...

And the black jaguar.

But what does an unconventional
coat mean for lucky?

One of the defining features
of zebra are their stripes.

So when you see
a genetic mutation like that,

You sort of wonder
whether they might have

Negative consequences
that come from that.

Narrator: So are stripes
essential for survival

Or just cosmetic?

♪

Narrator: In namibia, a rare
black zebra nicknamed lucky

Is spotted,
prompting the question,

Why do zebra
have stripes at all?

Could it be something to do
with where they live?

Across the african continent
in the warmer parts,

You see zebra with much bolder
stripes than in the cold parts.

Narrator: And in namibia,
where lucky was seen,

Temperatures regularly
reach 90 degrees fahrenheit,

Or 30 celsius.

Burke: One thought
was the stripes are creating

A kind of cooling system
along the zebra's hides.

The color black
and the color white

Have very famous properties.

Black absorbs heat really well
and white reflects it.

And if you take infrared
photography of a zebra,

You can see
that the black stripes

Are clearly warmer
than the white stripes.

So what you might get is heat

Being pumped off
the black stripes

And falling back down
on the white stripes,

And so you might get
these little micro air currents

Flowing against the skin.

Narrator: Lucky has a black coat
thanks to her melanism.

So is she roasting
without her white stripes?

Scientists in hungary
recently set out

To investigate
the air-conditioning theory.

They took some barrels,

And they wrapped them
in animal hides,

And some of them were black
and some of them were white,

And some of them
had black-and-white stripes.

And they found
absolutely no differences

In the internal temperature
of these drums.

There was just no evidence
from that study

That the black and white
stripes help with heat.

Narrator: Good news...

Lucky isn't overheating
because of her black coat.

Do stripes protect zebras
in other ways?

One of the original theories
about why zebras have stripes

Was to do with
evading predators.

And one thought was the stripes
might be confusing predators.

When a lion
is going after zebras,

It wants to pick out
one individual

That it's going to tackle,

And if the zebras are
running close to each other,

Maybe it's hard for the predator
to tell which one's which,

And it gets confused.

Perhaps the stripes
sort of fuse together

In that you can't really tell

When one zebra starts
and one zebra finishes.

Maybe that just gives the zebras

A little bit of an edge
for escape.

Narrator: If stripes do help
zebra to evade predators,

Lucky could be an easy target.

But predator eyesight
isn't the same as ours.

How: We find it very easy
to see the stripes of animals,

But a lion would only be able
to see the zebra stripes

When they're in
relatively close range.

The resolution of the predators'
eyes is a lot lower than ours.

Narrator: So from a distance,
a lion wouldn't spot the difference

Between lucky
and the other zebra.

And once lions get closer,
they're using other senses.

Caro: They'll probably
hear or smell the zebras,

And, furthermore, zebras
are an integral part

Of the diet of lions.

So if striping
was a form of confusion,

It really works badly.

Midcap: The stripes of the zebra
may not be deterring land predators.

There's a whole different
predator

That this may be affecting.

Narrator: For many animals
on the african savanna,

Flies are a menace.

[ Flies buzzing ]

Could the zebra's stripes
be a solution to this problem?

♪

So, there's an easy way
to test this idea,

And that's just to
dress up some horses.

Narrator:
Oh, this sounds fun.

♪

Narrator: In namibia,
lucky the black zebra

Is surviving without stripes.

But she might be
at a disadvantage

When it comes to flies.

[ Flies buzzing ]

Martin how studies the ways
animals view the world.

He's come up with a test to see
whether flies could be confused

And therefore repelled
by stripes.

Zebra can be stubborn subjects,

So he uses the next
best thing... horses.

We printed out lots of
different patterned rugs

That we could place over horses.

These rugs were either a solid
color like a black or a gray,

Or they had stripes.

Narrator:
Martin uses cameras

To track flies
as they approach the horses.

He then maps their paths
with a red line.

First up, the gray rug.

We've got a fly that comes in
from the side here,

Slows down,
hovers around a little bit,

Touches down,
and then it decides actually

It's going to land here,

So it's a really nice
controlled landing.

Narrator: No problems
with plain colors like gray.

But how do flies
react to stripes?

The fly comes in
from the side here.

It comes in really fast,

And then it does this
abort behavior at the end,

And it flies off
in the other direction.

So it's a really clear
difference in behavior.

Now, why would a fly
get freaked out by stripes?

Narrator:
Well, flies perceive the world

Very differently to us.

Their resolution
is much lower than ours,

But they're very interested
in movement.

They have a very fast lifestyle,

Flying around,
landing on objects,

And avoiding things,

And so their eyes
have to work extremely quickly.

Midcap: They can see four times
faster than the human eye,

So they essentially see
everything in slow motion,

Which is why it's so difficult

To swat at a fly that's been
bugging you all afternoon.

Narrator: But what effect
might stripes have on fly sight?

To find out,
martin has mocked up

What a zebra looks like
to a fly.

From a distance,
it's like a blurry gray horse.

But as it gets closer...

So, we can simulate
the approach of our fly

As it's coming to land
on a zebra.

As the fly comes in closer,
these stripes suddenly appear

Within the resolution
of the fly's eyes.

We think the stripes
are having an illusion effect

On the motion vision
of the flies.

Midcap: You can see this for yourself
when you look at a barber's pole.

Now, these have diagonal stripes
that are moving horizontally,

But they look like
they're moving upwards.

Narrator: So trying to land
on a zebra is a pretty weird

And disorienting experience
for flies.

For the flies,
it's like an optical illusion.

It's all trippy and crazy

And makes it feel like
the whole room is spinning,

And it's just too much
for the fly to handle,

And it doesn't land there.

It's unbelievable,
but it's true.

Flies get confused by stripes.

Burke: So it seems
the most likely explanation

As to why zebras have stripes

Is to avoid getting bitten
so frequently by flies.

Narrator: The question now is,
why isn't the savanna covered

With other stripy animals?

Zebra are quite susceptible
to attack by biting flies,

Given that they have
much shorter fur

Than most of the other animals
on the savanna.

Narrator: So what happens
to a zebra with no stripes?

Caro: Most biting insects

Are attracted
to large, dark objects,

And that's what they home in on.

Narrator: Uh-oh.
Sounds like someone we know.

Looks like
our black beauty, lucky,

Might be more popular with flies
than the other zebra.

But she's managing to survive
without her stripes.

Things aren't always
so black-and-white after all.

♪

August 2018. Hurgarda, egypt.

Underwater enthusiast rene thies

Is on a scuba-diving excursion
with his family.

♪

Nosal:
This is the red sea,

A diverse, unique area
with hundreds and hundreds

Of species of fish and corals.

Narrator: As the group heads
toward the open sea,

Rene suddenly spots
a strange swarm

Around his stepson tobias.

Nelson: Oh, my goodness.

It's like he's surrounded
by a force field of fish.

The big mystery here is,
why are all of those fish

Circling the diver?

Nosal: If I was the diver,
I would be very confused.

♪

Narrator: In the red sea,
a diver finds himself

Surrounded by
a mysterious sphere.

Clearly, there's something
fishy going on.

♪

Nelson: Could the diver
have found himself

In the middle of
some elaborate mating ritual?

We know that a lot of fish
form giant schools to mate.

Parrotfish do it.

Surgeonfish do it.
Groupers do it.

They'll go off of a reef,

And at one time,
they'll start mating.

Narrator: During these mass
mating, or spawning, events,

Females release eggs
into the water

And males release sperm.

But if this was
a spawning event,

You'd see a milky cloud
of sperm and eggs,

And we're not seeing that here.

Nelson: Could these fish just be
looking for some kind of shelter?

In the open ocean, you can
think of it like a giant desert,

And then here you are as a fish
and you got predators around.

So you have to find a way
to hide from them.

Nosal:
If these fish come across

Anything that resembles
a shelter,

It's going to be
a hot commodity.

They are going to be
attracted to it.

This is why fish like to gather

Underneath peers
and peer pilings

Because it provides them
some shelter.

Narrator:
Perhaps the fish in the clip

Are attracted to the diver

Because they see him as shelter.

But in this case, the fish
are not under the diver.

They're swimming all around him.

Narrator: And they appear to
be moving in a coordinated way,

Rippling around the diver
while staying in a tight ball.

Other animals like starlings
and also wildebeest

Will gather together
for safety in numbers.

Could the fish be using
a similar tactic?

♪

Nelson: A lot of fish that are
being preyed upon by larger fish

Will form a giant swirling mass.

Now you're not just one fish
that a predator's going after.

You're this mass,
and it can kind of confuse

A predator diving in

Because you have fish
going everywhere.

Narrator:
And that looks a lot like

The sphere of fish
around our diver.

Galante: What you're seeing here
is a bait ball.

There's safety in numbers,

So these fish
are all congregating

And getting as tightly packed
as they can.

Basically to dilute the risk
of an individual being eaten.

Narrator: The shoal of fish
contracts, expands,

And even parts
before coming back together

Without missing a beat.

There's no leader.

Each fish coordinates
with its neighbor,

Who coordinates with
its neighbor, and so on.

And the movement is synchronized
in the blink of an eye.

But why did these fish form
a bait ball to begin with?

There's an interesting twist,

Because if you watch
the entire video,

You see that out of nowhere
a large whale shark appears.

Nelson: At the beginning,
we didn't realize

There was a big predator around.

The fish knew it,
but we couldn't see it yet.

Nosal: So could these fish
have formed the bait ball

Because they were afraid
of the whale shark?

Narrator: These giant fish swim
with their mouths open wide

To scoop up plankton
and small fish.

Oddly, the whale shark
does not try to target the fish.

It doesn't react
to the fish in any way.

Just lazily swims on by.

Narrator:
Perhaps it's already had dinner,

Which is lucky for these fish.

The fish, they had to take
evasive action,

So they formed a bait ball
around the diver.

Narrator: The fish didn't see
the diver as a threat,

And he offered some rare shelter
in the open sea.

Nosal: And even though
there was a risk of everybody

Being in the same place
at the same time,

It was a gamble worth taking.

Narrator: The whale shark
wasn't the only threat here.

On closer inspection,
there are other predatory fish

Looking for an easy meal.

So forming a bait ball
was the right call.

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