Original subtitles

- These are clearly newer builds made out of stone and concrete.

This is a significant level of military infrastructure.

But this isn't the only structure built on this island.

[narrator] A strange underwater discovery is

made off of a Greek island.

- The piece of debris has a strange circular

design embedded in it.

What is this thing?

[narrator] Marine biologists tagging sharks off California's

Farallon Islands make an interesting observation.

- On the same day that the Great Whites disappeared,

orcas were spotted near southeast Farallon Island.

So why did these sharks vanish?

[narrator] Isolated, scarce on resources, islands are

worlds unto themselves.

Bizarre creatures, ancient gods, and haunting ruins.

Baffling murders and deadly spirits.

What will be discovered on Earth's mysterious islands?

[thunder rumbling]

[narrator] Northern Sudan's Sai Island is the largest

island in the Nile River, splitting the storied

waterway in two as it flows towards the

Egyptian border just 100 miles to the north.

Sai Island is roughly 7.5 miles long and 3 miles wide.

A pretty sizable island considering it sits in a river

and not a more substantial body of water like a

large lake or ocean.

Currently there are very few inhabitants of Sai Island,

but it has a rich history with signs of human occupation

dating as far back as 300,000 years.

And there's evidence of both ancient Egyptian

and Ottoman settlements, so it draws a lot of attention

from the scientific community.

[narrator] In 2015, a team of archaeologists are

excavating a burial site on Sai Island known as Tomb 26.

The tomb is accessed through a rock-cut shaft

that descends to a depth of around 17 feet into

a narrow passageway.

This opens up to the tomb's main chamber,

at the end of which is a small trench along the northern wall.

[narrator] Although some cursory archaeological work was

conducted in the 1970s,

the site has never been extensively explored, until now.

And it isn't long before Tomb 26 yields an

astonishing discovery.

- Under the trench, they find a small chamber

containing the remains of what appear to be two adults,

one male and one female, lying side by side.

It looks like a lot of time and effort went into

burying these people, so they must have been

held in high regard.

So who were they?

[narrator] As the team explores the chamber, they come

across several items that may provide some

clues as to the possible identity of the remains.

Near the head of one of the bodies, they find three

small vessels made of faience, a glazed ceramic, usually

blue-green in color.

Ancient Egyptians used this style of glaze to make jewelry,

sculptures and ritual objects, because they thought these items

had certain magical powers.

So given the presence of faience objects in the chamber,

it's safe to assume this is probably an

ancient Egyptian burial site.

But from what?

[narrator] Further exploration of the site reveals the

presence of more grave goods that could help the team

determine the age of the bodies and pinpoint when the

chamber was constructed.

In addition to the faience vessels, they find three

ceramic flower pots, deep conical bowls with

perforated bottoms.

Two are located at the feet of one of the bodies

and one near the head.

Based on previous archaeological finds on the island,

this kind of pot wasn't present before 1507 BCE

and then fell out of fashion by 1390 BCE.

So it can probably be dated to within that window.

[narrator] The region containing Sai Island was known as Nubia

and was part of the Kingdom of Kush,

which stretched across what is now northern

Sudan and southern Egypt.

Nubia was conquered by the Egyptians sometime

around 1500 BCE, and the Kush people fell

under the empire's rule.

The Egyptians relied on the Kush for the import of many items,

including ebony, incense, ivory, and other luxury goods.

So this area was a sort of overlap between

the two cultures.

[narrator] Expanding the scope of the excavation,

the team makes another astounding discovery.

There's a hidden chamber concealed by a plaster wall,

and inside they find the remains of 11 more individuals.

The remains belong to nine adults and two infants,

and like the first chamber there's an

abundance of grave goods-- faience objects, pottery

vessels, and jewelry, including a beautiful ring

made of gold and silver.

They also find canopic jars, which were used

to hold the organs that were removed from

the body during the mummification process,

usually the lungs, liver, intestines, and stomach.

[narrator] Canopic jars were commonly used for mummification

throughout many periods in ancient Egypt,

starting in the Old Kingdom around 2700 BCE

through the New Kingdom between 1600 and 1100.

They fell out of use during the Late Period.

Canopic jars were an important part of Egyptian

funerary traditions.

The earliest examples were quite plain and had unadorned lids,

but by the period of the New Kingdom,

they could sometimes be found sculpted with heads

that symbolized the four sons of the god Horus.

These were represented by a jackal, a falcon,

a human, and a baboon.

[narrator] Turning their attention back to the first chamber,

the team combs the area around the remains,

searching for any items that may have escaped their notice,

and they are not disappointed.

It's remarkable.

Near the chest area of the male remains an ornate stone scarab

inscribed with hieroglyphics.

Scarabs are beetle-shaped amulets that were hugely

popular in ancient Egypt, particularly in the

funerary context, because they represented

renewal and rebirth.

They were thought to bring good luck in the afterlife

and were as symbolically reverent to the Egyptians

as the cross is to Christians.

[James Ellis] The presence of these elaborate grave goods in

both chambers indicates that these people must have been

prominent members of Egyptian society.

But that still doesn't tell us exactly who they were.

[narrator] Not far from the scarab, the team discovers

another object that may just solve the

mystery once and for all.

They find a shabti, or a figurine in the

shape of a mummy.

The Egyptians placed them in the graves

to act as servants to the deceased in the afterlife.

Shabtis come in all sizes and materials.

The one discovered in the first chamber is made of stone,

and just like the scarab, it's inscribed with hieroglyphics.

[narrator] Armed with a scarab and shabti, the team sets about

translating the inscriptions, and the pieces of the puzzle

finally fall into place.

The inscriptions identify the male in the first chamber

as Khnummose, master of gold workers.

It's assumed that the female beside him is his wife,

and the occupants of the other chamber are members

of his extended family.

There were gold mines on Sai Island,

and the Egyptians relied heavily on the region

as a source for their favorite precious metal.

In fact, it's thought that the word "nubia"

may be derived from the Egyptian word "nub," which means gold.

Khnummose was considered a master goldsmith,

which afforded him a prominent place

within the island's social hierarchy,

hence the elaborate burial site and all the grave goods.

[narrator] As the team conducts an overall survey of Tomb 26,

they can't help but notice loose pieces of mudbrick

scattered around the area.

Most of the important New Kingdom tombs on Sai Island

have rock-cut chambers with adjacent mudbrick structures.

Given the layout of Tomb 26 and the mudbrick debris,

there may have been an impressive structure

here at one time, possibly even a small

pyramid with a courtyard or chapel inside.

[narrator] As the team wraps up its investigation of Tomb 26,

they decide to perform strontium analysis on the remains,

which produces some very unexpected results.

Khnummose was not Egyptian.

In fact, all the individuals found in the tomb

were members of the local Nubian population.

This is a bit shocking.

The style of tomb, the grave goods, evidence

of mummification, all these things point

to an Egyptian burial.

It just goes to show that although these were Kush people,

the culture and traditions of the Egyptians

seeped into many aspects of their lives,

including something as significant as

funerary practices.

[narrator] The lavish tomb of Khnummose, the master goldsmith,

exemplifies the influence of the Egyptian empire in Nubia

during the New Kingdom period, and shows that to the

inhabitants of Sai Island, it was worth its weight in gold.

In the middle of the Firth of Forth estuary,

two miles from the closest shore and 30 minutes by

boat from Edinburgh,

lies a little jagged hunk of volcanic rock

called Inchkeith Island.

It's just a mile long, with an area of 56 acres.

Set in the gateway to Scotland where the river connects

to the North Sea, a major trade route

for the country, the isles of the Firth of Forth

are home to abundant bird and marine life, including seals.

In 2000, a small group of grey seals

began giving birth on Inchkeith, and now more than 500 pups

are born there every year, drawing the interest

of local experts.

[narrator] Zoologists studying wildlife on the isles

are observing newborn seals on a small stretch

of Inchkeith Beach when they are drawn to a

derelict shed up the shore where the sickly smell of death.

The smell belongs to a seal pup that passed away here,

leaving behind a skull and tuft of white pup fur.

There is an eeriness to this young seal

passing in an abandoned structure like this.

What happened here?

- Wildlife has been steadily reclaiming

this uninhabited island for decades,

but while the animals are here now,

one good look at this place tells you

that was not always the case.

[narrator] Exploring the island further, up from the beach near

the island's highest ground and next to the lighthouse,

is a massive stone wall.

The wall is 150 feet long, 5 1/2 feet thick,

and can be up to 20 feet tall in some areas,

but it's very clearly fortified.

There are even some windows in the wall

that are like 2 feet wide.

So it kind of looks like a castle, but is that what it is?

The Firth of Forth is positively surrounded by castles.

Another on Inchkeith seems unnecessary,

but what castles do need is protection.

So perhaps this was a fort?

[narrator] Walking along the imposing structure

at the entrance to a courtyard, they find a panel with a symbol

of a shield carved into the stone with some residual paint.

This is the symbol of the Royal Arms,

the date 1564, and the initials M.R.

for Maria Regina, better known as

Mary Queen of Scots, who was Queen of Scotland

from 1542 until 1567.

This wall is what remains of a 16th-century

Franco-Scottish fort.

[narrator] Today, Scotland and England are part of

Great Britain, but before the Act of Union in 1707,

which united the two countries, the neighboring nations

were often in conflict.

From the late 13th until the mid-16th centuries,

Scotland and France were in a military alliance

against the English.

In its full glory, the massive fort

would have featured corner towers

and been visible for miles, acting as a deterrent to

Scotland's English enemies.

The window found earlier is more accurately a gun embrasure,

but this isn't the only structure built on this island.

[narrator] Just down the hill, they stumble upon more fortifications.

Only these structures aren't as rough or overgrown

as the 16th century fort.

These are clearly newer builds made out of stone and concrete.

This style of fortification was added at some point

to the northwest, the north, and the south side of the island.

They include trenches, towers, tunnels,

and much larger gunning positions.

This is a significant level of military infrastructure.

[narrator] While surveying the other structures,

they come across two different date stones

placed above the doorways in a way similar to the

royal arms of the first fort.

They read "VR 1880."

That VR is Victoria Regina, Queen Victoria.

These fortifications were commissioned by the War Office

in the late 1800s in response to rising European tensions.

There are even a number of large block houses or barracks

from the same period capable of housing a small army.

As a result, fortifications at Inchkeith grew

to include munition storage, mess halls,

and supporting infrastructure like medical services.

In 1914, European tensions finally reached boiling point,

and the world was plunged into war.

Britain, France, Russia, and later Italy in the United States

aligned against the central powers of

Germany, Austria-Hungary, Bulgaria,

and the Ottoman Empire.

[Alison Leonard] The war lasted 4 difficult years,

ending in 1918.

And while World War I didn't breach the shores of Scotland,

the Scots were a huge part of the British war effort.

Ultimately, the country lost many men,

and some estimate it could be as great as 10%

of the adult male population, so those aged 16 to 50.

This is an extraordinary loss.

When peace returned to Great Britain,

Inchkeith fell out of use apart from its

occasional maintenance.

In the absence of a near-constant military

and human presence, birds and other wildlife

began to come back.

But that still doesn't explain everything.

[narrator] Looking at the lay of the land today,

a number of modern structures stand out

among the graying fortifications associated

with the World War I era.

These other buildings are primarily red brick

and concrete structures.

They're scattered across a small island among,

and in some cases even attached to the older fortifications.

Why?

[narrator] The 1930s were marked by the rising threat of Nazism.

As such, Britain and many other European nations

began preparing for the very real possibility

of another war, at home and abroad.

[Anthony Cantor] The military began refurbishing Inchkeith

in the mid-30s, upgrading gunning positions and

building new support structures,

including anti-aircraft positions.

They converted old buildings to serve the

needs of modern warfare, so they upgraded the

radio station with state-of-the-art radar.

The island's wildlife was once again evicted,

as Inchkeith was gearing up to play an important

role in the war effort.

By the time the war started in 1939,

the island's capacity reached well above

1,000 service members, and that was possible

because of support structures and brick barracks for

additional lodging.

[narrator] War came to Inchkeith in October 1939,

when a dozen German bombers flew over the Firth of Forth

to carry out the very first air raid on Britain.

[James Ellis] Allegedly, a soldier stationed on Inchkeith

actually attempted to shoot down the German bombers,

but was unsuccessful.

Unlike in World War I, civilians in World War II

found themselves frequent targets of enemy attacks.

During this war, Scotland suffered over 500 air raids

from the Nazis, and across the UK as a whole,

the raids resulted in the deaths of more than 40,000 civilians.

Ultimately, Britain and her allies prevailed,

defeating Germany in 1945.

[narrator] Today, a bird's-eye view of the island highlights

the extraordinary extent of fortifications layering

the island's landscape.

Now, home not only to grey seals, but nesting

cormorants, puffins, and European shags, the

building's presence and history is still keenly felt.

[Alison Leonard] And yet, that is still not the most intriguing

thing about this rock in the middle of the Firth of Forth.

[narrator] King James IV was the King of Scotland from 1488 to 1513.

By most accounts, he was a unifying force for the country,

who greatly improved Scotland's standing abroad.

The King was an inquisitive man with an interest in

language and communication, as he was rumoured to speak more

than five languages himself.

So in 1493, he commissioned an experiment.

A deaf-mute woman and two infant children were sent to

live in exile on Inchkeith, the island's first

documented residence.

He commissioned this experiment in the hopes

that he'd be able to observe the true language of humanity.

It's very warped, but here's the idea.

By isolating the children and restricting their contact

with the outside world, he believed that they would

naturally grow to speak what was the first

language of man and God.

[narrator] There were reports that the children spoke Hebrew,

making the experiment a success.

However, others said that they would bleat

like the goats and sheep that were on the

island with them.

- The results of the experiment were unconfirmed,

and some even say that the family died on the island.

While their outcome remains a mystery,

they would not be the last people to be relegated

to isolation on Inchkeith.

[narrator] In the late 1400s, a terrifying and contagious

disease was sweeping the continent of Europe,

and no population was spared.

It ravaged its victims, leaving them covered in bursting

boils and rotting flesh.

This was the epidemic of syphilis,

a sexually transmitted disease caused by a bacterial infection.

Today, it can be treated with relative ease,

but centuries ago, it was feared and misunderstood.

By 1497, syphilis had reached Scotland's shores,

and it was particularly bad in Aberdeen and Edinburgh

because of their high populations

and their connections to international trade routes.

As the infection spread, victims began piling up,

so the kingdom was searching for a way to hide the problem

that was quite literally plaguing the nation.

Victims were rounded up to be placed in isolation,

and what's more isolated than Inchkeith?

[narrator] For years, Inchkeith was used to house the infected

as a convenient quarantine site, though most would

never leave the island.

No one knows how many sick people eventually

succumbed to illness and were buried on Inchkeith,

as there were no records of these people.

But what is known for sure is that this little island,

just 2 miles from the shore, has played an outsized role,

for better or for worse, in the perceived defense of

Scottish lives for centuries.

[narrator] These days, Inchkeith's rocky landscape,

covered in crumbling forts, is a constant reminder of

its rich and complex history.

Only now, its sole inhabitants are the seals

and birds once again.

[narrator] Antikythera is a tiny Mediterranean island

150 miles south of Athens.

It is nestled between Crete and the Peloponnesian Peninsula,

where 3 seas-- the Aegean, Ionian, and Cretan--

come together.

It's so small that you can get to most places

on the island by foot, and its longest paved street

is less than 2.5 miles long.

Its placid beaches and coves remain largely undisturbed,

and it doesn't receive many tourists.

In fact, there are only 24 full-time residents

in its main village and port, Potamos.

- All of the island's goods are imported by boat,

but the seas in this area are notoriously temperamental.

Sometimes they prevent ships from getting to

the island altogether.

So you can see why it's pretty cut off from

the rest of the world.

[narrator] In 2022, while conducting exploratory dives

off the northeast coast of the island,

divers from the joint Greek-Swiss archaeological

research vessel Typhoon see something curious.

At first, it looks like a giant boulder

covered in barnacles and sea sludge.

But on closer inspection, the divers are able to

make out eyes and hair.

Is this a human head?

Well, it is a head, but thankfully, it's

made from marble.

The head is massive, and the face is oddly familiar.

This is one of Greek mythology's main heroes,

a Greek demigod known for his incredible strength

and amazing feats.

It's Hercules.

But I've got to ask the obvious question--

where is the rest of him?

[narrator] In 1901, a group of Greek divers are sailing to

Tunisia when a storm forces them to alter their course

and take shelter on Antikythera.

When the storm ends, they decide to dive off

the coast of the island and are horrified

by what they find.

It's an eerie scene-- lifeless, naked bodies

scattered across the ocean floor at a depth of 150 feet.

But the thing is, thankfully, they're not actually bodies.

They're statues, and one of them is the

headless body of Hercules.

- This is a remarkable discovery, but what's truly

exciting is that there's an array of artifacts scattered

amongst the statues, including jewelry,

glassware, pottery, art.

And there are pieces of wood lying about as well,

so it seems like the site of an old shipwreck.

[narrator] Greek authorities are brought in to coordinate

salvaging and transportation of the artifacts

to the National Archaeological Museum in Athens

to unravel the mystery of how they found their

way to the sea floor.

A thorough examination and classification

of them is essential.

Analysis of the artifacts and wood reveals

that the wreck was a merchant ship sailing

across a busy shipping route in the Aegean Sea around 60 BCE.

It was most likely caught in a storm

and smashed into the cliffs of Antikythera.

The ship is estimated to have been about 50 meters long,

which was huge for the time, and its 300-ton capacity was

maxed out with luxury items.

[narrator] While analyzing a piece of algae-covered debris

from the shipwreck, a Greek archaeologist sees

something that is puzzling.

The piece of debris has a strange circular

design embedded in it, and what looks like algae

is actually the greenish patina caused by oxidation.

What is this thing?

It's a 7-by-6-inch hunk of heavily encrusted

corroded bronze, and given the embedded design,

it was crafted by human hands a very long time ago.

Could it be some form of ancient art piece?

The ancient Greeks had a long history of making

art out of bronze.

Works like the Delphi Chariteer from 480 to 460 BCE

and the Hellenistic Prince from the 2nd century BCE

speak to the extraordinary talents of early

Greek sculptors.

[Dan Riskin] Bronze is an alloy.

It's made out of 90% copper, 10% tin.

That makes it strong, ductile, and a whole

lot easier to work with than other materials,

especially marble.

[Anthony Cantor] Unfortunately, most ancient Greek bronze

statues were melted down at some point in history

to make things such as coins, weapons,

or even new works of art.

But the piece of bronze from this wreck doesn't

resemble part of a statue.

It's too large to be a coin, and it doesn't look

like any part of a weapon.

So what is it?

[Dan Riskin] Some of the pieces also have circular designs

with the largest circle being over 5 inches in diameter.

But here's the thing.

They look sort of mechanical, almost like

the gears found in a clock.

[Anthony Cantor] The ancient Egyptians divided the day into

two 12-hour parts using sundials to track

the sun's path in the sky.

The oldest sundial ever discovered was found in

Egypt's Valley of the Kings and dates from the

13th century BCE.

It consisted of a plate and a gnomon,

which was a stick that cast a shadow on the

plate displaying the time.

The sundial was introduced to Greece around 560 BCE

and was one of their primary ways of telling time.

But while it did track time, it didn't have any actual gears.

[narrator] The device's corroded fragments continue to baffle researchers.

But then, after a number of significant breakthroughs,

a British scientist and Greek radiologist subject the

pieces to X-ray analysis.

The results are astounding.

The scans reveal an incredibly elegant design,

including 30 gears.

Most notably, there is a 38-tooth gear that

drives a 127-tooth gear, forming a system where

the rotation of the first sets the others in motion.

And each tooth measures just one millimeter.

It's an incredible feat of precision.

[Dan Riskin] The fact that there are gears here is an exciting

step, but the real magic happens when you start counting how

many teeth are on the gears, because that's how you

can find out what it does.

Its gear ratio is connected to an ancient Greek cycle

linking the moon with the sun.

Early Greeks found out that the phases of the moon

repeat on the calendar dates almost perfectly every 19 years.

So one way to calculate where the moon would

be on any given date would be to have two

interconnected gears with exactly the

right number of teeth so that they move just

like the sky does.

An invention like that could help a person at sea based

on the position of the moon.

Day or night, if you could see the moon, you would know exactly

which way you were pointing.

So could this be an ancient navigational instrument?

[narrator] Ancient celestial navigation used heavenly bodies

such as the sun, stars, and moon for sea positioning.

One key tool used by the ancient Greeks was the astrolabe,

meaning "star holder" in Greek, that measured the

altitude of celestial bodies above the horizon

to determine latitudes on land and at sea.

The first geared astrolabe was invented in Iran.

It used mathematical ratios to replicate planetary

motions and orbits.

These functions advanced celestial studies,

improved navigation, and helped calculate

Muslim prayer times.

But this astrolabe was invented almost 1,300 years after the

device we're talking about.

This doesn't make sense.

If it's not an ancient navigational device,

what on earth could it be?

[narrator] In 2005, researchers employ advanced imaging

technology to uncover subtle surface details of the fragments

and produce 3D renderings of their internal structures.

Their findings unleash a storm of revelations.

We are looking at inscriptions that haven't been read

for over two millennia.

There are 15,000 of them, though researchers are only

able to decipher 3,000.

Despite the fact it's missing two-thirds of its

components, two-thirds of them, researchers are still

able to figure out that this incredible mechanism

would have been kept in a shoebox-sized wooden case

operated by a crank that turned bronze gears and pointers.

This thing was amazing.

[narrator] The artifact, now known as the

Antikythera mechanism, was recently digitally

reconstructed using advanced computer modeling,

unlocking even more insights into

its purpose and functionality.

[Anthony Cantor] It's considered the world's first computer,

capable of a variety of functions in one unit.

It tracked the movement of planets and stars

and predicted eclipses.

It also provided a calendar that connected celestial phenomena

to cultural and athletic events such as the Olympic Games.

And it could move its user forward or backward in time

with just the use of a hand crank and dials.

The Antikythera mechanism is the most technologically

complex device in antiquity, and there are no copies of

it anywhere in existence.

This is mind-blowing technology that defies

the era it hails from, raising far more questions

than it answers, like what was its exact purpose?

Who made it? What else could it do?

[narrator] Researchers hold out hope that, like the reuniting of

Hercules' head with its body, the 2,000-year-old mystery

of the Antikythera mechanism may one day be solved.

Until then, the wreck off the sleepy island of Antikythera

continues to hide its secrets beneath layers

of sand, rocks, and time.

[narrator] Roughly 30 miles west of San Francisco's

famous Golden Gate Bridge sit the Farallon Islands,

a rugged archipelago in the Pacific Ocean.

The Farallons are also known as the Devil's Teeth

for their jagged, somewhat menacing appearance.

They stretch roughly five miles in a northwestward direction

and are composed of four groups of islands,

Noonday Rock and the North, Middle, and

South Farallon Islands.

The first recorded landing was by Sir Francis Drake in 1579

when his expedition stopped to collect bird

eggs and hunt seals.

Nowadays, visitors are forbidden from visiting the islands,

but there are a handful of researchers that live here.

To say that the Farallons are home to an abundance of wildlife

would be putting it very mildly.

Nearly 300,000 birds call these islands home.

That makes it the largest colony of nesting seabirds in

the continental United States.

And the surrounding waters are teeming with sea life,

including everybody's favorite marine predators,

killer whales and great white sharks.

[narrator] In 2009, a team of marine biologists are

tagging great whites off the coast of

southeast Farallon Island in order to track their

migration patterns when they notice a

strange phenomenon.

They managed to tag 17 sharks, but when they looked

at the tracking data, within eight hours all of them

had disappeared from the area and only one returned.

The waters around the Farallons are prime

territory for great whites with an abundance of

prey at their disposal.

So why do these sharks vanish?

Maybe it has something to do with climate change.

It's no secret that ocean temperatures have been steadily

rising in recent years.

So it could be that the sharks are adapting to this change

by seeking out different waters.

Great whites are endotherms, meaning they produce and

control their internal body heat when their body temperature

is slightly higher than the water around them.

Because of this, they do especially well in cold water.

But juvenile great whites are too small to increase

their body temperatures as much as adults do, so they

tend to favor warmer waters.

Traditionally, this meant that they spent more time

in shallower areas closer to the coastline,

but the warming oceans have broadened their movements.

[narrator] A recent study showed that between 2014 and 2020,

increased water temperatures led young great white sharks

to migrate over 350 miles farther north

than their usual territory off the coast of California,

venturing into waters that were formerly too

cold to sustain them.

It's possible that the sharks that fled from

the Farallon Islands are simply choosing to

spend their time elsewhere in response to a

changing habitat.

But their disappearance happened really abruptly,

not gradually over time.

So you'd expect a less gradual explanation, something sudden.

Maybe it was something caused by humans, like noise pollution.

[narrator] Known scientifically as anthropogenic sound,

human-made noise pollution can have serious detrimental effects

on wildlife populations, both on land and at the oceans.

Think about all the ways that humans impose noise

on the world's oceans.

At any given time, there are thousands of ships on the water,

their powerful engines screaming into the depths below.

And it's not just boat engines causing the problem.

Offshore oil rigs, construction, dredging, sonar,

all these things interfere with the natural sound

frequencies in the ocean.

Aside from the interference, it's been shown that

anthropogenic sound can actually do physical

damage to marine life, causing hearing loss

and damaging tissue.

And this damage can affect the lateral line system,

which is a sensory system that's vital to the survival

of great white sharks.

[narrator] The lateral line system is a row of small pores

that run from the shark's snout to the tail.

Surrounding water flows through these pores,

and special sensory cells called neuromasts detect

any pressure changes.

The neuromasts have these tiny, hair-like projections on them,

and any change in the water around the shark--

turbulence, currents, vibrations--

shakes those hairs to stimulate the neuromasts.

It basically turns the whole side of the shark into this

super-sensitive eardrum.

And it is powerful enough to detect the

wiggle of a fish's fin.

[narrator] Along with the lateral line system,

sharks have other finely-tuned senses, including hearing,

and they are sensitive to very low frequencies.

So certain anthropogenic sounds could potentially cause them

to leave an area that's causing them distress.

But the waters around the Farallon Islands

are part of the Greater Farallones National

Marine Sanctuary.

So there wouldn't be much in the way of noise

pollution to spook them.

It has to be something else.

[narrator] Looking for answers, the team consults historical

data and comes across an interesting connection

between the shark's departure and another of

the ocean's apex predators.

On the same day that the great whites disappeared,

orcas were spotted near southeast Farallon Island.

Over the course of two and a half hours,

they killed three seals and then headed off in

a northerly direction.

There's overlap in the ranges of orcas and great whites

along the Pacific coast, so it's not unusual to find

them in the same areas.

Great whites are found from northern Mexico up to Canada,

and orcas have an even bigger range,

from southern Mexico all the way up to Alaska.

The territorial overlap is highest during

fall and early winter, when seals come ashore

on the Farallon Islands to molt, to breed,

and have pups.

Great whites will normally spend four to four and a half months

hunting at southeast Farallon during this time.

Not much is known about the relationship between

orcas and great whites.

But given the disappearance of the sharks when

the orcas were present, is it possible that

the great whites, one of the most ferocious

animals on the planet, are scared of orcas?

[narrator] Digging deeper into the data,

the team comes to realize that

the sharks' flight reaction is not unique to this one event.

Based on the records, in years when orcas were observed

around southeast Farallon Island,

before or during the peak fall seal hunting season,

rates of predation by great whites plummeted by three

and a half to seven times.

Let's put some numbers on this.

The sharks' hunting success in this area

is usually around six kills per 100 hours per shark.

But that number drops from six to as low as 0.84

when there are orcas around.

That is an 86% drop in hunting success.

The question is, why?

[Alison Leonard] Perhaps there is a fear factor.

While orca attacks on great whites around the

Farallon Islands are rare, they do occasionally happen.

[narrator] In October of 1997, a great white shark was

systematically hunted down and killed by orcas

near southeast Farallon Island in full view of a boat full

of whale-watching tourists.

And if that wasn't shocking enough,

what the whales did next would leave the

onlookers utterly stunned.

They surgically removed the shark's liver

and then simply let its massive, lifeless body

sink into the depths of the ocean.

That must have been wild to witness.

Shark livers are very attractive to orcas

because they're rich in a highly nutritious oil called squalene.

They're also quite large, making up a quarter of

the shark's body weight and occupying 90% of

their body cavity.

[narrator] In March of 2023, 20 disemboweled sharks washed

ashore on a beach on Gansbaai, a small fishing port around

70 miles southeast of Cape Town, South Africa.

Their livers had been methodically removed

by a notorious pair of orcas well-known to researchers.

They call these two whales Port and Starboard

because they both have collapsed dorsal fins

and on one of them it leans to the left, or Port side,

and on the other it leans to the right, or Starboard side.

It's thought that these two orcas were

responsible for killing at least 17 seven-gill

sharks in a single day.

These orcas really live up to their other name, Killer Whale.

[Alison Leonard] But their appetites are not limited to

smaller shark species.

Researchers believe that they've been responsible

for eight great white deaths since they were first spotted.

One such encounter was even caught on drone video,

marking the first time an orca attack on a great white

has ever been documented firsthand.

It's difficult to imagine the great white shark,

which is probably the most feared underwater predator,

being afraid of anything, but it does appear

that they might actually be scared of orcas.

This fear sets off a rapid migration,

which likely explains the exodus from Farallon Islands.

[Alison Leonard] It's kind of ironic, given that in

popular culture great whites have long been vilified as

monstrous killing machines hell-bent on terrorizing

anything that comes near them, whereas orcas have been

portrayed as the harmless, gentle panda bears of the sea.

But try explaining that to the liverless sharks.

[narrator] The Farallon Islands were given the nickname

"The Devil's Teeth" due to their frightening appearance.

And while there's little doubt that great whites

are one of the planet's most awe-inspiring apex predators,

in the waters around the Farallon Islands,

they may not be the most intimidating.