Narrator: A remote island in the Pacific Ocean.
A place forgotten by time.
Here, in one of the last great ocean sanctuaries,
a mysterious parade of giant sharks passes.
Most are pregnant females about to give birth.
What has drawn them here?
And where are they going?
Researchers have come to the Galapagos Island
chain to track these Dinosaurs of the sea.
To follow them wherever they travel across the globe.
On a journey of discovery
to the Galapagos.
REALM OF GIANT SHARKS
Jutting out from the sea,
at the far northern end of the Galapagos archipelago,
is an ancient, crumbling volcano called
Darwin Island.
And just to its south, a magnificent natural arch.
A group of scientists, working under the auspices of the Galapagos National Park,
has just arrived.
In the swirling currents below, something else is slowly approaching.
It's a whale shark, the largest fish ever to have lived.
It's part of a steady stream of giant sharks that passes by Darwin Island.
This team is hoping to find out what draws them
to this tiny stretch of ocean,
and where are they going.
They wait on a rocky reef.
Finally,
a massive silhouette appears.
At about twelve meters in length,
this female is almost fully grown.
The team rises up to meet her.
They'll attach satellite tracking devices
anchoring them in the thick skin on her back.
In his log, team leader, Jonathan Green, describes the encounter.
Jonathan Green: The shark had barely flinched.
So at this point, I swim down towards her head.
Once in front, I turn and let the current carry me
the full length of her body, past the tail.
Her colossal size is apparent as her body slides by.
The whale shark continues placidly on her way,
seemingly unaware of the procedures going on around her.
Narrator: Whenever she breaks the surface,
her tags will relay her location via satellite to the scientists.
Ranger, as this whale shark is called,
is now part of one of the most ambitious studies of marine
animal migration ever undertaken.
For several weeks, she stayed just north of the Galapagos Islands.
Then she headed south and east to the coast of Peru.
Over one thousand kilometers away.
Ranger's is not the only incredible journey documented by this team.
Take the case of Jaws, another mature female.
With tag in place,
Jaws headed north and west
out into the rugged undersea terrain of the Galapagos Rift Zone.
She appeared to be going out to sea.
Instead, she turned around and made her way back to the Galapagos Islands.
Like Ranger, she too went south to the coast of Peru.
Then there's Kimberly, a mere teenager at 5 meters in length.
She arrived at Darwin Island with Jaws and followed her to the west.
Kimberley split off, veering to the south.
Her route took her to another rugged zone known as the East Pacific Rise.
Along the way,
Kimberly zig-zagged through the ocean
in a pattern probably associated with feeding.
At a point 3500 kilometers away from Darwin Island
the transmissions showed that her tag had detached
and was floating on the surface.
Another creature could have bitten it off.
She may have removed it herself
by rubbing up against rocks.
Or she might have caught by fishermen who discarded it.
Where were these sharks headed?
Were they following familiar routes?
Or possibly shifts in water temperatures,
or the availability of food?
These are questions that captured the imagination of Jonathan Green,
a naturalist and photographer who has worked in the Galapagos
for over two decades.
Jonathan Green: For me, one of the main
interests that held me here is as a child,
I was very, very interested in dinosaurs, and
this is a real life Jurassic Park situation,
because we've got a 60, 70 million year old animal, in terms of the species.
Sharks have been around for perhaps 300 million years.
So they're definitely members of the dinosaur era.
They roam around our earth today, around the
planet, and we know absolutely nothing about them.
How can it be that we know more about mice or about the ant
than we do about a whale shark?
Narrator: Whale sharks belong to an ancient class of fish whose
bones are made of cartilage,
and to a subclass that includes sharks and rays, the Elasmobranchs.
Of at least 500 species alive today, the ground sharks are most common,
including hammerheads and the classic reef sharks.
Whale sharks belong to a relatively small group, called the carpet sharks.
They are known for the particular arrangement of their fins,
and for a distinctive fold of skin near their
nostrils and just above their mouths.
These may be sensors, handed down by
ancestors that dwelled on murky sea bottoms.
At full size, a whale shark can reach 18 meters in length and 30 tons.
Over a lifetime that can last 70 years, these giants roam the oceans,
scooping up a diet of plankton, krill, and small fish.
Struck by how little was known about how whale sharks live,
Jonathan helped spearhead an effort to get basic data.
He and other dive guides photographed their unique identifying markings,
the pattern of spots that line their bodies.
They submitted these 'fingerprints' to an international database.
In time, Jonathan enlisted scientists from the Galapagos National Park,
the Charles Darwin Foundation,
and the marine animal tracking program at the
University of California at Davis,
in an ambitious project to study the movements of whale sharks
that pass by Darwin Island.
Most attempts to track them have begun in places
where they come together in large numbers
like the Sea of Cortez, off the Pacific Coast of Mexico.
Here, billions of tiny crustaceans called Copepods hatch at once,
turning the sea a milky grey.
That draws dozens of whale sharks to feed on them.
You can often see them feeding vertically
to get at the dense food concentrations.
Their arrival is a welcome sight for schools of small
fish, which use them as shields.
With a band of skip-jack tuna nearby, a school
gets as close as it can to the giant shark.
The predators keep their distance.
This is only one of many gathering spots for whale sharks.
You can find them off the coast of Belize,
where they feed on the eggs of snapper fish that spawn here in spring.
Or, you can find them off the coast of Western Australia,
where coral spawn in massive numbers
just after the full moons of March and April.
Alex Hearn: Most of the studies that have been done to date
have been focused on aggregation sites where they come together to feed,
and those are mainly smaller individuals, they're mainly males.
We have almost a unique situation here, where we have
a large number of very large, pregnant females.
Nothing is really known about where they go to give birth,
how they mate, where they mate.
So there are a lot of questions that still need to be answered out there.
Narrator: The answers could bring crucial information
to the battle to preserve these ancient creatures.
Whale sharks have long been hunted on a small scale for their liver oil,
used as waterproofing for wooden boats.
Known as tofu sharks, they are now targeted by
fishing fleets for their characteristic white meat,
and for fins that can fetch around $50,000 each.
Shark fin soup is a staple at weddings and fancy dinners in China.
This custom is believed to be responsible for
millions of sharks killed each year.
Whale shark fins are in demand, not so much for soup,
as for bold displays designed to lure shark fin
buyers into stores, or customers into restaurants.
Whale sharks are now under the protection of the
of the Convention on International Trade of Endangered Species, or CITES,
and the Convention on Migratory Species.
There is a growing momentum to safeguard them,
especially in countries where tourists spend millions of dollars each year
to swim with these gentle giants.
The docile nature of whale sharks is what
allows the Galapagos team to approach them,
then to clip DNA samples from fins or
place satellite tracking tags into their skin.
But if startled, a whale shark is capable of moving swiftly out of reach.
At full size, a whale shark is powerful and potentially dangerous.
If the approach is not just right, or the tag inserted too deeply,
the response can be violent.
In the first of three expeditions to
Darwin Island, Jonathan Green and his team
managed to tag 14 whale sharks.
To get reliable results, the team needs at least twice that number.
So they are making the 30-hour journey again on a small
but trusty expedition boat, the Queen Mabel.
It's the heart of the cool season, and the boat is carried along by north-bound
swells generated by a current that flows from
Antarctica up the coast of South America.
On his journey to the Galapagos Islands, Charles
Darwin noted 'the singularly low temperature
of the surrounding water, brought here by the great southern Polar current.'
For thousands of humpback and other whales,
it offers a free ride north from summer feeding grounds off Antarctica.
The Humboldt current is thought to have transported many of the unique creatures
that Darwin observed on these islands.
From the mainland, giant tortoises were probably washed into the sea by storms.
The current carried them across the thousand kilometers
of ocean to reach the Galapagos.
They gradually dispersed among the islands, each one a world unto itself.
Down through the generations, the tortoises adapted
to unique local conditions
and developed differences, especially in their shells.
Iguanas most likely arrived on rafts of vegetation.
Once here, they adapted to feeding within intertidal zones.
It's in the sea that the Humboldt current has had its greatest impact.
You can see its fertile wake in a satellite image tracking chlorophyl,
a tracer for plankton blooms.
In combination with west-bound trade winds,
it causes deep nutrient-rich water
to well up along the South-American coast,
turning it into one of the world's most productive fisheries.
Rising up onto the Galapagos plateau,
the Humboldt mixes with the cool waters of the Cromwell Current,
surging in from the Pacific,
and with warmer currents moving down from the equator.
That combination sets off an explosion of sea life.
Manta rays arrive to sift the upper levels
of the ocean for microscopic plankton.
When conditions are right, sardines, anchovies,
mackerel and other bait fish fill the seas.
That can attract legions of striped marlin
from around the region and beyond.
Watching for a school to be caught out in the open,
these swift predators dart up from below.
The school closes ranks, forming a bait ball.
Sea lions join the attack.
The school evades them by twisting and turning as one.
But as fatigue finally sets in,
the predators move in to pick off individuals.
Moving through these fertile waters, riding the north-bound current,
a mysterious line of whale sharks is headed for a tiny, remote outpost:
Darwin Island.
What draws them here?
That's the question this team is hoping to answer
as they too arrive at Darwin island.
Jonathan Green: The blue skies give way to low cloud
and the ocean reflects gunmetal grey.
The morning is spent activating the satellite
tags, removing the old leaders,
and replacing them with shorter, plastic-covered steel wire.
We then paint them with an anti-fouling coat
and hang them to dry in the aft.
The guns are ready, lubricated and cleaned.
Narrator: Boarding a pair of small boats, the team sets out
for the turbulent waters of Darwin's arch.
Their strategy is simple:
Wait on the rocks.
If no whale sharks pass by,
they'll swim out into the current to search for them in open water.
Jonathan Green: After 30 minutes close to the rocks, we head out to the blue
and almost immediately spot a large female whale shark.
Clear markings, probably young, she is pregnant and measures around 11 meters.
I am able to get alongside and shoot the dart through the dorsal fin,
about 2/3 of the way, close to the leading edge.
The dart goes all the way through about 15 centimeters of cartilage.
Narrator: Then, the team witnesses a scene that can only
deepen the mystery of these giant sharks.
Another female suddenly appears.
It converges on the first,
then gives it a shove with its snout.
Was this a show of strength?
Or some other signal, just between sharks?
Their two paths diverge into the deep.
The expedition is off to a great start,
at least, that's how it appeared on its second day.
Jonathan Green: The current remains to the north, but is fluctuating.
Sea surface temperature still high, 25 degrees centigrade.
Big schools of hammerheads pass by, out in the blue and down, deep below us.
We do a shallow dive before lunch as skip-jack tuna
are feeding close to the anchorage.
Bright streams of quick silver weave a complicated dance with sharks.
Late afternoon, we photograph the sunset over Darwin,
and the light catches the spray from the crashing breakers.
The Arch appears to capture the last beams of sunlight,
like a magnifying glass,
concentrating them into a single spotlight of white and gold.
Quite ethereal, but then, so is the experience we are living.
Narrator: Day three brings an unexpected shift
in the currents that swirl around Darwin.
The north-bound flow has shifted to the south.
The hammerheads are now schooling much closer to the reef.
The whale sharks seem to have disappeared altogether.
Jonathan Green: Conditions are far from optimum,
as the current has swung around 180 degrees.
Ending the dive with a drift, we swim through a tornado of jacks,
and in less than three minutes, are being sucked in behind the Arch.
Time to surface quickly,
before we get taken over the platform and into
the maelstrom of crashing waves.
We find huge variations in currents. Daily
you can have very low current when you dive
first thing in the morning, 6:30 AM, virtually no current.
By mid-day, you've got a howling current going through.
What we've had here is not only a complete change in direction,
but the strength seems to be going up and down.
This morning when we jumped in, we had something
probably around a five-knot current, and that
simply becomes unworkable at that point.
Not only unworkable, but dangerous
because of the fact that you've got divers
then that may be swept away from the area that we're working in
and taken out into the very rough ocean beyond.
Narrator: The next day, Jonathan is eager to know
whether the tags they set are on securely.
Jonathan Green: Do you have any data on that, anything new?
Narrator: He calls Alex Hearn, who is monitoring the satellite signals
from the University of California at Davis.
Jonathan Green: Conditions that are not too good. We've got a southerly current.
We put the two tags on, but we just need to know if they're on the surface,
or if you have any data that might show what
they're doing, if the tags are still on, yeah.
Okay, you do. 1-0-7. Okay, fantastic, fantastic.
Narrator: One of the tagged sharks has surfaced 40 kilometers North
and West of Darwin Island.
It's following the same route taken by Jaws and Kimberley.
Are these sharks following the flow of food driven by the Humboldt current,
or are they pursuing some other imperative?
Consider their response to conditions below Darwin's Arch.
As deep currents hit the island, they carry
a flood of nutrients to the surface.
As a result, the rocky reefs beneath the arch
are enveloped by what one biologist called,
"a Great Wall of Mouths."
Everything from microscopic zoo-plankton to schools of fish.
Moving through them are predators such as sharks, and jacks,
along with those giant filter feeders, the whale sharks.
And yet, even as they encounter enormous schools
of small fish and dense plankton,
they keep their mouths shut tight.
There must be another reason they are coming here.
Jonathan Green: We know that they are coming here for a specific reason,
but it's got to be something important enough that we see literally
hundreds of whale sharks in an area like the
Darwin Arch during the season. And we don't see
whale sharks anywhere else in the Galapagos Archipelago,
so they're coming to Darwin's Arch
for a specific reason. I still think that
the Whale Sharks are coming here for birthing.
One thing that just about all the females,
the big female whale sharks have in common
is that they're pregnant, they seem to be in an advanced
stage of pregnancy, and so
we think that they are probably birthing down at depth.
Alex Hearn: There's a steady trickle of sharks coming through.
Why aren't they all coming at once, you know? Are they coming
when they're ready to come perhaps? I suspect that there's an internal
clock that's telling them it's time to move up to Darwin, and then,
out to wherever it is that they're giving birth.
Narrator: If not in the deep channels surrounding
Darwin Island, then perhaps these
females are giving birth out in the Galapagos rift zone to the north.
This region took shape millions of years ago,
when titanic sections of the Earth's crust began pulling apart.
The undersea terrain is lined with ridges and sea-mounts,
and hydrothermal vents that attract a variety of deep ocean creatures.
The nooks and crannies of the ocean bottom could offer
could offer myriad safe havens for infant whale sharks to grow.
Where and when the females give birth
is just one of the mysteries of whale shark reproduction.
A single pregnant female captured by fishermen in Taiwan
offered some remarkable clues.
Scientists moved in quickly to dissect the shark.
They found that she was carrying 300 offspring.
They represented all stages of development,
from tiny embryos to pups ready to be born.
That's not all - Genetic tests showed that each of
the offspring was fathered by the same male.
The female had been able to maximize an encounter with this
male, by storing up his semen,
then using it over time to fertilize her eggs.
This may be an adaptation to lives spent traveling alone over long distances.
One of the longest documented whale shark journeys, was made by
a mature female named Rio Lady.
She was tagged off Mexico's Yucatan Peninsula in the year 2007
by researchers from Florida's Mote Marine Lab and Mexico's Domino Project.
They watched as she headed over to the coast of Cuba,
then turned south into the Caribbean.
Past Jamaica, she turned and swam straight for the Atlantic Ocean.
Moving out to the middle of the Atlantic, Rio Lady crossed the equator.
That's where her tag stopped transmitting,
after a journey of more than 7,000 kilometers.
But that wasn't the end of Rio Lady.
Four years later, scientists photographed her back off
the Yucatan, identifying her by her spots.
She had returned as part of the largest known gathering of whale sharks,
with hundreds arriving to feed on eggs spawned by a type of tuna.
If Rio Lady's story is any indication,
whale sharks swim with a purpose, with clear routes and destinations.
How do they navigate the featureless and murky depths of the ocean,
to reach places like the Yucatan or Darwin's arch?
The answer may lie in another shark species: The scalloped hammerhead.
For the last decade, Alex Hearn, from the University of California
at Davis, has been spearheading an effort
to track the movement of hammerheads and other sharks throughout the region.
It's part of a much larger effort by the Galapagos National Park
to understand the role these islands play in
the survival of migratory marine species.
This team's goal is to find out where various shark populations go,
what routes they use, and how far they travel.
The study centers on a series of 'listening stations, '
set up all around the archipelago in conjunction
with the Charles Darwin Foundation.
Placed in shallow water, the stations record high frequency beeps,
emitted by tags that have been placed on the sharks.
Attaching a tag to a hammerhead is a special skill.
The noise from scuba tanks is known to scare them off,
so team members must free dive down to get close.
The object: To jab the tag into the muscle on the shark's back.
The tags usually fall off after about a year.
The data shows that while hammerheads travel throughout the region,
they congregate in large numbers only
where strong south currents sweep the edges of Darwin and nearby Wolf island.
It's a remarkable sight,
considering that these strange creatures were practically
fished out of here in the mid 1990's.
Their population surged again with protections offered by
the Galapagos Marine Reserve, established in 1998.
Since then, Darwin and Wolf Islands have become a Mecca for divers,
who come from all over the world to take in the spectacle.
Hammerheads are among the few sharks that must always
swim forward to force water through their gills.
Facing into the current here during the day offers them a period of rest.
The warm surface waters may also aid their digestion.
While the sharks are here, they can swing in close to the rocks,
where king angel fish come out to clean them of parasites.
At times, larger ocean creatures do return the favor.
A sea turtle draws the attention of a school of pompano,
who prize its rough shell as a kind of scraping stone.
After a day spent at the reef, the hammerheads
peel off into the surrounding waters,
where they use their acute senses to hunt.
How do they find their way back to Darwin
through the featureless and murky depths?
Sea turtles, along with some migrating bird species and whales,
are thought to orient themselves by reading the
alignment of Earth's magnetic field.
If sharks possess their own navigational super-sense,
it's probably related to sensory abilities
that have allowed them to thrive all these millions of years.
The snouts of most sharks are dotted with specialized organs
that pick up electrical impulses given off
by the heartbeats or muscle action of prey.
Research shows that hammerheads may use this electrical mastery
to read magnetic signals given off by
volcanic formations that lead like roads,
up the sides of Darwin and and other
landmarks strewn about the world's oceans.
Whale sharks may be reading these same signals,
but that doesn't mean they always arrive on cue.
Day Five.
The team spreads out on the rocks to increase
the chances of spotting a whale shark.
With none in sight, they move out into the blue and drift.
Toward the end of the scheduled 40-minute dive,
a whale shark finally appears.
But it's about 40 meters down.
It will take considerable effort to reach it,
and their air is already running low.
With few other sharks around, Jonathan decides to take the risk.
Jonathan Green: I see her, deeper than where I am,
a few more kicks is all it will take.
The next few seconds are a blur.
I see her dorsal fin is bent over, but still go for a fin shot.
Narrator: The shot bounces off the dense tissue at the base of the fin.
Jonathan signals a team member to try another tag.
But there's just not enough time.
As the shark swims off into the deep, they must rise up slowly
to expel the excess nitrogen that builds up in divers' bodies at depth,
and can lead to a life-threatening condition known as the bends.
But several divers, including Jonathan,
do not have enough air to safely reach the surface.
Fortunately, teammates are there to assist.
Day six. No whale sharks in sight.
To widen their search, the team tries snorkeling out into the blue.
Jonathan Green: Three dives punctuated by a snorkle in deep water.
But there was nothing.
Swam with dolphins though, so the day has not been without its moments.
Narrator: Even a series of time-lapse shots, taken throughout the day,
fails to turn up any whale sharks.
The current has now picked up speed.
The team struggles to hold on to the reef.
The end of this expedition is just days away.
Finally, on Day 8, with only three more days of diving left,
there is a subtle shift in conditions below the arch.
The south-bound current has slowed.
Jonathan Green: Dropping in we feel the change.
Galapagos sharks are hugging the rocks,
silkies patrolling the blue,
and yes, swimming gently along the wall,
a small, approximately 3.5 meter whale shark.
Narrator: This one is too small to tag.
But it could be a sign that the whale sharks are back.
By afternoon, the north-bound current is surging.
Cesar Penaherrera, from the Charles Darwin Foundation,
spots a large whale shark approaching and signals the others.
Eduardo Espinosa, a scientist with the Galapagos National Park,
and a seasoned shark tagger, is on it.
But the shark is racing away.
He struggles to catch up.
His shot is off.
The tag breaks off and is lost.
Another setback.
The sharks may be back, but the cables that
hold the satellite tags keep breaking.
Later, on the Queen Mabel, Moab Villagomez, a crew
member, suggests a type of knot used by fishermen,
to secure the tags to their steel cables.
Because some of the shots have not been penetrating the whale shark's skin
they give the air guns fifty percent more power.
Day nine.
In his log,
Jonathan notes that the trip now hangs in the balance.
But that it may not be in his power to tip it in their direction.
Hanging at twenty-five meters, I see a dark form above and out to the blue,
then clearly the outline of a shark.
I head out to swim under and then rise up on the left flank.
The shot will be easier from the right.
So exchanging sides, I move forward.
And the shot goes in just for and to the right of the dorsal fin.
The harpoon slides back out
and the tag, 108-103, glides off to an unknown destination.
This time, it’s the beginning of the dive.
And Jonathan has enough air to stay and take in the scene.
I crawl south, across the balcony.
And just lie there for about ten minutes as the hammerheads just stream by.
Their silver and bronze sheen, almost aglow in the midday light.
Like celestial bodies floating in aquatic space.
Far too beautiful to capture in mere words.
I wish I could exchange my gun for my camera.
But instead, capture the image in my mind.
Mine,
forever.
It’s the final day of the expedition.
Eduardo Espinosa sees a shark they’ll come to know as Margarita.
Based on her size, twelve meters long,
Margarita is thirty to forty years old.
And a survivor,
judging by the circular bites or propeller marks on her lower abdomen.
Later on,
Jonathan finds Margarita still at the reef.
Identifying her by tag number.
Here’s an opportunity to get a closer look.
With the current sweeping him away,
he descends to the rocks below.
She’s barely moving against the current.
I drop back then use the rocks to get ahead.
I float up, then pass below her,
checking her huge belly for signs of birthing.
Nothing I can detect,
but then, this is hardly my area of expertise.
If a newborn shark does come in to the world,
several jacks are there, ready to grab a meal.
The cool season is now drawing to a close.
On land,
the turbulence of mating season is overtaking
the colonies of marine iguanas.
The big males keep a watchful eye on their harems.
And on the other sires that may challenge them.
Out at sea, the water is getting warmer,
as the Humboldt current slows and Equatorial currents push south.
This is the time when Humpbacks and other whales
head back south to summer feeding grounds off Antarctica.
With less prey in the waters off Darwin Island,
jacks, tuna, and other large predators move away.
So do the crowds of sharks.
Including the whale sharks.
Margarita, the shark with the circular bites or propeller marks, headed north.
She wandered about for a month.
Then her signal disappeared.
She'll be easy to recognize if they see her again
on a future trip to Darwin's Arch.
Most likely, she headed south with the
other sharks that still had their tags on.
Including Jaws,
a shark they called "Sin Nombre",
George, the only male in the group,
and Carla.
They all went to a region off the coast of Peru, lined with steep ridges.
As the chlorophyll data shows, these are some of the most
fertile waters on the planet.
Deep nutrient rich currents rise to surface, and
sea life is abundant year round.
If the female sharks are giving birth up north,
perhaps this is where they are finding their males,
as well as the food supply that will sustain them on their
way back to the Galapagos and beyond.
The data include a few notable exceptions.
Like Ranger, who was on her way down the coast of
South America when her tag stopped transmitting.
And Kimberly, the teenager last seen heading south in the Mid-Pacific.
When the study began,
almost nothing was known about the parade of whale sharks
that passes by Darwin Island.
More years of research are needed to find out just how widely they travel,
where they go to give birth,
and what is it that draws them in such numbers to this narrow, rocky reef.
Darwin Island was born in the formation of the Galapagos Rift Zone
around three and a half million years ago.
That's recent compared to the tens of millions of years
that whale sharks have plied the oceans.
As we search for fleeting glimpses into their lives and history,
we marvel at their return to this Realm of Giant Sharks.