0:00:14 > 0:00:16This great white shark
0:00:16 > 0:00:18is about to attack.
0:00:38 > 0:00:40But hunting is only a small part
0:00:40 > 0:00:41of any shark's life.
0:00:42 > 0:00:45New discoveries are revealing
0:00:45 > 0:00:47another side to their character.
0:00:49 > 0:00:51They have an intricate social life...
0:00:51 > 0:00:54complex courtship rituals....
0:00:56 > 0:00:57..surprising ways
0:00:57 > 0:00:59of bringing up their young...
0:01:00 > 0:01:02..and extraordinary powers of navigation.
0:01:08 > 0:01:10They forge relationships
0:01:10 > 0:01:12with the strangest of partners...
0:01:14 > 0:01:15..even with us.
0:01:17 > 0:01:18This...
0:01:19 > 0:01:20..is the secret life...
0:01:21 > 0:01:23..of the shark.
0:01:33 > 0:01:35Some sharks are solitary...
0:01:36 > 0:01:38..roaming the ocean alone
0:01:38 > 0:01:39for years on end.
0:01:43 > 0:01:46But there's one event in every shark's life
0:01:46 > 0:01:48where they must come together.
0:01:51 > 0:01:56Scalloped hammerheads are travelling to a tiny island in the Pacific.
0:02:00 > 0:02:03They're coming here to find a mate.
0:02:13 > 0:02:16Of all the sharks, these hammerheads select
0:02:16 > 0:02:19a partner in the most elegant way.
0:02:29 > 0:02:31Soon, a graceful dance begins.
0:02:40 > 0:02:42They swim together in formation,
0:02:42 > 0:02:44with the males on the outside
0:02:44 > 0:02:46and the females in the centre.
0:03:19 > 0:03:22Males seek out the largest females -
0:03:22 > 0:03:24the ones most likely to breed successfully.
0:03:30 > 0:03:31They pair up,
0:03:31 > 0:03:34then swim side by side,
0:03:34 > 0:03:36to continue their courtship.
0:03:40 > 0:03:42As night falls,
0:03:42 > 0:03:45each couple disappears to mate.
0:03:46 > 0:03:50Those without a partner can return tomorrow,
0:03:50 > 0:03:52to dance again.
0:03:59 > 0:04:04Hammerheads are just one of over 500 species of shark...
0:04:07 > 0:04:11..but the shark family tree has two branches.
0:04:14 > 0:04:17The other half of the family are the rays.
0:04:20 > 0:04:22They are flattened sharks.
0:04:22 > 0:04:26They share the same flexible cartilage skeleton.
0:04:26 > 0:04:30In rays, this has squashed and stretched.
0:04:35 > 0:04:37Many still have the tell-tale dorsal fin...
0:04:40 > 0:04:43..but their pectoral fins have developed into enormous wings.
0:04:49 > 0:04:51Some glide on ocean currents...
0:04:58 > 0:04:59..while others "fly",
0:04:59 > 0:05:02by undulating their bodies like a wave.
0:05:06 > 0:05:10Many species of rays travel the oceans in groups...
0:05:11 > 0:05:14..occasionally, in huge numbers.
0:05:26 > 0:05:28Just once a year,
0:05:28 > 0:05:31off the coast of Baja, Mexico,
0:05:31 > 0:05:34Mobula rays gather in the darkness.
0:05:54 > 0:05:57They begin by feeding -
0:05:57 > 0:06:00fuelling up before the big event.
0:06:36 > 0:06:38As the sun rises,
0:06:38 > 0:06:41the full extent of their numbers becomes clear.
0:06:42 > 0:06:46Like hammerheads, they come together to find a mate.
0:06:52 > 0:06:56But with 250,000 in a single shoal,
0:06:56 > 0:06:58this is on a completely different scale.
0:07:00 > 0:07:03It's the largest aggregation of rays in the world.
0:07:36 > 0:07:38But in a group as big as this,
0:07:38 > 0:07:41the problem is standing out from the crowd.
0:07:51 > 0:07:54Mobula rays have the most extraordinary way
0:07:54 > 0:07:55of getting noticed.
0:08:35 > 0:08:37As they land,
0:08:37 > 0:08:39the impact sends a huge boom through the water.
0:08:45 > 0:08:46The higher they leap...
0:08:48 > 0:08:50..the bigger the bang.
0:09:05 > 0:09:07It's mainly males who jump like this...
0:09:09 > 0:09:11..signalling their prowess as a mate.
0:09:13 > 0:09:16Females also join in,
0:09:16 > 0:09:18drawing attention to themselves.
0:09:36 > 0:09:40It's thought that those who make the biggest impact on the spectators
0:09:40 > 0:09:44give themselves the best odds of leaving with a mate.
0:10:28 > 0:10:32Once the leaping subsides, the rays disperse.
0:10:34 > 0:10:37Where they go to mate is still a mystery.
0:10:42 > 0:10:45But finding a mate is just the first step.
0:10:53 > 0:10:56Port Jacksons come from an ancient order of sharks.
0:10:59 > 0:11:01Older than the dinosaurs.
0:11:09 > 0:11:12But even these primitive creatures put a huge amount of effort
0:11:12 > 0:11:15into giving their young the best start in life.
0:11:18 > 0:11:21Each spring, for four months,
0:11:21 > 0:11:24they gather here in Jervis Bay, Australia.
0:11:26 > 0:11:30At the peak of the breeding season, they can number in their thousands.
0:11:37 > 0:11:40Wherever the females go, they're pursued by a male.
0:11:50 > 0:11:52Courtship is less seduction,
0:11:52 > 0:11:54more a wrestling match.
0:12:01 > 0:12:02But, eventually...
0:12:05 > 0:12:06..they mate.
0:12:14 > 0:12:16The male will have nothing more to do with
0:12:16 > 0:12:18caring for the next generation.
0:12:22 > 0:12:23It's all down to her now.
0:12:28 > 0:12:31Two weeks later, she's ready to lay an egg,
0:12:31 > 0:12:34one of just a handful she will lay each year.
0:12:35 > 0:12:38It's almost as large as her head,
0:12:38 > 0:12:39and shaped like a corkscrew.
0:12:42 > 0:12:44She's invested a vast amount of energy,
0:12:44 > 0:12:46growing her egg inside her.
0:12:47 > 0:12:50Unless she finds a safe place to hide it,
0:12:50 > 0:12:52all that effort will be for nothing.
0:12:55 > 0:12:57Finally,
0:12:57 > 0:12:58the perfect spot.
0:13:15 > 0:13:19The egg has evolved this shape to wedge securely under rocks.
0:13:22 > 0:13:26A female may carry her egg around in her mouth
0:13:26 > 0:13:28until she finds the ideal place to stash it.
0:13:32 > 0:13:35It needs to stay hidden for 11 months.
0:13:38 > 0:13:40There's an egg thief here,
0:13:40 > 0:13:42a wolf in sheep's clothing.
0:13:47 > 0:13:49It's a crested horn shark.
0:13:50 > 0:13:53They look almost identical to a Port Jackson,
0:13:53 > 0:13:56but they are the main predator of their eggs.
0:14:02 > 0:14:06The shell is tough, but the horn shark simply crushes it,
0:14:06 > 0:14:08squeezing the yolk from inside.
0:14:21 > 0:14:25These eggs, hidden in a gulley, are safe from the predators.
0:14:28 > 0:14:30The female's work is done.
0:14:30 > 0:14:32She can leave now, heading south to feed.
0:14:36 > 0:14:40Her developing youngster has everything it needs,
0:14:40 > 0:14:42enclosed in the egg's protective casing.
0:14:45 > 0:14:48From "corkscrews" wedged under rocks
0:14:48 > 0:14:52to mermaid's purses hidden on the sea bed,
0:14:52 > 0:14:54or suspended by spiralling fronds...
0:14:56 > 0:14:59..shark eggs come in all shapes and sizes.
0:15:04 > 0:15:08Inside each armoured capsule is one of the most extraordinary
0:15:08 > 0:15:11life-support systems found anywhere in nature.
0:15:14 > 0:15:17The embryo is dwarfed by the yolk sac, which will provide
0:15:17 > 0:15:21all the nutrients the youngster needs until it's ready to hatch.
0:15:25 > 0:15:28For some species, that can take nearly a year.
0:15:34 > 0:15:36A few weeks after being laid,
0:15:36 > 0:15:41eyes, mouth, fins all begin to form.
0:15:47 > 0:15:51Veins drain nutrients from the yolk sac,
0:15:51 > 0:15:52feeding the growing shark.
0:15:59 > 0:16:02At this stage, their gills are just wavy fronds
0:16:02 > 0:16:04sticking out from the side of their head.
0:16:06 > 0:16:08Tiny capillaries within
0:16:08 > 0:16:11capture oxygen from the water that surrounds the embryo.
0:16:19 > 0:16:22The youngster continually beats its body back and forth
0:16:22 > 0:16:24to circulate fresh water through the egg.
0:16:36 > 0:16:40As they grow, patterns start to form on their skin,
0:16:40 > 0:16:43crucial camouflage for the hatchling.
0:16:50 > 0:16:54Their gills are now inside their bodies.
0:16:54 > 0:16:56Their teeth are formed.
0:16:57 > 0:16:59But their food is running out.
0:17:00 > 0:17:02The yolk sac has shrunk to almost nothing.
0:17:06 > 0:17:08It's time to hatch.
0:17:11 > 0:17:14Under the cover of darkness,
0:17:14 > 0:17:16this zebra shark slips out of the casing
0:17:16 > 0:17:18that has kept it safe for months.
0:17:35 > 0:17:39It emerges as a fully formed eight-inch shark...
0:17:41 > 0:17:43..ready to fend for itself.
0:17:50 > 0:17:52But not all sharks lay eggs.
0:17:53 > 0:17:56There's one group that breed more like mammals.
0:17:58 > 0:18:00Instead of eggs,
0:18:00 > 0:18:04this lemon shark has 15 babies developing inside her.
0:18:06 > 0:18:08And, like a mammal,
0:18:08 > 0:18:11she feeds each one through a placenta and an umbilical cord.
0:18:17 > 0:18:19She's been carrying her young for 12 months.
0:18:22 > 0:18:24It's nearly time to give birth.
0:18:28 > 0:18:31It's May in the Bahamas,
0:18:31 > 0:18:33and high tide briefly gives her access
0:18:33 > 0:18:35to the safest place for her pups' birth.
0:18:41 > 0:18:43After swimming for days,
0:18:43 > 0:18:46she's returning to the same place that she was born.
0:18:57 > 0:19:01She finds an isolated spot on the borders of the mangrove forest.
0:19:09 > 0:19:10She's ready.
0:19:18 > 0:19:19When they're born,
0:19:19 > 0:19:21her pups are perfect miniature sharks.
0:19:24 > 0:19:27Their umbilical cords break off after birth.
0:19:30 > 0:19:33Like us, these sharks have belly buttons.
0:19:42 > 0:19:45Their mother can't stay in the shallows to look after her young.
0:19:46 > 0:19:50She must leave now before the tide goes out and she's marooned.
0:19:53 > 0:19:54From now on,
0:19:54 > 0:19:57the newborns will have to fend for themselves.
0:20:02 > 0:20:06Instinct tells the pups to head for the refuge of the mangrove forest.
0:20:26 > 0:20:29The tangled roots mean predators can't follow them in here.
0:20:32 > 0:20:34But the pups aren't safe yet.
0:20:40 > 0:20:43They need to find their way through the maze.
0:21:05 > 0:21:08Hidden within this twisted forest are clearings,
0:21:08 > 0:21:10places of safety for the pups.
0:21:15 > 0:21:18This is a shark nursery,
0:21:18 > 0:21:21where they will spend the first seven years of their lives.
0:21:25 > 0:21:28It's the same secret place their mother knew as a baby.
0:21:33 > 0:21:39In here, juvenile lemon sharks have been shown to form friendships.
0:21:42 > 0:21:44They can learn from each other.
0:21:50 > 0:21:53Even so, with no adults to teach them,
0:21:53 > 0:21:57they need time to learn what it takes to be a shark.
0:22:00 > 0:22:01Like how to hunt.
0:22:20 > 0:22:23At last - success.
0:22:30 > 0:22:32After seven years,
0:22:32 > 0:22:35it will be time to leave the nursery for good
0:22:35 > 0:22:36and head out to sea.
0:22:43 > 0:22:46Life as a shark in the open ocean
0:22:46 > 0:22:48means facing a whole new set of challenges.
0:22:51 > 0:22:55Out here, it's a desert -
0:22:55 > 0:22:56vast and empty.
0:23:04 > 0:23:08Yet somehow it can support the largest fish in the world.
0:23:20 > 0:23:23Whale sharks weigh up to 20 tonnes,
0:23:23 > 0:23:25and can live for 60 years.
0:23:28 > 0:23:30They feed mainly on plankton,
0:23:30 > 0:23:32the tiniest creatures in the sea.
0:23:40 > 0:23:43With their enormous mouth and gills,
0:23:43 > 0:23:48they filter food from over a million gallons of water every day.
0:24:09 > 0:24:13Feeding on such tiny prey means they're always on the move,
0:24:13 > 0:24:15constantly searching for food.
0:24:19 > 0:24:21A ball of small fish
0:24:21 > 0:24:23under attack by a pack of tuna.
0:24:26 > 0:24:30It's a chance for the whale shark to change the way she feeds.
0:24:33 > 0:24:34From filter feeder...
0:24:36 > 0:24:37..to hunter!
0:24:49 > 0:24:52She can swallow hundreds of the tiny fish in a single gulp.
0:25:01 > 0:25:04It's only the mayhem caused by the tuna
0:25:04 > 0:25:06that gives her this opportunity.
0:25:11 > 0:25:14Chances like this are few and far between.
0:25:36 > 0:25:38Soon she'll return to a life
0:25:38 > 0:25:41scouring the vast, featureless ocean.
0:25:45 > 0:25:48But when all day long all you can see is blue,
0:25:48 > 0:25:50how do you find your way?
0:25:55 > 0:25:58Sharks and rays travel the seas with remarkable precision.
0:26:03 > 0:26:05Some are thought to be able to navigate
0:26:05 > 0:26:08using the position of the sun,
0:26:08 > 0:26:09or even the moon.
0:26:14 > 0:26:17But in the dark depths
0:26:17 > 0:26:18they can't rely on this alone.
0:26:22 > 0:26:25Two-thirds of their brain is devoted to smell.
0:26:25 > 0:26:28Each nostril works independently,
0:26:28 > 0:26:32detecting tiny differences in the strength of an odour,
0:26:32 > 0:26:35allowing them to smell in stereo
0:26:35 > 0:26:37and track scents over huge distances.
0:26:42 > 0:26:45They have tiny sensors on their nose,
0:26:45 > 0:26:47which they use like a compass,
0:26:47 > 0:26:51allowing them to take bearings from the Earth's magnetic field.
0:26:57 > 0:27:01A great white shark was tracked swimming from Africa to Australia,
0:27:01 > 0:27:03and found its way back again.
0:27:10 > 0:27:15But even this extraordinary journey has been trumped.
0:27:18 > 0:27:23One tiger shark was tracked for 27,000 miles.
0:27:26 > 0:27:28They can circle the ocean,
0:27:28 > 0:27:31yet still return to the same place,
0:27:31 > 0:27:32on the same date...
0:27:34 > 0:27:35..year after year.
0:27:40 > 0:27:42Of all the sharks,
0:27:42 > 0:27:47these are the masters of both navigation and timing.
0:27:56 > 0:27:58This is Raine Island,
0:27:58 > 0:28:02a tiny speck off the east coast of Australia.
0:28:02 > 0:28:05It's less than a quarter of a mile across.
0:28:08 > 0:28:10She's travelled for weeks to get here.
0:28:21 > 0:28:24More green turtles breed on Raine Island
0:28:24 > 0:28:26than anywhere else in the world.
0:28:26 > 0:28:3065,000 of them come here every year to lay their eggs,
0:28:30 > 0:28:33their numbers peaking in the first week of December.
0:28:39 > 0:28:43The tiger sharks time their arrival to coincide exactly with that peak.
0:28:47 > 0:28:49The turtles may be protected by their armour.
0:28:51 > 0:28:54But the tiger sharks wouldn't have come all this way
0:28:54 > 0:28:56unless it was worth their while.
0:29:09 > 0:29:12They crush through the shells with their formidable jaws.
0:29:32 > 0:29:36After the feast, the tiger sharks set off again,
0:29:36 > 0:29:39and they know exactly where to go for their next meal.
0:29:41 > 0:29:44One thing's for certain -
0:29:44 > 0:29:45they won't be late.
0:29:49 > 0:29:52Navigating the ocean is as much about intelligence
0:29:52 > 0:29:53as it is endurance.
0:29:57 > 0:30:01Giant manta rays are perfectly designed for flying
0:30:01 > 0:30:03thousands of miles through the sea.
0:30:07 > 0:30:09The largest of all the rays,
0:30:09 > 0:30:12their huge wings allow them to glide on ocean currents.
0:30:16 > 0:30:19But they also have the biggest brains of any fish.
0:30:25 > 0:30:30It's thought that mantas find their way using giant signposts
0:30:30 > 0:30:32hidden beneath the waves.
0:30:40 > 0:30:44This towering undersea mountain rises up from three miles below.
0:31:07 > 0:31:11But the visibility of the water means she can only see it
0:31:11 > 0:31:14when she's within 100 feet or so of its sheer sides.
0:31:18 > 0:31:22So manta rays build up a map in their heads using these landmarks.
0:31:26 > 0:31:28When they get to each one,
0:31:28 > 0:31:31they can remember the direction to the next.
0:31:45 > 0:31:48But the seamounts are more than just waypoints on a journey.
0:31:58 > 0:32:01The mantas have come to the island of Socorro,
0:32:01 > 0:32:05more than 300 miles off the coast of Mexico,
0:32:05 > 0:32:08to visit this group of angel fish,
0:32:08 > 0:32:11who pick parasites from the rays' bodies.
0:32:21 > 0:32:24When you've got no way of having a scratch on your own,
0:32:24 > 0:32:28the services of enthusiastic cleaners like these
0:32:28 > 0:32:30are indispensable.
0:32:39 > 0:32:42Once they're clean, the mantas head off.
0:32:44 > 0:32:48They leave the angel fish behind until their next visit.
0:32:59 > 0:33:02Some sharks have formed an even more surprising relationship.
0:33:04 > 0:33:07One that requires an extraordinary level of trust.
0:33:13 > 0:33:19Normally, grey reef sharks eat anything on the reef they can catch.
0:33:20 > 0:33:22Most fish know to avoid them.
0:33:31 > 0:33:34But today the grey reefs don't look like they're hunting.
0:33:38 > 0:33:40By tilting up their bodies in the water,
0:33:40 > 0:33:43the sharks are signalling to these fish.
0:33:46 > 0:33:48They want them to clean their teeth.
0:33:55 > 0:33:59Eating fish all day means scraps get stuck in their teeth,
0:33:59 > 0:34:01and a shark with rotten teeth can't feed.
0:34:04 > 0:34:08However, saying "Aah" is quite a challenge for a shark.
0:34:11 > 0:34:13They slow down as much as they can,
0:34:13 > 0:34:19but grey reefs have to keep swimming to force water across their gills,
0:34:19 > 0:34:20otherwise they'd drown.
0:34:29 > 0:34:31The brave little cleaner wrasse
0:34:31 > 0:34:35are the only fish that can swim right into the sharks' mouths,
0:34:35 > 0:34:37and leave with their lives.
0:34:55 > 0:34:59Occasionally, the sharks snap their mouths closed
0:34:59 > 0:35:00when the wrasse nip a bit of gum.
0:35:11 > 0:35:12But they never harm the cleaners.
0:35:15 > 0:35:17The sharks need this vital service
0:35:17 > 0:35:20from the bravest dentists on the reef.
0:35:26 > 0:35:30Sharks have not only learned to take advantage of other fish.
0:35:32 > 0:35:34They've learned to take advantage of us, too.
0:35:47 > 0:35:50A sheltered bay off West Papua.
0:35:51 > 0:35:55Young whale sharks have discovered that, here,
0:35:55 > 0:35:57the fishing has been done for them.
0:36:03 > 0:36:06At first, they head for the nets,
0:36:06 > 0:36:09and try to suck the fishermen's catch out through the mesh.
0:36:13 > 0:36:16But there is a simpler way.
0:36:23 > 0:36:26Far from trying to scare the sharks away,
0:36:26 > 0:36:28the fishermen actually feed them.
0:36:50 > 0:36:53Feeding the sharks stops these enthusiastic giants
0:36:53 > 0:36:55from damaging the nets.
0:37:03 > 0:37:05It started out with just a few sharks,
0:37:05 > 0:37:09but over the years more and more have learned to come here
0:37:09 > 0:37:11for a free meal.
0:37:14 > 0:37:19Encounters like this give us a rare, valuable glimpse into their lives.
0:37:22 > 0:37:25But to really understand sharks,
0:37:25 > 0:37:26we need to enter their world.
0:37:37 > 0:37:41Once a year, around a tiny island in the Pacific,
0:37:41 > 0:37:45over 150 great white sharks come together to feed.
0:37:49 > 0:37:51This gives divers a unique opportunity
0:37:51 > 0:37:54to get closer to the sharks than ever before.
0:38:06 > 0:38:09Great whites can reach 18 feet long
0:38:09 > 0:38:10and weigh over two tonnes.
0:38:21 > 0:38:23Normally solitary, they go for months,
0:38:23 > 0:38:27or even years, without seeing another of their own kind.
0:38:32 > 0:38:36Now, with so many great whites in one place,
0:38:36 > 0:38:40arguments over food or territory could be deadly.
0:38:49 > 0:38:53But, by observing them so closely,
0:38:53 > 0:38:56it's been discovered that these sharks keep the peace
0:38:56 > 0:38:58using body language.
0:39:00 > 0:39:03Great whites respect each other's personal space.
0:39:07 > 0:39:09They swim directly at each other,
0:39:09 > 0:39:13and then both change course,
0:39:13 > 0:39:16signalling to one another that they're no threat.
0:39:21 > 0:39:24They've been shown to have individual personalities,
0:39:24 > 0:39:27and the bigger they are,
0:39:27 > 0:39:29the more confident they're likely to be.
0:39:33 > 0:39:36With divers, as well as with other sharks.
0:39:52 > 0:39:56The language of great whites is based on subtle signals
0:39:56 > 0:39:59that we are only just beginning to interpret.
0:40:05 > 0:40:07She's lowering and bending her fins,
0:40:07 > 0:40:09showing the black tips on the inner edge.
0:40:11 > 0:40:14Her mouth is beginning to open in a threat display.
0:40:16 > 0:40:19These are clear signals to the diver.
0:40:19 > 0:40:21It's time to give her a bit more space.
0:40:29 > 0:40:31The more we observe these predators,
0:40:31 > 0:40:35the more we realise they're not mindless killers.
0:40:37 > 0:40:40They're actually sophisticated communicators
0:40:40 > 0:40:42and, when treated with respect,
0:40:42 > 0:40:45they'll avoid conflict whenever they can.
0:40:50 > 0:40:53However, far too often,
0:40:53 > 0:40:55when sharks and humans meet,
0:40:55 > 0:40:57it ends badly...
0:40:58 > 0:40:59..for the shark.
0:41:19 > 0:41:23Oceanic whitetips are used to being at the top of the food chain...
0:41:30 > 0:41:32..with very little to threaten them.
0:41:37 > 0:41:42Their acute senses allow them to follow sounds and smells
0:41:42 > 0:41:44which may lead them to their next meal.
0:41:47 > 0:41:50But this can also lead them into danger.
0:41:57 > 0:42:00Fishing boats -
0:42:00 > 0:42:02towing miles and miles of baited hooks.
0:42:06 > 0:42:09Oceanics have learned to follow the boats,
0:42:09 > 0:42:11stealing fish from the lines.
0:42:14 > 0:42:16Some are caught accidentally.
0:42:18 > 0:42:22Others are the targets of specialised shark boats.
0:42:25 > 0:42:27This shark is a lucky one.
0:42:31 > 0:42:34For many, the outcome is much worse.
0:42:44 > 0:42:48100 million sharks are killed every year.
0:42:52 > 0:42:54In some places,
0:42:54 > 0:42:5899% of the oceanic whitetips have been wiped out.
0:43:10 > 0:43:13Even if they escape the hooks,
0:43:13 > 0:43:17fishing line can get wrapped around a shark's fins or tail.
0:43:18 > 0:43:22They'll jump again and again to try to dislodge it.
0:43:36 > 0:43:38This is a dangerous new world.
0:43:45 > 0:43:49Sharks simply haven't had time to adapt to being prey...
0:43:51 > 0:43:52..rather than predator.
0:44:03 > 0:44:06But, despite the threats they face,
0:44:06 > 0:44:08it isn't yet too late for sharks.
0:44:38 > 0:44:42There are places where fishing, poaching and pollution
0:44:42 > 0:44:45haven't sent shark and ray populations plummeting.
0:44:56 > 0:45:01In 2006, off the Yucatan Peninsula in Mexico,
0:45:01 > 0:45:05local fishermen led scientists to an extraordinary event,
0:45:05 > 0:45:07on a scale never seen before.
0:45:16 > 0:45:20Here, spawning fish attract whale sharks
0:45:20 > 0:45:22from hundreds of miles around.
0:45:26 > 0:45:28They're joined by giant manta rays,
0:45:28 > 0:45:32flying through the water on wings over 20 feet across.
0:45:39 > 0:45:42They're drawn here for just a few weeks each year
0:45:42 > 0:45:45to feed on billions of tiny fish eggs.
0:46:05 > 0:46:09The food here is so abundant that it brings together the greatest
0:46:09 > 0:46:12gathering of sharks and rays anywhere in the world.
0:46:32 > 0:46:35Even schools of mobula rays have come to join the feast.
0:47:12 > 0:47:13Their numbers build and build.
0:47:25 > 0:47:30Around 800 whale sharks and 300 manta rays
0:47:30 > 0:47:33converge on an area less than half a mile wide.
0:47:51 > 0:47:55Extraordinary places like this allow us to understand
0:47:55 > 0:47:58more of the hidden lives of sharks and rays.
0:48:01 > 0:48:05Language, courtship and social lives.
0:48:07 > 0:48:09They're far more than just hunters.
0:48:27 > 0:48:31If a shark gathering on this scale can remain secret until now...
0:48:33 > 0:48:36..who knows what else is out there,
0:48:36 > 0:48:39still waiting to be discovered?
0:48:59 > 0:49:00The Bahamas.
0:49:03 > 0:49:07Here there are sharks living in the most unexpected places.
0:49:11 > 0:49:14The flooded forests of the island of Bimini.
0:49:19 > 0:49:23Living in these mangrove swamps are baby lemon sharks.
0:49:27 > 0:49:30Cameraman Duncan Brake's aim was to film these sharks
0:49:30 > 0:49:32in their nurseries,
0:49:32 > 0:49:34hidden in the heart of this tangled maze.
0:49:37 > 0:49:39A glimpse -
0:49:39 > 0:49:40but it's off in a flash.
0:49:45 > 0:49:49So far, probably done over 200 hours
0:49:49 > 0:49:52in and amongst the mangroves.
0:49:53 > 0:49:56With almost 3,000 acres of mangrove,
0:49:56 > 0:49:59there are a lot of places for the young sharks to hide.
0:50:01 > 0:50:02They're in there somewhere.
0:50:03 > 0:50:06You can't get frustrated with the wild animals,
0:50:06 > 0:50:09they're wild animals at the end of the day, completely unpredictable.
0:50:09 > 0:50:12You just have to hope you point the camera in the right direction
0:50:12 > 0:50:16and have everything in focus when something happens.
0:50:18 > 0:50:20But that's harder than it sounds.
0:50:34 > 0:50:38And even when he does get close, with a kick of their tails
0:50:38 > 0:50:40the sharks disappear in a cloud of sediment.
0:50:48 > 0:50:50Duncan is in this for the long haul.
0:51:00 > 0:51:03Meanwhile, the rest of team are trying a different approach.
0:51:08 > 0:51:10ROTOR BLADES WHIRR
0:51:15 > 0:51:18So just go to your right a little bit, Chuck.
0:51:18 > 0:51:20This is good.
0:51:22 > 0:51:25This remote-controlled octocopter gives a bird's-eye view
0:51:25 > 0:51:29of the sharks swimming through the sunken forest -
0:51:29 > 0:51:32revealing secret highways through the maze.
0:51:40 > 0:51:45Using the octocopter gives a new perspective on the hidden nursery,
0:51:45 > 0:51:48but the team still need the detailed underwater shots.
0:51:54 > 0:51:56For the next 11 months,
0:51:56 > 0:51:58Duncan perseveres in the mangroves.
0:52:02 > 0:52:05At last, he's able to get close to the sharks,
0:52:05 > 0:52:08inside their nursery.
0:52:08 > 0:52:12These little sharks, they're quite cute, dare to say it.
0:52:12 > 0:52:15Um, they all seem to have their own little personalities.
0:52:22 > 0:52:24After months in the swamps,
0:52:24 > 0:52:29Duncan was finally able to capture the character of these young sharks.
0:52:39 > 0:52:42However, these weren't the only sharks
0:52:42 > 0:52:43with surprising personalities.
0:52:48 > 0:52:52Every year, over 150 great white sharks
0:52:52 > 0:52:54gather around Guadalupe,
0:52:54 > 0:52:56a remote island in the Pacific.
0:53:15 > 0:53:19Here, the sharks use a secret body language to communicate.
0:53:24 > 0:53:26Morne Hardenberg's task
0:53:26 > 0:53:29is to capture these subtle signals on camera.
0:53:30 > 0:53:33I've been doing this for about 15 years now,
0:53:33 > 0:53:35it's taken me quite some time
0:53:35 > 0:53:37to start understanding their body language.
0:53:40 > 0:53:44Morne is willing to do something very few others would dare to...
0:53:45 > 0:53:47..swim with a great white shark.
0:54:05 > 0:54:09Only by getting out of the cage can the team get close enough
0:54:09 > 0:54:12to reveal the details of a shark "conversation".
0:54:13 > 0:54:17The biggest challenge is finding the right animal.
0:54:17 > 0:54:20You can get an animal that is afraid of you.
0:54:20 > 0:54:23An animal that is afraid poses a threat.
0:54:33 > 0:54:36Yes, it's dangerous, they're a top predator,
0:54:36 > 0:54:39but they're not mindless killing machines.
0:54:40 > 0:54:44Surprisingly, the team look for the biggest sharks.
0:54:46 > 0:54:51The best animals for us to dive with are the five-metre-plus females.
0:54:51 > 0:54:54They've got a presence about them, they are not nervous around divers,
0:54:54 > 0:54:56they're actually quite inquisitive.
0:54:59 > 0:55:02This shark's pectoral fins are flattened.
0:55:02 > 0:55:03She's swimming slowly.
0:55:03 > 0:55:05She's not aggressive.
0:55:08 > 0:55:11But communication is two-way.
0:55:11 > 0:55:14The team must also remain calm.
0:55:14 > 0:55:17Their behaviour in the water is crucial for their own safety.
0:55:19 > 0:55:22Our body language and knowledge of the animal makes it
0:55:22 > 0:55:25where they don't feel like they're in charge of us and we don't feel
0:55:25 > 0:55:29like we're in charge of them, and we're all just getting along.
0:55:32 > 0:55:34With the relationship established,
0:55:34 > 0:55:36the team make their move.
0:55:39 > 0:55:42We had to get really, really close to the animals,
0:55:42 > 0:55:44sometimes within two feet,
0:55:44 > 0:55:47when they allowed us to do it.
0:55:47 > 0:55:49And being close to a five-and-a-half-metre white shark
0:55:49 > 0:55:51is an amazing feeling.
0:55:54 > 0:55:57Sometimes you can see her eyeball actually just turning
0:55:57 > 0:56:00and looking at you while you're swimming next to her,
0:56:00 > 0:56:03and it's a feeling of acceptance.
0:56:03 > 0:56:05The shark is accepting you being there.
0:56:13 > 0:56:17But sometimes a shark lets you know you've outstayed your welcome.
0:56:19 > 0:56:22A change in her behaviour is often a sign that, listen here,
0:56:22 > 0:56:26she doesn't like you entering her space at the moment,
0:56:26 > 0:56:27and then the best thing to do
0:56:27 > 0:56:30is absolutely listen to what she's telling you!
0:56:34 > 0:56:38Her pectoral fins are lowered, with the black tips showing.
0:56:40 > 0:56:41Her back is arching.
0:56:43 > 0:56:44It's time to say goodbye.
0:56:48 > 0:56:51Understanding the social side of sharks
0:56:51 > 0:56:54is only one of many recent breakthroughs.
0:56:56 > 0:56:59For scientists, it's a golden age of discovery.
0:57:01 > 0:57:04And that's what we explore in the next programme.
0:57:07 > 0:57:11Scientists are unlocking the secrets of sharks,
0:57:11 > 0:57:14and they're finding they've got extraordinary senses.
0:57:14 > 0:57:17They're smart and, what's more,
0:57:17 > 0:57:19they can help us!
0:57:19 > 0:57:21From medical breakthroughs
0:57:21 > 0:57:23to making faster cars,
0:57:23 > 0:57:26sharks could hold the answer!