0:00:05 > 0:00:06The Great Barrier Reef.
0:00:12 > 0:00:15It's home to an extraordinarily diverse community
0:00:15 > 0:00:17of animals and plants.
0:00:25 > 0:00:29'Here, unknown species are still being found
0:00:29 > 0:00:33'and astonishing things discovered about creatures we thought we knew.
0:00:36 > 0:00:39'In this series, our research vessel, the Alucia,
0:00:39 > 0:00:44'will allow us to explore and understand the reef as never before.
0:00:47 > 0:00:50'This marine paradise may be best known
0:00:50 > 0:00:52'for its spectacular coral reefs...
0:00:54 > 0:00:56'..but it also has 300 sand islands.'
0:01:00 > 0:01:02600 continental islands.
0:01:06 > 0:01:08Miles of lush forest.
0:01:11 > 0:01:13And deep ocean channels.
0:01:16 > 0:01:19Each of these habitats attracts a very different set of visitors.
0:01:23 > 0:01:26When I first came here almost 60 years ago,
0:01:26 > 0:01:29we knew very little about these communities.
0:01:31 > 0:01:34But today, new tracking systems are allowing us
0:01:34 > 0:01:37to follow the lives of these creatures in new ways.
0:01:39 > 0:01:41From the ocean's great predators...
0:01:43 > 0:01:46..to a mysterious whale that seeks out human contact.
0:01:50 > 0:01:54I'll discover their surprising reasons for visiting
0:01:54 > 0:01:57and reveal why the reef is so important for their survival.
0:02:28 > 0:02:31Last time, we looked at the rich community of animals
0:02:31 > 0:02:33that lives among the coral,
0:02:33 > 0:02:36but the reef also receives visitors.
0:02:36 > 0:02:41Some travel for thousands of miles in order to get here
0:02:41 > 0:02:43and stay for only a few weeks.
0:02:43 > 0:02:47Others linger on the fringes and come in every day.
0:02:47 > 0:02:51Each has its own particular reason for doing so.
0:02:53 > 0:02:59The Great Barrier Reef consists of 3,000 individual coral reefs.
0:02:59 > 0:03:04It stretches for 1,400 miles along Australia's northeast coast.
0:03:04 > 0:03:09And every year, it attracts over a million migrating animals.
0:03:14 > 0:03:16We're beginning our exploration in the north,
0:03:16 > 0:03:19on the outskirts of this vast wilderness.
0:03:25 > 0:03:27Our research vessel, the Alucia,
0:03:27 > 0:03:30has brought us out here to Osprey Reef.
0:03:30 > 0:03:3490 miles, 150 kilometres out in the Coral Sea
0:03:34 > 0:03:37from the edge of the Great Barrier.
0:03:37 > 0:03:40Isolated though it is, it nonetheless plays a crucial part
0:03:40 > 0:03:44in the lives of many of the inhabitants of the Barrier Reef.
0:03:45 > 0:03:48What makes Osprey so interesting
0:03:48 > 0:03:52is that it lies in the path of the south equatorial current.
0:03:54 > 0:03:57This is a moving highway
0:03:57 > 0:04:00that sweeps a host of different visitors towards the great reef.
0:04:03 > 0:04:04We are here to discover
0:04:04 > 0:04:07why this remote outpost is so important to them.
0:04:11 > 0:04:15To do that, we're going to use a very special piece of technology,
0:04:15 > 0:04:18the Alucia's Triton submarine.
0:04:24 > 0:04:28It's the first submersible of its kind ever to dive in these waters.
0:04:33 > 0:04:38Huh! It does look as though water's gurgling up here,
0:04:38 > 0:04:41but in fact, my feet aren't wet.
0:04:44 > 0:04:48S-O, S-O, this is Nadir. Am I clear to vent? Over.
0:04:48 > 0:04:53'Copy Nadir. So you are clear to vent, clear to vent.
0:04:53 > 0:04:55'Have a good dive, guys.'
0:04:55 > 0:04:57Roger. Venting now.
0:05:00 > 0:05:01There we are!
0:05:04 > 0:05:09'The sub not only gives us stunning 360-degree views,
0:05:09 > 0:05:14'it allows us to dive to depths where no unprotected human has ever been.'
0:05:18 > 0:05:21For this dive, we are only going down to about 35 metres,
0:05:21 > 0:05:23just over 100 feet,
0:05:23 > 0:05:27where much of the wildlife we're hoping to film will be feeding.
0:05:32 > 0:05:36Marine geologists have recently gathered sufficient data
0:05:36 > 0:05:39for us to create an accurate three-dimensional picture
0:05:39 > 0:05:42of Osprey Reef for the very first time.
0:05:44 > 0:05:48It is, in fact, a huge mountain hidden beneath the waves
0:05:48 > 0:05:52and rising steeply from the seafloor 2,400 metres below.
0:05:55 > 0:05:59The top of this vast seamount creates a shallow lagoon
0:05:59 > 0:06:02that supports a flourishing community of corals.
0:06:07 > 0:06:12This wall of rock ahead of me is the flank of Osprey Reef.
0:06:12 > 0:06:16When cold, deep, nutrient-rich currents from the ocean
0:06:16 > 0:06:20come in and strike it, they defect it upwards.
0:06:20 > 0:06:25And that creates an oasis for living creatures of all kinds.
0:06:32 > 0:06:34Many creatures live here throughout the year.
0:06:34 > 0:06:38And the boss of them all is one kind, sharks.
0:06:46 > 0:06:47There's one! Close up.
0:06:49 > 0:06:53Whatever else you say about sharks, they are so beautiful in the water.
0:06:56 > 0:06:59Resident predators mean one thing -
0:06:59 > 0:07:01a plentiful supply of food.
0:07:04 > 0:07:08For creatures travelling vast distances to get to the reef,
0:07:08 > 0:07:11that makes Osprey a very desirable waypoint on their journey.
0:07:16 > 0:07:19Seamounts are stopping-off points for visitors.
0:07:19 > 0:07:21They come from far and wide.
0:07:21 > 0:07:23From tiger sharks to turtles.
0:07:23 > 0:07:29And they come to refuel and also, it seems, recalibrate.
0:07:37 > 0:07:40It appears that this is a signpost
0:07:40 > 0:07:42and a checkpoint on the way to the reef.
0:07:46 > 0:07:48Visitors arrive year round.
0:07:50 > 0:07:52Among them are hammerheads.
0:07:57 > 0:08:00Like all sharks, they have tiny sensors on their nose
0:08:00 > 0:08:04which can pick up signals from the earth's magnetic field.
0:08:05 > 0:08:09And that helps them navigate through the blue infinity of the open ocean.
0:08:18 > 0:08:20There are tiger sharks here, too.
0:08:23 > 0:08:25They come to the reef to feed.
0:08:25 > 0:08:27And they seem to know exactly where they're going.
0:08:34 > 0:08:38The proportion of their brain dedicated to smell
0:08:38 > 0:08:40is the largest of any shark.
0:08:42 > 0:08:44Their two nostrils work independently,
0:08:44 > 0:08:49allowing them to smell in stereo and track prey over huge distances.
0:08:52 > 0:08:54From Osprey, some tiger sharks
0:08:54 > 0:08:58travel to a very specific destination on the reef.
0:09:02 > 0:09:06230 miles north of Osprey lies Raine Island.
0:09:12 > 0:09:16Every summer, the tiger sharks arrive without fail.
0:09:16 > 0:09:20They're here to take advantage of a major event on the reef -
0:09:20 > 0:09:24the arrival of the female green turtles.
0:09:30 > 0:09:35The tiger sharks aren't here to kill, they've come to scavenge on the dead.
0:09:35 > 0:09:38The unlucky turtles who have not survived
0:09:38 > 0:09:40their exhausting immigration.
0:09:41 > 0:09:45This is why the tiger shark has earned the unflattering title...
0:09:47 > 0:09:49..Dustbin of the Sea.
0:09:54 > 0:09:57They prefer the easy life of the scavenger,
0:09:57 > 0:10:02so the majority of green turtles have little to fear from these predators.
0:10:08 > 0:10:12In the summer months, the turtles arrive in thousands.
0:10:16 > 0:10:19They have come from as far as New Guinea, Vanuatu
0:10:19 > 0:10:21and New Caledonia to the east,
0:10:21 > 0:10:25as well as from the Torres Straits and beyond to the west.
0:10:28 > 0:10:32Some have travelled an impressive 1,500 miles
0:10:32 > 0:10:34to reach this particular beach.
0:10:36 > 0:10:39It measures only a few hundred metres across,
0:10:39 > 0:10:41a tiny speck in a vast ocean.
0:10:41 > 0:10:45But Raine Island plays a major role in their lives.
0:10:48 > 0:10:5270% of the Barrier Reef's breeding green turtles come here to lay.
0:10:54 > 0:10:58It's one of the most important nesting sites in the world.
0:11:03 > 0:11:06I first visited Raine for a television series
0:11:06 > 0:11:09called Zoo Quest back in 1957.
0:11:11 > 0:11:14At the time, Raine was little known and rarely visited.
0:11:16 > 0:11:20It was then I met my first green turtle hatchling.
0:11:26 > 0:11:28Back then, we had no idea
0:11:28 > 0:11:31just how extraordinary a story these turtles had to tell.
0:11:35 > 0:11:37We now know that if they survive,
0:11:37 > 0:11:40they'll spend the next 40 years of their lives at sea.
0:11:43 > 0:11:46Only then do they return to Raine to breed.
0:11:49 > 0:11:53And astonishingly, they return to exactly the same beach
0:11:53 > 0:11:55where they themselves hatched.
0:11:59 > 0:12:01How they find their way back after decades at sea
0:12:01 > 0:12:04is one of the mysteries that surround this species.
0:12:08 > 0:12:11But new research is suggesting that, just like the sharks,
0:12:11 > 0:12:14they navigate using the earth's magnetic field.
0:12:16 > 0:12:18They weigh up to 130 kilos,
0:12:18 > 0:12:21so hauling themselves up the beach is a gruelling task.
0:12:23 > 0:12:26But it's expected that 30,000 of them
0:12:26 > 0:12:29will come ashore to lay their eggs this year.
0:12:37 > 0:12:40With space in short supply, it's every female for herself.
0:12:53 > 0:12:56Once they've dug a hole, laying can begin.
0:13:01 > 0:13:04Each egg is roughly the size of a Ping-Pong ball.
0:13:04 > 0:13:08A female may lay up to 120 of them at a time
0:13:08 > 0:13:12and she's able to do this six times in a single breeding season.
0:13:20 > 0:13:23Once the eggs are laid, she buries them.
0:13:23 > 0:13:27For the next 60 days, the sand will conceal them from predators
0:13:27 > 0:13:30and protect them from the blistering sun.
0:13:46 > 0:13:49Keeping a very close eye on the turtles' progress
0:13:49 > 0:13:54is Dr Andy Dunstan of the Great Barrier Reef Marine Park Authority.
0:13:56 > 0:14:01Raine Island is the biggest green turtle rookery in the world.
0:14:01 > 0:14:03So it's incredibly important
0:14:03 > 0:14:05with the state of green turtles at the moment.
0:14:05 > 0:14:09Because of this, Raine is the most protected island on the reef.
0:14:14 > 0:14:18Only a handful of biologists are allowed to land here
0:14:18 > 0:14:21and Andy and his team have done so for very good reason.
0:14:27 > 0:14:30A huge number of turtles are certainly coming ashore
0:14:30 > 0:14:32to lay their eggs on the island,
0:14:32 > 0:14:35but the team's observations have revealed a worrying trend.
0:14:38 > 0:14:42The number of young hatchlings surviving incubation in the sand
0:14:42 > 0:14:44has dropped to just 20%.
0:14:44 > 0:14:46It's a serious cause for concern.
0:14:49 > 0:14:51The hatchlings we're seeing coming out
0:14:51 > 0:14:54are nowhere near the numbers that they should be.
0:14:54 > 0:14:57The nests, when we dig them up,
0:14:57 > 0:15:01have got really low levels of successful eggs hatching.
0:15:03 > 0:15:05And that is happening because of the very substance
0:15:05 > 0:15:10that makes this island so suitable for nest-building in the first place.
0:15:10 > 0:15:13Raine Island's a sand island. They move.
0:15:13 > 0:15:17But specifically for the green turtles here,
0:15:17 > 0:15:22the nesting area has become lower, so what we're seeing now
0:15:22 > 0:15:27that we never saw 30 years ago is inundation of tidal waters.
0:15:29 > 0:15:33This means that at high tide, the island is being flooded from below
0:15:33 > 0:15:36and the developing turtle eggs are being drowned.
0:15:38 > 0:15:4375% of the beach-nesting area is not suitable.
0:15:44 > 0:15:47Because turtles take a long time to mature,
0:15:47 > 0:15:51we expect to see a crash in those adult turtle numbers in the future.
0:15:51 > 0:15:56If we do something about hatchling success and nesting success now,
0:15:56 > 0:15:58we should see that recover again.
0:16:00 > 0:16:03Last year, Andy and his team made an ambitious plan.
0:16:07 > 0:16:10In a trial sector, they have raised the turtles nesting area
0:16:10 > 0:16:13by one and a half metres.
0:16:13 > 0:16:16They hope this will keep the developing eggs
0:16:16 > 0:16:19clear of the tidal waters and out of harm's way.
0:16:26 > 0:16:28Two long months after the egg laying began,
0:16:28 > 0:16:31the team returns to see if their plan is working.
0:16:36 > 0:16:37Under the cover of darkness,
0:16:37 > 0:16:42the first of the evening's hatchlings start to emerge.
0:16:45 > 0:16:47They started to push their way up
0:16:47 > 0:16:50through the sand about two days earlier.
0:16:57 > 0:17:01Now comes the moment that Andy and his team have been waiting for.
0:17:11 > 0:17:16A shallow trench helps to delay the new arrivals temporarily
0:17:16 > 0:17:17and allow the team to count them.
0:17:25 > 0:17:27So far, the signs are very encouraging.
0:17:27 > 0:17:30And as the night wears on, it gets better and better.
0:17:33 > 0:17:37This is looking great. We're getting much better nesting success,
0:17:37 > 0:17:39much better hatching success,
0:17:39 > 0:17:42the turtles are nesting right across the whole area
0:17:42 > 0:17:45and not disturbing each other so much.
0:17:45 > 0:17:47And those clutches which are underneath the sand
0:17:47 > 0:17:49are hatching much more successfully.
0:17:51 > 0:17:55It's confirmation that Andy and his team have found the right way
0:17:55 > 0:17:57to restore this vital breeding area.
0:18:01 > 0:18:06But for the young hatchlings, the trials of life have only just begun.
0:18:07 > 0:18:12Each new arrival will have to make a perilous dash to reach the ocean.
0:18:16 > 0:18:18Now they're on their own.
0:18:18 > 0:18:21Andy and his team must not interfere at this stage.
0:18:23 > 0:18:26Inevitably, the tiny, defenceless hatchlings
0:18:26 > 0:18:28attract scores of predators.
0:18:28 > 0:18:31SQUAWKING
0:18:32 > 0:18:34Terns and herons patrol the beach.
0:18:45 > 0:18:49And in the shallows, reef sharks lie in wait.
0:19:42 > 0:19:44Great numbers are lost,
0:19:44 > 0:19:49but enough will make it to the ocean to ensure the species' survival.
0:20:00 > 0:20:03As the young turtles leave the reef,
0:20:03 > 0:20:07they get a helping hand from the ocean currents.
0:20:07 > 0:20:12Swept out into the open ocean and there, they face new hazards.
0:20:12 > 0:20:15If they survive, they will eventually return
0:20:15 > 0:20:19to the very same beaches where they hatched.
0:20:22 > 0:20:25Remote islands like Raine are hugely important
0:20:25 > 0:20:27to both turtles and birds
0:20:27 > 0:20:30that come to the reef to lay their eggs.
0:20:33 > 0:20:37There are 900 isolated islands on the Great Barrier from which to choose
0:20:37 > 0:20:40and there's a habitat to suit every visitor.
0:20:43 > 0:20:46Turtles need sandy beaches
0:20:46 > 0:20:48and many birds need trees.
0:20:51 > 0:20:55'The Alucia is taking us to one of these wooded islands
0:20:55 > 0:20:58'near the southern end of the Great Barrier.'
0:21:00 > 0:21:04Almost 1,000 miles south of Raine is Heron Island.
0:21:04 > 0:21:05And every year, it attracts
0:21:05 > 0:21:08thousands of birds seeking somewhere safe to nest.
0:21:12 > 0:21:15The island is surrounded by fragile coral reef.
0:21:15 > 0:21:20So to reach the shore, I'm leaving the Alucia anchored in deeper water.
0:21:29 > 0:21:31FAINT BIRDSONG
0:21:38 > 0:21:42The warm waters of the Barrier Reef are full of fish.
0:21:42 > 0:21:44Full of food, as far as birds are concerned.
0:21:44 > 0:21:50There are immense numbers of seabirds throughout the year on the reef.
0:21:50 > 0:21:54But the moment comes in the year when, in fact, a bird has to lay.
0:21:54 > 0:21:57And to do that, it has to go onto land.
0:21:57 > 0:22:02And the number of sites where they can build a nest are very limited.
0:22:02 > 0:22:06So they will put up with a great deal of crowding
0:22:06 > 0:22:10and even with intruders, like myself, without deserting their nest.
0:22:14 > 0:22:16Hello.
0:22:17 > 0:22:20'Noddies are very protective parents.
0:22:20 > 0:22:24'Very little deters them from their chick-rearing duties.'
0:22:30 > 0:22:33Over one-and-a-half million birds
0:22:33 > 0:22:36come to the Great Barrier's islands every year to breed.
0:22:39 > 0:22:43To see one of the most intriguing, you'll have to wait until after dark.
0:22:53 > 0:22:55WAILING
0:22:56 > 0:23:00'The first indication that this secretive character has arrived
0:23:00 > 0:23:03'is its rather unusual song.'
0:23:03 > 0:23:05WAILING
0:23:10 > 0:23:13The old sailors used to call it the ghost bird
0:23:13 > 0:23:16because of its extraordinary call.
0:23:16 > 0:23:19More properly known as the wedge-tailed shearwater.
0:23:19 > 0:23:21WAILING
0:23:29 > 0:23:34'The birds' haunting calls guide me to their breeding grounds.'
0:23:34 > 0:23:36WAILING
0:23:51 > 0:23:55These are true seafaring birds. Out at sea when they're feeding,
0:23:55 > 0:23:58they are very expert at flying just above the surface,
0:23:58 > 0:24:01or indeed swimming on the surface, catching their fish.
0:24:01 > 0:24:04But when they come into land, well,
0:24:04 > 0:24:06they have to come in in the dark, for a start.
0:24:06 > 0:24:09And their landing is sometimes not very expert.
0:24:12 > 0:24:14Night-vision cameras probably give us
0:24:14 > 0:24:18better pictures of their landing ground than they seem to have.
0:24:33 > 0:24:36Their legs with which they paddle over the surface of the sea
0:24:36 > 0:24:41are placed far back on their body, and that makes them clumsy walkers.
0:24:44 > 0:24:46These birds have travelled
0:24:46 > 0:24:48an extraordinary 4,000 miles to get here.
0:24:52 > 0:24:54After spending months feeding at sea,
0:24:54 > 0:24:56they've had to come to land in order to breed.
0:24:59 > 0:25:01Once paired, they're devoted couples
0:25:01 > 0:25:04and both male and female share the tasks of parenthood.
0:25:09 > 0:25:11Even though there are trees here,
0:25:11 > 0:25:15the shearwaters prefer to make their nests underground.
0:25:21 > 0:25:24At the bottom of the nest hole, their three-week-old chick
0:25:24 > 0:25:27is waiting for its next meal.
0:25:30 > 0:25:32TWEETING
0:25:35 > 0:25:37Being a shearwater parent is a demanding job.
0:25:40 > 0:25:42Their young requires constant feeding.
0:25:44 > 0:25:45It consumes so much food
0:25:45 > 0:25:49that eventually, it'll outweigh its own parents.
0:25:52 > 0:25:57But its demands compel the adults to continually fly out to sea
0:25:57 > 0:25:59and come back again with more food.
0:26:01 > 0:26:05And their takeoffs are often just as clumsy as their landings.
0:26:37 > 0:26:39Fortunately for their nestlings,
0:26:39 > 0:26:41there's no shortage of fish in the summer months.
0:26:43 > 0:26:47And scientists have only just discovered why that is.
0:26:54 > 0:26:57In the waters just beyond Heron Island,
0:26:57 > 0:27:01there's a rich, swirling current known as the Capricorn Eddy.
0:27:06 > 0:27:10As it spins clockwise, it pulls up cool waters from below,
0:27:10 > 0:27:15which bring rich nutrients to the surface.
0:27:15 > 0:27:21That fuels the growth of huge blooms of tiny marine creatures, plankton,
0:27:21 > 0:27:23the foundation of the entire marine food web.
0:27:25 > 0:27:29So this part of the reef is particularly rich with fish.
0:27:29 > 0:27:32Vital food for the hungry young.
0:27:37 > 0:27:40By choosing Heron Island as a nesting ground,
0:27:40 > 0:27:44the birds can give their nestlings the best possible start in life.
0:27:49 > 0:27:52When I first came to the Barrier Reef,
0:27:52 > 0:27:55we knew very little about these seasonal visitors.
0:27:57 > 0:27:59We could only speculate as to why they came here
0:27:59 > 0:28:02and where they came from.
0:28:04 > 0:28:08Today, new research is enabling us to understand more clearly
0:28:08 > 0:28:13why, every year, particular species come to specific locations to breed.
0:28:15 > 0:28:17But there are still large animals
0:28:17 > 0:28:21whose movements remain something of a mystery.
0:28:21 > 0:28:25Manta rays are the nomads of the reef.
0:28:25 > 0:28:27They're huge creatures.
0:28:27 > 0:28:31They can measure 15 feet, five metres across
0:28:31 > 0:28:34and weigh almost one-and-a-half tonnes.
0:28:34 > 0:28:37They come to the reef to feed on plankton,
0:28:37 > 0:28:40but they also use it as a sanctuary,
0:28:40 > 0:28:43where they can breed, or get a good clean.
0:28:47 > 0:28:51Many make their way to the waters that surround Lady Elliot Island
0:28:51 > 0:28:53on the southern end of the Great Barrier.
0:28:58 > 0:29:01For the visiting manta rays, this is a paradise.
0:29:01 > 0:29:05A place where these ocean giants can get a little pampering.
0:29:13 > 0:29:16These are the beauty salons of the reef.
0:29:16 > 0:29:19And they're often run by a pair of wrasse,
0:29:19 > 0:29:22small fish with a stripe running from head to tail.
0:29:27 > 0:29:29These committed cleaners
0:29:29 > 0:29:31regularly tend to a host of different creatures.
0:29:36 > 0:29:38They provide a vital service,
0:29:38 > 0:29:42removing the dead skin and parasites from outside
0:29:42 > 0:29:45and even inside their clients' bodies.
0:29:48 > 0:29:50It may seem like a thankless task,
0:29:50 > 0:29:53but the cleaner fish are getting a good meal out of it.
0:29:58 > 0:30:02And of all their clients, the manta rays are their star customers.
0:30:09 > 0:30:12When business is brisk, they patiently wait in line.
0:30:18 > 0:30:20Like planes in a holding pattern,
0:30:20 > 0:30:23they circle until an opportunity arrives.
0:30:32 > 0:30:36When it's their turn, the manta rays surrender themselves completely.
0:30:40 > 0:30:43Within seconds, a host of fish rush to their side.
0:30:44 > 0:30:47Manta rays are rarely left waiting for long.
0:30:56 > 0:31:00Each fish tends to a very specific part of the manta's body.
0:31:01 > 0:31:04And the cleaning can last a full hour.
0:31:09 > 0:31:12For the most part, the service is second to none.
0:31:12 > 0:31:16But occasionally, the cleaners can get a little carried away.
0:31:22 > 0:31:26A female wrasse has taken a nibble out of the manta ray's flesh.
0:31:27 > 0:31:31She's broken the rules, and there's a price to pay.
0:31:31 > 0:31:34Her partner chases after her.
0:31:34 > 0:31:37It's the cleaner fish equivalent of a stern telling off.
0:31:40 > 0:31:44Scientists believe males do this to protect future business.
0:31:46 > 0:31:50If the bite is a one-off, the manta ray will return.
0:31:50 > 0:31:53But research has shown that if it happens too often,
0:31:53 > 0:31:57the pair risks driving regular visitors away.
0:32:02 > 0:32:04Fortunately, it seems her indiscretion
0:32:04 > 0:32:06hasn't put their client off.
0:32:06 > 0:32:10The manta is back and business has resumed.
0:32:14 > 0:32:17Manta rays come here in such numbers
0:32:17 > 0:32:21that the island has become the focal point for a research project.
0:32:27 > 0:32:30Dr Kathy Townsend has been tracking the manta's movements
0:32:30 > 0:32:32and numbers for the last seven years.
0:32:43 > 0:32:46Lady Elliot Island is like the centre of the universe
0:32:46 > 0:32:49for manta rays on the east coast of Australia.
0:32:49 > 0:32:51We come back time and time again
0:32:51 > 0:32:54because we get large aggregations of these animals.
0:32:55 > 0:32:58We are doing several things with the manta rays.
0:32:58 > 0:33:00First of all, we're trying to understand
0:33:00 > 0:33:02how many there are potentially here.
0:33:02 > 0:33:04And to do that, you need to do some sort of tagging.
0:33:07 > 0:33:11This is a key part of Kathy's work in tracking these gentle ocean giants.
0:33:11 > 0:33:14And the team has already attached acoustic tags
0:33:14 > 0:33:18to a large number of study animals.
0:33:18 > 0:33:22We have six acoustic listening stations around Lady Elliot Island.
0:33:22 > 0:33:24And as an animal goes past,
0:33:24 > 0:33:27within a 500-metre radius of this listening station,
0:33:27 > 0:33:31it picks up the tag and we know that that animal's been past.
0:33:34 > 0:33:37That has revealed that many of the mantas have travelled
0:33:37 > 0:33:41hundreds of miles up the eastern coast of Australia to get here.
0:33:45 > 0:33:47One of the lovely things about working with manta rays
0:33:47 > 0:33:49is that they're extremely curious
0:33:49 > 0:33:52and they'll seek you out to come and see what you're up to.
0:34:07 > 0:34:09It's really unusual behaviour.
0:34:09 > 0:34:11Most sharks and rays have no interest
0:34:11 > 0:34:13in having any interaction with people whatsoever.
0:34:13 > 0:34:17But for whatever reason, manta rays are highly-curious creatures
0:34:17 > 0:34:20and will basically look at you eye to eye.
0:34:22 > 0:34:26The manta ray's inquisitive nature works to Kathy's advantage.
0:34:26 > 0:34:31It means she can get close enough to photograph them for identification.
0:34:32 > 0:34:37And one of the best places to do that is at the cleaning stations.
0:34:49 > 0:34:51We need to get in underneath the animal
0:34:51 > 0:34:54and take a photograph from below.
0:34:54 > 0:34:58Each individual has a very unique spot pattern
0:34:58 > 0:35:01that stays with them from birth until they pass away.
0:35:01 > 0:35:03That's very handy for us.
0:35:08 > 0:35:11When Project Manta began seven years ago,
0:35:11 > 0:35:15it was thought that fewer than 40 individuals came to Lady Elliot.
0:35:15 > 0:35:20Today, Kathy and her team have catalogued more than 800.
0:35:23 > 0:35:26I think manta ray research is quite important
0:35:26 > 0:35:29because first of all, this is a very large-bodied animal
0:35:29 > 0:35:32that very little information is known about.
0:35:32 > 0:35:34Various places around the world,
0:35:34 > 0:35:37the manta ray populations have declined dramatically,
0:35:37 > 0:35:40to the point where they've now been listed as threatened
0:35:40 > 0:35:42on that list for endangered species.
0:35:45 > 0:35:49For the visiting mantas, the Great Barrier Reef really is a sanctuary.
0:35:51 > 0:35:54Here, this ocean giant is properly protected.
0:35:56 > 0:35:57While they're in these waters,
0:35:57 > 0:36:01they're safe from the fisheries that threaten them elsewhere.
0:36:05 > 0:36:08Manta rays aren't the only animals that find refuge here.
0:36:09 > 0:36:13The Great Barrier protects its visitors in many different ways.
0:36:20 > 0:36:24'That becomes clear when you look at the reef from above.
0:36:27 > 0:36:29'This part of tropical Australia
0:36:29 > 0:36:33'lies right in the path of regular seasonal cyclones.
0:36:33 > 0:36:36'And from up here, you can see what valuable protection
0:36:36 > 0:36:38'the reef can provide.'
0:36:40 > 0:36:42This tangle of limestone walls
0:36:42 > 0:36:47acts as a barrier against the open ocean.
0:36:47 > 0:36:51Between it and the land, the waters are warm and shallow.
0:36:51 > 0:36:54An ideal haven for visitors.
0:36:56 > 0:36:59In the winter, many creatures come up here to escape
0:36:59 > 0:37:01the freezing temperatures of the Antarctic.
0:37:09 > 0:37:12Among them are humpback whales.
0:37:32 > 0:37:34WHALE SONG
0:37:34 > 0:37:36Weighing up to 40 tonnes,
0:37:36 > 0:37:39they're the largest of the Great Barrier Reef's visitors
0:37:39 > 0:37:42and they have also travelled great distances to get here.
0:37:52 > 0:37:57Each year, they make an exhausting 6,000-mile-round trip
0:37:57 > 0:37:59from the Antarctic and back again.
0:38:04 > 0:38:06Incredibly, 20,000 of them do it.
0:38:13 > 0:38:15Here, in these warm and sheltered waters,
0:38:15 > 0:38:18they give birth and suckle their newborn calves.
0:38:23 > 0:38:26But in fact, we still know very little
0:38:26 > 0:38:28about what else they do once they get here.
0:38:33 > 0:38:36Where exactly do they go during their time on the reef?
0:38:40 > 0:38:42The fact that we don't know
0:38:42 > 0:38:45is a reminder of just how vast this great wilderness is.
0:38:49 > 0:38:52But not all whales make the task of tracking them so hard.
0:38:55 > 0:38:58In fact, there's one species which does quite the opposite.
0:38:58 > 0:39:02Incredibly, this whale actively seeks out the scientists
0:39:02 > 0:39:04who are trying to study them.
0:39:15 > 0:39:19This endearing little character is the dwarf minke whale.
0:39:22 > 0:39:25And surprisingly, it was only first observed
0:39:25 > 0:39:27here on the reef in the 1980s.
0:39:30 > 0:39:35But since then, we've realised that they're extremely faithful visitors,
0:39:35 > 0:39:38returning every year to the same location on the northern reef.
0:39:47 > 0:39:50Why they do so, we still don't understand.
0:39:52 > 0:39:55But research is beginning to reveal their story.
0:39:57 > 0:40:00Dr Alistair Birtles knows more about
0:40:00 > 0:40:04this still-mysterious species than anyone else.
0:40:04 > 0:40:07So he's affectionately known as Professor Minke.
0:40:10 > 0:40:15To observe the whales in detail, he has to step into their world.
0:40:17 > 0:40:20The very first time I got in the water, um...
0:40:20 > 0:40:26was with a degree of apprehension, great excitement.
0:40:26 > 0:40:30Um...I don't think I'd ever been in the water with a whale before.
0:40:30 > 0:40:34And the first thing you see is the white shoulder, um...
0:40:34 > 0:40:38and then the rest of the grey animal emerges around it.
0:40:38 > 0:40:42It's very special being in the water
0:40:42 > 0:40:45with these animals in their own environment.
0:40:45 > 0:40:48It's an extraordinary experience.
0:40:51 > 0:40:54Every year, Alistair and his research team
0:40:54 > 0:40:56return to spend time with the dwarf minkes.
0:40:59 > 0:41:03These annual reunions are beginning to reveal more and more
0:41:03 > 0:41:05about these fascinating creatures.
0:41:08 > 0:41:12It seems that they spend most of their lives out in the open ocean,
0:41:12 > 0:41:15leading what's thought to be a solitary existence.
0:41:18 > 0:41:21But surprisingly, when they get here, on the Great Reef,
0:41:21 > 0:41:23they actively seek human contact.
0:41:28 > 0:41:30Behaviour like this happens nowhere else.
0:41:32 > 0:41:35It is entirely the whale's curiosity that brings them in.
0:41:35 > 0:41:38I think we're a rather strange object.
0:41:38 > 0:41:41We're a visitor into their world.
0:41:41 > 0:41:45I'm sure they're wondering exactly what we are
0:41:45 > 0:41:48and what we're doing, just as we're wondering what they're doing.
0:41:51 > 0:41:54For Birtles, there are many familiar faces here.
0:41:54 > 0:41:57And he has his own pet names for regular visitors.
0:42:00 > 0:42:04Bento, I have seen every year for the last eight years.
0:42:05 > 0:42:07She has a bent-over dorsal fin
0:42:07 > 0:42:12from I think where she was fairly savagely mauled by a shark.
0:42:12 > 0:42:15And last year's encounter was a particularly special one
0:42:15 > 0:42:17because she had a calf with her.
0:42:17 > 0:42:21That's the first time in eight years that we've known she had a calf.
0:42:21 > 0:42:25And it was a little male and it was a very special interaction.
0:42:34 > 0:42:37What Birtles and his team want to discover
0:42:37 > 0:42:39is why this usually-solitary whale
0:42:39 > 0:42:43suddenly becomes so extremely social when it gets here.
0:42:45 > 0:42:47There are a number of clues.
0:42:47 > 0:42:51We know they're not feeding. We've never seen them feed.
0:42:51 > 0:42:53But we see a lot of socialising going on.
0:42:55 > 0:42:58Minkes were known as the silent whale when we began working on them
0:42:58 > 0:43:01and there were no recordings of dwarf minkes.
0:43:02 > 0:43:06It went on for quite a while before we heard any sounds.
0:43:13 > 0:43:15And then there's an extraordinary sound they make
0:43:15 > 0:43:19which the researcher who labelled it
0:43:19 > 0:43:22called it the Star Wars sound.
0:43:22 > 0:43:25I thought it was a little more like Beethoven's Fifth
0:43:25 > 0:43:29because it's got a triple beat and then a long shwang
0:43:29 > 0:43:31that he thought was the lightsaber.
0:43:31 > 0:43:34So it goes, da-da-da-dang.
0:43:35 > 0:43:37WHALE SONG
0:43:38 > 0:43:39WHALE SONG
0:43:39 > 0:43:43When you hear it underwater, it kind of reverberates through your chest.
0:43:43 > 0:43:45It's a very powerful sound.
0:43:45 > 0:43:47WHALE SONG
0:43:51 > 0:43:53The song is only produced by males
0:43:53 > 0:43:56and it's thought to be related to courtship.
0:43:56 > 0:43:58WHALE SONG
0:43:58 > 0:44:01Curiously, two thirds of the individuals
0:44:01 > 0:44:04Alistair encounters are adolescents.
0:44:06 > 0:44:10One theory is that the whales are coming here to find potential mates
0:44:10 > 0:44:14and learn the dos and don'ts of minke social behaviour.
0:44:16 > 0:44:18Though Birtles' team has amassed
0:44:18 > 0:44:20a huge amount of data over the decades,
0:44:20 > 0:44:23there is clearly still much to learn.
0:44:24 > 0:44:29Where, for example, do the whales go after this social gathering?
0:44:32 > 0:44:35But now, a brand-new tagging programme
0:44:35 > 0:44:38is shedding more light on their annual journey.
0:44:41 > 0:44:44Tagging is not easy.
0:44:47 > 0:44:49The diver has to get into position,
0:44:49 > 0:44:52choose his mark and then discharge the tag,
0:44:52 > 0:44:54all on a single breath.
0:44:57 > 0:45:00There's no room for error.
0:45:22 > 0:45:23After initially taking fright,
0:45:23 > 0:45:26the whale comes back to the dive boat.
0:45:26 > 0:45:30It seems that minkes aren't too distressed by the process.
0:45:34 > 0:45:37The tracking data the team is now collecting
0:45:37 > 0:45:41may reveal the piece of the puzzle that, until now, has been missing.
0:45:41 > 0:45:44So for 20 years, we've been studying what the whales do
0:45:44 > 0:45:47in this area of the Great Barrier Reef.
0:45:47 > 0:45:50We know they're only here for a few weeks
0:45:50 > 0:45:52and we had no idea where they went
0:45:52 > 0:45:54when they left the Great Barrier Reef
0:45:54 > 0:45:56at the end of their sojourn here.
0:45:58 > 0:46:00It really is an extraordinary journey
0:46:00 > 0:46:02that we now know that they make.
0:46:02 > 0:46:06Spot, the young male that was the first ever minke
0:46:06 > 0:46:10to have a satellite tag attached in 2013,
0:46:10 > 0:46:16he travelled over 7,000 kilometres deep into the Subantarctic.
0:46:16 > 0:46:22That's an extraordinary journey for what is a little whale, to make.
0:46:22 > 0:46:26The tagging tells us where the whales are travelling fast
0:46:26 > 0:46:28and where they're spending extra time.
0:46:28 > 0:46:32There's a few places along the east coast of Australia and Bass Strait
0:46:32 > 0:46:36where they may spend one, two or even three weeks of time
0:46:36 > 0:46:39milling around, probably feeding.
0:46:39 > 0:46:43So we may have discovered some of these feeding sites
0:46:43 > 0:46:46for the dwarf minke whale along their migration path.
0:46:48 > 0:46:50For Birtles, it's not just about
0:46:50 > 0:46:53solving the mystery of where the whales go.
0:46:53 > 0:46:56I am worried about them when they leave the reef.
0:46:56 > 0:46:58The dwarf minkes are well protected
0:46:58 > 0:47:00when they're in the Great Barrier Reef,
0:47:00 > 0:47:06but when they leave there, they face many threats and dangers
0:47:06 > 0:47:09and they have to cross major shipping channels.
0:47:09 > 0:47:13There are all sorts of threats from fishing.
0:47:13 > 0:47:18I mean, if commercial whaling is resumed in the Southern Ocean,
0:47:18 > 0:47:22which is the objective of the research that's going on
0:47:22 > 0:47:26at the moment from the Japanese, then these whales would be at risk.
0:47:31 > 0:47:35It's hoped the new tagging programme may help us understand
0:47:35 > 0:47:39how best to protect these whales throughout the entire year.
0:47:41 > 0:47:46By venturing into their underwater world, Birtles and his team
0:47:46 > 0:47:49are discovering valuable new facts about these whales.
0:47:50 > 0:47:53But their research has only just begun.
0:47:57 > 0:48:01The more we learn about the creatures that come here, the more we discover
0:48:01 > 0:48:04just how important the Great Barrier Reef is to their survival.
0:48:08 > 0:48:09The reef is immense.
0:48:11 > 0:48:15Millions of visitors travel great distances to get to it.
0:48:15 > 0:48:19And there, find food, shelter and an opportunity to meet a mate.
0:48:23 > 0:48:26A global community of animals rely on this great wilderness.
0:48:29 > 0:48:31And that makes it one of the most important
0:48:31 > 0:48:34and influential habitats on the planet.
0:48:39 > 0:48:42Next time, in our final programme...
0:48:43 > 0:48:47..we'll investigate the dangers that now threaten the reef
0:48:47 > 0:48:48and its inhabitants.
0:48:52 > 0:48:54THUNDERCLAP
0:48:54 > 0:48:56We'll meet the extraordinary people
0:48:56 > 0:48:58who are doing everything in their power
0:48:58 > 0:49:00to protect this marine paradise.
0:49:00 > 0:49:05It is one of the most magnificent ecosystems on the planet.
0:49:05 > 0:49:07What's really quite shocking is that we may lose it
0:49:07 > 0:49:10before we truly understand it.
0:49:10 > 0:49:13And we'll attempt our most ambitious dive yet.
0:49:13 > 0:49:18Nobody has ever dived as deep as this before on the Great Barrier Reef.
0:49:20 > 0:49:25As we search for new species and try to predict what the future holds
0:49:25 > 0:49:27for the Great Barrier.
0:49:45 > 0:49:48For this episode, one of our underwater teams
0:49:48 > 0:49:51travelled to Lady Elliot Island in the south.
0:49:55 > 0:49:58Here, the reef's majestic manta rays
0:49:58 > 0:50:02are stripped of dead skin and parasites by tiny cleaner fish.
0:50:05 > 0:50:08The crew's goal was to film a rare behaviour.
0:50:09 > 0:50:12The moment when the cleaner fish breaks the rules
0:50:12 > 0:50:15and bites a manta ray's flesh.
0:50:17 > 0:50:19To film the story, the team worked closely
0:50:19 > 0:50:21with marine biologist, Dr Kathy Townsend.
0:50:25 > 0:50:29Manta rays will often seek out and spend time with divers,
0:50:29 > 0:50:33which, of course, makes them amazing animals to be in the water with.
0:50:34 > 0:50:38Manta rays may be inquisitive, but they can easily be spooked.
0:50:38 > 0:50:41The challenge for cameraman, Mike Pitts,
0:50:41 > 0:50:44was to make himself as unobtrusive as possible.
0:50:46 > 0:50:48You are bulky and clumsy,
0:50:48 > 0:50:50you've got large cameras, lights.
0:50:50 > 0:50:55So what you don't want to do is to obstruct the manta ray.
0:50:55 > 0:50:59The manta ray might get disturbed and it'll just swim off.
0:50:59 > 0:51:01I generally keep as low as possible.
0:51:01 > 0:51:04So your profile sort of matches in with the reef.
0:51:04 > 0:51:06And so what you notice after a while is
0:51:06 > 0:51:09the manta rays will come closer and closer and closer to you.
0:51:09 > 0:51:14And I can literally... I feel them brushing over my head as they go.
0:51:14 > 0:51:17While the team's objective was to film the cleaning station,
0:51:17 > 0:51:19on the fourth day of the shoot,
0:51:19 > 0:51:22they were treated to something truly unexpected.
0:51:25 > 0:51:27We were close to the end of the dive
0:51:27 > 0:51:30and we hadn't really seen anything for about 58 minutes
0:51:30 > 0:51:32and then I spotted a pair.
0:51:35 > 0:51:39I saw Kathy and suddenly she zoomed off and we followed.
0:51:39 > 0:51:42And I could see out in the distance, there was a male above a female
0:51:42 > 0:51:45and he was following her every move
0:51:45 > 0:51:48as she moved through the water.
0:51:48 > 0:51:49Kathy got really excited.
0:51:52 > 0:51:54They were undergoing behaviour I'd never seen before.
0:51:54 > 0:51:56I'd seen various types of courtship behaviour
0:51:56 > 0:51:59that involves having trains,
0:51:59 > 0:52:02where there's a female at the front followed by several males.
0:52:02 > 0:52:06What was happening between these two was really quite unique.
0:52:06 > 0:52:09The male was obviously trying to court her,
0:52:09 > 0:52:11but in a very unusual way.
0:52:11 > 0:52:14He was taking his front cephalic lobes
0:52:14 > 0:52:16and he was actually stroking her on her back.
0:52:18 > 0:52:20Obviously trying to entice her to say,
0:52:20 > 0:52:23"Listen, you know, I'm the one for you".
0:52:24 > 0:52:27She, on the other hand, was not quite enthusiastic
0:52:27 > 0:52:30about the attention that he was bestowing upon her.
0:52:31 > 0:52:34And all of sudden, she'd just fling up into the air to shake him off
0:52:34 > 0:52:36and say, "No, it's not ready for that yet".
0:52:36 > 0:52:38And then she would settle back down.
0:52:47 > 0:52:49I knew it was something very special because,
0:52:49 > 0:52:52seeing Kathy's reactions to what was going on,
0:52:52 > 0:52:56she was so excited about it, she was bubbling.
0:52:58 > 0:53:01You could wait a lifetime to see something like that.
0:53:01 > 0:53:02Just a very rare event.
0:53:05 > 0:53:08In the far north, another wildlife crew had their sights set
0:53:08 > 0:53:12on filming a very special seasonal visitor.
0:53:12 > 0:53:16In winter, dwarf minke whales come to the reef
0:53:16 > 0:53:18for just a few short weeks.
0:53:20 > 0:53:22Wildlife cameraman, Dean Miller,
0:53:22 > 0:53:25has been documenting these whales for 15 years.
0:53:27 > 0:53:29It's a little bit unnerving sometimes jumping in
0:53:29 > 0:53:33and seeing a seven-tonne, seven-metre animal
0:53:33 > 0:53:35come out from the gloom.
0:53:35 > 0:53:37And you're hoping that it is going to be the whale
0:53:37 > 0:53:40and not something with a few more teeth.
0:53:41 > 0:53:43Every animal presents a very different challenge
0:53:43 > 0:53:45when it comes to filming behaviour,
0:53:45 > 0:53:49but over the years, Dean has learned the minke tricks of the trade.
0:53:52 > 0:53:54It's sometimes a game of cat and mouse, in a way.
0:53:54 > 0:53:57Because if you're not looking, they tend to come a lot closer.
0:53:57 > 0:54:00So if I can see a whale approaching in the distance
0:54:00 > 0:54:02and I know it's going to be a good approach this time,
0:54:02 > 0:54:05I'll purposely hold off and turn my dome around
0:54:05 > 0:54:08and actually see in the reflection of the dome the whale coming to me
0:54:08 > 0:54:11and then, when I think it's probably about five to six metres away,
0:54:11 > 0:54:14I'll turn around and get the best shot I've had all day.
0:54:14 > 0:54:16They sneak up on you.
0:54:17 > 0:54:19Over time, they build up that confidence
0:54:19 > 0:54:23and they just really, really try to edge much closer
0:54:23 > 0:54:25each and every time and get a good look.
0:54:27 > 0:54:30I do have other tricks, as well. I'll sing through my snorkel.
0:54:30 > 0:54:32HUMMING
0:54:34 > 0:54:37You can be in the water for seven, eight hours a day
0:54:37 > 0:54:39and you might only get two of these passes for that whole day.
0:54:39 > 0:54:43And when they happen, they're just mind-blowing.
0:54:43 > 0:54:44You've got this big, big animal.
0:54:44 > 0:54:47I mean, it's the size of a minibus, coming to look at you.
0:54:50 > 0:54:53You can get out at the end of a day and just have the biggest smile.
0:54:53 > 0:54:55I've just watched the sunset from in the water.
0:54:55 > 0:54:59A whale nearly touched me. It just doesn't get any better.
0:55:04 > 0:55:06'While our underwater crews
0:55:06 > 0:55:09'were rewarded with spectacular interactions,
0:55:09 > 0:55:12'on Heron Island, I had the opportunity
0:55:12 > 0:55:14'to meet one of my favourite visitors.'
0:55:17 > 0:55:18The noddy.
0:55:20 > 0:55:23The birds' relaxed nature and attachment to their nests
0:55:23 > 0:55:27meant we could tell their story without disturbing them.
0:55:28 > 0:55:30Without deserting their nest.
0:55:33 > 0:55:34Hello.
0:55:34 > 0:55:37But when cameraman, Mike Pitts returns
0:55:37 > 0:55:39to film the hatchlings three months later,
0:55:39 > 0:55:42disaster hits the island on his first night.
0:55:44 > 0:55:45THUNDERCLAP
0:55:50 > 0:55:52WIND GUSTS
0:56:00 > 0:56:03The following morning, Mike discovers that the storm has destroyed
0:56:03 > 0:56:05the very spot where I had filmed.
0:56:08 > 0:56:10It was shattered. It was like a warzone.
0:56:10 > 0:56:13You think of these idyllic, tropical islands
0:56:13 > 0:56:15and you couldn't be further from the truth.
0:56:22 > 0:56:23Are you still rolling?
0:56:23 > 0:56:26You can see that many of the trees are down.
0:56:26 > 0:56:29And it's brought down the chicks with them and the nests.
0:56:29 > 0:56:31Eggs are smashed, chicks are dying.
0:56:31 > 0:56:33And the chicks that have survived
0:56:33 > 0:56:36are now on these trunks and branches
0:56:36 > 0:56:38and on the ground of the forest itself,
0:56:38 > 0:56:40hoping for their parent birds
0:56:40 > 0:56:42to find them and bring the food they need.
0:56:42 > 0:56:44But the parent birds are so confused
0:56:44 > 0:56:46because so many of the trees are gone.
0:56:46 > 0:56:50It's very disheartening to see it, and, er...it's a real sad sight.
0:56:54 > 0:56:57I'd never seen the aftermath of such a strong storm.
0:56:58 > 0:57:01But, of course, your emotions always get the better of you.
0:57:05 > 0:57:10You still see survivors, just sitting on the nest,
0:57:10 > 0:57:12protecting the egg or the chick.
0:57:12 > 0:57:15It really is quite amazing, their resilience.
0:57:16 > 0:57:20It puts the whole reef into a context whereby
0:57:20 > 0:57:23you're following the rhythms of life.
0:57:23 > 0:57:26We were there to record it and film it
0:57:26 > 0:57:28and that's part of the Great Reef story.