The Hunt (2015) s01e04 Episode Script

The open ocean.
It covers more than half the surface of our planet.
Yet, for the most part, it's a watery desert, empty of life.
Hunters here spend their lives in a constant search for scarce and elusive prey.
Remarkably, this seemingly barren wilderness is home to the largest hunter of them all, the blue whale.
Weighing 200 tonnes and 30 meters long, these are the biggest animals ever to have lived.
Despite their immense size, blue whales are one of the most streamlined and energy-efficient of all swimmers.
Their food is so scarce and widely spread that blue whales must journey across whole oceans just to find a single meal.
They can travel over 100 miles a day for weeks at a time.
The ocean's largest animal feeds on one of its smallest.
Krill, small shrimp-like crustaceans.
Opening its gigantic mouth takes so much effort that they only do so when the swarms of krill are rich and concentrated.
The krill here is too scattered, not even worth slowing down for.
This blue whale's lonely search for food must go on.
Out here, feeding opportunities are always few and far between.
And they never last long.
Prey is devoured within minutes.
When it's all over, the hunters must resume their endless search.
Frigatebirds, the pirates of the high seas.
Soaring effortlessly on the gentle trade winds, they can scan vast tracts of ocean for food.
Frigates must be so lightweight that they can't afford the heavy oils that waterproof the plumage of other sea birds.
So getting wet would be lethal.
This may seem an impossible limitation for a seafaring hunter.
But frigatebirds overcome this handicap with help from others.
Dorado.
One of the fastest and most voracious of ocean predators.
They patrol close to the surface, searching for prey.
Little fish try to hide amidst the undulating swell of the ocean, the only cover there is.
It's a game of hide and seek played out amongst the waves.
Their cover blown, escape seems impossible.
But these particular fish have a unique ability.
They're flying fish.
With an extra thrust from their tails, the flying fish get airborne once more.
With a good wind, they can glide for hundreds of meters.
But this is just what the frigatebirds have been waiting for.
When frigates join the hunt, the flying fish are literally caught between the devil and the deep blue sea.
If the flying fish get too much lift they become easy prey for the frigates.
If they dive to evade attack from above they could fall into the mouths of the dorado.
With the help of the dorado, the wily frigatebird has become a flying fish specialist.
And without getting a single feather wet.
Not all open-ocean hunters are able to travel in search of their food.
Some have no choice but wait for a meal to come to them.
A mat of sargassum weed drifts in the middle of the Atlantic.
Sargassum is the only seaweed to live entirely at the surface.
It never attaches to the sea floor.
This floating tangle of fronds is home to a surprising open-ocean predator, the sargassum fish.
Every part of his body mimics the weed.
His fins are more suited to walking than swimming.
In fact, he can barely swim at all.
He will spend his entire life marooned on this weedy raft.
This sargassum fish must lie in wait for those seeking shelter amongst the weed.
Unfortunately his mat is empty for now.
But at least he's not wasting valuable energy searching for food.
In the featureless ocean, these mats are much-sought-after sanctuary for juvenile fish.
At last, his first opportunity for weeks.
He must get closer.
He can only strike when he's within a few centimeters of his prey.
Trusting his perfect camouflage, he hides in the weed.
Patience.
Still not close enough.
Hunger is clearly getting the better of him.
Surely this time.
Blown it.
It may be weeks before he gets another chance.
The open ocean is so vast that some hunters can only find enough prey by searching as a team.
Dolphins live in highly sophisticated social groups.
Working together, they can cover a huge area of ocean.
These are spinner dolphins.
Why they make these twisting leaps is still debatable.
Perhaps it's a form of communication.
Or perhaps it's just fun.
Small groups sometimes come together, forming super pods 5,000 strong.
And these are on the hunt.
Spinners are the most vocal of all the dolphins.
They use echolocation, a kind of sonar, to find their prey.
Each hunter sends out a series of clicks and then listens for returning echoes.
Allowing them to scan for distant prey, hundreds of meters away.
The super pod spreads out into a wide hunting line, up to a mile across producing a wall of sound.
They're searching for their favorite prey.
Lanternfish.
They are the most numerous fish on the planet.
But these small fish spend most of their time down in the deep ocean, way beyond the reach of dolphins.
It's only when they come up to the surface to feed that they become prey.
Once they've found a shoal, the dolphins use their sonar in a different way.
They stun the fish with loud blasts, then simply gather them up.
As they feed, the dolphins work the underside of the shoal to stop their prey from escaping back into the safety of the deep.
Within a few minutes, all that's left is a shower of scales drifting downwards to the ocean depths.
The deep ocean is by far the largest habitat for life on Earth.
And home to some of the most bizarre hunters of all.
Down here, food is much scarcer than at the surface, so deep-sea predators must do all they can to save precious energy.
Waiting patiently, a viperfish.
Special light-producing organs on its head entice prey towards fearsome teeth.
Strange yet deadly jelly hunters also live here.
Most simply drift, trailing tentacles loaded with lethal stings.
Others, propelled by lines of beating hairs, glide gently through the darkness.
Beroe, the top deep-sea jelly predator.
They actively hunt other jellies.
Like this ctenophore.
To grasp its gelatinous prey, Beroe has special teeth-like spikes in its mouth.
Many deep-sea hunters just hang in the abyss, saving their energy, luring their prey to come to them.
Chiroteuthis.
This deep-sea squid fishes for prey using long, sticky tentacles.
Each has a glowing lure, pulsing to attract passing prey.
A gentle twitch adds to the temptation.
Down here in the darkness, this meal is a rare bonanza.
The open ocean may be a vast blue desert, but like all deserts, it has oases.
Scattered widely across this endless space are thousands of small islands.
These are the summits of underwater mountains, which rise up from the sea floor many miles below.
The seamounts deflect deep-ocean currents upwards, forcing nutrient-laden water to the surface.
A busy oasis in the emptiness of the big blue.
For potential prey, there's plenty of shelter amongst the coral and in the caves that are hidden beneath the reef itself.
Small fish take refuge here, out of the reach of most of their predators.
But not all.
Lionfish.
They're not built for speed.
Success here depends on delicate maneuvering.
Their strategy is to hide in plain sight, lulling their prey into a false sense of security.
The lionfish's stripes are visually confusing, making it difficult for their prey to judge how close it is.
Using its extravagant fins to hide slow and deliberate tail movements, it edges ever closer.
It must get to within a few centimeters, close enough for a sudden strike.
Got one.
The deep-water currents that sustain so many residents also attract visitors to these oases.
Silky sharks.
They journey hundreds of miles between seamounts, using them as gathering places in the featureless ocean.
They're joined by hammerheads.
Both these sharks constantly travel between the Galapagos and other isolated seamounts in the Eastern Pacific.
No-one knows for sure why they gather in such numbers, but some certainly come to these oases in search of food.
A school of resident silversides cloaks the seamount.
If these little fish stay close to the coral, the sharks won't be able to get at them.
Other, more agile visitors are attracted by the potential feast.
Striped bonito and golden trevalley.
To get a meal, they'll need to drive their prey up and away from the reef into open water.
As long as the silversides stick close to the sea floor, they should evade their predators.
This time, the frustrated hunters will have to search elsewhere.
There's never an easy meal in the open ocean.
The Southern Ocean encircling Antarctica.
The wildest seas on our planet.
Here, it's the storm-tossed waters that bring nutrients to the surface, creating isolated patches of richness.
Far from the calm tropics, this weather-beaten ocean is home to the albatross.
Black-browed albatross are the same size as frigatebirds but three times as heavy, and so they need a totally different flying technique.
Albatross have the longest wingspan of any bird, and that enables them to exploit the power of the Southern Ocean winds.
First, they glide into the wind, harnessing its energy to give them lift.
Then they turn and descend downwind, picking up speed.
Soaring on wind fronts like this, an albatross can search hundreds of miles of ocean in a day, barely beating its wings.
They often spend weeks at sea, searching for prey without ever returning to land.
Food at last, a patch of krill close to the surface.
Because the winds are so strong here, albatrosses can afford the extra weight of waterproofing oils on their feathers.
They can duck-dive to no more than a meter, so they rely on the churning of the Southern Ocean to bring their prey up into range.
Like all birds, albatross have to breed on land, but suitable islands are so few in the South Atlantic that most are heavily overcrowded.
Steeple Jason, one of the largest albatross colonies in the world.
Nearly half a million come back here each year to raise their young.
Adults share parenting duties, returning every few days to feed their chick.
Feeding done, it's time to head out to sea.
They need to make their way to the edge of the packed colony where there's more room for takeoff.
Albatross are so heavy that they can only get airborne in places where the wind is strong enough.
Using a special runway with a good headwind she's off.
From the air, the ocean may appear featureless, but beneath the surface, a network of powerful currents is constantly on the move.
It's these currents, more than any other force, that determine the distribution of life out here.
A whole community of ocean drifters hitches rides on these rivers in the sea.
Pelagic red crabs.
They've gathered to feed on tiny floating plants and animals, a bloom of plankton fueled by the currents.
Fine hairs on their legs slow their descent and then, with a few flicks of the tail, they swim back up to continue feeding.
The currents that carry these wandering crabs also serve as highways for the ocean's larger predators.
Striped marlin.
Beautifully streamlined, they can travel huge distances with minimum effort.
These hunters patrol the boundaries between ocean currents, where their prey often gathers.
Each predator has an incredible sense of smell, able to detect faint trails left by their prey.
Somewhere out here is the big prize and hunters of all kinds are looking for it.
Great shoals of fish are attracted to a plankton bloom.
A single school of sardines can be many miles long.
The fish swim tightly together.
There's safety in numbers.
Their defense relies on coordination.
When attacked, the sardines move as one.
Each fish instantly matches the movements of its neighbor and the whole shoal moves in synchrony.
A lone sea lion can't keep up with their rapid reactions.
Even when more sea lions arrive, they can't seem to break down the sardines' coordinated defenses.
With a shoal this big, the sea lions need to isolate a smaller, more manageable group of fish.
But with so few predators, the fish still have the advantage.
All the sea lions can do is keep the sardines at the surface and wait for others to join them.
Tuna.
Their arrival changes everything.
Tuna attack from below, cutting off the sardines' escape route down to deeper water.
Next to appear, shearwaters, excellent fliers, but also surprisingly agile underwater.
With so many predators attacking from all sides, the advantage starts to shift away from the sardines.
As the fish pack ever tighter, their shoaling strategy now makes it easier for the hunters.
Copper sharks.
They've scented blood in the water.
Surprisingly, perhaps, the predators never attack one another.
They work together to corral the ball of fish, taking turns to grab a mouthful.
Common dolphins.
As the shoal gets ever smaller, each sardine scrambles desperately to hide in the middle.
But now, there's no escape.
A Bryde's whale finishes off the feast, tonnes of sardines devoured in less than an hour.
The predators melt away into the blue, going their separate ways once more.
This blue whale is still searching for a meal to satisfy its giant hunger.
Being so large, it must catch an average of four tonnes of food a day.
But many days may pass without feeding at all.
It is their great size that enables blue whales to travel the furthest, roaming every ocean from the tropics to the poles.
Trapped against the surface by fish, a dense patch of krill.
This blue has finally found what it's been searching for for so long.
A meal big enough to make opening its massive mouth worthwhile.
The krill swarm is hundreds of meters across and packed tight.
The whale lines up on its prey, targeting the densest part of the shoal.
It takes so much effort to swim with a fully extended throat that the whale virtually comes to a standstill.
The whale uses its tongue to force the water out of its mouth, trapping the krill on plates of hairy bristles that line its jaw.
But it takes time to sieve so much water.
And that gives more nimble hunters their chance.
Blue whales may not be as agile as other hunters, but they don't need to be.
In one giant mouthful, they can swallow whole swarms of krill.
No other predator is better suited to exploit the scattered riches that the open ocean can provide.
The blue whale, the greatest hunter in all the world's oceans.