0:00:39 > 0:00:43The coast - the frontier between land and sea.
0:00:46 > 0:00:50This is the most dynamic of all the ocean habitats.
0:00:50 > 0:00:55The challenge here is to survive change, EXTREME change.
0:01:22 > 0:01:26Cape Douglas, on the most westerly of the Galapagos Islands,
0:01:26 > 0:01:31totally unprotected from the massive rollers of the Pacific Ocean,
0:01:31 > 0:01:36and one of the roughest coastlines in the world.
0:02:09 > 0:02:15The marine iguanas of the Galapagos are the world's only seagoing lizards.
0:02:23 > 0:02:29Seaweed is all they eat, but doing so is a dangerous business.
0:02:29 > 0:02:33The local crabs have become specially flattened,
0:02:33 > 0:02:37minimising the effect of the pounding waves,
0:02:37 > 0:02:42and the iguanas have huge claws to grip the rocks.
0:02:42 > 0:02:44This seaweed really is fast food.
0:02:44 > 0:02:49There are only a few seconds to grab a few mouthfuls
0:02:49 > 0:02:52before the next breaker comes pounding in.
0:02:57 > 0:03:02Female iguanas feed only on the exposed rocks.
0:03:02 > 0:03:06But the larger males swim and dive beneath the surface
0:03:06 > 0:03:08to reach the weed.
0:03:11 > 0:03:14They go as deep as ten metres.
0:03:14 > 0:03:19For there, beyond the reach of the waves, they find the best fronds.
0:03:19 > 0:03:26Being cold-blooded, they have to return to land after ten minutes or so, to warm up again in the sun.
0:03:41 > 0:03:46Finding food is not the only challenge for coastal residents.
0:03:46 > 0:03:52These rocky shores are hardly a safe place to lay their eggs and, each year,
0:03:52 > 0:03:57the marine iguanas have to journey inland to find a more suitable one.
0:03:58 > 0:04:01The females lay eggs in burrows
0:04:01 > 0:04:06and leave them there to hatch. To do THAT, they need nice, soft sand.
0:04:14 > 0:04:19At the water's edge, it was easy to escape danger in rocky crevices.
0:04:19 > 0:04:25But, up here, the females are dangerously exposed.
0:04:25 > 0:04:28A Galapagos hawk.
0:04:58 > 0:05:02The lizards don't give up without a struggle.
0:05:22 > 0:05:27These hawks stay on the coast all year. But they are exceptional.
0:05:27 > 0:05:35The majority of the birds that come here spend most of their time elsewhere - in or above the ocean.
0:05:35 > 0:05:40However, all seabirds have to come to land in order to lay their eggs.
0:05:40 > 0:05:48After spending lonely months looking for food, they have to re-establish their social relationships.
0:05:50 > 0:05:55Frigate birds display, and exchange nesting material.
0:05:57 > 0:06:00Waved albatross dance.
0:06:12 > 0:06:17The need to lay eggs on firm ground ties the albatross to the coast,
0:06:17 > 0:06:22but parental responsibilities are shared - one looks after the egg,
0:06:22 > 0:06:25and the other can go off to feed.
0:06:51 > 0:06:58The need to breed brings many different animals to the coast each year, for a few weeks.
0:06:58 > 0:07:02Male sea turtles spend all their lives at sea.
0:07:02 > 0:07:08But the females, like birds, must come to land to lay their eggs.
0:07:12 > 0:07:17To do that, green turtles that live and feed off the coast of Brazil
0:07:17 > 0:07:22swim 1,500 miles to the tiny island of Ascension,
0:07:22 > 0:07:26that lies bang in the middle of the Atlantic.
0:07:37 > 0:07:40How they manage to navigate with accuracy
0:07:40 > 0:07:46and find this tiny lump of rock - just seven miles wide - is a mystery.
0:07:49 > 0:07:53But, each year, up to 5,000 turtles manage to do so
0:07:53 > 0:07:58and then, close to the coast of Ascension, they mate.
0:07:58 > 0:08:03Travelling to and from Ascension, and nesting here, takes six months.
0:08:03 > 0:08:08Throughout that entire time, none of them feed at all.
0:08:09 > 0:08:11After mating,
0:08:11 > 0:08:16the female has to leave her natural element and haul herself onto land.
0:08:16 > 0:08:23She does so at night, laying three or four times at 15-day intervals.
0:08:23 > 0:08:26Then she swims back to the seas off Brazil.
0:08:26 > 0:08:32She returns to this very same island throughout her life.
0:08:32 > 0:08:39Remarkably, all the world's sea turtles return each year to just a few traditional breeding sites.
0:08:41 > 0:08:45Crab Island, in Australia, is one of them.
0:08:46 > 0:08:50This tiny, two-mile long crescent of sand,
0:08:50 > 0:08:53lying off Queensland's northerly tip,
0:08:53 > 0:08:59provides nesting sites for half the entire population of one of the rarest turtles.
0:08:59 > 0:09:03Flat-backed turtles are large - over a metre long.
0:09:03 > 0:09:07They have to be careful. There are other giant reptiles here -
0:09:07 > 0:09:11saltwater crocodiles.
0:09:15 > 0:09:17Every night throughout the year,
0:09:17 > 0:09:22flat-backs bury their eggs all along this lonely stretch of land.
0:09:34 > 0:09:37Nine weeks later,
0:09:37 > 0:09:40and things are about to happen.
0:09:46 > 0:09:51These eyes shining in the darkness belong to night herons.
0:09:54 > 0:09:57As if from nowhere,
0:09:57 > 0:10:00hundreds of birds appear on the sand dunes.
0:10:00 > 0:10:04Pelicans wait patiently.
0:10:04 > 0:10:08Jabiru storks pace up and down.
0:10:11 > 0:10:16Before long, they see what they've been waiting for.
0:10:36 > 0:10:42Because these turtles lay their eggs throughout the year,
0:10:42 > 0:10:49the hatchlings emerge each night in a steady trickle of beak-sized meals.
0:11:07 > 0:11:15Pelicans' beaks allow them to dig out the hatchlings before the herons can spear them on the surface.
0:11:20 > 0:11:27The surf may be hundreds of metres away and a third of the tiny turtles do not survive the journey.
0:11:28 > 0:11:31It's not just birds that take them.
0:11:34 > 0:11:39Crocodiles, sharks and hungry fish are all waiting in the shallows.
0:11:39 > 0:11:44Only one in every hundred hatchlings will survive to adulthood.
0:11:54 > 0:11:58Another beach, another continent and a very special night.
0:11:58 > 0:12:03In Costa Rica, there is a turtle which has found a way
0:12:03 > 0:12:10to reduce these dangers. When Ridley's turtles arrive to lay their eggs, they don't come in hundreds,
0:12:10 > 0:12:12but in thousands.
0:12:12 > 0:12:18Over the next six days, around 400,000 females will visit this beach.
0:12:20 > 0:12:26At the peak time, 5,000 are coming and going each hour.
0:12:26 > 0:12:33The beach gets so crowded, they have to clamber to find a bare patch of sand where they can dig a nest hole.
0:12:35 > 0:12:4240 million eggs are laid in these few days. These turtles ensure that, six weeks later,
0:12:42 > 0:12:47when THEIR hatchlings emerge, it's not just a trickle -
0:12:47 > 0:12:50it's a flood.
0:12:59 > 0:13:05On some nights, over two million hatchlings race to the sea together.
0:13:14 > 0:13:19With so many appearing at once, their predators are overwhelmed,
0:13:19 > 0:13:24and most of the young turtles reach the sea safely.
0:13:33 > 0:13:37Leaving the sea and emerging onto land
0:13:37 > 0:13:42is hard enough for turtles. It's even harder for fish.
0:13:48 > 0:13:54Each year, for hundreds of miles along the Newfoundland coast,
0:13:54 > 0:13:57capelin throw themselves onto the beaches.
0:14:23 > 0:14:28At least a million tons of fish floundering out of the water -
0:14:28 > 0:14:32a real gift for scavenging eagles and gulls.
0:14:51 > 0:14:54Odd though it may seem for a fish,
0:14:54 > 0:15:00these capelin, like the turtles, have come out of the sea to breed.
0:15:10 > 0:15:16The males are trying to fertilise the eggs the females are depositing in the sand.
0:15:16 > 0:15:22Like the Ridley's turtles, they have synchronised their mass laying with the tide.
0:15:22 > 0:15:25In a few days, it will be over.
0:15:26 > 0:15:31Most of them die, but only after they've left their eggs in the sand.
0:15:34 > 0:15:41Other capelin populations lay their eggs in the ocean, so why do the Newfoundland fish spawn on land?
0:15:41 > 0:15:48It seems that eggs left on the beach may be safer from predators and develop faster than in colder water.
0:15:52 > 0:15:56Wherever they do so, the huge spawning shoals provide
0:15:56 > 0:16:02the concentration of food that seabirds need when THEY assemble to breed.
0:16:05 > 0:16:0895% of the world's seabirds
0:16:08 > 0:16:13nest together, mostly in large, spectacular colonies.
0:16:14 > 0:16:19This is Funk Island, 40 miles off the coast of Newfoundland -
0:16:19 > 0:16:24an isolated rock crammed with breeding seabirds.
0:16:30 > 0:16:37This was the last breeding ground for the flightless great auk, now extinct.
0:16:37 > 0:16:41Today, it's still the world's largest guillemot colony -
0:16:41 > 0:16:46over a million of them share the island with 250,000 gannets.
0:16:49 > 0:16:55It's not the lack of suitable sites that causes the seabirds to breed in such densities.
0:16:55 > 0:17:01In the North Atlantic, there's a wide choice of coastline they COULD use.
0:17:01 > 0:17:08The key factor limiting the size and location of seabird colonies seems to be the availability of food
0:17:08 > 0:17:11in the surrounding ocean.
0:17:14 > 0:17:20There are lots of hungry mouths to feed and a constant demand for fish.
0:17:25 > 0:17:29Throughout the days at colonies like Funk,
0:17:29 > 0:17:34there's a continual stream of birds heading to the ocean to find food
0:17:34 > 0:17:37and returning to feed their young.
0:17:45 > 0:17:50Gannets travel up to 200 miles from the colony on one foraging trip.
0:17:50 > 0:17:53They're not fussy eaters
0:17:53 > 0:17:58and will take everything, from tiny sand eels to herring.
0:18:09 > 0:18:13Puffins are very particular about what they eat.
0:18:13 > 0:18:17And because they can only fly short distances,
0:18:17 > 0:18:22they only nest where there's a good supply of suitable food close by.
0:18:27 > 0:18:32One such place is the sea of Okhotsk in far eastern Russia.
0:18:34 > 0:18:38This is the island of Talan.
0:18:41 > 0:18:45Throughout the long Arctic winter, it's encircled by ice.
0:18:45 > 0:18:48As spring approaches, it breaks up,
0:18:48 > 0:18:53and seabirds that have spent winter feeding on the ocean to the south
0:18:53 > 0:18:56begin to return.
0:18:59 > 0:19:03Its isolated position and steep cliffs
0:19:03 > 0:19:06make Talan a perfect nesting site.
0:19:06 > 0:19:10The tufted puffins arrive first.
0:19:10 > 0:19:12These are the Pacific cousins
0:19:12 > 0:19:16of our less spectacular Atlantic species.
0:19:18 > 0:19:20Horned puffins soon follow.
0:19:22 > 0:19:2514 different species return each spring
0:19:25 > 0:19:30and, in just a few weeks, the once silent cliffs
0:19:30 > 0:19:35come alive to the calls of 4 million breeding seabirds.
0:19:39 > 0:19:42This is a multistorey avian city.
0:19:50 > 0:19:57Assembling in these dense colonies, after having spent a largely solitary life at sea,
0:19:57 > 0:20:04provides the birds with the social stimulation that is the key to co-ordinating their breeding.
0:20:04 > 0:20:07By nesting and laying together,
0:20:07 > 0:20:12they ensure that most chicks will leave the nest at the same time.
0:20:12 > 0:20:17Like the turtles, this is the way they spread the impact of predators.
0:20:20 > 0:20:24The world's largest eagle - Stellar's sea eagle -
0:20:24 > 0:20:27as third as big again as a golden.
0:20:29 > 0:20:34Throughout the summer, the eagles hunt in Talan's crowded colonies.
0:20:44 > 0:20:48Riding on the updraughts, they patrol the cliffs,
0:20:48 > 0:20:54looking out for any kittiwake that ventures too far from the rock face.
0:20:59 > 0:21:01Suddenly, the huge eagle stoops
0:21:01 > 0:21:04with the aerial agility of a falcon.
0:21:12 > 0:21:18Co-ordinated panic among the kittiwakes confuses their attacker.
0:21:31 > 0:21:33But the eagle doesn't give up.
0:21:46 > 0:21:49And it has got one!
0:22:14 > 0:22:22The birds that face the greatest challenge in coming to the coast to nest are surely the penguins.
0:22:33 > 0:22:38Unable to fly, they have no choice but to brave the immense waves.
0:22:49 > 0:22:56Most penguins live in the southern oceans, and they have to accept being hurled about by the surf.
0:23:13 > 0:23:16Whatever the weather,
0:23:16 > 0:23:20the penguin parents have to come back to feed their chicks.
0:23:29 > 0:23:33A southern sea lion bull.
0:23:33 > 0:23:37He knows the penguins always use the same beach.
0:23:40 > 0:23:44The penguins now have to make a mad dash
0:23:44 > 0:23:47across open rock to reach the nests.
0:24:08 > 0:24:13Despite his massive size and a body adapted for swimming,
0:24:13 > 0:24:18the bull chases the penguins for 40 or 50 metres across the rocks.
0:25:09 > 0:25:14Having caught his penguin, the sea lion carries it out into deep water,
0:25:14 > 0:25:18where, by violently thrashing the little body,
0:25:18 > 0:25:21he skins his meal.
0:25:35 > 0:25:38The Alaskan coast.
0:25:38 > 0:25:42It's spring and the last of the winter storms is subsiding.
0:25:42 > 0:25:48The plankton in the sea is in bloom again and, just offshore,
0:25:48 > 0:25:51humpback whales have returned to feed.
0:25:56 > 0:26:02For these huge animals, there's a real risk of coming into such shallow water,
0:26:02 > 0:26:06and each year, a good number of them pay the price.
0:26:09 > 0:26:13It's an ignominious ending for an ageing whale.
0:26:13 > 0:26:18But so much flesh will not go to waste...
0:26:18 > 0:26:22A black bear emerges cautiously from the woods.
0:26:31 > 0:26:38Visitors to the coast that don't come to breed have usually come to scavenge.
0:26:38 > 0:26:44A whole range of animals exploit the enormous quantity of food that washes up every day
0:26:44 > 0:26:47on the coastlines around the world.
0:26:49 > 0:26:57But the quantity of flotsam and jetsam is unpredictable. Nobody can rely on it alone.
0:27:00 > 0:27:05This carcass even attracted a shy pack of wolves,
0:27:05 > 0:27:09only too happy to anoint themselves with the scent of rotting whale.
0:27:13 > 0:27:18It was months before the scavengers cleaned up all the meat
0:27:18 > 0:27:21on this huge and unpredictable gift
0:27:21 > 0:27:23from the sea.
0:27:27 > 0:27:34Whales give birth to their young at sea and so can spend their entire lives there.
0:27:34 > 0:27:39Other marine mammals - ones that are in fact distant cousins of bears -
0:27:39 > 0:27:43return each year to their ancestral home on land.
0:27:46 > 0:27:49The high Arctic.
0:27:49 > 0:27:52Here lives one of them - the walrus.
0:28:01 > 0:28:07Walruses spend nearly all their lives at sea. But each year, for just a few weeks,
0:28:07 > 0:28:10they have to return to the coast.
0:28:11 > 0:28:16They seek out isolated beaches like this one on Round Island,
0:28:16 > 0:28:22in the northern Pacific. Sites like this - free from bears - are so scarce
0:28:22 > 0:28:29that, at times, as many as 14,000 animals will cram themselves onto this one beach.
0:28:37 > 0:28:41When they first emerge from the sea, the walrus are white.
0:28:41 > 0:28:47That's because, being warm-blooded in a cold ocean, they conserve heat
0:28:47 > 0:28:51by keeping blood concentrated in the core of their bodies.
0:28:51 > 0:28:56On land, it's warm enough to allow their outer blood vessels to dilate,
0:28:56 > 0:28:59and that turns their skin pink.
0:29:07 > 0:29:12Now they can moult the outer layers of their skin, rubbing themselves
0:29:12 > 0:29:15up against the rocks.
0:29:16 > 0:29:19But more than anything else,
0:29:19 > 0:29:24coming to land brings the walrus relief from spending energy
0:29:24 > 0:29:28maintaining their body temperature in an icy cold ocean.
0:29:30 > 0:29:35Heat conservation, in fact, may well be the primary reason
0:29:35 > 0:29:40so many sea mammals are forced to return to the land each year.
0:29:43 > 0:29:46The world's coldest seas
0:29:46 > 0:29:52are in Antarctica. Each spring, half the world's southern elephant seals
0:29:52 > 0:29:55return to the island of South Georgia.
0:29:55 > 0:30:01Elephant seals have a thick insulation of blubber that keeps them warm.
0:30:01 > 0:30:06For them, breeding is the ONLY reason to leave the sea.
0:30:10 > 0:30:13With temperatures down to minus 20,
0:30:13 > 0:30:18and 100mph winds, it can't be comfortable on the beach,
0:30:18 > 0:30:23but heat dissipates more rapidly through water, so even in these conditions,
0:30:23 > 0:30:30their young, which at first don't have a thick coat of blubber, will be far warmer on the land.
0:30:30 > 0:30:35Once the males are established on the beach, the females soon follow.
0:30:39 > 0:30:41Within just ten days,
0:30:41 > 0:30:46the empty beach fills up with 6,000 elephant seals.
0:30:48 > 0:30:53Immediately, the females give birth to pups sired the previous year.
0:31:02 > 0:31:08Their milk is very rich and the pups grow astonishingly quickly.
0:31:15 > 0:31:19In just three weeks, they turn from thin bags of skin
0:31:19 > 0:31:22to fat balls of blubber.
0:31:22 > 0:31:28As soon as they've given birth, the females become sexually receptive again.
0:31:28 > 0:31:33Now the advantages of breeding in such dense colonies become clear.
0:31:33 > 0:31:41Females can make their choice from many males, while successful males can have access to lots of females.
0:31:45 > 0:31:50But to GAIN that access and control a harem of females,
0:31:50 > 0:31:54a bull must be prepared to fight.
0:32:14 > 0:32:20The larger the male, the louder the roar and the more likely he is to win.
0:32:29 > 0:32:35When males are well-matched, these bloody battles will last 20 minutes or more.
0:32:54 > 0:33:00Eventually, the loser retreats into a stream already pink with his own blood.
0:33:10 > 0:33:16These battles certainly help females select the strongest bulls
0:33:16 > 0:33:19but they bring great dangers for the pups.
0:33:28 > 0:33:34Each year, in the denser parts of the colony, a fifth of the pups are crushed to death.
0:33:34 > 0:33:41This is why it may be better to mate at the edge of the beach, close to the sea.
0:33:45 > 0:33:48Less dominant males hide in the surf.
0:33:48 > 0:33:54They're waiting to steal an illicit mating, as the females come and go.
0:33:57 > 0:34:04This male knows he's been spotted by the big bull, who claims all the females on this part of the beach.
0:35:07 > 0:35:12Breeding in groups brings advantages to pups as well as to adults.
0:35:18 > 0:35:25On the coast of Patagonia, southern sea lions breed together each year, in groups several-hundred strong.
0:35:26 > 0:35:31For the growing pups, these colonies act rather like a school.
0:35:31 > 0:35:37The bonds developed here on the beach may be vital for the rest of their lives.
0:35:37 > 0:35:42Sea lions are social animals and, as adults and young forage together,
0:35:42 > 0:35:47they share information about the location of good feeding sites.
0:35:49 > 0:35:53Conditions could hardly be better for the youngsters.
0:35:53 > 0:35:59As the tide goes out, it leaves a selection of sheltered pools.
0:36:01 > 0:36:04Perfect places for learning to swim.
0:36:38 > 0:36:44At high tide, it's easy for the pups to take their first dips in the surf.
0:37:17 > 0:37:19A killer whale.
0:37:21 > 0:37:25These pups have never seen anything like it before.
0:37:37 > 0:37:40The whales, though, are experienced.
0:37:40 > 0:37:47Each year, this same group turns up along the coast at the same time as the pups are starting to swim.
0:37:57 > 0:38:04The whales need to surprise the pups, so they've stopped calling to one another and keep silent.
0:38:12 > 0:38:15Speed is everything.
0:38:16 > 0:38:21The whales do not take pups that are out of the water,
0:38:21 > 0:38:28but sometimes their momentum drives them up the beach. Then, there's real danger of getting stuck.
0:40:00 > 0:40:05The whale has to thrash in this frenzied way to get off the beach.
0:40:05 > 0:40:10Most of the pups are taken to deep water while they're still alive.
0:40:10 > 0:40:14There, the whales apparently play with them.
0:40:37 > 0:40:42Often, an adult whale is joined in the game by a youngster.
0:40:42 > 0:40:48It may be learning how to grab a seal pup before it risks a drive up the beach.
0:40:55 > 0:41:02Whatever the reason, the seal pup, still alive, is tossed back and forth for over half an hour.
0:41:35 > 0:41:40Even when the pup is dead, the sport is not completely over.
0:42:09 > 0:42:16We can only speculate at the real reasons behind this extraordinary behaviour.
0:42:28 > 0:42:33But, for the whales, the hunting season is a short one.
0:42:33 > 0:42:40Before long, the pups learn to stay clear of the water, and the whales become less and less successful.
0:42:40 > 0:42:43After just two weeks, they move on.
0:42:43 > 0:42:47The killing season is over.
0:42:56 > 0:43:01That's how it often happens along the coast - things always change.
0:43:01 > 0:43:04They're never the same for long
0:43:04 > 0:43:09in this, the most dynamic of all the oceans' habitats.
0:43:18 > 0:43:23Orcas, or killer whales, are highly intelligent social animals
0:43:23 > 0:43:25that hunt in close family groups.
0:43:25 > 0:43:31For Blue Planet, we filmed two very different pods of killer whales,
0:43:31 > 0:43:36one hunting off the Californian coast, the other in Argentina.
0:43:36 > 0:43:39Each had a totally different hunting technique
0:43:39 > 0:43:43and filming their behaviour required not only patience
0:43:43 > 0:43:47but an understanding of killer whale culture.
0:43:47 > 0:43:55Only by getting under the skins of whales had we any chance of predicting what they would do next.
0:44:00 > 0:44:05This windswept beach in Argentina is visited each year
0:44:05 > 0:44:10by a particular pod of killer whales that come to prey on sea lion pups.
0:44:12 > 0:44:18I was going to stand a much greater chance of filming the orcas
0:44:18 > 0:44:24attacking young sea lions if I knew them as individuals.
0:44:24 > 0:44:30Fortunately, park guard, Roberto Bubas, had watched orcas for many years
0:44:30 > 0:44:34and could tell me not only what sex they were
0:44:34 > 0:44:36but which was most likely to attack.
0:44:36 > 0:44:39The problem was that when I first arrived
0:44:39 > 0:44:43they weren't behaving as we expected.
0:44:43 > 0:44:48They weren't attacking the sealion colonies. We had a long wait ahead.
0:44:48 > 0:44:52Much further north, off California's Pacific coast,
0:44:52 > 0:44:58a Blue Planet team spent two seasons working with another group of killer whales.
0:45:02 > 0:45:07Yearly, this pod patrols the waters off Monterey Bay, San Francisco,
0:45:07 > 0:45:10looking for very large prey indeed -
0:45:10 > 0:45:15Gray whales migrating north in search of rich feeding grounds.
0:45:26 > 0:45:30The main challenge was just finding the killer whales.
0:45:30 > 0:45:33A plane searched round the clock,
0:45:33 > 0:45:36giving directions to a boat-based team.
0:45:39 > 0:45:45This was to prove one of the most ambitious of Blue Planet's missions.
0:45:45 > 0:45:50Our team was advised by marine biologist, Nancy Black,
0:45:50 > 0:45:56who had only witnessed one complete killer whale attack in 14 years of research at Monterey Bay.
0:46:00 > 0:46:05Even when they were lucky enough to track down the killer whales,
0:46:05 > 0:46:08rough weather made filming very difficult.
0:46:08 > 0:46:12Frustrating! We followed these killer whales,
0:46:12 > 0:46:16but as you can see, the sea's just got up.
0:46:16 > 0:46:20It's 30, 35 knots and we couldn't keep up with them.
0:46:29 > 0:46:35We've been 16 days out on the water - we've another six to go.
0:46:35 > 0:46:38We're not gonna see it.
0:46:38 > 0:46:44We're not really hitting big time. It's a funny kind of filming, its...frustrating!
0:46:44 > 0:46:49Day after day at sea, with not a single frame of film to show for it.
0:46:50 > 0:46:57Andy the dog is going to tell you what we saw... See? Nothing.
0:46:57 > 0:47:01Back in Argentina, after two weeks of waiting,
0:47:01 > 0:47:06Simon noticed a change in the behaviour of his killer whales.
0:47:06 > 0:47:13The group of female orcas and their young, who had a reputation for being fine hunters,
0:47:13 > 0:47:19at last moved towards the sea lion colony where our hide was situated.
0:47:24 > 0:47:28The problem now was predicting when an attack might occur.
0:47:34 > 0:47:39With Roberto's help, I could choose an individual,
0:47:39 > 0:47:44and film it with high speed cameras that would reveal the action.
0:47:51 > 0:47:55Ah! The film ran out at a crucial moment.
0:47:55 > 0:48:00It's a real risk when you're running film through a camera at high speed.
0:48:03 > 0:48:09But with careful timing and good fortune, everything came together.
0:48:29 > 0:48:31LAUGHING
0:48:31 > 0:48:35'After four weeks of working from dawn to dusk,
0:48:35 > 0:48:40'the emotional release of finally witnessing this phenomenal behaviour
0:48:40 > 0:48:43- 'is indescribable.' - INAUDIBLE
0:48:48 > 0:48:52Back in California, things were also looking up.
0:48:52 > 0:48:56Grey whale mothers and their calves had started to arrive at Monterey
0:48:56 > 0:48:59on their migration north.
0:49:00 > 0:49:04These are the killer whales' favoured prey.
0:49:46 > 0:49:49These guys are pretty impressive,
0:49:49 > 0:49:54It looks like they're heading somewhere, so fingers crossed.
0:49:59 > 0:50:02Doug's hunch was right.
0:50:02 > 0:50:05The killers kept up the hunt for five hours
0:50:05 > 0:50:10until the calf was so exhausted, the mother was forced to stop.
0:50:10 > 0:50:15And we had to watch as the pod came in to finish off the calf,
0:50:15 > 0:50:18just a few metres from our inflatable.
0:50:21 > 0:50:26If they'd taken a mind to it, they could have flipped us over.
0:50:26 > 0:50:31On the other hand, I think they were concentrating on the whale.
0:50:31 > 0:50:35We were able to get closer and not interfere.
0:50:35 > 0:50:38It's just so completely exciting,
0:50:38 > 0:50:43being beside it and almost filming down this animal's blowholes.
0:50:43 > 0:50:51The whole thing is just turmoil and you really get a feeling for what the whale is going through.
0:51:26 > 0:51:30It was only after the killer whales had moved on
0:51:30 > 0:51:35that Doug felt it safe enough to dive in with the camera.
0:51:35 > 0:51:40And I do remember it being almost spooky and eerie going underwater
0:51:40 > 0:51:45and seeing the wounds on that baby whale
0:51:45 > 0:51:49and feeling you should be looking over your shoulder,
0:51:49 > 0:51:53to see if the big boys were coming back.
0:51:53 > 0:51:57You're left with just an immense sense of relief,
0:51:57 > 0:52:02which leaves you completely emotionally drained.
0:52:17 > 0:52:20Subtitles by BBC
0:52:20 > 0:52:23E-mail: subtitling@bbc.co.uk