Original subtitles

Around a tiny chain of islands

off the coast of Oman,

the stage is set for one of nature's greatest spectacles.

Summer weather drives nutrients in

from the oceans depths,

where they meet the Arabian sun,

causing an explosion of life.

For four months,

there's a feeding opportunity like no other.

Creatures journey from far and wide to join the feast.

Ocean travelers like hawksbill turtles

and seabirds.

But no visitor is more dramatic...

than the largest fish on earth:

the whale shark.

This whale shark is a tiny giant.

Nine feet long, just a third of his full potential.

Based on his small size,

he's probably just entering his teenage years.

The little giant's on the move.

But he's not alone.

A larger male...

and a huge female are traveling nearby.

Whale sharks are mysterious.

Despite being the biggest fish on the planet,

they're poorly known and endangered.

These three are part of a population

of 500 whale sharks

that live most of the year in the Arabian Gulf.

The gulf stretches between Iran and Saudi Arabia

for more than 600 miles...

providing nearly 100,000 square miles of inland sea.

Setting out on an epic journey,

the sharks are leaving waters north of Qatar,

passing the coast of the United Arab Emirates

on the Arabian Peninsula.

They avoid the shallows,

as they pass the coast off Abu Dhabi.

The shallow seas of the Arabian Gulf

can reach over 95 degrees.

The waters here are sweltering and very salty.

They create the perfect conditions for mangroves

and a number of bird species.

(Squawking)

Below the waves, seagrass meadows waft

like open prairies.

Rich in fish, the meadows are a favorite hunting ground

for humpback dolphins...

..and fish-loving osprey.

Despite the abundance,

for the whale sharks it might as well be a desert.

They typically avoid the shallows

because there's little here that they can eat.

Instinct drives them forwards.

They know there are feeding opportunities ahead.

Beyond the Arabian Gulf lies the Gulf Of Oman:

cooler, deeper water where life abounds.

Within this safe haven,

tucked nine miles off the coast of Oman,

is a chain of rocky islands

known as the Damaniyat Islands.

At first glance, the dramatic rocks appear barren

and uninviting.

But the real riches lie beneath.

Here, the slightly cooler waters

create the perfect conditions

for corals to grow.

Like an oasis in the desert,

the coral reefs are magnets to marine life...

..offering food and shelter

to a colorful community of residents.

The reefs support over 100 species of coral

and nearly 600 species of fish.

It's June.

Along the southern shores of the Arabian Peninsula,

the waves are churning.

This brooding sea marks the start of the monsoon.

(Thunder rumbles)

Driving weather fronts, winds and currents

race north across the Arabian Sea...

..stirring up cold water from the ocean depths...

..and battering the Arabian Peninsula.

But tucked inside the Gulf Of Oman,

the Damaniyats are protected.

Ideally located, the islands are sheltered

from the ocean storms,

but do receive swirling eddies of cold water...

..that bring with them nutrients from the abyss.

The Damaniyat Islands are in a prime position

to host a dramatic explosion of life.

Seabirds spend most of their lives offshore

but, sensing a change in the seasons,

they start homing in on the islands.

They need to return to their breeding sites

and find their mates.

A critically endangered female hawksbill turtle

joins the journey.

She was born on the islands

and it's also time for her to return to breed.

She travels 600 miles

between her feeding and breeding grounds

and can set a good pace...

..covering 12 miles a day.

She's been swimming continuously for weeks.

But her effort is about to pay off.

Any day now...

she'll reach the islands.

When nutrients from the ocean meet Arabian sunlight,

it creates the perfect conditions for growth.

Thanks to this seasonal fertilizer,

productivity of marine life can increase tenfold.

Tiny plant-like algae bloom,

the basis of the ocean's food chain.

The dominant species covering the reef is coral.

These tiny animals form huge colonies,

laying down protective shells

that become the foundation of the reef.

Corals are prolific,

but they grow slowly and only when it's warm.

The cooler monsoon conditions tip the balance

in favor of microscopic plant-like algae

that thrive in the frigid currents.

They grow faster than the corals,

cloaking the reef in thin green filaments.

It's a welcome feast for some of the smaller locals.

So-called dancing shrimps use their tiny pincers

to pick the algae from the coral fronds.

These seasonal greens

break up their typically carnivorous diet.

Their foraging will help ensure

the algae doesn't drown out the coral.

Wrasse, in turn, enjoy feasting

on the small creatures of the reef.

Wrasse are key players in the reef ecosystem.

They comprise the second largest family of marine fish

and are abundant on reefs all over the world.

The most common around the Damaniyat Islands

are these big shoals of crescent wrasse.

They're also known as moon wrasse

in both cases because of the yellow,

crescent-shaped portion of their tails.

This gang has a complex social structure.

A larger and more colorful dominant alpha male

maintains a harem of lesser males and females.

They're a rowdy bunch, constantly squabbling,

nipping at their shoal mates...

..or any other fish that get in their way.

The big dark-blue male is about 18 inches long.

His minions are smaller and greener in color.

They may be small, but they have fiery tempers

and can hold their own on the reef.

As the monsoon conditions heighten,

productivity increases,

filtering through every level of the food chain.

The churning waters become cloudy

with dense wafting blooms of tiny algae

called phytoplankton.

These, in turn, feed zooplankton,

the minute larval forms of shrimps and crabs

that drift in the ocean.

Carried by currents through the open water,

the bloom of plankton acts as a dinner gong

to the creatures of the reef.

Many small species of fish dart away

from their safe crevices in the coral

to snack on this profusion of plankton.

The larger crescent wrasse join the feast.

Everyone wants to eat as much as they can

as quickly as they can.

The monsoon will only produce these riches

for a few months.

But this abundance of food

is a mixed blessing for the fish.

(Squawking)

Birds flock over the waves.

They've travelled vast distances to take advantage

of the densely-packed pickings.

White-cheeked terns pluck small prey from the surface.

(Chattering of terns)

Bridled terns have also made the journey,

but not solely to feast.

They've timed their breeding season

to coincide with this abundance of fish.

But first they must find their mates.

About a third of bridled terns are monogamous

and will reconnect with the same partner

for several years.

Not all couples will be reunited.

The sea's a dangerous place.

Storms and predators can take their toll,

and some travelers don't make it back

to the sanctuary of the islands.

This male bridled tern scans the horizon.

The faithful featherweight ignores the singletons.

He hasn't seen his mate for nine months

while he's been out at sea.

He waits to see if she can find her way back to him.

The tern colony is very strategic

in where it makes landfall.

Away from the mainland, the islands are free

of mammalian predators like rats

that would eat their eggs.

The Damaniyat Islands also provide easy access

to the food-rich reefs.

Below the waves, the feasting continues.

Thousands of deadly ocean wanderers

emerge from the blue,

lured to the islands by the smaller fish

feasting on the plankton bloom.

These are striped, or Indian, mackerel,

each a foot of muscle built for high-speed pursuit.

Larger still, the three-foot Talang queenfish,

a powerful solitary hunter.

Joining them, six-foot stripy brown cobias.

All of these predators usually trawl the open sea

looking for prey.

But they have easy pickings here.

Their targets are smaller fish

that risk leaving the safety of the reef

to enjoy the plankton soup.

The appearance of these deadly shoals is a prelude,

a sign that summer is well underway,

and conditions are just right to lure in the ocean giants.

The unmistakable form of a shark

dwarfs the huge cobia.

The first of the travelers

arrives from the Arabian Gulf.

The largest whale shark ever recorded was 65 feet long,

and tipped the scales at 37 tons.

Whale sharks are the biggest fish on earth.

But, mysteriously,

all of these newcomers are juveniles,

only a fraction of that size.

Whale sharks can live for a century,

but, based on their size,

these are probably twenty-somethings.

Despite their relatively young age,

they've made this journey before.

Whale sharks are highly migratory,

ranging over vast distances

around the warm oceans of the world.

Between June and October, the juvenile giants

grace the reefs of Oman with their presence.

They bring with them numerous other ocean travelers.

These three-foot-long remoras are hitch-hikers.

Their dorsal fins are highly modified,

with a sucker on the top of their heads.

They swim up to larger animals

and clamp onto the host's skin with the suction cup.

When space is running out below,

they cling to the top of the fin,

which means turning upside-down.

Though with their streamlined shape,

it's hard to tell which way is up.

When a remora wants off,

it simply swims forwards, releasing the vacuum.

By riding bigger animals,

the remoras travel over large distances,

but hardly expend any energy.

They steal crumbs

from whatever their host is eating and consume its waste.

To pay their way, they remove parasites

from the whale shark's skin.

It seems the whale shark is fed up

of quite so many uninvited guests.

The remoras won't be easy to shake off.

They know their ride is taking them

to good feeding grounds.

Unlike many sharks,

the whale shark is not armed with ferocious teeth.

He's a filter feeder,

carefully sieving plankton from the sea.

Like all sharks,

whale sharks can detect the faint electrical pulses

of other animals in the water,

so that they can sniff out the tiniest traces of food.

An ever-growing entourage of cling-ons gathers

to take advantage of the young behemoth.

These golden trevally edge towards the giant,

looking to shelter against his bulk.

The juvenile trevallies will become

fearsome hunters in adulthood,

reaching nearly four feet in length.

But these infants are still small enough

to be food for fish like the large cobia.

Riding the pressure wave ahead of the huge shark,

they can also save energy and pick off plankton

before it disappears down the shark's gullet.

As June progresses, more and more whale sharks arrive.

There are other species too.

The female hawksbill finally makes it to the Damaniyats.

At three feet long, and weighing in at 170 lbs,

she's no small fry.

Though she will occasionally eat fish,

the profusion of prey doesn't interest her.

She's quickly greeted by another hawksbill,

a curious younger female.

But the older turtle isn't here to socialize.

She's on a mission.

She's come here to mate and lay eggs.

Mature males, distinguished by their long thick tails,

are already making themselves at home on the reef.

An old salty seadog...

..this male has spent decades at sea.

Like the whale sharks, he's picked up hitch-hikers.

Not just barnacles, but also a huge conch.

The conch is a sea snail and uses a rasp-like tongue

to scrape algae off the turtle's shell.

The first month of monsoon conditions

brings in many new visitors.

And now, as June moves into July...

..the next phase of life gets underway in the Damaniyats.

The male bridled tern is still waiting for his mate.

But around him the colony grows.

Like the turtles,

the seabirds time their arrival on the reef to breed,

knowing that the seasonal abundance

will provide well for their chicks.

The island's low vegetation

gives the male a vantage point to scan for his mate.

This tern's lost a leg on its journey

perhaps to a large ocean predator like a shark.

He's one of the lucky few that survive such trauma.

The injury doesn't seem to have affected his health

and won't impact his fishing skills.

But he's a reminder of the hardships of life at sea.

Bridled turns are characterized

by their striking black and white faces.

Each of the birds has distinctive markings

to help them recognize each other in a crowd.

Most settle on the ground...

..near other birds like sooty gulls...

(Shrieking)

..and these swift terns

with their large yellow beaks.

Close cousins to the bridled terns,

the swift terns are pale with black caps.

They bundle together in tightly packed colonies.

(Squawking)

There are about 4,000 breeding pairs

around the coast and islands of Oman.

(Squawking and cackling)

They space themselves out at neck length from each other.

The occasional peck

reminds neighbors of the boundary lines.

Nesting so close together

provides safety from predators.

There are more pairs of eyes to look out for danger,

and more birds to work together

to drive away any threats.

The bridled terns, however, prefer a bit more space.

The love-struck male's mate has finally made it back

from her winter at sea.

The couple reaffirm their bond

through a courtship dance.

They need to maintain their close bond

to present a united front against other pairs

that would like to muscle in on their relationship,

or their newly chosen nest site.

They're going to have to work closely together

if they're to successfully raise a chick.

Usually ground nesters, the bridled terns

will use the barest scrapes in the rocks

in which to lay their eggs.

Some seek a springier mattress.

The low-lying vegetation

provides a little more cover for the nest

to keep out the neighbors.

Sooty gulls can be egg thieves.

(Thunder rumbles)

By the end of July, the monsoon reaches its peak,

stirring things up for the Damaniyat islands.

Both residents and visitors make the most

of its seasonal riches.

The young whale shark,

still looking like a floating commune,

plows on in his mission to feed.

The great arching slits along the side of his head

are modified gills.

Water goes in through the mouth

and out through these openings.

They house gill rakers,

hair-like structures that catch particles in the water,

trapping even microscopic plankton

as the water passes through.

The retained food can be wafted to the throat

and swallowed.

A medium-sized whale shark like this one

filters more than 160,000 gallons,

collecting 6 lbs. of food per hour.

Recent studies suggest a shark like this male

will consume around 46 lbs. of food a day.

That's the equivalent of 184 typical hamburgers.

In addition to filtering food,

the gills are also responsible for breathing.

The whale shark must always keep swimming

to pass oxygenated water through its gills.

Like other open-water sharks,

if he stops swimming, he'll die.

(Squawking)

By mid August, thousands of birds

are nesting on the islands.

The reunited bridled terns have a nest site

and are ready to lay their eggs.

The swift terns have already laid theirs.

It's hot weather for brooding.

They all face into the breeze and pant,

trying to keep cool.

Some stand over their eggs,

shading them and allowing the breeze to circulate.

The eggs are mottled for camouflage.

For many species of birds,

the unique markings also allow the parents

to distinguish their eggs

from those of their neighbors.

It's been shown that swift terns

don't have these skills.

Even after they hatch, it takes a few days

before these birds are able to recognize their own young.

Occasionally, an egg is damaged or infertile,

or one of the parents is lost at sea

and the nest is abandoned.

Without an adult shading it from the sun,

the egg will boil in the heat.

Nearby, the sooty gulls have laid two.

The female takes over nest-shading duties

while the male patrols the tern colony.

This abandoned hard-boiled egg

would make a good meal.

But the terns stand shoulder to shoulder,

so that there is no way through

the densely-packed flock.

It's not just the birds laying eggs.

With so much food available,

the Damaniyats' marine life is also ready to breed.

All crescent wrasse are born female,

but as they mature, some of them will become male,

a process that takes just ten days.

Now that the breeding season is getting underway,

that transformation is taking place for some.

With new males around,

the big blue dominant male will have to work harder

if he wants to be the one to breed with the females.

Parrotfish are also breeding.

Like the wrasse, their shoals are a mixture

of drab youngsters, mature females,

and a big, colorful, dominant male.

As the excitement grows,

the males follow the females.

They all dash out

and release sperm and eggs by the millions.

It's a scattergun approach.

The idea is that if enough are pumped out,

at least a few of the eggs and sperm

will fertilize each other

and manage to escape the other fish

that gather to feed on them.

Some of the crescent wrasse risk venturing

far above the safety of the reef

to launch their eggs directly into the current,

so that they'll be carried away from the hungry mouths.

The fish orgy creates a soup of caviar.

Mass spawning events are common.

It makes sense for many animals

to release their eggs at the same time

to limit the chances

of them all being picked off by predators.

Despite the abundance of eggs,

perhaps only one in a million will survive to adulthood.

The hungry wrasse gang,

and a vast array of other opportunists,

hang around below, waiting for any eggs

that sink to the sea floor,

even if it means cannibalizing their own.

This is a fish-eat-fish world.

Only a lucky few will survive the onslaught.

This breeding bonanza is what has prompted the whale sharks

to swim hundreds of miles to join the feast.

Individual sharks sometimes hover over particular reefs

for as long as 14 hours,

waiting for the spawning to take place.

The male uses a gulping technique

to vacuum up thousands of eggs.

Despite their fame as the world's biggest fish,

whale sharks are still an enigma.

The species itself has only been known to science

for 200 years.

Many aspects of their biology remain poorly known.

Both accidental and deliberate fishing

for meat and fins

are driving down whale shark numbers.

As their populations diminish,

greater efforts are being made to understand them.

It's believed that around

three-quarters of the world's whale sharks

live in the Indo-Pacific.

But even these populations have declined by around 63%

in just 75 years.

Protected reserves, such as the Damaniyat Islands,

are a vital sanctuary.

Hawksbill turtles, too, are in trouble.

They're critically endangered

due to hunting, entrapment in fishing gear,

harvesting of their eggs

and the destruction of their nesting beaches.

But they, too, find protection

in the Damaniyat Islands.

This female hawksbill was likely born here.

After hatching, she will have gone out to sea for 20 years

until she reached maturity.

Now she returns to the same beach

every two or three years to lay her eggs.

Since arriving on the reef, she's mated and now carries

over a hundred fertilized eggs inside her.

Hawksbills feed mostly on sponges and soft coral,

which they demolish

with the tough beaks that give them their name.

But the female's not eating as much sponge as usual.

Instead she's devouring harder pieces of the reef

for calcium carbonate

that will help with the formation of eggshell.

As the turtle feeds, she's breaking off bits of coral,

flushing out the small creatures

that were hiding there.

For that reason, she has a posse in tow.

The crescent wrasse and other reef opportunists

are hot on her heels,

picking off any scraps in her wake.

She will wait until the cover of darkness

before she drags herself ashore,

digs a nest and lays her eggs.

The island has so much to offer

that both the turtles and the whale sharks

make their vast journeys to get here.

Both cover similar distances, roughly 500 miles.

The turtles move up from southern Arabia...

..whereas the whale sharks travel down the Arabian Gulf

from the north.

Unlike the breeding turtles,

only juvenile whale sharks migrate to the Gulf of Oman

for the plankton feast.

It's possible the reef's like a summer camp,

a seasonal, teenage hangout,

where the sharks can bulk up

and ready themselves for adulthood.

This male is the smallest whale shark

ever recorded in the region

at just nine feet long.

Scientists can distinguish individuals

by the patterns on their skin.

Each is as unique as a fingerprint.

So far, 500 have been identified

in the Arabian Gulf.

By September,

the whale shark numbers are reaching their peak.

This larger individual,

a huge female about 26 feet long,

is a rare sight in the Damaniyat Islands.

Only 30% of the sharks that come here are female.

Just why isn't clear.

The season's passing quickly.

Fish have spawned,

the bird colony's well fed,

and the sharks continue their gorging.

But the favorable conditions that follow the monsoon

only last for four months.

By October, things are changing.

The nutrient-rich upwellings decrease,

and higher temperatures return to the reef,

as warm surface waters once again

push in towards Oman from the Indian Ocean.

(Squawking)

Exhausted from raising their families,

the last small flocks of terns bathe,

cleaning their feathers, readying themselves

for the next eight months feeding out at sea.

These will be the last days together

for the young couple this season.

Soon, they'll head off

to drift around the Indian Ocean.

But, hopefully, they'll pair up again next summer.

As the birds leave, the stage is set for new arrivals.

60 days after their eggs were laid,

tiny turtles emerge from the sand.

The sheltered bays of the Damaniyats offer sanctuary

to green and hawksbill turtles,

both of which are critically endangered.

Most turtles hatch during the night,

but it's not uncommon to see some emerge

during daylight hours.

With soft shells an inch and a half long,

they're extremely vulnerable to predators.

Somehow, imprinted in their tiny brains,

is the knowledge to migrate.

Instinctively, they head for the water.

Where these little ones will grow up is unknown.

They'll drift with the ocean currents,

feeding far out at sea.

Only a fraction will survive.

But those that do might not visit the reef again

until they're sexually mature in about 20 years.

As October draws to a close,

things calm down for the inhabitants.

The birds and migratory fish move offshore.

The adult turtles return to their feeding grounds.

After four months of binging,

the whale sharks have big round bellies,

and are ready to move on.

The young males will head back to the Arabian Gulf.

They still have time before they reach adulthood

and will likely return next year.

The large female that's been feeding here

is about 30 years old and reaching maturity.

She may never return to this reef.

She'll mix with the older sharks of the Arabian Gulf,

looking for a mate.

Once she's mated,

she's likely to disappear into the ocean depths

to have her young.

Though exactly where she'll go and what she'll do

is still largely unknown.

The giants leave the reef,

taking with them the many mysteries of their lives.

Only when the monsoon again stirs up the reef

will they return and grace the waters of Oman once more.

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