- 5 days ago
Set out on a thrilling ocean adventure to discover why and to reveal the underwater mystery to the world....
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AnimalsTranscript
00:00:02Over half of all animals in the open ocean drift in currents.
00:00:17Jellyfish cross entire oceans, feeding on whatever happens to tangle with their tentacles.
00:00:29Some can go to a metre, even two metres across.
00:00:34And when, by lucky chance, they encounter a patch of sea rich in plankton, their numbers explode.
00:00:55The air is filled with nocturnal energy.
00:01:04The air is filled with nocturnal energy.
00:01:13The air is filled with nocturnal energy.
00:01:25It's such a successful strategy that jellies are one of the most common life forms on the
00:01:32planet.
00:01:42But among the jellies, and looking somewhat like them, is a rather more complex and sinister
00:01:49creature, the Portuguese man o' war.
00:02:03It floats with the help of a gastile bladder, topped by a vertical membrane.
00:02:10With that serving as a sail, it maintains a steady course through the waves.
00:02:39Long threads trail behind it, some as much as 30 metres long.
00:02:49Each is armed with many thousands of stinging cells.
00:02:55A single tentacle could kill a fish, or in rare cases, a human.
00:03:04But among its lethal tentacles lurks a man o' war fish, that feeds by nibbling them.
00:03:18Whilst this fish has some resistance to the stings, it must still be extremely careful.
00:03:28Most other fish are not so lucky.
00:03:52A tentacle has caught this one, and wheels it in.
00:04:06It's already paralysed.
00:04:20It's already paralysed.
00:04:30Eventually, all that is left is a scaly husk.
00:04:45This voracious man o' war may collect over a hundred small fish in a day.
00:05:15It's already paralysed.
00:05:19The struggle to survive in our green seas can have far-reaching consequences.
00:05:27Once a year, one particular meadow in Australia is transformed.
00:05:40Around the first full moon of winter, an army materializes.
00:05:50Spider crabs.
00:05:59For the past year, they'd been feeding in deeper waters.
00:06:13Now, they march across the seagrass plains.
00:06:35Hundreds of thousands of them.
00:06:46They clamber over one another.
00:06:55Creating great mounds.
00:07:03Nearly a hundred meters long.
00:07:09They're not seeking mates.
00:07:11Neither are they laying eggs.
00:07:14They have come here in order to grow.
00:07:21Like all crabs, their bodies are enclosed in a hard, unexpandable shell.
00:07:29So, to grow, they have to break out of it.
00:07:42And that allows the soft one, that has developed belief, to expand.
00:07:56It will take days for the new shell to harden.
00:08:11It's legs are so limp, that they won't work properly.
00:08:18The crab is unprotected and in great danger.
00:08:32A smooth stingray.
00:08:37It's huge, about four meters long.
00:08:43It wants a soft, freshly molted crab.
00:08:46That will be easier to eat.
00:09:09The crabs try to stick together.
00:09:16The crabs try to stick together.
00:09:20But now, disturbed by the ray, they're scattering.
00:09:30A newly molted crab is too weak to keep up the crowd.
00:09:50The safest place is right in the middle of the pile.
00:09:55That is why they have all assembled here.
00:10:07There is safety in numbers.
00:10:25But the vast majority of the crabs escape.
00:10:29And within the next few days, they will be ready to return to the depths
00:10:34and resume their lonely wanderings in search of food.
00:10:50This is no graveyard.
00:10:54But the triumph of 100,000 crabs successfully molted.
00:11:06A Sally Lightfoot crab.
00:11:11One of thousands of shore crabs just waiting for their moment.
00:11:19Every day, they gather on the tropical shores of Brazil.
00:11:26Waiting for the tide to go out.
00:11:28Waiting for the tide to go out.
00:11:37Which exposes their feeding grounds.
00:11:41Seaweed-covered rocks 100 meters from the shore.
00:11:55Getting there is a race against the tide.
00:12:05They leap from rock to rock.
00:12:21These crabs seem to be afraid of the water.
00:12:37And for good reason.
00:12:50The moray eel.
00:12:54The chain moray is a specialist crab hunter.
00:13:04Its blunt teeth can easily grip and crush across the sea.
00:13:09crab shell. It's the crab's deadliest enemy. But the crab's feeding grounds are still a
00:13:31long way off. They must press on.
00:14:07Halfway. But the enemy has other ideas. Crossing the land to reset the ambush.
00:14:31To feed, the crabs must keep going. But nowhere is safe. An octopus, also a crab killer.
00:15:15The crabs make a dash for it.
00:15:44Made it.
00:15:55Risking life and limb to graze on these seaweed pastures. But in two hours' time, when the
00:16:06tide starts to turn, they will have to run the gauntlet all over again.
00:16:24In the far corner of Southeast Asia lies the Coral Triangle. A cluster of the richest coral
00:16:36reefs in the world. Undersea cities crammed full of life. As in any crowded metropolis, there
00:16:56is fierce rivalry for space, for food, and for a partner. But the reef is also a place full
00:17:16of opportunity. A cuttlefish.
00:17:45fish. It specializes in hunting crabs. But a large fish is a fish. It's a fish. It's a fish.
00:18:01The elf crab. It has a fish. It has a fish. It has powerful claws. The cuttlefish, however,
00:18:19However, has a remarkable talent.
00:18:27Its skin contains millions of pigment cells with which it can create ever-changing colors
00:18:33and patterns.
00:18:43And that, apparently, hypnotizes the crab.
00:19:09A cuttlefish may be clever, but a shark is bigger.
00:19:16And it eats cuttlefish.
00:19:20Time to disappear.
00:19:38Back to the hunt.
00:19:43A new target, but the same mesmerizing technique.
00:20:03For those that manage to establish themselves in these bustling undersea cities, there can
00:20:10be great rewards.
00:20:15During the dry season, over half a million terns crowd onto this remote atoll in the Indian
00:20:22Ocean.
00:20:30Their chicks are still in their dark juvenile plumage.
00:20:38They vary in age.
00:20:49Whilst the more advanced chicks take to the air...
00:20:59Others aren't quite ready yet.
00:21:22Those just starting to learn to fly use the shallow lagoon that occupies the centre of
00:21:28the atoll as their training ground.
00:21:33It's difficult for some of them to stay aloft for long.
00:22:00Giant tree valleys.
00:22:02Giant tree valleys.
00:22:02Giant tree valleys.
00:22:15Usually, they are solitary hunters.
00:22:18But about 50 of them have come here from neighboring reefs, attracted by this abundance of potential
00:22:25prey.
00:22:34The fledglings stay out of the water if they can.
00:22:39They easily drink on the wing.
00:22:53Qiq!
00:22:59If the peaballia are to catch one now...
00:23:02they have to up their game!
00:23:06Qiq!
00:23:14So there is a fish here that, amazingly, has a brain capable of calculating the airspeed,
00:23:22altitude and trajectory of a bird.
00:23:56The time comes when every fledgling has to take to the air and collect food for itself.
00:24:25Their parents lead them to the training grounds.
00:24:31The time comes when every fledgling has to take to the air and collect food for itself.
00:24:32The time comes when every fledgling has to take to the air and collect food for itself.
00:25:13The time comes when every fledgling has to take to the air and collect food for itself.
00:25:14The time comes when every fledgling has to take to the air and collect food for itself.
00:25:55Even within the ground is a very difficult.
00:26:04If they are to survive, they must learn quickly.
00:26:16After a month of practicing over the lagoon, the youngsters start to leave and take their
00:26:23chances out over the open sea.
00:26:33Out here on the sand flats, there is safe accommodation for some.
00:26:47The family of saddleback clownfish have found an excellent home.
00:26:56The tentacles of this carpeted anemone can kill, but the clownfish are immune to the poison.
00:27:11So they can shelter from danger.
00:27:18In return, the fish keep the anemone clean of debris.
00:27:27As with all clownfish, the family is ruled by a big female.
00:27:34Her white face marks her out as the boss.
00:27:43The diminutive male has to prove his worth, so he works tirelessly, removing debris and
00:27:50generally keeping on top of the housework.
00:28:14His greatest challenge is to find a safe place where the boss can lay her eggs.
00:28:23But there is nothing solid here for the female to lay them on.
00:28:33A nearby shell could be the solution.
00:28:46If only he can move it to the protection of the anemone.
00:28:58Too heavy.
00:29:04Besides, it has a mind of its own.
00:29:10A hermit crab.
00:29:20But out here, twice a day, the anemone is swept by tidal currents, and they bring in
00:29:28new opportunities.
00:29:32An old plastic bottle.
00:29:38Perhaps this will do.
00:29:47Not heavy enough.
00:30:01A coconut shell.
00:30:08It looks just right, but it's a long way from home.
00:30:32And he can't move it by himself.
00:30:47So prepare, and I'll work together.
00:30:50So prepare, and I'll work together.
00:30:50How do I get you all exact空, I will still be able to go out just a few minutes.
00:31:08Very wrong one, I can feel and get trust some of my favorites.
00:31:09But, like, I have entered here.
00:31:18Potentially, I'll work together with the sod.
00:31:19Brother Melanie and Del проблем could be in front of trabajar from ellos.
00:31:31A little adjustment to the anemones tentacles in order to clear a space for it, and the
00:31:40shell is tucked in.
00:31:46The female lays, a safe nursery at last.
00:32:07He has proved himself worthy to father her young, and he fertilizes them.
00:32:17Now he will meticulously tend the eggs, keeping them clean and healthy until they hatch in
00:32:3210 days time.
00:32:54The blue shark.
00:33:02It travels over 8,000 kilometers a year, riding on the currents supported by its broad,
00:33:09wing-shaped fins.
00:33:16This one may not have eaten for two months.
00:33:25But the currents can carry promising traces of fatty oils from many kilometers away, and
00:33:32will lead it to its next meal.
00:33:41After days of travel, the smell of food gets stronger.
00:34:07A dead whale, recently struck by a ship.
00:34:14This could be a real feast, but the blue shark must be cautious.
00:34:29Green white sharks, ten times heavier than a blue, are highly possessive around a whale
00:34:52carcass.
00:35:09Great whites are eager to feed on energy-rich whale blubber, which we now know forms a major
00:35:15part of their diet.
00:35:24great white.
00:35:29Once the great white has had its fill, smaller sharks, like the blue shark, tackle what's
00:35:35left of a carcass.
00:35:46As the oils from this dead whale spread more widely, more and more blue sharks appear.
00:36:13within days, the carcass will be stripped of its blubber.
00:36:26Then, no longer kept buoyant by its oil, it will sink into the depths below.
00:36:36The blue, with its reserves of fat replenished, can now survive for another two months without eating.
00:36:55But most of the creatures come together for a very different reason.
00:37:01To breed.
00:37:07The giant cuttlefish.
00:37:10The largest of all cuttlefish.
00:37:20They live for just one or two years.
00:37:29Now, as the Australian summer draws to an end, they have one last act complete.
00:37:40To find a mate.
00:37:46Now, there are over 100,000 males competing for the arriving females in this one bay.
00:38:00Among them, a giant.
00:38:02A true goliath.
00:38:04He probably weighs about 10 kilos.
00:38:10Bands of color sweep across his skin.
00:38:13That's how cuttlefish communicate.
00:38:35This smaller male couldn't possibly take him on.
00:38:47This smaller male couldn't possibly take him on.
00:38:51A female who has just mated with him.
00:38:57But other rivals are still interested.
00:39:04It seems a small male wouldn't stand a chance.
00:39:10The female is now displaying a white stripe along her side nearest goliath.
00:39:18It's a clear signal that she no longer wants to mate with him.
00:39:27It's all the encouragement that the little male needs.
00:39:54He's going to have to use trickery.
00:40:11He tones down his colors.
00:40:14And tucks in his arms.
00:40:18He's just the right size to mimic a female.
00:40:33Goliath is deceived.
00:40:38The small male now displays a white stripe.
00:40:42Just like the real female.
00:40:44To deter his advances.
00:40:51He slips beside her.
00:40:56And they mate.
00:41:09By mating with multiple partners.
00:41:12The female ensures the greatest genetic diversity for her young.
00:41:23The sneaky male leaves.
00:41:27His final act complete.
00:41:34So even among giant cuttlefish it seems.
00:41:40It's not all about size.
00:41:53In the underwater forests of northern Japan.
00:41:58The residents of this sunken wreck are waiting for the summer temperatures to reach 16 degrees Celsius.
00:42:17That, for some, is the time for mating.
00:42:34A kind of giant wrasse called a gobbodai.
00:42:39A kind of giant wrasse called a gobbodai.
00:42:45This is a male.
00:42:51And in female terms, he's particularly handsome.
00:43:03He's a meter long and weighs 15 kilos.
00:43:10Much larger than the diminutive female.
00:43:17And he is ready to breed.
00:43:23He attempts to mate with her.
00:43:26And with any of the other dozen or so females that live in his territory.
00:43:32Whenever he gets the chance.
00:43:48But females from around 10 years old take little notice of his advances.
00:43:54he's a independent man of the world and the other organization is 일단 the truthIf.
00:43:54of the world.
00:44:14And Heil poke It's this game.
00:44:23No one pays for us.
00:44:24And yeah,
00:44:24When any large female reaches a critical body size, she can begin a dramatic transformation.
00:44:48Over just a few months, particular enzymes inside her body cease to work.
00:44:55And male hormones start to circulate.
00:45:04As time passes, her head expands and her chin gets longer.
00:45:13A she has changed into a he.
00:45:27And with this comes a change in temperament.
00:45:36The old male who ruled all the females here is challenged to a face-off.
00:45:51The more bulbous the head, the more it intimidates an opponent.
00:46:22The Territory has a new ruler.
00:46:38Only the largest females transform themselves in this way.
00:46:48But the change enables them to have more mates, so they will have many more offspring carrying their genes.
00:47:01But a new male can't afford to be complacent.
00:47:07Inside the body of every Kobudai female, there is a new male in waiting.
00:47:23And wave power creates towering fortresses like these cliffs in the Arctic, home to tens of thousands of breeding seabirds.
00:47:38The faces of the cliffs are accessible only from the air and have plenty of nooks and crannies for those
00:47:45that can get there.
00:47:50But to feed, seabirds must still master the ocean world beyond.
00:48:00A puffin.
00:48:05He's a fisherman and a father.
00:48:10A puffin.
00:48:12A puffin.
00:48:14A puffin.
00:48:15A puffin.
00:48:15A puffin.
00:48:20A puffin.
00:48:23A puffin.
00:48:25A puffin.
00:48:28A puffin.
00:48:29A puffin.
00:48:30A puffin.
00:48:31A puffin.
00:48:33A puffin.
00:48:34A puffin.
00:48:35A puffin.
00:48:35A puffin.
00:48:38A puffin.
00:48:39A puffin.
00:48:40A puffin.
00:48:40It's Dad's turn.
00:49:05When fish stocks are low,
00:49:07Huffins must fly as much as 50 kilometres out to sea,
00:49:12to reach the good fishing grounds.
00:49:27Once there, they plunge into another world.
00:49:39Good fishing spots are hard to come by,
00:49:42and they have company.
00:49:45Gillimots.
00:49:54Like the puffin, their wings are short and good for diving.
00:50:01Puffins can hold their breath for over a minute
00:50:04and dive as deep as 40 metres.
00:50:12A catch!
00:50:32But it's a long way home.
00:50:48After an exhausting round trip of almost 100 kilometres,
00:50:52this puffin's nearly made it.
00:50:57But there are pirates on this coast.
00:51:03Arctic skewers.
00:51:30All around returning parents are being robbed.
00:51:59The skewer's long, raked-back wings
00:52:03to make them faster and more manoeuvrable.
00:52:05In a while.
00:52:13Any questions?
00:52:17The spewer's long?
00:52:21The smell.
00:52:30The storm is a battle...
00:52:30The storm is a battle...
00:52:32The urge is not to die.
00:52:33The storm is a battle...
00:52:33The storm...
00:52:34and to the storm...
00:52:43Puffins must choose their moment wisely.
00:53:07A near miss, a last desperate burst of speed, and it's made it.
00:53:33A near miss, a last desperate burst of speed, and it's made it.
00:54:03One trip, where his patient partner is waiting.
00:54:29Today, their puffling will eat.
00:54:39But where fish numbers are in decline, many puffins now find it hard to get enough food
00:54:45for their chicks.
00:54:48In the changing season today, it can be even harder to be a successful puffin parent.
00:55:05A kilometer from the surface, beyond the reach of the sun.
00:55:15A giant black void, larger than all the rest of the world's habitats combined.
00:55:27There's life here, but not as we know it.
00:55:42Alien-like creatures produce dazzling displays of light.
00:55:59Nearly all animals need to attract mates and repel predators.
00:56:06This language of light is so widespread here that these signals are probably the commonest
00:56:13form of communication on the entire planet.
00:56:17light.
00:56:19And yet, we still know little about them.
00:56:22one of the most beautiful animals.
00:57:03This is Fang Tooth.
00:57:07It has the largest teeth for its size of any fish.
00:57:14There are pressure sensors all over its head and body
00:57:17which can detect anything moving in the surrounding water.
00:57:27It's the Midnight Zone's most ferricious fish.
00:57:32But prey use light as a distraction.
00:57:40A decoy of luminous ink.
00:57:52Down here, in this blackness,
00:57:57creatures live beyond the normal rules of time.
00:58:07Siphonophores are virtually eternal.
00:58:11They repeatedly clone themselves.
00:58:14Some eventually growing longer than a blue whale.
00:58:42Down here, it snows.
00:58:54Continuous clouds of organic debris drift slowly down from above.
00:59:06This is food.
00:59:08And a whole variety of filter feeders depend on it.
00:59:15Jellyfish.
00:59:24And delicate sea cucumbers.
00:59:47The 1% of marine snow they miss
00:59:50eventually settles on the sea floor.
00:59:58It has become more.
01:00:03It has become more.
01:00:17more.
01:00:20Over millions of years,
01:00:23it forms a layer of mud
01:00:25up to a kilometer thick.
01:00:31It's an empty plane that covers half the surface of our planet.
01:01:01The deep sea bed may at first appear lifeless.
01:01:07But it's home to a unique cast of mud dwellers.
01:01:14The sea toad.
01:01:19It is an ambush predator,
01:01:21with an enormous mouth
01:01:24and infinite patience.
01:01:37This fish has been living for so long here
01:01:41that its fins have changed into something more useful.
01:01:50feet.
01:01:56They help it shuffle about on the sea floor.
01:02:19The frapjack octopus.
01:02:27It hovers just above the surface of the mud
01:02:30as it delicately sifts through it,
01:02:32searching for worms.
01:02:37But it can jet away at the first sign of danger.
01:03:05In the Gulf of Mexico,
01:03:06these eruptions also release a super salty liquid.
01:03:19Brine.
01:03:32It's heavier than sea water,
01:03:34and it accumulates in great pools on the sea floor.
01:03:43It's difficult to make sense of the site.
01:03:53A lake of concentrated salt water,
01:03:5615 meters deep,
01:03:59at the bottom of the sea.
01:04:09Around its margin,
01:04:10perhaps even more strangely,
01:04:12there is a profusion of life.
01:04:22Giant mussels that can live and grow for a century or more,
01:04:26pack it tightly together,
01:04:28dwarfing the shrimps and squat lobsters
01:04:30that feed around them.
01:05:01cutthroat eels, scavengers,
01:05:04come to the shores of the Bryan Lake
01:05:06in search of something edible.
01:05:16Some even venture into the brine.
01:05:31Some even venture into the brine.
01:05:53Spending too long in it,
01:05:54can send an eel into toxic shock.
01:06:08It's only hope is to rise above it.
01:06:26It manages to escape.
01:06:37Others are not so lucky.
01:06:46The brine embalms their bodies,
01:06:50and the casualties of decades
01:06:52accumulate around the margins.
01:07:12The big