0:00:42 > 0:00:47The frozen seas are worlds unto themselves.
0:00:47 > 0:00:49Beneath their ceiling of ice,
0:00:49 > 0:00:56they have an eerie stillness, cut off from the storms that rage above.
0:00:59 > 0:01:04In the winter, the feeble slanting rays of the sun bring little warmth
0:01:04 > 0:01:10and the temperature seldom rises above minus 50 degrees centigrade.
0:01:21 > 0:01:26For much of the year, it is dark and cripplingly cold.
0:01:26 > 0:01:30Yet there is life here at both ends of the earth -
0:01:30 > 0:01:33the Arctic and the Antarctic.
0:01:42 > 0:01:46For most animals, whether they live in or out of water,
0:01:46 > 0:01:49the winters, when much of the sea is frozen,
0:01:49 > 0:01:51bring the greatest challenge.
0:01:54 > 0:01:57The northern hemisphere.
0:01:57 > 0:02:00It's February, and as the Earth tilts on its axis,
0:02:00 > 0:02:04the sun's rays creep slowly northwards
0:02:04 > 0:02:08and the Arctic emerges from its harsh winter.
0:02:08 > 0:02:14The Arctic is a frozen ocean surrounded by continents
0:02:14 > 0:02:19and when the surface of the sea freezes from shore to shore,
0:02:19 > 0:02:24land predators walk out onto it to hunt.
0:02:28 > 0:02:34It's early March and the sea is still covered with ice.
0:02:34 > 0:02:39But there are patches of open water - polynyas - that never freeze over.
0:02:39 > 0:02:44Here, where tidal currents are squeezed between islands,
0:02:44 > 0:02:49the water movement is so strong that ice cannot form.
0:02:51 > 0:02:56Walruses spend the winter in polynyas.
0:02:56 > 0:02:59Here, they have permanent access to the air,
0:02:59 > 0:03:04but they can also retreat to the sea to shelter, to hunt.
0:03:15 > 0:03:20Other sea mammals overwinter in the polynyas as well.
0:03:20 > 0:03:23In this one, a young bowhead whale.
0:03:31 > 0:03:36Here, the current is really fast and the shifting ice is dangerous.
0:03:41 > 0:03:47This whale became trapped when ice encircled it last autumn.
0:03:53 > 0:03:57There is no food here, but a whale must breathe
0:03:57 > 0:04:01and the only place that it can do so, for miles around,
0:04:01 > 0:04:03is in this tiny hole.
0:04:04 > 0:04:10It's living entirely on its reserves of fat,
0:04:10 > 0:04:13but now they are dangerously low.
0:04:13 > 0:04:17It will be some months yet before it can escape.
0:04:27 > 0:04:32Elsewhere, other whales have also been trapped.
0:04:32 > 0:04:37These are belugas. Their tiny hole in the ice has been kept open,
0:04:37 > 0:04:42not by currents, but by the belugas' continuous movements
0:04:42 > 0:04:44as they rise to breathe.
0:04:48 > 0:04:51Open water is now some 20 miles away.
0:04:51 > 0:04:56It will be two months yet before the ice melts.
0:05:06 > 0:05:12The belugas are extremely thin and most of them are horribly scarred.
0:05:20 > 0:05:25But their wounds were not inflicted by the ice.
0:05:32 > 0:05:38A whale would be a huge prize for any meat-eating hunter
0:05:38 > 0:05:40and these belugas, trapped by the ice,
0:05:40 > 0:05:43are within reach of polar bears.
0:05:54 > 0:06:00Aware of the danger, the belugas stay submerged as long as they can.
0:06:00 > 0:06:05But they can only hold their breath for about 20 minutes.
0:06:22 > 0:06:28Catching a four-metre long whale that weighs one ton is no easy task,
0:06:28 > 0:06:33even if that whale is weakened by starvation.
0:06:43 > 0:06:47But a beluga is well worth waiting for.
0:07:09 > 0:07:12Day by day, as the hole gets bigger,
0:07:12 > 0:07:17it becomes increasingly difficult for the bear to land a whale.
0:07:17 > 0:07:23Keeping its fur in good condition and free from salt
0:07:23 > 0:07:29is important for warmth, and the bear uses snow like blotting paper.
0:07:39 > 0:07:44These belugas have been attacked by many bears over the last six months
0:07:44 > 0:07:47and some have been caught.
0:07:47 > 0:07:52It may have taken a long time and a lot of patience,
0:07:52 > 0:07:56but a catch, when it's made, brings abundant rewards
0:07:56 > 0:07:59of energy-rich blubber.
0:08:07 > 0:08:12Gulls rely on bear-kills at this time of the year
0:08:12 > 0:08:15and the colour of blood staining the ice
0:08:15 > 0:08:18attracts them from a long way away.
0:08:21 > 0:08:24The remaining belugas still have a long wait
0:08:24 > 0:08:29before they are released from their prison and the threat of slaughter.
0:08:35 > 0:08:38In late March and into April,
0:08:38 > 0:08:43female bears emerge from winter dens with their cubs.
0:08:43 > 0:08:47The mother has not eaten for at least five months.
0:08:47 > 0:08:50She's hungry. Very hungry.
0:09:03 > 0:09:06This is a crucial time for the cub.
0:09:06 > 0:09:11By watching its mother hunt and copying her actions,
0:09:11 > 0:09:16it begins to acquire the rudiments of its own hunting skills.
0:09:19 > 0:09:21Play is also important
0:09:21 > 0:09:24for developing muscles and co-ordination.
0:09:43 > 0:09:45As the days go by,
0:09:45 > 0:09:49the sun rises higher and remains above the horizon.
0:09:57 > 0:10:01The female bear continues to hunt
0:10:01 > 0:10:05until her cub is too tired and can't keep up.
0:10:09 > 0:10:12She's smelt something.
0:10:35 > 0:10:37The pup escapes through a hole in its lair
0:10:37 > 0:10:40that leads to the sea below.
0:11:02 > 0:11:06Only one in 20 hunts is successful.
0:11:06 > 0:11:08The mother must find a seal pup soon
0:11:08 > 0:11:12if her cub is not to starve to death.
0:11:26 > 0:11:29As spring turns into summer,
0:11:29 > 0:11:33the sun's heat begins to melt the sea ice.
0:11:36 > 0:11:42Now the ocean is accessible and the Arctic's summer visitors return.
0:11:42 > 0:11:46Migrating birds arrive from the south to nest and feed on sea food
0:11:46 > 0:11:49that is now within their reach.
0:11:49 > 0:11:53Brunnich's guillemots are the northern equivalent of penguins.
0:11:53 > 0:11:57But they have the power of flight to reach cliff ledges
0:11:57 > 0:12:03where their nests will be safe from predatory bears and foxes.
0:12:18 > 0:12:25Nonetheless, they are as at home in the water as they are in the air.
0:12:25 > 0:12:30They dive down to a depth of 50 metres or more to catch fish.
0:12:39 > 0:12:42In June, the ice begins to fracture.
0:12:42 > 0:12:48Cracks form useful corridors of open water for air-breathing animals.
0:12:51 > 0:12:55Belugas migrating to their feeding grounds
0:12:55 > 0:12:59can penetrate the ice-covered seas to reach areas
0:12:59 > 0:13:05where their preferred food - arctic cod - has spent the winter.
0:13:09 > 0:13:15Males regularly dive to about 500 metres to find fish.
0:13:15 > 0:13:21The females and young, which have smaller lungs, only go to about 350.
0:13:32 > 0:13:37In late June and July, narwhals arrive.
0:13:38 > 0:13:43The females, who usually lack tusks, come first with their new calves.
0:13:43 > 0:13:46The males follow a little later.
0:13:59 > 0:14:04They also move up the leads in search of fresh feeding grounds.
0:14:15 > 0:14:20Bowheads. Up to 18 metres long and weighing 100 tonnes.
0:14:20 > 0:14:26These are the only large whales that stay in the Arctic all year round.
0:14:40 > 0:14:45They're not after fish. They're seeking smaller prey.
0:14:46 > 0:14:52Despite having the largest mouths - the size of a small garage -
0:14:52 > 0:14:55they eat tiny crustaceans - copepods,
0:14:55 > 0:15:01straining them from the water with the four-metre strips of baleen
0:15:01 > 0:15:04that hang from their upper jaws.
0:15:11 > 0:15:16In the summer, they store enough energy to last them until winter
0:15:16 > 0:15:20when food will be less abundant.
0:15:20 > 0:15:22As the ice melts away,
0:15:22 > 0:15:27the polar bears are forced to head for land.
0:15:28 > 0:15:30They're excellent swimmers
0:15:30 > 0:15:34and can cover 100 miles of open water if need be.
0:16:10 > 0:16:14Off east Greenland, there is little ice left by August,
0:16:14 > 0:16:18so walruses haul out to rest on land.
0:16:18 > 0:16:20They're moulting,
0:16:20 > 0:16:24getting rid of their old, parasite-ridden skin.
0:16:26 > 0:16:29WALRUSES GRUNT
0:16:33 > 0:16:39A bathe in the cold water brings some relief from the itching.
0:16:57 > 0:17:01But even there, the odd scratch is irresistible.
0:17:19 > 0:17:24They make daily excursions out to deeper water.
0:17:34 > 0:17:38Down at 20 metres, they root around in the sediment
0:17:38 > 0:17:42using their bristles to search out soft-shelled clams.
0:18:01 > 0:18:05Once they find a clam, they suck its flesh from the shell
0:18:05 > 0:18:09with their powerful, muscular mouths.
0:18:11 > 0:18:15Walruses can feed for five minutes this deep
0:18:15 > 0:18:19before they have to return to the surface to breathe.
0:18:24 > 0:18:27Elsewhere in the Arctic,
0:18:27 > 0:18:30belugas are gathering in their thousands.
0:18:30 > 0:18:35They congregate in just a few large estuaries.
0:18:35 > 0:18:40Belugas of all ages and sizes come here.
0:18:40 > 0:18:42There are even young calves.
0:18:52 > 0:18:57Some are so young - born only a week or so ago -
0:18:57 > 0:18:59that they need help.
0:18:59 > 0:19:03They swim on their mothers' backs to breathe more easily.
0:19:14 > 0:19:17As the tide moves up the estuary,
0:19:17 > 0:19:21the belugas follow, swimming into shallow water.
0:19:28 > 0:19:32Like walruses, they also need to moult.
0:19:40 > 0:19:42A combination of warm, fresh water
0:19:42 > 0:19:47and vigorous rubbing against the gravel does the trick.
0:19:58 > 0:20:01They remain here for days or even weeks,
0:20:01 > 0:20:04so it's likely that socialising
0:20:04 > 0:20:08is also important to them.
0:20:09 > 0:20:15After moulting, they head back out to sea to feed.
0:20:21 > 0:20:26It's now autumn and the sea begins to freeze over once again.
0:20:31 > 0:20:34Thin sheets of ice form at the surface
0:20:34 > 0:20:36and pile up layer upon layer,
0:20:36 > 0:20:40gradually creating an impenetrable barrier.
0:20:47 > 0:20:49By late November,
0:20:49 > 0:20:54the Arctic ocean is sealed once again by ice.
0:21:07 > 0:21:12The lights of the aurora play in the winter sky.
0:21:22 > 0:21:25At the other end of the planet in the Antarctic,
0:21:25 > 0:21:28there is the southern aurora.
0:21:41 > 0:21:46Antarctica is now emerging from winter.
0:21:46 > 0:21:50This is the coldest, windiest place in the world.
0:21:50 > 0:21:54Temperatures are hovering at a numbing -50.
0:21:54 > 0:21:57The returning sun has very little warmth.
0:21:57 > 0:22:02Very few animals can survive such extreme conditions.
0:22:02 > 0:22:06But emperor penguins can.
0:22:12 > 0:22:18Standing on the frozen sea, they endure the full force of the storms.
0:22:26 > 0:22:32Only by huddling together can they survive the appalling winter months.
0:22:37 > 0:22:44They take it in turns to bear the brunt of the gales.
0:22:44 > 0:22:46They can only live here at all
0:22:46 > 0:22:51because Antarctica is surrounded by the great southern ocean.
0:22:51 > 0:22:53No land predators have reached it
0:22:53 > 0:22:59so, unlike Arctic animals, they are not threatened by polar bears.
0:22:59 > 0:23:02The sea is still frozen
0:23:02 > 0:23:06but one seal, nonetheless, manages to stay here
0:23:06 > 0:23:10even throughout the winter.
0:23:12 > 0:23:15The Weddell seal.
0:23:28 > 0:23:33Underwater, it's protected from the storms above
0:23:33 > 0:23:37but it must have access to the air all year in order to breathe.
0:23:48 > 0:23:53And they keep their breathing holes open with their teeth.
0:24:02 > 0:24:06Only by continually scraping away at the ice
0:24:06 > 0:24:09can they maintain access to the air.
0:24:09 > 0:24:12That means their teeth get worn down.
0:24:12 > 0:24:16Then they can no longer hunt or eat effectively.
0:24:16 > 0:24:19Weddell seals die young.
0:24:27 > 0:24:32The continent of Antarctica is so isolated and so high -
0:24:32 > 0:24:34almost 5,000 metres in places -
0:24:34 > 0:24:38that it's considerably colder than the Arctic.
0:24:40 > 0:24:45Ice slides slowly down from its centre towards its rim
0:24:45 > 0:24:47in immense glaciers.
0:24:47 > 0:24:52During winter, the continent effectively doubles in size
0:24:52 > 0:24:54as the sea freezes over.
0:24:54 > 0:24:57Ice forms around its shores
0:24:57 > 0:25:03and extends outwards for hundreds of miles around the entire land mass.
0:25:07 > 0:25:12Under the sea ice live small, shrimp-like creatures.
0:25:12 > 0:25:15Krill. They have been here all winter.
0:25:17 > 0:25:19During these dark months,
0:25:19 > 0:25:23they feed by scraping algae from the ice.
0:25:24 > 0:25:28Remarkably, they also shrink in size
0:25:29 > 0:25:32and revert to their juvenile form to save energy.
0:25:37 > 0:25:43As the temperature rises in spring, the ice begins to melt
0:25:43 > 0:25:46and little air bubbles are released.
0:25:46 > 0:25:49Microscopic algae grow around the bubbles
0:25:49 > 0:25:54and the krill graze on them, gathering them up with their legs.
0:26:10 > 0:26:13As the sun's rays grow stronger
0:26:13 > 0:26:18and penetrate deeper into the water, floating algae begin to flourish.
0:26:18 > 0:26:21The krill leave the dwindling ice
0:26:21 > 0:26:25and gather in swarms to harvest this new crop.
0:26:34 > 0:26:39Far to the north, beyond the blanket of sea ice,
0:26:39 > 0:26:44chinstrap penguins have been overwintering in the open ocean.
0:26:51 > 0:26:55An iceberg gives them the chance of a rest -
0:26:55 > 0:26:57if they can get on it.
0:27:00 > 0:27:04THEY SQUAWK
0:27:26 > 0:27:27But at this time of year,
0:27:27 > 0:27:31where they really want to be is on land.
0:27:31 > 0:27:34It's getting there that's tricky.
0:27:52 > 0:27:57It's spring, and the penguins are returning to breed.
0:28:01 > 0:28:06Their need to get ashore is now urgent and imperative.
0:28:18 > 0:28:21Doing so is a matter of timing -
0:28:21 > 0:28:24and picking the right wave.
0:29:10 > 0:29:13But their journey has only just begun.
0:29:13 > 0:29:20Most of them will have to walk many miles in order to find a nest site.
0:29:27 > 0:29:30PENGUINS CRY
0:29:32 > 0:29:35This is Zavodovski Island,
0:29:35 > 0:29:39which has the largest penguin colony in the world.
0:29:39 > 0:29:44About two million chinstraps breed here and they come to this island
0:29:44 > 0:29:47for a good reason.
0:29:51 > 0:29:56It's an active volcano. The heat from the crater and the fumaroles
0:29:56 > 0:30:01keeps the slopes free from the ice and snow,
0:30:01 > 0:30:07allowing these chinstraps to breed earlier than those further south.
0:30:08 > 0:30:14But then again, living on an active volcano is not without its risks.
0:30:15 > 0:30:21Unlike the emperors, these penguins can lay eggs on the bare ground.
0:30:21 > 0:30:26Little wonder so many of them brave the mountainous waves to get here.
0:30:32 > 0:30:35Further south, near the continent,
0:30:35 > 0:30:39the blanket of sea ice is beginning to break up.
0:30:42 > 0:30:45Icebergs are gigantic fragments of ice
0:30:45 > 0:30:49that have broken off the front of glaciers.
0:30:49 > 0:30:53Over winter, they were frozen into the sea ice,
0:30:53 > 0:30:56but now they are adrift once more.
0:31:33 > 0:31:38As the bergs break up, they form brash ice.
0:31:38 > 0:31:43It litters the backwaters of the Antarctic Peninsula.
0:31:47 > 0:31:50WHOOSHING
0:32:01 > 0:32:06Minke whales make their way into these placid waters in summer.
0:32:06 > 0:32:11This is the most abundant whale in the Southern Ocean.
0:32:20 > 0:32:25Minkes are one of the smallest of all the baleen whales.
0:32:25 > 0:32:29Like all others, they come here to feed.
0:32:40 > 0:32:45The majestic humpback whales are also summer visitors.
0:32:53 > 0:32:59They have come thousands of miles from their tropical breeding grounds
0:32:59 > 0:33:04to gather the food that is available here in summer.
0:33:16 > 0:33:19In four months,
0:33:19 > 0:33:21they accumulate enough fat
0:33:21 > 0:33:26to provide energy for the rest of the year.
0:33:42 > 0:33:47All these animals have come here in search of one thing -
0:33:47 > 0:33:49the krill.
0:33:49 > 0:33:54Krill is the mainstay of the Antarctic food web.
0:34:01 > 0:34:04It occurs in phenomenal quantity -
0:34:04 > 0:34:07billions of individuals in one swarm,
0:34:07 > 0:34:10and swarms can stretch for miles.
0:34:15 > 0:34:19Fur seals also collect this rich, superabundant food.
0:34:19 > 0:34:22Krill swarms are very patchy,
0:34:22 > 0:34:25but once found, feeding is easy.
0:34:51 > 0:34:56Humpbacks engulf hundreds of thousands of them
0:34:56 > 0:34:59in a single gargantuan mouthful.
0:35:08 > 0:35:13When the going is good, the whales feed continuously,
0:35:13 > 0:35:18each eating up to two tonnes of krill in 24 hours.
0:35:20 > 0:35:25Further south, near the continent, the sea ice is still sound.
0:35:25 > 0:35:29The ice remains for most of the summer.
0:35:29 > 0:35:32Emperor penguins make their home here.
0:35:32 > 0:35:35These have been feeding out at sea
0:35:35 > 0:35:40and are now ready to return to the colony to feed their chicks.
0:35:42 > 0:35:46Instead of going straight for the ice edge,
0:35:46 > 0:35:49the penguins hesitate some distance away.
0:35:49 > 0:35:52They are nervous.
0:36:03 > 0:36:08They dive down and investigate the ice edge.
0:36:21 > 0:36:23And for good reason.
0:36:23 > 0:36:26Leopard seals patrol this border.
0:36:33 > 0:36:38Leopard seals are the Antarctic's equivalent of polar bears.
0:36:38 > 0:36:44They are the top predators, but they hunt most successfully in the water,
0:36:44 > 0:36:49so by and large, the animals they prey on are safer out on the ice.
0:36:49 > 0:36:53RATTLING WHINE
0:36:56 > 0:37:01They have a lazy grace that belies their ferocious nature.
0:37:14 > 0:37:17Confident that the coast is clear,
0:37:17 > 0:37:21the emperor penguins head for the ice.
0:37:21 > 0:37:23But they don't linger.
0:38:03 > 0:38:08Now they have a long walk back to the colony.
0:38:13 > 0:38:17Emperor colonies are set back from the ice edge.
0:38:17 > 0:38:22In winter, they may be 100 miles from it,
0:38:22 > 0:38:25but as summer progresses and the ice melts,
0:38:25 > 0:38:29the edge comes ever closer to the colony.
0:38:29 > 0:38:34When the chicks are ready for their first swim, the water is close by.
0:38:40 > 0:38:44This colony is in the lee of a headland
0:38:44 > 0:38:49and that prevents the ice from being broken up by ocean currents.
0:38:49 > 0:38:54The returning adults are so full of food, they can barely walk.
0:38:54 > 0:38:57But no predator threatens them now.
0:38:57 > 0:39:00They can take their time.
0:39:00 > 0:39:03HIGH-PITCHED CRIES MINGLE WITH SQUAWKS
0:39:07 > 0:39:12Somehow, in this melee of 60,000 or so penguins,
0:39:12 > 0:39:15a parent has to find its chick.
0:39:23 > 0:39:28It returns to the place where it last left its chick
0:39:28 > 0:39:33in the hope that it might still be close by.
0:39:33 > 0:39:36But chicks tend to wander,
0:39:36 > 0:39:38so the adult has to call to it.
0:39:51 > 0:39:54The chick responds
0:39:54 > 0:39:57and they home in on one another.
0:39:57 > 0:40:00The chick's cries stimulate the adult
0:40:00 > 0:40:03to regurgitate some fish.
0:40:13 > 0:40:19With the return of one parent, the other is free to feed for itself.
0:40:33 > 0:40:36Aware of the leopard seal's presence,
0:40:36 > 0:40:40the penguins press together at the ice edge,
0:40:40 > 0:40:43unwilling to be the first to dive in.
0:40:59 > 0:41:04Occasionally, the seal comes onto the ice and attempts to grab one.
0:41:18 > 0:41:23But its most successful strategy by far is to lie in wait.
0:41:31 > 0:41:34It hides behind a corner of ice.
0:41:36 > 0:41:40The penguins decide to make a dash for it.
0:41:51 > 0:41:54The first wave of penguins escape.
0:41:56 > 0:41:59Once in open water, they will be safe.
0:42:03 > 0:42:07But the seal is alerted by the noise,
0:42:07 > 0:42:10and makes its attack.
0:42:20 > 0:42:23Almost invariably, it makes a kill.
0:42:30 > 0:42:34Encouraged by the absence of the seal,
0:42:34 > 0:42:39the remaining penguins make a break for the open sea.
0:42:55 > 0:42:58In time, their chicks will fledge.
0:42:58 > 0:43:01And when the Antarctic autumn is near its end,
0:43:01 > 0:43:05these adults will walk across the newly formed ice,
0:43:05 > 0:43:09to endure yet another winter on the frozen sea.
0:43:16 > 0:43:18Of all the ocean habitats,
0:43:18 > 0:43:22the Poles have to be one of the most demanding places in which to film.
0:43:22 > 0:43:27Not only do you have the problems of keeping filming equipment working
0:43:27 > 0:43:29in temperatures well below zero,
0:43:29 > 0:43:33but you also have your own survival to consider.
0:43:33 > 0:43:37Ice may be beautiful, but it's treacherous.
0:43:37 > 0:43:42Pieces can break off, leaving you drifting in the freezing seas.
0:43:42 > 0:43:46Diving under the ice requires special skills.
0:43:46 > 0:43:50Cameraman Doug Allan has those skills in abundance,
0:43:50 > 0:43:54having spent much of his life filming around the Poles.
0:43:59 > 0:44:02On the Arctic Islands of Svalbard,
0:44:02 > 0:44:05Doug Allan and polar expert Jason Roberts
0:44:05 > 0:44:07are in search of polar bears.
0:44:11 > 0:44:16They are carrying everything they need to live up here for four weeks.
0:44:16 > 0:44:20But almost straight away, they run into a problem.
0:44:20 > 0:44:24We've got "white-out" - we've got no contrast.
0:44:24 > 0:44:31The next route lies out over the sea ice and we need good conditions.
0:44:31 > 0:44:34So we've decided to stop here at this snow-covered cabin
0:44:34 > 0:44:38in the hope that the weather gets better.
0:44:38 > 0:44:44And the snow covering the cabin wasn't just on the outside.
0:44:45 > 0:44:48Cup of tea, stage one!
0:44:50 > 0:44:54Cabins like this one are set up by hunters and fishermen,
0:44:54 > 0:44:57who use them in season.
0:44:57 > 0:45:02They provided a vital base camp for our film makers.
0:45:19 > 0:45:23Near the shore line of Svalbard, the ice is moving.
0:45:23 > 0:45:27Polar bears come here to try to catch seals.
0:45:27 > 0:45:33To find a white bear in this white wilderness requires persistence.
0:45:41 > 0:45:44Brrr. 11 hours.
0:45:44 > 0:45:48I feel as though these things have been glued on my eyeballs.
0:45:48 > 0:45:54One bear - but just much too wary of us to let us get anywhere close.
0:45:54 > 0:45:57A long day for not very much.
0:46:02 > 0:46:05Several months earlier, filming in the Antarctic,
0:46:05 > 0:46:09Doug had had better luck finding the animals.
0:46:09 > 0:46:13Emperor penguins are regular commuters.
0:46:13 > 0:46:16Every day, they return from feeding out at sea
0:46:16 > 0:46:21using exactly the same exit point along the ice edge.
0:46:28 > 0:46:31Keep rolling!
0:46:31 > 0:46:33Still coming!
0:46:33 > 0:46:35A remote camera under the ice
0:46:35 > 0:46:40helped us predict exactly when the penguins would emerge.
0:46:41 > 0:46:45Penguins may be more predictable than polar bears,
0:46:45 > 0:46:49but survival logistics in Antarctica are very demanding.
0:46:51 > 0:46:56With the nearest civilisation a thousand miles away,
0:46:56 > 0:46:59everything you need has to be brought in.
0:47:07 > 0:47:09An Italian Antarctic scientific research team
0:47:09 > 0:47:13kindly flew in a special camp which was set up near the ice edge.
0:47:16 > 0:47:21Back in the Arctic, the weather is still holding things up.
0:47:21 > 0:47:26This is definitely not a day to be looking for bears.
0:47:26 > 0:47:31It's about minus 15. Wind chill is something ferocious.
0:47:31 > 0:47:34I'm gonna go back in the hut.
0:47:36 > 0:47:41No matter how bad the weather, we always put up our trip-wires.
0:47:41 > 0:47:46Just in case we get a visitor in the night, when we're asleep.
0:47:46 > 0:47:51We put up trip wires, which are basically explosion fences.
0:47:51 > 0:47:56A bear comes along, trips a wire and an explosion goes off,
0:47:56 > 0:48:01which will hopefully scare the bear off, or at least wake us up.
0:48:03 > 0:48:10Two bottles! One Bacardi, one Cointreau found in the hut...
0:48:12 > 0:48:16However, both unmistakably paraffin.
0:48:16 > 0:48:19Well, we may get driven to them!
0:48:22 > 0:48:26In Antarctica, the Italian scientific research
0:48:26 > 0:48:28involved diving under the ice
0:48:28 > 0:48:34to measure light coming from the surface to analyse algal growth.
0:48:38 > 0:48:43This gave Doug the opportunity to get some shots below the ice.
0:48:43 > 0:48:46A dubious pleasure.
0:48:47 > 0:48:53It's quite nice, really big platelets of ice, like this.
0:48:53 > 0:48:56And very impressive when Mac was crawling in amongst it
0:48:56 > 0:48:58trying to find a space for the light sensor.
0:48:58 > 0:49:02Very nice. Browns, greens, all kind of colours.
0:49:02 > 0:49:05Even a Weddell seal came by briefly
0:49:05 > 0:49:08and swam away. Good. Nice.
0:49:08 > 0:49:13The main problem under the ice is NOT the cold.
0:49:13 > 0:49:18The water has quite a constant temperature, just above freezing -
0:49:18 > 0:49:20far warmer than at the surface.
0:49:20 > 0:49:25The real danger of diving under the ice is losing your way out.
0:49:39 > 0:49:42One of the advantages of working in the polar regions
0:49:42 > 0:49:45is that in the summer, the sun never sets.
0:49:45 > 0:49:48You can work out on the ice round the clock.
0:49:48 > 0:49:50Just as well for Doug and Jason,
0:49:50 > 0:49:53who still haven't found their polar bear.
0:50:00 > 0:50:02Freeze-dried chicken in curry.
0:50:02 > 0:50:06Absolutely lovely at minus 20, nice and warm.
0:50:07 > 0:50:11Mix it with a bit of water.
0:50:11 > 0:50:15Despite the food, things did seem to be looking up.
0:50:15 > 0:50:19At long last, after days of searching,
0:50:19 > 0:50:21they had found a polar bear cub...
0:50:23 > 0:50:25..and its mother.
0:50:26 > 0:50:29The light was ideal for filming,
0:50:29 > 0:50:33but the bears were not being co-operative.
0:50:33 > 0:50:36That was so frustrating.
0:50:36 > 0:50:41We had this female and cub, we've been kind of watching her,
0:50:41 > 0:50:45doing a bit of hunting and never very close.
0:50:45 > 0:50:50She came into this nice position, then I took a few steps towards her.
0:50:50 > 0:50:56She was a long way away, but she completely reacted the wrong way,
0:50:56 > 0:51:01and I lost all her confidence, and now she's off somewhere
0:51:01 > 0:51:04and it's such a nice day for filming.
0:51:04 > 0:51:07I thought we had it, and, oh...
0:51:13 > 0:51:19Despite the setbacks, two days later, Doug's persistence paid off.
0:51:19 > 0:51:23He was able to win back the confidence of the bears.
0:51:30 > 0:51:35It's five o'clock in the morning, and the 18th day of the shoot.
0:51:35 > 0:51:40I think we just cracked it. We had a female there,
0:51:40 > 0:51:45with the cub. She did a lot of pouncing about.
0:51:45 > 0:51:4950, 80 metres away. A nice sort of distance.
0:51:51 > 0:51:56You know what she did when she was finished?
0:51:56 > 0:51:59She was so relaxed, she sat down,
0:51:59 > 0:52:04and gathered the cub into her and suckled her head onto the camera.
0:52:04 > 0:52:08I tell you, it's a weight off your mind
0:52:08 > 0:52:11when you get something like that. It's incredible.