700 requins dans la nuit (2018) - full transcript

[tense music playing]

[male narrator] This is the biggest pack
of gray sharks on Earth.

Seven hundred of them.

These awesome predators
gather under the full moon

for a single purpose:

to feed.

Now, a team of scientists is diving in,

using state-of-the-art tech

to capture the epic hunt
like never before,

and find out what really goes on
inside this massive shark swarm.

Seven hundred gray sharks



live in the middle of the vast
Pacific Ocean,

around an island invisible from space,

about 250 miles from the island of Tahiti,

the atoll of Fakarava.

The atoll is a ring of coral

pierced by breaches
that link the lagoon to the ocean.

The deepest of these
are called "channels."

Hidden away in Fakarava's
southernmost channel

is the world's densest population
of gray reef sharks.

700 of them live right here
in this valley of coral,

classified as a UNESCO biosphere reserve.

Much of their behavior is a mystery.

What attracts them here
in such huge numbers?

Are there leaders whom the rest follow?



[indistinct chatter]

A team of more than
20 divers and scientists

are here to find out.

Leading the team is biologist
and photographer Laurent Ballesta.

[indistinct chatter]

Laurent and his team
have been here before,

four years ago, to check out rumors
of vast schools of thousands of groupers

coming here to reproduce
during the June full moon,

which acts as a signal to them
to start laying their eggs.

The rumor was true.

The Fakarava channel is the site

of one of the largest aggregations
in the world,

17,000 groupers.

Inevitably, they drew the sharks.

There were so many of the predators

that the team kept counting
and recounting them.

One camera traveled the whole
length of the southern channel,

about half a mile.

The footage revealed
an astonishing count of 700;

705 to be precise.

That's the highest density
anyone's ever seen.

Laurent and his team's curiosity
is stronger than their fear.

They decided to scout
the location at night,

amidst hundreds of sharks.

[in French] What we observed,
when we discovered these grounds,

was that during the day, the sharks
that were clustered at mid-depth

would suddenly swim to the bottom,

and start raiding hither and thither
at the bottom of the pass.

We didn't dare get close to them.

We stayed above, 10 meters above them.

We filmed them from afar, with our knees
curled up near our shoulders.

We were terrified to let
anything dangle near those jaws.

The water was seething with sharks,
an impenetrable ball of them.

[rustling]

We started daring to dive a little deeper,
on the edges.

Maintaining a distance,
but a little closer to the bottom.

It was still impenetrable. What goes on,
in the very center of the pack

when we're around it?

Filming at that depth, once in a while
we would get nudged by the sharks.

[grunting]

Damn!

We realized that we weren't targets

we were just obstacles.

[grunting, yelling]

Damn!

That's when we figured there was
a semblance of a social system.

We began to suspect we were
seeing various predatory strategies.

We had a hunch...
It aroused our intuition.

I thought, let's test this hunch.
Let's see if it's scientific fact.

[narrator] Laurent hopes to prove

that the sharks are
much smarter than we think.

The next few days are critical:

the June full moon will trigger
the grouper gathering.

That's when the sharks
will go on the rampage.

The moon is a ticking clock
for both the scientists and the fish;

a countdown to a massacre.

[loud explosion]

700 sharks aren't gathering
at Fakarava by chance.

They're here because of
the history of this island.

Knowing the geological past
reveals the biological present.

Fakarava was born around
70 million years ago.

[rumbling]

No sooner had the volcano surged up
from the depths of the Pacific Ocean

than the reefs started
colonizing its shoreline.

Soon the island was surrounded
by a ring of coral.

In the north,
the freshwater from the rivers

stopped the coral from growing there,

which left a gap in the reef
almost two miles wide.

Its fires extinct,
over the next two million years,

the volcano disappeared,
while the reef kept on growing.

But it still bears the imprint
of the ancient rivers:

the channels.

The pass in the north
takes the brunt of the tides,

so the residual current that reaches
the south channel here is gentle.

This easy current is a real boon.

It's weak enough for the coral to develop,

and provides shelter for fish,

yet it's strong enough to allow
a constant flow of food for everyone.

[soft instrumental music playing]

Sharks thrive in this current, too.

By day they use it to rest;
by night they use it to hunt.

This perfectly adapted current
is the first clue

to understanding why sharks gather here.

[birds calling]

But to see the whole picture,

Laurent needs to dissect
the predators' movements.

He's tasked three scientists
to create a 3D model

to help him do just that.

They'll begin by placing antennas
down at the bottom of the pass.

[Yannis Papastamatiou]
The strength of the current isn't equal.

If we know approximately where they are

in the channel, and how active they are,

and we have some understanding
of current strength,

then we can really see
how their behavior varies.

[Charlie Huveneers]
Based on the range of testing we did,

we probably need to space the
receivers about 100 meters apart.

[Johann Mourier] Yeah. Exactly.

[Huveneers] Right now
we're trying to find the best position

for these acoustic receivers

to make sure that we are going
to get the tagged shark

where the sharks are spending
most of their time,

so on the hot spots around the walls.

Uh, but also, where they're going to be,
uh, hunting at night

so we can compare the activity
during the day and the night.

[Mourier] We have a big school
of sharks usually staying here,

all along this place.

So, all these receivers
can get, uh, the detection.

[Huveneers, off screen] Cool.
We'll just have to deploy them now.

[tense instrumental music playing]

[narrator] They have to get
government permission

to install 25 antennas,

since the sharks here
are protected by law.

[Papastamatiou] 22 is 101799.

113122.

[narrator] But installing
25 antennas is the easy part.

[Papastamatiou] 115334.

[narrator] The next step is to
equip 40 sharks

with electronic chips, so they
can track their every move.

[tense instrumental music playing]

The gray sharks are keeping
their distance;

like the divers, they're cautious.

These predators are also prey
to 13-foot-long hammerheads.

[dramatic music playing]

[grunting]

[dramatic instrumental music playing]

[Papastamatiou] Good with that,
so we have the VHF works just fine.

[narrator] With the antennas installed,

it's time to figure out
how to plant the chips

in the sharks' abdomens.

The chips will let the scientists know
exactly when the predators go into action;

whether they sometimes leave the channel;

and if all 700 act as one,
or independently.

[Huveneers] It's pretty handy
to have a shark right here.

[Mourier] Yeah.

[narrator] If everything goes as planned,

they'll be able to track
the movements of each shark.

And the team has another tool
at its disposal:

a spy camera covered in sensors,

ready to be attached to a shark.

[Papastamatiou]
Well, let's try it and see.

[narrator] This is Yannis's first
dive at night

into the middle of the pack.

He and Laurent are going to test placing
the spy camera on a shark

using a surprising technique.

But the sharks may not cooperate.

[narrator] Scientists in
the Pacific atoll of Fakarava

have to work in the dark,

because the sharks are
too cautious during the day,

and unapproachable.

At night, they're emboldened by the hunt.

[dramatic music playing]

Research has shown that turning
a shark over on its back

puts it into a hypnotized,
cataleptic state.

But that was done with sharks
familiar with divers

and fed by them.

Now Laurent and his team
are testing it here,

amid a feeding frenzy.

Amazingly, the immobilization
technique works.

This is one circus move that
could end up scientific protocol.

[muffled speaking]

They need a big shark to carry the camera.

Coordination between
the two scientists is crucial.

Each shark reacts differently.

Some won't be hypnotized,
and that's when they might bite.

Yannis thinks this one's too small.

Laurent lets it go.

While they're searching
for a larger shark,

a never-before-documented hunt
is going on.

It's a moray eel.

-[dramatic music playing]
-[camera shutter clicking]

A lone gray shark will never
attack a moray eel this big,

but together, this pack doesn't hesitate.

After two hours,
Yannis and Laurent give up.

It's too difficult to attach the camera.

They need to find another way, and soon.

[thunder rumbling]

Back at HQ, Yannis screens
the first images.

Something strikes him.

It looks like the sharks
might form partnerships

to hunt in pairs.

One of the most, uh, fascinating things

about the, uh,
the sharks in Fakarava channel

is the social systems
of the sharks themselves.

The question is, why do they
form these social associations?

By remaining close to each other,

one shark could see another
shark taking some prey,

and benefit from that.

So if you imagine,
there's a reef fish here,

one shark sees it, charges,
goes after the reef fish, it escapes.

Another shark sees that shark
chasing the reef fish,

then it sees the reef fish,
and it actually successfully gets it.

By hanging out close to each other,

I can see if you get some food or chase
some prey, and that can benefit me.

Very simple, but that could still drive
us forming social associations.

[narrator] There might
be something to this partnership theory,

but it uncovers more mysteries to solve.

Are the pairs partners or rivals?

Does a pair always hunt together?

Do they hunt every night?

A shark only needs from seven
to nine pounds of fish a week;

so theoretically, it doesn't
need to go hunting every 24 hours.

The electronic chips may help
the team find answers.

But only if they can
find a way to attach them

to these deadly predators.

[splashing]

[intense instrumental music playing]

Everywhere else in the world,

scientists fish for sharks
with hook and line

in order to mark them.

But here in Fakarava Atoll,

the scientists have decided
to immobilize them by hand

and then lasso them to get them
up next to the boat.

Nobody's ever tried
this old cowboy technique

on a gray reef shark before...
only on whitetip reef sharks.

It's much less invasive for the shark,

but there's a high risk
of someone getting bitten.

One problem with hypnosis
is the creature's weight.

If a shark's not swimming, it sinks.

So if you immobilize one,
it tends to drop down,

bringing its jaws
right up against your legs.

[muffled speaking]

[Ballesta] Damn!

No!

[narrator] Laurent's taken it on
as a challenge.

He's determined to get it done.

[Huveneers] Okay, Yannis,
you need to do the slack,

-you can do the slack.
-[Papastamatiou] Yup.

[Huveneers] Johann.

Watch out, Yannis, I'm going to
pull it from the other side.

-Watch out, watch out.
-[Papastamatiou] Here?

[Huveneers] Good, good.

[Mourier, in French] Slack.
Give it slack, slack, slack, slack.

[Huveneers] Good one,
good one, guys. We're on.

[indistinct chatter]

One, two, three.

-[thrashing]
-[grunting]

[man] There you go.

[Mourier] Yep.

[Papastamatiou] Oh, there goes the...

[Mourier] Good boy.

[Huveneers]
Gonna touch again. Here you go.

-[Papastamatiou] There we go.
-[Huveneers] Close, close, close, close.

[Mourier, in French]
When the shark is belly up,

he's much calmer,
so it's easier for us to tag him.

Also, the shark is much less stressed
out, when he's belly up.

[narrator] Yannis tries to
implant the first electronic chip.

[intense music playing]

[Mourier] The surface of the skin
is very hard, eh?

[Papastamatiou] There's a lot of
really thick muscle layer

until you get into the body cavity.

So, although these incisions
look quite dramatic,

there's a few things to keep in mind.

First of all is that sharks
naturally have pretty violent lives,

especially when they mate.

So the male will bite the female,

and the females in particular
can get pretty torn up.

So we get females with huge, huge scars,
much, much larger than anything

we're inflicting with this,
with this blade.

So they're naturally adapted
to having a lot of damage.

And because of that, they have
very impressive immune systems

and very, very fast healing rates.

So we've caught sharks a couple
days after, after tagging,

and the wound is already healed up.

-[Huveneers] You can let go.
-[Mourier] Yeah.

[Huveneers] Uh, one, two, three.
Flip it and untie him.

Flip it. It's gonna go by itself. Perfect.

At least we know she's healthy.

[narrator] The team hopes to tag
at least 40 sharks

and then follow them for a whole year.

They'll know everything
the sharks get up to:

if they leave the channel or stay there;

if they hunt every night;

if they all hunt together;

and if they're influenced
by the lunar cycles.

[dramatic music playing]

But tagging 40 sharks
is easier said than done.

[Ballesta] Oh, my God!

[narrator] Here in the Fakarava channel,

scientists are tagging sharks
using a lasso technique,

while trying to avoid being
attacked by other sharks.

[Huveneers, off screen] One, two, three.

[Papastamatiou] Oh, there it goes.

[Mourier, in French] This shark may have
been bitten while mating...

Or while they were attacking prey.

Sometimes they snap at each other.

[Huveneers] It's a male, guys. First male.

[narrator] This shark's bigger,

so Yannis will try to attach
the spy camera.

[Papastamatiou] Come back to me. [kisses]

[Huveneers] Find it out. Yeah.

[Mourier] Okay, I know.

[splashing]

-[Papastamatiou] Good?
-[Huveneers] Yeah.

[Papastamatiou] Okay.

[Huveneers] It's the best way to do it.

[Papastamatiou] Okay.
Push forward, Johann, let go.

[narrator] They've tagged
nine sharks on the first night,

but they're still a long way
from their goal of 40.

[soft instrumental music playing]

The team's been counting
the sharks every three days:

416, then 480, 520;

the number keeps rising
as the full moon approaches.

By day, the sharks form three
groups that the divers call "walls,"

an expression coined
by explorers in the 1960s

who were the first to see
hundreds of sharks lined up like this.

The walls form at very precise locations.

For four years, Laurent's team
has been observing

that the sharks rest on veins
of current in the channel.

Whenever they leave the vein of current,
others come in to replace them:

just like migrating birds in v-formations.

They only stop to get their teeth cleaned
by the cleaner fish.

The scientists discover that the camera

has fallen off the shark.

Yannis Papastamatiou looks for clues
to the pack's behavior.

[Papastamatiou]
So one of the things we can see

when we take a look at this video

is that our shark carrying the camera

is often associating
with this individual here

with the damaged dorsal fin.

So that may mean that there may
be some form of social bond

between those two sharks.
And next we want to know

if that also applies at night.
So do these animals, for example,

form social bonds while they are hunting?

[soft instrumental music playing]

[narrator] It's almost the full moon.

So it's time to deploy
Laurent's most complex brainchild.

This arch combines both
photography and video

in order to capture the hunt
at one-hundredth of a second,

and then, with its
32 synchronized cameras,

move around inside the 3D image.

The team has no idea what

the sharks will make
of this high-tech stranger.

The first shots are taken in
daytime, amidst all the fish.

But only the oncoming darkness will reveal

what happens when 700 sharks
become 700 hunters.

[diver] Go, go, go, go!

[narrator] In daylight, results
from the shark scientists'

3D arch look promising.

Now they must wait for light
to turn to night.

The channel is not so much
a well-stocked pantry.

It's more like a conveyor belt of food,

rolling ever faster as
the June full moon approaches.

There's enough prey now
to feed a lot of hungry sharks.

One after another, dozens of
species of fish from the lagoon

are arriving to the channel, as
if to a prearranged rendezvous.

They're all getting into place
at the ocean gate

to give their larvae a chance of survival

far from all of the predators of the reef.

They are ready to launch
their spawn into the current,

and out to sea.

[dramatic music playing]

[dramatic music continues]

For the moment,

there are only a few
grouper fish in the channel;

but soon there will be as many as 17,000.

And the sharks know it.

This honeymoon is about
to turn into a bloodbath.

[narrator] Just days until
the 700-shark feeding frenzy,

scientists prepare to document
the spectacular event.

[whooshing]

While Antonin and Thibault
work on the arch,

it's Yannis's last night on the mission.

He's at last placing the 40th
and final electronic tag.

As the darkness of night falls,

the fish are half asleep
and less aware of danger.

That's when a shark makes its move.

The high-speed video reveals

the different phases of an attack.

The sharks are obviously
attracted by sound.

Vision helps, too,
but here in the shadows,

the shark has a special advantage:

It can detect the
electromagnetic field of the fish

with the aid of sensitive cells

all around its mouth,
called ampullae of Lorenzini.

The electrical stimulation

only works up to a foot
from the shark's mouth.

[dramatic music playing]

The more agitated the fish,

the more intense
its electromagnetic field.

If it could play dead,
the shark would think

it was an inanimate object, and ignore it.

[intense music playing]

On its own, a shark is clumsy.

It's at its best in a pack,
with everyone moving together.

The images reveal that 25% of
the pack's attempts are successful.

Compare that to a pack of wolves,
renowned for its efficiency,

that only catches 14% of its prey.

The photos show them encircling
their prey to cut off any escape.

Teamwork is clearly an advantage.

Once the prey's cornered,
though, it's a different story.

Every shark demands their share.

At Fakarava, there's no lack
of prey, so it's not a problem.

Sooner or later, every one
of those snapping jaws will be fed.

But jaws are useless
if the prey stays hidden.

The team makes a remarkable observation:

the gray sharks follow
the whitetip sharks,

also known as coral sharks,

who, with their ability to slip into holes

and come out again backwards,

are the only ones who can flush
out prey hiding in the reef.

[intense music playing]

It's a new and enlightening
facet of their behavior:

This shark pack can exploit
the skills of another species.

The chips on the tagged sharks
send information

each time they pass close
to one of the many antennas.

After a week, Johann and Antonin

collect the data to assess it.

[speaking French]

The antennas will be returned

each night to continue the tracking.

[Ballesta, in French]
So, there's a different color

for each of the sharks we tagged.

[in French] You can really see two groups.
One group stays around here...

On the ocean side of the dropoff.

And the other group is much more active...

They mainly use that main pass by day.

These waters, here...
And actually, after nightfall,

they swim much more in this area.

Another thing we'll be able
to see is if there are leaders.

We see there are groups of sharks
that move together, more or less.

We'll see if it's always the same shark
who starts the move.

[narrator] With only three days
until the full moon,

the team makes their final preparations.

The arch will make its debut
among hundreds of sharks,

right in the middle
of a massive shark attack.

[narrator] As night falls
two days before the full moon,

the sharks seem undisturbed by the arch

and just keep on hunting,
right under the divers' feet.

It's becoming clear that whether

they're resting during the day
or on the attack at night,

the sharks form partnerships,
subgroups that work together.

High-speed footage from
the arch reveals what happens

at the heart of an attack.

The shark on the right is driving the prey

straight towards the other.

Slow motion reveals hunting duos.

In addition to the pack's
overall synchronization,

they seem to have a deeper
level of organization

based on either momentary or
more durable mutual interests.

The prey can escape once,
maybe twice, but not forever.

In fact, this coordination is a mixture

of cooperation and competition.

They watch more than they help
each other; but it works.

If one doesn't win out, the other does.

Nearly 600 sharks hunt here now:

The ranks of the predators
are swelling every night.

[beeping]

[Ballesta, in French]
We're part of the pack, now!

[Cedric Gentil, in French]
That's the feeling I had.

And there you go... You're with them.

Sometimes you feel like taking one under
each arm, and walking along with them.

Sharks everywhere!
They didn't let us down!

It seems like there are more every year.

[Yanick Gentil, in French]
Youngsters. Lots of youngsters.

Right... There are lots of
youngsters who are... about yay big.

[Gentil] Didn't you call one "Papa?"

[Ballesta] I didn't dare admit it.

[soft instrumental music playing]

[narrator] For 50 nights
they've been diving,

and now on the 51st,
it's the day before the full moon,

the most important night for the sharks
and for Laurent and his team.

The surveillance camera
gives the go-ahead.

And just like every year
at this same time,

the groupers are back.

They're solitary all year round,

but get together for the annual spawn.

No one misses the date:
the full moon in June.

And you don't need to study the stars

to see that all the females are pregnant.

This is the day the sharks
have been waiting for...

all 700 of them.

Tonight will put to the test
all the latest theories

about how the pack functions.

The attack will come
from within the channel

where the sharks are resting.

The countdown to a massacre has begun.

[ominous music playing]

The groupers come here
to reproduce once a year,

entirely driven by instinct.

While waiting for the females
to spawn, the males hide.

Don't hide, and you're dead.

Night is falling now.

The pack is waking up,

and they're hungry.

[narrator] 700 sharks swarm their prey.

[intense music playing]

A tornado of jaws,
followed by a rain of scales.

It's a deadly roundabout.

[lively, intense music playing]

Electroreceptors help
the sharks zero in on prey.

For the groupers,
this is the price they pay

to spawn the next generation.

Though the sharks hunt in a pack,
they don't like to share.

[intense music playing]

Some bear deep scars,

perhaps from battles with
other sharks at the hunt.

[intense music playing]

This grouper has managed to
slip through three sets of jaws.

But not the fourth.

[intense music playing]

A parrotfish, half asleep,
bumps into a coral shark.

In its haste, the gray shark
bites the coral shark

and the parrotfish escapes.

Weighed down by her huge belly,
a female can't get away.

Her eggs are scattered... and lost.

At midnight,
the full moon is at its zenith

and lights up the whole ocean bed.

But by 5:00 in the morning
it's low on the horizon

and the sharks are all left
in the dark, exhausted.

The hunt finally eases,
the groupers know it,

and the spawning begins.

In the darkness,
the sharks seem less alert.

The lights from the cameras
don't affect them;

they're too patchy.

Sharks have evolved
into the ultimate predators;

but their prey has evolved, too.

The groupers, with speed
and perfect timing,

have learned to spawn
at this opportune moment.

[lively music playing]

Both prey and predator have
strengths and weaknesses.

The groupers are less vulnerable

than the biologists imagined,

and sometimes the sharks
fail to hit their target.

Four months have gone by
since the start of the mission,

and the electronic tags continue to
reveal the secrets of the shark pack.

They seem to obey some rules.

By day, they stay in three groups,

make their rounds, and sleep a bit.

They begin to form pairs.

As night falls, they band
together for the hunt,

forging partnerships that
persist for the night,

like sub-units within the pack,

although it does not mean
these pairings will be the same

on the next night.

This behavior has never
been documented before.

Three thousand hours of underwater filming

reveals for the first time that
a big school of gray sharks

is more deadly than a pack of wolves.

Even more remarkable
and never before revealed,

the sharks' activity
follows the lunar cycle

much more than it follows
the abundance of prey.

The level of moonlight
determines the intensity of the hunt.

And come morning, the sharks all return

to their respective walls,

with the exception of
at least two of the tagged 40,

who leave the channel,
and to this day have never returned.

There are still mysteries to be solved
in the Fakarava channel,

but one thing is clear:

In these pristine waters,

gray sharks rule.