All language subtitles for Bull.Shark.vs.Hammerhead.2023.

[dramatic music throughout]

[Narrator] Locals are still talking about
what happened here last spring.

It was a perfect day for fishing.

[man] Whoo! That's a big one.

[Narrator] But below the surface,
two heavyweights of the shark world

were on a collision course.

[man] That's insane!

[Narrator] It's a rare face-off between a
bull shark and a great hammerhead,

prompting a team of experts
to dig deeper into the encounter…

[man] One, two, three.

[Narrator] …in the hope to uncover
surprising behaviors…

[Valerie Hagan] We might have a predation.

[Dr. Yannis Papastamatiou] I have no idea
what is going on here.

[Narrator] …and come face-to-face
with two of the biggest…

[man] She is massive!

[Narrator] …baddest…

[Dr. Mike Heithaus] Look out! Look out!

[Narrator] …super predators on the planet.

But which one takes the crown?

Several people captured the event
in the spring of 2021.

[man] That's insane!

[Narrator] The video quickly went viral.

A bull shark chases a monster great
hammerhead and pins it to the beach.

There's no escape.

The bull shark circles…

followed by a second.

Then the hammerhead is ripped to pieces.

[splashing]

Marine biologist
Dr. Mike Heithaus was floored.

[Dr. Heithaus] I've never
seen anything like this.

A lot of times, we've got
these big, top predators

but they don't usually
pay much attention to one another.

In this case,
it was a head-to-head battle.

We had a winner and a loser.

[dramatic music]

[Narrator] An encounter
of this magnitude is rare.

It provides the perfect opportunity
to understand how these apex predators

stack up in a one-on-one battle.

Fishing Charter Captain Mike Myers
saw the whole thing.

[Capt. Mike Myers] Oh, my gosh.

Can you walk me through what happened
that day?

[Capt. Myers] I had clients onboard.
I just saw it.

"Oh, my gosh, a huge hammerhead."

[Dr. Heithaus] How big do you
think that hammerhead was?

I'm estimating somewhere around 12 to 13
foot.

They kinda swam up towards the beach

and people were over there
screaming and hollering

because he kept beaching himself.

Every once in a while,
one of the bull sharks

would come up and grab 'em by the tail
and jerk it and then swim up real fast.

And all of a sudden, you look down…

and then…

-[dramatic music]
-[splashing]

…the sand just exploded.

We looked as hard as we could
after that whole mess happened.

There wasn't a fin on the ground.
There wasn't anything in the water.

He was gone.

You've been out here a long time.

[Capt. Myers] I've seen a lot of bizarre
things with these sharks over the years.

Oh, my gosh.

I've never seen anything close to that.

[Narrator] Big sharks are known to attack
and eat smaller sharks.

But these two apex predators
are powerful equals.

The hammerhead, sleek, massive,
and can turn on a dime.

In a one-on-one fight,
they are fearsome opponents.

Great hammerheads can grow
to be nearly 20 feet long,

almost twice as big as the bull shark.

Bull sharks may be
in a different weight class,

but they pack a lot of punch
for their size.

Stocky with a superior jaw strength.

Bull sharks have a bad reputation
for a good reason.

[Dr. Heithaus] Lots of questions
come out of this video.

[Capt. Myers] Oh, my gosh.

[Dr. Heithaus] They're both top predators.

You don't really think about
one going after the other.

So to see them battling it out
is incredibly unique.

If these sharks are going head-to-head,
who's gonna come out on top?

When top predators battle it out with one
another or have interactions,

that can cascade through
the rest of the ecosystem.

So learning about the interactions
among top predators is really important.

[Narrator] To investigate
this surprising new dynamic,

Mike has assembled a team of experts.

[Dr. Heithaus] We're gonna try to get
to the bottom of this

by first studying bull sharks
and great hammerheads separately

and then going to a place
where they might come together

to see if it's a collision or if
they go their separate ways.

[Narrator] First up, the great hammerhead.

Team member Erin Spencer
leads this part of the investigation.

They're one of the most
recognizable sharks in the ocean.

When you see that cephalofoil and just see
the eyes and how big that head can get,

it really kinda takes your breath away.

[Narrator] Famous for its elongated head
extensions called cephalofoils,

the great hammerhead has an advantage
over the bull shark

in its uniquely positioned eyes.

With a nearly 360-degree field of vision,

it has the best
depth perception of any shark,

giving it pinpoint accuracy on attack.

Its wide head also contains
more electrosensory receptors

than other sharks.

[Spencer] All of these pieces
come together to make them

as good a predators as they are.

But because they're
so big and wide ranging,

they're really difficult to study.

We use something called bio-loggers
which are essentially

animal mounted data collecting devices.

And the bio-loggers
are like Fitbits for sharks.

[Dr. Heithaus] So by putting
that on the back of the shark,

it can give you a three-dimensional path

of how it's moving
through its environment,

how it's speeding up, slowing down,
pitching, rolling.

We just gotta get out there,
catch a hammerhead

and get one of our accelerometer tags
on its dorsal fin.

[Narrator] While Erin readies
a hammerhead 3D bio-logger,

Mike heads back out
to the scene of the crime…

to look for more clues with Captain Myers.

For a few months a year,

this relatively deep channel west of Fort
Myers is a fisherman's paradise.

[man] I told you it's a big one.

[Dr. Heithaus] It is packed full of these
giant fish called tarpon.

They could be more than 200 pounds

and they're one of the world's
most coveted game fish.

[Narrator] As the water warms each spring,
thousands upon thousands of tarpon

migrate north to Boca Grande to spawn.

Anglers come from all over
the world to try their luck.

As they fight these mammoth fish,

bull sharks and hammerheads cross paths
in their quest for easy prey.

Over the years, Captain Myers
who captured the video of the attack

has observed both predators
on a daily basis.

Have you ever seen the bull sharks or
hammerheads

go after tarpon that aren't hooked up?

-So--
-Oh, God, yeah.

[Capt. Myers] The bull sharks will get
around these schools.

That's 10,000 fish
running up and down this beach.

I have seen numerous, numerous times
the hammerheads come in.

People don't realize
how agile that fish actually is.

[Narrator] What Captain Myers
recalls next intrigues Mike.

[Capt. Myers] And what's really cool, when
a hammerhead comes, bulls aren't around.

They don't want nothing to do with it.

[Narrator] It contradicts the behavior

Captain Myers captured
on video a year earlier.

[Capt. Myers] The hammerheads come in
and there's no more bull sharks.

What I saw floored me.

[Narrator] The team decides to deploy

the hammerhead tag right here
in Boca Grande Pass.

But the next morning,
Mike gets some bad news.

[sighs]

[Dr. Heithaus] Unfortunately,
we just heard

from Erin and she's been exposed to COVID,
so she can't make it out today.

But she's programmed the tag
for us and we've got a crew.

So we're gonna go out and try
to catch a great hammerhead.

Anything we need to be thinking
of to get this on for you?

Not having her on the boat
is gonna be a big challenge

'cause that's one less experienced person
to handle a shark.

But hopefully we can get it done
and get some great data for her.

[Narrator] Mike will work with
Mote Marine Laboratory biologists

Valerie Hagan and Jack Morris

to see if they can get the tag
on a hammerhead by themselves.

[Hagan] Jack and I work with one another
for most of our field work.

[Jack Morris] That's fishing, right?
So you always come up with the expectation

that you hope you're
gonna get what you want.

And when you do, it's amazing.

[Narrator] They set ten fishing lines
along the mouth of Boca Grande Pass,

its prime hammerhead territory.

That is a piece of stingray.

And the hammerheads loves stingrays.

They'll actually use their head
to pin 'em to the bottom

to hold them down so they can get a bite.

[Narrator] While they wait for a catch,
Mike preps Erin's 3D bio-logger.

[Dr. Heithaus] What it can do is help us

recreate a three-dimensional
track of the hammerhead.

And it samples at such a fast rate.
We can see if they're doing burst swims

to try to catch something.
And you're out here in Boca Grande,

we know that bull sharks and hammerheads
can be on a collision course.

So learning more about each
is really important to understand

how they're going after a prey
or are they maybe eating one another?

[Narrator] By the time
the last line is in the water,

it's time to circle back and check the
first where something is already on.

[dramatic music throughout]

[Dr. Heithaus] So, this is a
blacktip shark

and they're one of the more common species
along the coast of Florida.

And these are snacks
for great hammerheads.

[Narrator] Catching the hammerhead's prey
is a good sign for the mission.

[Morris] Let it go. Take it.
Oh, there he goes.

[Dr. Heithaus] And away.

[Narrator] The next hook
looks more promising.

[Dr. Heithaus] Yeah, it's dragging it.

[Hagan] I saw the buoy
actually made a splash.

[Dr. Heithaus]
Yeah. This is not nurse shark,

not blacktip.

-Yes! Hammerhead!
-[Hagan] Whoo!

-[Dr. Heithaus] Whoo!
-[Hagan] That's a biggun.

[Dr. Heithaus] Two of 'em.
There's another one right here.

-[Hagan] What?
-[Dr. Heithaus] We got two hammerheads.

[Narrator] The second hammer is free
swimming, analyzing the situation.

Hammerheads are known to eat their own
when the opportunity arises.

[Hagan] We might have a predation
about to happen.

[Narrator] They need to secure the hooked
shark as quickly as possible.

But there's another problem.

[Hagan] I tried to pull on that,
but there's no give.

[Dr. Heithaus] We've got a hammerhead here
wrapped up in a crab pot.

[Narrator] Until they untangle it,

the hammerhead is a sitting duck.

And the second hammerhead circles,
closer and closer.

[Dr. Heithaus] Okay.
You gotta go to the right.

-You gotta get reverse.
-[Hagan] Port side.

[Morris] We gotta get him away
from that other shark.

[Dr. Heithaus] I know.

[dramatic music throughout]

[Dr. Heithaus] Ahh! Look out! Look out!
Look out! Look out!

[Morris] How about we swing it out?

[Narrator] The team
struggles to untangle the line

before the great hammerhead
becomes shark bait.

[dramatic music throughout]

[Dr. Heithaus] [grunts] Forward.

Let go. Let go. Let go.

-Yes, free!
-[Hagan] Oh.

-[Dr. Heithaus] Nice job.
-[Hagan] Yeah. [laughs]

[Dr. Heithaus] Okay,
we just have the shark now.

-[Hagan] Holy cow.
-[Dr. Heithaus] That is a big animal.

Well, we got a really nice
10-foot-plus great hammerhead.

We have another
slightly smaller one around.

This is the exact size
we want for this tag.

Oh, beautiful.

I don't see the other one now.

[Hagan] We probably
spooked the other one off.

[Narrator] But the battle to subdue
the shark is only beginning.

[Morris] You know, the hairs on your skin
start to stand up a little bit.

Once you get what you want,
you wanna keep it.

[Dr. Heithaus]
Look out. Look out. Look out.

-Don't try this at home, kids.
-[Morris] Nicely done.

[Hagan] Definitely female.

Hello, gorgeous.

[Narrator] Val attempts to secure
the shark's powerful tail.

-[Dr. Heithaus] Get it?
-[Hagan] No.

I couldn't get that lower lobe.
It was close.

[Narrator] Handling a shark this big
is proving difficult

without the help of their teammate Erin.

[Hagan grunts]

[Dr. Heithaus] You're gonna lose the top
lobe.

[grunts]

We're gonna lose this shark.

-[Hagan] Okay.
-[grunts sharply]

[Narrator] The urgency
is compounded by the fact

that great hammerheads are fragile.

[Morris] There's theories
that they fight an awful lot

when they're on a hook
and they overexert themselves

and they run out of energy very quickly.

[Hagan] It's wearing us out.
It's wearing her out.

And we want this animal to survive.

[Dr. Heithaus] Hey, slow it, slow it.

[Narrator] The shark zooms around

to the other side of the boat,
trying to throw the hook.

[Dr. Heithaus] Jack, can you come back?

[Morris] Yeah.
Okay, what do you want me to do?

[Dr. Heithaus]
I want you to get the dorsal.

Let's clamp this thing on and get it.

Otherwise we are gonna lose this animal.
-[Morris] Alright.

[Narrator] Finally,
the tail rope is secured.

[Hagan] On!

[Dr. Heithaus] Put the tag on.

Get it as far as you can.

Excellent.

[Hagan] I was very focused on the tail

and then I looked up
and I saw that the tag was on.

[dramatic music throughout]

[Dr. Heithaus] Good. Let's get a quick
measurement and go.

Fast, fast, fast, fast.

[Hagan] 345.

[Dr. Heithaus] The hook is bent and out.
You gotta get that tail rope up fast.

-Good swim.
-[Hagan] Whoo!

[Narrator] The biologging tag will capture
3D data, providing valuable insight

into how great hammerheads
move through the water.

And help the team see how these giants
stack up against bull sharks.

With the tag finally recovered
and a clean bill of health,

Erin's back on board to walk Mike
through the hammerhead data.

[Dr. Heithaus]
She can build a computer model

so we can see not just how
it navigates and where it went,

but maybe how it's attacking its prey.

[Spencer] This is when
the hammerhead is released.

We start at the surface
and then just go straight down.

And then we can actually see
how the animal starts to move around.

[Narrator] The shark heads down
to a depth of about 40 feet.

It swims away from the boat
in sweeping lateral movements.

Here, we see that the shark

is kind of meandering down a little bit
slower and is kinda midrange,

and then there's
a really quick turnaround.

[Narrator] It cuts through the water
with its hydrodynamic head,

making several tight, very rapid turns.

And then there's a really quick
bolt up to the surface,

almost a vertical line.

[Dr. Heithaus] There's probably
a reason for that

because why else
would you burn that energy

-if you didn't have to?
-Yeah.

We can say, okay,
using the mathematical models,

actually how many calories
would a shark need

to consume to sustain
that sort of movement pattern?

[Dr. Heithaus] If you need a
lot of energy,

you gotta eat that bigger prey
to get you more energy like other sharks.

[Narrator] Erin's tags were only beginning

to reveal the secret abilities
of the great hammerhead.

When it tilts its head,
the hydrodynamic potential

of the great hammerhead
cephalofoil is unleashed,

allowing the shark to move
and turn with rapid precision.

And this makes hammerheads more nimble and
agile than other sharks,

including bulls.

Look, you combine the speed,

the size, and maneuverability,
I mean, that's an impressive predator.

Bull shark versus hammerhead, who wins?

-I vote hammerhead.
-[Dr. Heithaus] One for team hammerhead.

[Narrator] The awesome power of the great
hammerhead is coming into focus.

But Mike and the team
are no closer to understanding

why the hammerhead was attacked
by bull sharks at Boca Grande.

[Narrator] The team has proven that great
hammerheads are formidable opponents,

but what about the other
contender in the battle?

[Dr. Heithaus]
Now it's time to investigate

the other species in this matchup.
Bull sharks.

[Narrator] Maxing out at around ten feet,

the bull shark is smaller
than the great hammerhead.

But what it lacks in size,
it makes up for it elsewhere.

It's thick with a broad head and big
mouth, built for taking out large prey.

The bull shark is super adaptable.

It has a reputation for being aggressive.

[Dr. Heithaus] Seeing that video
really shows us that bull sharks

might attack great hammerheads
and kill 'em.

But the question is,
is this a common event

that's happening more often when they're
out there coming into contact?

[Narrator] To dig deeper into the bull
shark component of this matchup,

Mike enlists Dr. Yannis Papastamatiou.

[Dr. Heithaus] Yannis is one of the top
shark scientists in the world,

and has helped developed new technologies
to get more insights into their behavior.

For this project, we're gonna try
something that's never been done before.

We wanna put a camera
on the back of a bull shark.

And until now, that's only been done with
sharks that have been caught,

and that might really change
the behavior of the shark,

so we're gonna go out there
and try to put a camera

on a bull shark without catching it.

[Narrator] Along
the southeast coast of Florida,

there's a thin band
of warm, shallow water.

It creates a shark super highway,

bringing all sorts of species
in contact with one another,

including lots of bull sharks.

[Dr. Papastamatiou] I'm really hopeful
we'll get this tag on,

but I, you know,
I'm also a little bit nervous

because it's going to be
somewhat challenging

to get a tag on a free-swimming bull shark
in blue water, in a current.

I'm hopeful. But it's going to require
a well-behaved shark.

And I also hope she won't bite me.

[Dr. Heithaus] We're heading
about four miles offshore,

and that's where we should be
able to find bull sharks.

We should get about
ten hours of video footage.

[Dr. Heithaus] Then that
dissolves in a couple days,

-there's nothing left on it.
-Yep, yep.

So within a week, there'll be nothing
on the shark's fin at all.

[Narrator] To keep the shark at arm's
length, they'll use a spring-loaded pole

to snap the tag on the shark's fin.

[Dr. Papastamatiou] Okay, so that's now
primed.

Right.

[Dr. Papastamatiou] If you
now click the small trigger…

-[Dr. Heithaus] Watch your fingers.
-[Dr. Papastamatiou] Yep.

[Dr. Heithaus] One, two, three.

-[Dr. Papastamatiou] And that'll pop.
-[Dr. Heithaus] Yeah.

We just need one to behave the right way
and we'll get it on.

[Dr. Heithaus] If we pull this off,
it'll be a world first.

[Dr. Papastamatiou] No pressure. [laughs]

[Dr. Heithaus] No one's ever done it.
There's no pressure. Just go do it.

[Narrator] If bull sharks are hunting
hammerheads more commonly than thought,

this camera could pick up hard evidence.

-[bubbling]
-[dramatic music throughout]

To bring a bull shark in
and keep it close enough

for a tag deployment, bait is needed.

It injects a constant scent trail
into the current,

drawing a roadmap directly to the divers.

[Dr. Papastamatiou] Oh! Shark!

[Narrator] It's a silky shark.

[dramatic music throughout]

She makes tight circles, sniffing out the
food and sizing up the human competition.

Silky sharks are a bold species that spend
a lot of time in the open ocean,

where food is scarce.

The bait is working…

but it's not the species they're after.

[Dr. Heithaus] Silky sharks don't really
have a sense of personal space,

especially if you have
a camera in your hand.

[dramatic music throughout]

[Narrator] Then as quickly as they came,
the silkies disappear.

[Dr. Papastamatiou] There! We got a bull!

[Narrator] The bull shark
zeroes in on the bait.

It's a big female.

[dramatic music continues]

In order to tag a free-swimming bull,

they'll need the most
bold and inquisitive shark they can find.

Experts generally agree that bulls are one
of the most dangerous shark species.

Most bull shark-human interactions
take place in murky water,

where biting is the only way
to identify possible prey.

In clear open water,
the team and the bull shark

can see one another
and maintain healthy boundaries.

She's a good candidate for the camera tag.

[Dr. Heithaus] We got
the bull sharks we wanted.

If this goes well,
the shark's gonna swim away

with the camera on it,
and we will be done.

[Narrator] With daylight fading, the team
has limited time to pull this off.

It's a deployment
that's never been done before.

[dramatic music continues]

The big female comes in closer.

She's curious.

Confident.

The perfect shark.

Yannis readies the trigger.

He needs to slip the opening of the clamp
over the dorsal fin of the shark.

It's a game of inches.
One miss and the shark will be spooked.

[Narrator] Clamping the tag
on a free-swimming bull shark

is a cat-and-mouse game.

Every time he gets close,
the bull changes direction.

[dramatic music throughout]

[Dr. Papastamatiou] Yeah, woo hoo!

[Narrator] Success.

[Dr. Heithaus] Way to go Yannis, yeah!

[Narrator] In a first for science,

the bull shark swims off,
unfazed by its new bling.

[triumphant music throughout]

[Dr. Papastamatiou]
So the tag is on an animal.

First part is done.

She's the perfect size, she came in close,
I took my shot, and, uh, it worked.

In the end, she responded perfectly,
didn't seem to bother her much at all,

she just slowly swam off.

[Dr. Heithaus] Camera on.
Everybody's okay.

-[Dr. Papastamatiou] Yeah.
-[Dr. Heithaus] Now, one more step.

Get the camera back.

[Dr. Papastamatiou] Getting the camera
back.

[Narrator] The tag will remain on the
shark for two days.

Tracking one bull will allow the team

to see everything
from the shark's point of view.

But camera tags only tell
one part of the story.

To see if hammerheads are on the bull
shark menu, like in the video,

the team has to take a cloacal swab,
otherwise known as a fecal sample.

[Dr. Heithaus] One of the most
important things

we need to know about predators
is what they eat.

Usually, that's been figured out
by looking at the stomachs of dead sharks.

[Dr. Heithaus] It turns out, if you just
get a little swab and collect shark poop,

you can run that through a DNA test
and see what had been in its stomach.

This cloacal swabs
are gonna help us figure out

if these bull sharks are
eating a lot of other sharks

and may even go after great hammerheads.

[Narrator] The next morning,

Mike and PhD student Davon Strickland
head off shore to swab bull sharks.

Davon is part of the next generation
of marine biologists

trying to unravel the mystery
of how sharks interact with one another.

[Dr. Heithaus] He also happens to be a
co-captain of FIU's football team.

[Davon Strickland] With football being
a game of inches,

how that's translated in the shark work
is you gotta make sure you know your role,

because there's so many things
that could go wrong,

you gotta be able to work as a team.

[Dr. Heithaus] He also
is a pretty good person

to have on the boat when
we're handling big sharks.

We need those long arms.

[Strickland] I'm gonna try and get it.

[Dr. Heithaus] Oh, my gosh.
The visibility here is insane.

[Narrator] They set their lines just
at the edge of deep water.

[Dr. Heithaus] So we are right where we'd
expect to find bull sharks,

the perfect depth range,

so that's why we're just gonna
drift along here with the bait.

I thought I saw a shadow there.

Oh, there's a shark right there.

[Narrator] It's an eight- to nine-foot
bull shark.

[Strickland]
Let me take it, let me take it.

-[Dr. Heithaus] Yeah.
-[Strickland] Oh, there's two of 'em.

[Dr. Heithaus] Okay, that should help.

[Narrator] The larger shark
makes the first move.

There, it's right, it's right next to the
bait, it's taking a look at it.

Take it, take it, take it.

Oh, oh, oh. Yup. It took it. Okay, get
ready. Watch your feet.

Okay, I think we're in business.

[splashing]

Careful, careful.

Yup, slow, slow.

Heads up, heads up. Clear, clear, clear.

Move, move, move, move, move.

That is a big bull shark.
Neutral.

Heads up now. Oh!

[Dr. Papastamatiou] He go?

[Dr. Heithaus] Bit the line.

[Strickland] So close, but yet so far.

[Dr. Heithaus] Bummer.

The shark actually bit through the mono.
She was fresh, so she was really strong.

So we got her up to the surface,
but she had the mono in her mouth.

That tooth just sliced through it.

It's the way it goes.

[Narrator] It's not long before they have
another curious shark.

[Dr. Heithaus] Shark.

[Narrator] A big female.

[Dr. Heithaus] Back up, back up, back up!

Oh, damn!

[dramatic music throughout]

[Dr. Papastamatiou] Okay. Pull the line.

[Dr. Heithaus] Nice. Yes.

Okay. Whoo!

Good job.

[Narrator] The team makes sure she is calm
and getting water through her gills.

[Dr. Heithaus] This is perfect.

[Narrator] Then they take a measurement.

-[Strickland] 187.
-[Dr. Heithaus] Yup.

It probably outweighs you
by a hundred pounds.

[Strickland] Oh.

And this fish is longer than I am tall.

-[Dr. Heithaus] Okay.
-[Dr. Papastamatiou] Alright.

[Dr. Heithaus] So what we need to do
is get her upside down,

we're gonna do this cloacal swab, we need
to try to keep it out of the water.

[Narrator] Flipping the shark on its back
puts it into tonic immobility,

a relaxed, trance-like state. It helps
keep everyone safe during workups.

They'll send the swab off to be analyzed
for hammerhead DNA.

While they have the shark,
they will also implant

a permanent tracking
transmitter in her belly.

-[Dr. Heithaus] Right there?
-[Dr. Papastamatiou] Yeah, that's fine.

[Narrator] The shark will now alert the
team any time it passes a receiver

in a network along the coast
of Florida and beyond.

We can follow them for years,
so using the transmitters, video cameras,

and the DNA techniques,
we can start to piece together

a much better picture
of bull shark life in general.

[Narrator] The acoustic tags can help

the team see where and when
bull sharks may overlap

with great hammerhead habitat.

It could also reveal whether bull sharks
are gathering in groups.

[Dr. Heithaus] Okay, it's in.

[Narrator] All that's left is to suture
the wound and release the shark.

Everything's in place.

[Dr. Heithaus] Let me know when you're
ready.

[Dr. Papastamatiou] Okay.

-[Strickland] It's out.
-[Dr. Heithaus] Nice!

[Narrator] The team is confident.

If these bulls are hunting hammerheads,
evidence will be with them soon.

Two days later, the bull shark's
fin cam surfaces.

[Dr. Papastamatiou] It did pop off about
six miles offshore.

But then we had a pretty strong current,
so it was very rapidly moving offshore.

[Narrator] When they
finally catch up to it,

it's in deep water,
way out in the Gulf Stream.

[Dr. Papastamatiou] I was really, really
happy when that tag was in my hands.

[Narrator] Back at the lab, the team
discovers the tag captured hours of video.

[Dr. Papastamatiou] This is the first time
that one of these camera tags

is being put on
a free-swimming bull shark,

and so I'm really excited to see
what the tag is going to show.

[Narrator] The shark swims away
as if nothing happened.

It's proof their tagging technique
is minimally stressful to the animal.

It cruises alone for hours.

-Then…
-[Dr. Heithaus] Whoa.

[Dr. Papastamatiou] So, there's another
shark came right over it.

-[Dr. Heithaus] Yeah.
-[Dr. Papastamatiou] There's another one.

That's one, two, three, four,
five, six, seven.

[Narrator] It's a gang of bull sharks.

Yeah, look at that.

I mean, that's right on top of each other.

-There's a lot of sharks here.
-[Dr. Heithaus] One there.

-There's another one there.
-Look at that.

[Dr. Papastamatiou]
It's just bull sharks all over the place.

And we're seeing at least
six, seven, eight individuals in frame.

-Camera's only pointing forward.
-[Dr. Heithaus] Yeah.

[Dr. Papastamatiou] It tells nothing about
on the sides or behind.

[Dr. Papastamatiou] So whatever number we
calculate, the group size will be larger.

[Dr. Heithaus] And these are big animals.

[Dr. Papastamatiou] I have
no idea what is going on here.

I mean, a lot of this is just not known.

You know, why are all these sharks
hanging out in these regions?

[Narrator] The footage didn't show
any interactions with great hammerheads,

but it has confirmed a remarkable social
life between bull sharks.

[Dr. Heithaus] Are they feeding in groups?
Maybe these bull sharks are actually

maintaining relationships
with other sharks

or working together when they're hunting.

[Narrator] And the results
from the cloacal swabs also arrived.

[Dr. Heithaus] It turns out that these
bull sharks were eating other sharks.

We didn't get any great hammerheads,
but it does show that these bull sharks

are eating big prey,
and it's plausible

that they could go after
other larger sharks.

[Narrator] Scientists already know
that sharks are hesitant

to take on the risk of a one-on-one fight
with an equal.

It's possible the video evidence points

towards something scientists
haven't considered before,

multiple sharks using
their collective strength

to take down another apex predator.

In order to see
whether this dynamic exists

between multiple bulls and hammerheads,

Mike jumps into the ring himself.

The Bahamian islands of Bimini
are only 50 miles east of Florida.

But worlds away
in terms of shark activity.

Bulls regularly patrol these waters,

and great hammerheads visit in the winter.

It's a prime location
to observe them up close.

[Dr. Heithaus] That water is crystal clear
and so you can actually get in the water

with the great hammerheads in a way
that you couldn't in Boca Grande.

It's also an area where
both of them are coming into

at least some semblance of proximity,
but are they actually battling it out?

Or do they give each other space?

[Narrator] It's the ideal spot to witness
these two predators coming head-to-head.

Local scientist Candace Fields
will lead this leg of the expedition.

[Candace Fields] I'm from Nassau, Bahamas,
so Bimini is an absolutely amazing place

for great hammerhead sharks,

mainly because of the fact that there's so
much prey available for these guys.

[Narrator] Candace brings Mike to a dive
site known for hammerhead aggregations.

But the occasional bull
shows up here, too.

When they arrive, a swarm of nurse sharks
is already on patrol.

We're really interested to see if, like,
one bull shark comes in

or if maybe a group shows up
because it sure is seeming like

bull sharks may not be
as solitary as we used to think.

Mm-hmm. Hopefully we'll see both
hammerheads and maybe bull sharks.

And so I'm just super pumped to get in the
water and just see what we got.

[Narrator] They don't have to wait long.

-Got one?
-[Fields] Yeah.

Oh. Oh, yup. Hammer.
Time to get geared up.

[dramatic music throughout]

[Narrator] The team drops to the bottom
and camps out next to the chum crate.

It's not long before the great hammerhead
comes in to investigate.

It's a nine-foot male.

His body posture is relaxed
as he circles closer.

They watch the great hammerhead
make sharp, agile turns.

Just like what Erin is seeing in her data.

Then a second hammerhead enters,

a female, about the same size as the male.

She's no threat to the other shark.

They're solitary individuals
here investigating the bait.

[Dr. Heithaus] Candace and I could see
that maneuverability they have,

you know, how they're
able to move up and down,

and also how they interact
with one another.

[Narrator] Both hammerheads
look strong and healthy.

[Dr. Heithaus] It's really awe-inspiring
to be so close to such big animals.

[Narrator] Then shadows
appear from the surface.

Bull sharks.

They glide in to survey the scene below.

Three of them.

A potential gang.

Here's our opportunity to see how these
sharks interact when they get together.

[Narrator] The bulls descend,

swimming a wide, careful arc
around the two hammerheads.

They size each other up,

pushing in closer.

The bulls are smaller

but they have numbers.

A challenge over bait
could happen at any second.

Then they move in
to investigate the humans.

[Dr. Heithaus] They seem
to be a little less focused

on what's going on,
kind of out front of us and more,

"How do I get close
when you don't see me?"

[Narrator] The hammerheads are dominant,
showing no sign of fear.

The body language of the bulls
is relaxed and confident.

It's a bull versus hammerhead standoff.

Suddenly, a game-changer
appears on the horizon.

[Dr. Heithaus] That hammerhead is massive!

[Narrator] The new hammerhead on the scene
dwarfs the other sharks.

It's a 13-foot female.

Now, it's a three-on-three showdown
between bull sharks and hammerheads.

The imposing shark works her way
to the center of the group.

[Dr. Heithaus] She is massive!

[Narrator] She's about the same size

as the hammerhead attacked
in Boca Grande Pass.

[man] That's insane.

[Narrator] But this super predator

brings a completely different
power dynamic to the face-off.

[Fields] It felt as though
she was running the show.

She was making much closer passes to us
than the other sharks were,

perhaps because she feels far less
threatened by us as potential predators.

[Narrator] The bull sharks circle,
sizing her up.

The hammerhead makes quick turns,

possibly bracing for a three-on-one fight.

[Dr. Heithaus] You can practically feel…

…the tension growing in this gathering.

[Narrator] The bull sharks
take turns coming in…

closer and closer.

The 13-foot great hammerhead
stands her ground.

[tense music throughout]

The bull flinches first.

As the hammerhead approaches,
the bull gets a sense of her true size…

and retreats.

[Fields] Things underwater
kind of changed.

The dynamic changed a bit. So it was
really cool to see that she kind of

made everybody else
clear out a little bit.

[Narrator] The team has now seen
first-hand the power and dominance

a giant great hammerhead
has over bull sharks.

Bull shark kinda gave way first.

They both turned,
but it's like that bull shark was kinda,

-"You can have the swim lane first."
-Exactly. And like most people think

that all sharks are
at the top of the food chain,

but that's obviously not the case, right?

Yeah, you can really see
the difference in maneuverability.

Those bull sharks are, like,
a tank trying to get turned around

-and the hammerheads just spin on a dime.
-[Fields] Absolutely.

I mean, maybe that's another reason
why the bulls aren't coming in as much.

You know, the hammerheads
have so much body

and so much capacity to move around,
whereas the bulls don't.

[Dr. Heithaus] That's just
what we were looking for,

an opportunity to see these
two big predators together,

but it doesn't mean
when they get together,

it's gonna be one eating the other.
It might actually take special situations

for bull sharks to go after
hammerheads or vice versa.

[Narrator] After bearing witness
to the head-to-head showdown,

Mike believes there's an answer
to which shark would come out on top.

Based on what we've seen, I think if it
actually came down to a battle

and you had a bull shark
and a great hammerhead,

the great hammerhead's
gonna come out on top.

They are bigger, they are fast,
they are maneuverable.

[Narrator] So how did the hammerhead
become a victim in Boca Grande?

Back in Florida, Mike sits down
with the video one more time.

Instead of focusing on the aggressive
behavior of the bull sharks,

he takes a closer look at the hammerhead.

[Dr. Heithaus] The thing that I noticed
is that the hammerhead's

not really swimming quite right.

Think about that 3D track from Erin,
those sharks are able to turn on a dime.

[Narrator] Unlike the giant
great hammerhead in Bimini,

when faced with a threat, these sharks
swim stiffly in a straight line.

I would've expected it to be accelerating
rapidly, turning quickly,

or even turning the tables
'cause that hammerhead was bigger

than the biggest bull shark that's there.

That suggest to me that that was a
hammerhead that was in trouble.

[Narrator] The great hammerhead
may have been injured before the attack.

It was the height of tarpon season.

It's possible the hammerhead
was hit by a boat,

or accidentally hooked on a fishing line
while pursuing a tarpon.

It's likely the bulls sensed that it was
compromised and went in for the attack.

And the bull sharks were then able to just
follow it and wait for the hammerhead

to be too exhausted
or injured to fight back.

And then they finished it off.

This video is amazing,
but probably the exception to the rule.

In the end, bull sharks
and great hammerheads

are both amazing top predators
in their own right,

but when it comes to
bull shark versus great hammerhead,

they probably don't go after one another
unless the scales are really unbalanced.

But if a great hammerhead
or a bull shark's in trouble,

they can become dinner.