0:00:28 > 0:00:32Both poles of our planet are covered with ice.
0:00:32 > 0:00:37They're the largest and most demanding wildernesses of all.
0:00:38 > 0:00:43Nowhere else on Earth is seasonal change so extreme.
0:00:43 > 0:00:48It causes the ice to advance and retreat every year.
0:00:50 > 0:00:54And all life here is governed by that.
0:01:12 > 0:01:15When the first polar explorers headed south,
0:01:15 > 0:01:21giant cathedrals of ice marked their entry into uncharted territory.
0:01:25 > 0:01:27Passing the towering spires,
0:01:27 > 0:01:31they must have wondered what unearthly sights lay in store.
0:01:36 > 0:01:40As they battled on, the ice became increasingly dominant,
0:01:40 > 0:01:44but nothing could have prepared them for the ice world
0:01:44 > 0:01:46that finally loomed into view.
0:01:52 > 0:01:54Terra Incognita.
0:01:54 > 0:01:56The unknown land.
0:02:08 > 0:02:13At the southernmost extreme of our planet, the continent of Antarctica
0:02:13 > 0:02:16is as large as the United States of America.
0:02:22 > 0:02:2690% of all the world's ice is found here.
0:02:29 > 0:02:37This frozen world is largely deserted until the start of spring.
0:02:40 > 0:02:43Adelie penguins.
0:02:43 > 0:02:45In a hurry.
0:02:51 > 0:02:53The clock is ticking.
0:02:53 > 0:02:58Instead of waiting for the summer melt, the new arrivals hasten south
0:02:58 > 0:02:59over the frozen sea.
0:03:11 > 0:03:16They have come here to breed, but polar summers are so short,
0:03:16 > 0:03:20they must be in position before the thaw starts.
0:03:24 > 0:03:29As the sea ice retreats, life can journey farther south.
0:03:35 > 0:03:37Antarctic waters are so rich
0:03:37 > 0:03:42that visitors come from far and wide to harvest them.
0:03:49 > 0:03:54Vast numbers of chinstrap penguins come ashore to breed.
0:04:03 > 0:04:07No bird will lay their eggs directly onto ice,
0:04:07 > 0:04:10so bare rock is a vital commodity.
0:04:10 > 0:04:13The best patches are worth the climb.
0:04:17 > 0:04:21The cliff tops are soon stained pink
0:04:21 > 0:04:25with the droppings of tens of thousands of nesting penguins.
0:04:33 > 0:04:37Only in a land almost entirely covered in ice
0:04:37 > 0:04:40could bare rock be reckoned an oasis.
0:04:42 > 0:04:47Some will travel into the heart of the continent to find it.
0:04:49 > 0:04:54These are nunatacks, the exposed peaks of vast mountain ranges
0:04:54 > 0:04:58buried in ice over a mile deep.
0:04:59 > 0:05:05The eerie silence here is only broken in spring.
0:05:06 > 0:05:08SQUAWKING
0:05:12 > 0:05:16The snow petrels have arrived and are courting.
0:05:16 > 0:05:19SQUAWKING
0:05:23 > 0:05:28Antarctic petrels now join the most southerly bird colony on Earth.
0:05:29 > 0:05:33The birds have flown inland for over 300 miles
0:05:33 > 0:05:35to reach this breeding site.
0:05:40 > 0:05:43Once their eggs have hatched, they will be forced repeatedly
0:05:43 > 0:05:48to make the 600-mile round trip to gather food in the ocean.
0:05:49 > 0:05:53First though, valuable nesting places must be defended
0:05:53 > 0:05:55from property thieves.
0:06:02 > 0:06:08After laying their eggs, the petrels take time out to clean their plumage.
0:06:28 > 0:06:33The south polar skua is a formidable opportunist.
0:06:35 > 0:06:39But the skuas have not chanced upon the petrels.
0:06:39 > 0:06:41They've been waiting for them.
0:06:45 > 0:06:50These birds do not need to go to the ocean for their food.
0:07:07 > 0:07:12The skuas can survive further south than any other predator
0:07:12 > 0:07:16by exploiting the petrels' desperate need for bare rock.
0:07:16 > 0:07:19SQUAWKS
0:07:26 > 0:07:32Even at the height of summer, less than 3% of Antarctica is free of ice
0:07:32 > 0:07:34and nearly all of that exposed rock
0:07:34 > 0:07:39is found in one place - the Antarctic Peninsula.
0:07:45 > 0:07:49Its long arm extends further north than the rest of the continent,
0:07:49 > 0:07:52so spring arrives here first.
0:08:06 > 0:08:11The thaw unlocks sheltered bays that provide refuge
0:08:11 > 0:08:14from the relentless battering of the Southern Ocean.
0:08:18 > 0:08:21In the depths, something stirs.
0:08:46 > 0:08:48Humpback whales.
0:08:48 > 0:08:53They have travelled over 5,000 miles to reach these waters.
0:08:59 > 0:09:02The whales are harvesting krill,
0:09:02 > 0:09:05shrimp-like creatures that begin to swarm here
0:09:05 > 0:09:08as soon as the ice retreats.
0:09:21 > 0:09:24Diving into the heart of the swarm,
0:09:24 > 0:09:29teams of whales spiral round each other in close co-ordination.
0:09:30 > 0:09:31WHALE TRUMPETS
0:09:31 > 0:09:35Now they turn, blasting air from their blowholes,
0:09:35 > 0:09:38and ascend towards their prey.
0:09:38 > 0:09:40WHALE TRUMPETS
0:09:40 > 0:09:42The krill becomes concentrated
0:09:42 > 0:09:45as the spiralling net of bubbles draws inwards.
0:09:45 > 0:09:48WHALE CRIES
0:09:51 > 0:09:53WHALE CRIES
0:09:54 > 0:09:58WHALE RUMBLES
0:10:11 > 0:10:17The team of whales work round the clock, for the boom is short-lived.
0:10:17 > 0:10:19Summer is already fading
0:10:19 > 0:10:23and the whales will soon be forced north as winter returns.
0:10:27 > 0:10:32The sun's influence diminishes and the ocean starts to freeze.
0:10:32 > 0:10:36The greatest seasonal change on our planet is under way.
0:10:42 > 0:10:45The ice grows at an extraordinary rate,
0:10:45 > 0:10:48advancing two and a half miles a day.
0:10:48 > 0:10:53In a matter of weeks, the continent effectively doubles in size.
0:10:56 > 0:10:59Life flees from Antarctica.
0:11:06 > 0:11:09But one creature is just arriving.
0:11:13 > 0:11:19Every winter, emperor penguins leave the comfort of their ocean home
0:11:19 > 0:11:21and begin a remarkable journey.
0:11:23 > 0:11:26They head towards their breeding grounds
0:11:26 > 0:11:29almost a hundred miles inland.
0:11:51 > 0:11:53Eventually, the emperor penguins
0:11:53 > 0:11:56reach the place where they were hatched,
0:11:56 > 0:12:00an area sheltered by icebergs trapped in the frozen ocean.
0:12:00 > 0:12:04Here they will raise the next generation.
0:12:11 > 0:12:14But first, each must find a mate.
0:12:17 > 0:12:20The males begin to serenade.
0:12:24 > 0:12:29And if a female replies, they pair up, posing like statues.
0:12:33 > 0:12:37New couples quickly form a strong bond.
0:12:37 > 0:12:41They seem oblivious to the noisy crowd around them.
0:12:43 > 0:12:48To cement their relationship, the male steps out with his female.
0:12:57 > 0:13:02The brief courtship complete, there isn't a moment to lose.
0:13:02 > 0:13:04With so much pressure to perform,
0:13:04 > 0:13:08any male would struggle to stay on top.
0:13:15 > 0:13:20Several weeks later, and it seems that most couplings were successful.
0:13:20 > 0:13:25But producing the egg has taken its toll.
0:13:25 > 0:13:29The females no longer have the energy to incubate.
0:13:31 > 0:13:32The male takes over.
0:13:32 > 0:13:36It's still minus 20 degrees centigrade
0:13:36 > 0:13:40so the transfer must be done quickly or else the egg will freeze.
0:13:40 > 0:13:42With no bare rock to nest on,
0:13:42 > 0:13:45the male tucks the egg into a special pouch
0:13:45 > 0:13:48where he can keep it warm.
0:13:48 > 0:13:51It requires an extraordinary piece of teamwork.
0:13:56 > 0:13:57Driven by hunger,
0:13:57 > 0:14:01the exhausted females now return to the ocean on their own,
0:14:01 > 0:14:07repeating the epic journey they made with the males only a month before.
0:14:12 > 0:14:16Now the sun barely appears above the horizon.
0:14:17 > 0:14:22As the days shorten, its warmth is withdrawn from the continent.
0:14:23 > 0:14:26WIND HOWLS
0:14:32 > 0:14:39With the females gone, the colony undergoes a strange transformation.
0:14:39 > 0:14:41The males shuffle into groups,
0:14:41 > 0:14:45their eggs still tucked away above their feet.
0:14:48 > 0:14:51They lock together in tightly packed huddles
0:14:51 > 0:14:53as they struggle to keep warm.
0:14:57 > 0:14:58Speeding up the action reveals
0:14:58 > 0:15:02how these huddles constantly shift and change
0:15:02 > 0:15:06as each penguin works its way towards the warmer interior.
0:15:08 > 0:15:12Crammed into this scrum, the birds are remarkably good-natured,
0:15:12 > 0:15:13but they have to be.
0:15:13 > 0:15:18If the huddle breaks, even for a moment, precious heat escapes.
0:15:36 > 0:15:41It's imperative they reform as quickly as possible,
0:15:41 > 0:15:45for only by acting as one, can the males withstand the elements
0:15:45 > 0:15:46and protect their eggs.
0:15:51 > 0:15:55But their greatest test lies ahead.
0:15:55 > 0:16:00As winter advances, frequent blizzards drive the temperature down.
0:16:01 > 0:16:05It's now 60 degrees below zero.
0:16:07 > 0:16:14The birds at the edge of the huddle bear the brunt of the 100mph winds,
0:16:14 > 0:16:18and so provide shelter to those taking their turn in the middle.
0:16:26 > 0:16:31Abandoned by the sun, the males are left alone with their eggs
0:16:31 > 0:16:34to face the coldest, darkest winter on Earth.
0:16:42 > 0:16:45At the northern extreme of our planet,
0:16:45 > 0:16:48the sun rises for the first time in months,
0:16:48 > 0:16:51illuminating a very different ice world.
0:16:54 > 0:17:01Unlike Antarctica, the Arctic is a vast frozen sea surrounded by land.
0:17:03 > 0:17:07Here, winter is coming to an end,
0:17:07 > 0:17:11but this bleak wilderness remains locked in ice.
0:17:19 > 0:17:21Eider ducks break the silence.
0:17:21 > 0:17:25They have stayed here, braving the northern winter,
0:17:25 > 0:17:28instead of flying south to warmer climes.
0:17:32 > 0:17:37Flocks, 40,000 strong, sweep across the frozen wastes.
0:17:51 > 0:17:54They all have the same goal - a polynya,
0:17:54 > 0:17:58a permanent hole in the sea ice kept open throughout the winter
0:17:58 > 0:18:01by strong ocean currents.
0:18:04 > 0:18:09This unusual duck pond provides an overnight sanctuary
0:18:09 > 0:18:13and, when day breaks, a rare chance to feed.
0:18:25 > 0:18:28Just ten metres beneath the ice,
0:18:28 > 0:18:32the seafloor is carpeted with dense mussel beds.
0:18:33 > 0:18:37These can only be reached during a brief lull in the currents.
0:18:37 > 0:18:41The ducks must quickly prise the mussels free
0:18:41 > 0:18:44before the tide starts to turn.
0:18:49 > 0:18:52The window of opportunity is short.
0:18:52 > 0:18:58As the current begins to build, it's up, up and away.
0:19:08 > 0:19:11These permanent holes in the ice
0:19:11 > 0:19:15provide seafood throughout the winter.
0:19:15 > 0:19:18The diners attract others.
0:19:24 > 0:19:30In the Arctic, any breach in the icy barrier can be a lifeline.
0:19:33 > 0:19:35Musk oxen create their own.
0:19:37 > 0:19:41These giants have the strength to smash through the frozen crust
0:19:41 > 0:19:44to graze on the vegetation below.
0:19:48 > 0:19:52These icebreakers create an opening for other over-winterers.
0:19:54 > 0:19:59Flocks of ptarmigan make unusual grazing companions to the musk oxen,
0:19:59 > 0:20:02whose entourage grows throughout the day.
0:20:11 > 0:20:16This odd assembly of vegetarians doesn't go unnoticed.
0:20:16 > 0:20:19An Arctic fox.
0:20:24 > 0:20:28The musk oxen have recently given birth.
0:20:28 > 0:20:31For the fox, it's a chance to scavenge.
0:20:38 > 0:20:40But half a ton of mad, hairy cow...
0:20:41 > 0:20:44..is not to be trifled with.
0:20:52 > 0:20:55The calves are born well before the spring melt,
0:20:55 > 0:21:00giving them a head start when summer finally arrives.
0:21:03 > 0:21:09It must get to grips with its new ice world - benign one minute,
0:21:09 > 0:21:11life-threatening the next.
0:21:11 > 0:21:14WIND HOWLS
0:21:17 > 0:21:21Even in spring, winds chill to the bone.
0:21:24 > 0:21:26The calf must stay close to its mother
0:21:26 > 0:21:30to avoid getting lost in the sudden blizzard.
0:21:38 > 0:21:41Arctic wolves.
0:21:45 > 0:21:49In the whiteout, the threat is almost impossible to detect,
0:21:49 > 0:21:53but the musk oxen instinctively retreat to higher ground.
0:22:08 > 0:22:11Forming a defensive ring around their calves,
0:22:11 > 0:22:15the adults present a barricade that few hunters could breach.
0:22:18 > 0:22:21But the wolves need not risk injury today.
0:22:23 > 0:22:27A calf has been left behind in the panic.
0:22:29 > 0:22:31WOLF HOWLS
0:22:39 > 0:22:44With each passing day, the sun climbs higher in the sky
0:22:44 > 0:22:48and its rays strike the Arctic more directly.
0:22:48 > 0:22:53It's spring and new life stirs.
0:22:56 > 0:23:01The polar bear cubs emerge from the den in which they were born.
0:23:01 > 0:23:06Their mother stretches her legs after five months under the snow.
0:23:11 > 0:23:16They're just two months old and instinctively follow her lead.
0:23:31 > 0:23:35A steep slope makes the best site for a den
0:23:35 > 0:23:39but it's a tricky place to take your first steps.
0:23:57 > 0:24:03It may look like fun, but this is serious training for the task ahead.
0:24:03 > 0:24:05There's no food on the slopes
0:24:05 > 0:24:08and the family will need to head out across the frozen sea
0:24:08 > 0:24:11before the mother's milk runs dry.
0:24:17 > 0:24:22Two weeks later, they're ready.
0:24:22 > 0:24:25Out on the sea ice, the female can hunt for seals,
0:24:25 > 0:24:30but it will take all her mothering skills to keep her cubs safe
0:24:30 > 0:24:33in this dangerous world of ice.
0:24:47 > 0:24:52The annual melt has begun.
0:24:52 > 0:24:56This is a challenging time for the bear family.
0:24:56 > 0:25:00One out of every two cubs do not survive their first year
0:25:00 > 0:25:02out on the ice.
0:25:12 > 0:25:15As the sun's influence increases,
0:25:15 > 0:25:18the sea ice seems to take on a life of its own.
0:25:26 > 0:25:29Glacial meltwaters pour from the land,
0:25:29 > 0:25:33mingling with the sea and speeding up the thaw.
0:25:38 > 0:25:41The seascape is in constant flux
0:25:41 > 0:25:46as broken ice is moved on by winds and currents.
0:25:54 > 0:25:59The ice is becoming too weak to support a male polar bear.
0:26:06 > 0:26:09He attempts to spread his weight,
0:26:09 > 0:26:13but the ice that has supported him all winter
0:26:13 > 0:26:15is rapidly disintegrating.
0:26:16 > 0:26:21Each year, as the climate warms, the Arctic holds less ice.
0:26:21 > 0:26:24This is a disaster for polar bears.
0:26:24 > 0:26:26Without its solid platform,
0:26:26 > 0:26:30they can't hunt the seals they need in order to survive.
0:26:33 > 0:26:37This may be a glimpse of the unstable future
0:26:37 > 0:26:40faced by this magnificent creature.
0:27:12 > 0:27:17As the ice disappears, seabirds return to the high Arctic.
0:27:19 > 0:27:22SQUAWKING
0:27:26 > 0:27:29Little auks arrive in their millions.
0:27:32 > 0:27:35In some ways, these birds are the penguins of the north.
0:27:35 > 0:27:39They seek bare rock on which to lay their eggs
0:27:39 > 0:27:41and they look rather like penguins too.
0:27:48 > 0:27:53Unlike Antarctica, the Arctic can be reached by land-based predators,
0:27:53 > 0:27:56which is why little auks have kept the ability to fly.
0:27:56 > 0:27:58SQUAWKING
0:28:01 > 0:28:05They use scree slopes to protect their eggs,
0:28:05 > 0:28:07burrowing up to a metre beneath the rocks.
0:28:14 > 0:28:18At the height of summer, the sun never sets
0:28:18 > 0:28:22but just skims the horizon before rising again.
0:28:26 > 0:28:31Migrants return to the Arctic from far and wide.
0:28:32 > 0:28:35They've come to make the most of the brief flush of food
0:28:35 > 0:28:38and to produce their young.
0:28:38 > 0:28:43Sandhill cranes have travelled all the way from New Mexico.
0:28:48 > 0:28:54Their chicks join the growing band of youngsters exploring the tundra.
0:29:01 > 0:29:03For a few months each year,
0:29:03 > 0:29:07the Arctic becomes the land of the midnight sun,
0:29:07 > 0:29:12and 24 hours of daylight allow animals to feed around the clock.
0:29:14 > 0:29:20The Arctic fox finally has enough food to raise her large family.
0:29:34 > 0:29:39If you choose to nest in the open, you must be prepared for a fight.
0:29:40 > 0:29:41FOX SCREECHES
0:29:44 > 0:29:45BIRD SQUAWKS
0:29:47 > 0:29:53Arctic skuas will see off any trespassers, even large vegetarians.
0:29:54 > 0:29:56GRUNTING AND SQUAWKING
0:30:37 > 0:30:43The male polar bear's ice world has finally vanished beneath him.
0:30:54 > 0:30:59While the female is still kept on land by her dependant cubs,
0:30:59 > 0:31:03the male can take to the sea in search of food.
0:31:03 > 0:31:04Ducking and diving,
0:31:04 > 0:31:10he hopes to ambush seals resting on the remaining fragments of ice.
0:31:36 > 0:31:41In these new surroundings, he is a surprisingly adept swimmer.
0:31:52 > 0:31:55Once an extremely rare sight,
0:31:55 > 0:31:59polar bears have recently been seen over 60 miles from the shore.
0:32:12 > 0:32:17There is now no turning back for this bear.
0:32:17 > 0:32:20He's forced to head out into deeper water.
0:32:28 > 0:32:33His giant front paws help him to fight the ocean currents.
0:32:53 > 0:32:59He seems at home in the sea, but he can not swim indefinitely.
0:33:02 > 0:33:07He will drown if he doesn't find land somewhere in this vast ocean.
0:33:34 > 0:33:38Walruses are now gathering on low lying islands.
0:33:38 > 0:33:43They gave birth on sea ice but with this platform now gone
0:33:43 > 0:33:47they need a new place to haul out and nurse their young.
0:33:49 > 0:33:54After several days at sea, the male bear finally makes landfall,
0:33:54 > 0:33:59drawn by pungent smells emanating from the island.
0:34:07 > 0:34:11By the end of summer, the bear has lost half his weight.
0:34:11 > 0:34:16With the ice long gone, he is forced onto land in search of food.
0:34:25 > 0:34:29There will be no easy meals on this island.
0:34:29 > 0:34:32Walruses are the largest seals in the world.
0:34:32 > 0:34:37They weigh over a tonne and are armed with tusks a metre long.
0:34:40 > 0:34:45Exhausted from his swim, the bear must regain his strength.
0:34:51 > 0:34:56The next day, a sea fog shrouds the island.
0:34:56 > 0:34:58The walruses sense that they're in danger.
0:35:01 > 0:35:06Using the fog as cover, the bear approaches the herd.
0:35:10 > 0:35:14The adults close ranks around their young,
0:35:14 > 0:35:17presenting a wall of blubber and hide.
0:35:24 > 0:35:27He tests the barrier,
0:35:27 > 0:35:29but it stands firm.
0:35:30 > 0:35:35It appears that the world's largest land carnivore has met his match.
0:35:42 > 0:35:45There must be a chink in the armour somewhere.
0:35:49 > 0:35:51Not here!
0:35:59 > 0:36:02This female walrus is shielding her pup.
0:36:02 > 0:36:05If he can just prise her off...
0:36:11 > 0:36:17The bear's paws and teeth can't penetrate her thick hide.
0:36:24 > 0:36:29With the herd retreating to water, the bear must move quickly.
0:36:34 > 0:36:38Having failed with one, he heads straight for another.
0:36:54 > 0:36:59The chance of his first meal in months is slipping away.
0:37:06 > 0:37:09He seems increasingly desperate.
0:37:13 > 0:37:17It's now or never!
0:37:17 > 0:37:21He must avoid the stabbing tusks if he's to win.
0:37:28 > 0:37:30The flailing walrus is immensely powerful
0:37:30 > 0:37:33and drags the bear away from the shallows
0:37:33 > 0:37:35towards the safety of the herd.
0:37:51 > 0:37:53It slips from his grasp.
0:38:01 > 0:38:03Only at the height of summer,
0:38:03 > 0:38:06when bears are on the verge of starvation,
0:38:06 > 0:38:09will they risk attacking such dangerous prey.
0:38:13 > 0:38:17It was a gamble that this bear took and lost.
0:38:20 > 0:38:24The stab wounds he received from the walrus
0:38:24 > 0:38:27are so severe that he can barely walk.
0:38:31 > 0:38:34The walruses are calm again,
0:38:34 > 0:38:37seemingly aware that the injured bear
0:38:37 > 0:38:40no longer poses a threat to them or their young.
0:38:40 > 0:38:43BEAR GROWLS
0:38:55 > 0:39:00Unable to feed, this bear will not survive.
0:39:12 > 0:39:15If the global climate continues to warm
0:39:15 > 0:39:18and the Arctic ice melts sooner each year,
0:39:18 > 0:39:22it's certain that more bears will share this fate.
0:39:44 > 0:39:46At the southern end of our planet,
0:39:46 > 0:39:50fiery ribbons are illuminating the winter skies -
0:39:50 > 0:39:53the Aurora Australis.
0:39:56 > 0:40:00This light brings no warmth to the male penguins
0:40:00 > 0:40:02who are still huddling,
0:40:02 > 0:40:05defying the coldest conditions on the planet.
0:40:19 > 0:40:22Their ordeal is drawing to a close.
0:40:29 > 0:40:3730 days after it last set, the sun rises once more on Antarctica.
0:40:57 > 0:41:02Their appalling trials have all been for this.
0:41:16 > 0:41:18CHICK SQUEAKS
0:41:18 > 0:41:23Each father has just one meal left inside him.
0:41:23 > 0:41:27He's been saving it all winter.
0:41:27 > 0:41:32This single feed will sustain the chicks for a few more days.
0:41:32 > 0:41:36But the males have not eaten for nearly four months.
0:41:36 > 0:41:40If they do not eat soon, they and their chicks will die.
0:41:49 > 0:41:53But there is hope on the horizon.
0:42:05 > 0:42:10The females are returning and their bellies are full with fish.
0:42:16 > 0:42:21As they approach, waves of excitement ripple through the huddle.
0:42:29 > 0:42:32Each female calls to her mate
0:42:32 > 0:42:36and he, recognising her song, trumpets back.
0:42:38 > 0:42:42Reunited at last.
0:42:44 > 0:42:46The mother sees her chick
0:42:46 > 0:42:48for the first time.
0:42:51 > 0:42:54She's keen to start parenting,
0:42:54 > 0:42:56but the father needs persuading
0:42:56 > 0:43:00to surrender the chick he's been caring for all winter.
0:43:04 > 0:43:07He must now put his chick at risk.
0:43:07 > 0:43:10In these temperatures, it could freeze in seconds.
0:43:14 > 0:43:17The male will have to let go.
0:43:23 > 0:43:28Eventually, the transfer to the mother is safely made.
0:43:41 > 0:43:46The chicks grow quickly on a diet of fish and squid.
0:44:00 > 0:44:03Soon they're keen to explore,
0:44:03 > 0:44:05but always with mother in tow.
0:44:08 > 0:44:14This chick is less fortunate. Its mother has not returned to claim it.
0:44:14 > 0:44:18Another orphan is searching for a new family
0:44:18 > 0:44:21but this female already has a chick of her own.
0:44:30 > 0:44:34Some orphans receive too much mothering from penguins
0:44:34 > 0:44:36whose own chicks have not survived.
0:44:36 > 0:44:40The urge to parent is so strong that they will compete with one another
0:44:40 > 0:44:43to adopt any chick they find.
0:44:48 > 0:44:51Many of these squabbles end in tragedy
0:44:51 > 0:44:54as the poor chick is trampled to death.
0:45:05 > 0:45:11Those chicks that DO have parents quickly learn survival skills.
0:45:12 > 0:45:16Even in spring, they must huddle together for warmth
0:45:16 > 0:45:19just as their fathers did in the depths of winter.
0:45:22 > 0:45:26A group of chicks has got lost in the blizzard.
0:45:33 > 0:45:38Cold and disorientated, they search for the colony.
0:45:43 > 0:45:48It will not be long before the storm claims its first victims.
0:46:05 > 0:46:11By early summer, the chicks are surprisingly well developed
0:46:11 > 0:46:14and now look ready to take on the world.
0:46:16 > 0:46:19Those that survive their first year
0:46:19 > 0:46:21have the best possible start in life,
0:46:21 > 0:46:26thanks to the extraordinary hardships endured by their parents -
0:46:26 > 0:46:32parents who battled with the Antarctic winter and won.
0:46:40 > 0:46:43In the Arctic,
0:46:43 > 0:46:47the two polar bear cubs are now independent of their mother
0:46:47 > 0:46:51and they briefly reunite where their home ranges overlap.
0:46:57 > 0:47:01Their time together will be fleeting.
0:47:01 > 0:47:04Most of their lives are now spent alone,
0:47:04 > 0:47:07wandering the vast tracts of frozen ocean.
0:47:35 > 0:47:40Following their mother has prepared them for life at the pole,
0:47:40 > 0:47:44an ever-changing land ruled by ice.
0:47:46 > 0:47:49Whether they are ready for the bigger changes
0:47:49 > 0:47:52that have begun to shape the ice worlds of our planet
0:47:52 > 0:47:54remains to be seen.
0:48:25 > 0:48:30Filming at the poles calls for extraordinary dedication.
0:48:30 > 0:48:32To capture the private life of penguins,
0:48:32 > 0:48:36cameraman Wade and his partner Frederique
0:48:36 > 0:48:38would spend a year in Antarctica,
0:48:38 > 0:48:42with only 20,000 emperors as neighbours.
0:48:47 > 0:48:50As you can probably see, we've got a bit of weather.
0:48:50 > 0:48:51Somewhere behind me is the birds.
0:48:51 > 0:48:53Every now and then, when the snow clears,
0:48:53 > 0:48:55you can just catch a glimpse of them.
0:48:55 > 0:48:58Poor buggers, they'll all be huddled in tight.
0:48:58 > 0:49:01That's where I'd rather be. So we'll go over and have a look.
0:49:03 > 0:49:05It's cold out here. Cold and windy.
0:49:05 > 0:49:08In fact, it was minus 50 degrees centigrade
0:49:08 > 0:49:11and the winds were close to hurricane force.
0:49:14 > 0:49:19Wade had waited six months for this chance to film the penguin huddle,
0:49:19 > 0:49:21but the extreme cold soon took its toll.
0:49:21 > 0:49:24Oh, it's really frustrating.
0:49:24 > 0:49:28It takes so much effort to film in these sort of blizzard conditions.
0:49:28 > 0:49:30I mean, just to get here and...
0:49:30 > 0:49:34Had a pretty good run there but the camera's just jammed.
0:49:34 > 0:49:35The film's jammed.
0:49:35 > 0:49:39There's nothing I can do about it out here, there's just no way.
0:49:39 > 0:49:43Wade was forced to retreat to the relative comfort of the hut,
0:49:43 > 0:49:45leaving the penguins out in the cold.
0:49:45 > 0:49:48I was just lying in bed thinking about those penguins
0:49:48 > 0:49:51and all the huddles - all the males will be huddled together -
0:49:51 > 0:49:54and how they can possibly survive in this sort of weather
0:49:54 > 0:49:56is just absolutely extraordinary,
0:49:56 > 0:49:59and I really feel quite sorry for them at this moment.
0:50:03 > 0:50:05With the camera fixed,
0:50:05 > 0:50:10Wade set off again the next day, but the storm was even worse.
0:50:16 > 0:50:18The 100mph winds
0:50:18 > 0:50:21forced Wade onto his knees,
0:50:21 > 0:50:25as he struggled to haul the weight of the camera.
0:50:25 > 0:50:29The two-mile walk to the colony now became an epic struggle.
0:50:31 > 0:50:34It's hard to imagine a more brutal challenge
0:50:34 > 0:50:36for a natural history cameraman.
0:50:44 > 0:50:48Wade's extraordinary endurance finally delivered remarkable images
0:50:48 > 0:50:52of penguins braving the worst winter on the planet.
0:50:52 > 0:50:56These are scenes that few humans have ever witnessed.
0:51:00 > 0:51:02In sharing the ordeal with the emperors,
0:51:02 > 0:51:06Wade and Fred developed a deep bond with their penguin neighbours.
0:51:10 > 0:51:14Two months on and the colony is bustling with new life.
0:51:14 > 0:51:17But there was trouble for one young chick.
0:51:20 > 0:51:23We saw a chick's head sticking out of the snow
0:51:23 > 0:51:27and we just realised he's been trapped in a hole
0:51:27 > 0:51:30as the snowdrift surrounded him.
0:51:30 > 0:51:34So, during the last blizzard, he must have been there for a few days.
0:51:34 > 0:51:36So we're going to try and get him out.
0:51:36 > 0:51:40Don't be scared, chicken. I'm gonna cut the snow.
0:51:40 > 0:51:43Without help, this youngster would soon have starved.
0:51:45 > 0:51:48Natural history film crews do not normally interfere
0:51:48 > 0:51:50with the course of nature,
0:51:50 > 0:51:54but having shared the penguins' six-month struggle for survival,
0:51:54 > 0:51:57it was impossible for Fred to just sit back.
0:51:57 > 0:52:00The chick's mother looked on helplessly.
0:52:00 > 0:52:02Come here. Yes, grab my hand.
0:52:06 > 0:52:09That's it, come, chicken.
0:52:09 > 0:52:10There you go.
0:52:12 > 0:52:15CHICK WHISTLES
0:52:18 > 0:52:22Luckily, the chick was none the worse for its experience.
0:52:22 > 0:52:25CHICK WHISTLES
0:52:27 > 0:52:31As soon as the chick got out, it bound with its parent again
0:52:31 > 0:52:35and it straight away got a feed, so that's really good.
0:52:35 > 0:52:39Thanks to the remarkable efforts of its parents
0:52:39 > 0:52:42and with just a little help from its human neighbours,
0:52:42 > 0:52:44this chick has a bright future.
0:52:47 > 0:52:50HELICOPTER WHIRRS
0:52:57 > 0:53:00For one of our Arctic filming crews,
0:53:00 > 0:53:03visits from the neighbours were to prove less welcome.
0:53:18 > 0:53:22Hungry polar bears are extremely dangerous and, given the chance,
0:53:22 > 0:53:25will kill and eat humans.
0:53:25 > 0:53:28Drawn by the smell of Doug's home cooking,
0:53:28 > 0:53:31this male bear seems particularly fearless.
0:53:32 > 0:53:36Jason fires blanks to scare it away.
0:53:36 > 0:53:37GUNSHOTS
0:53:40 > 0:53:42- Was that him?- That was him.
0:53:44 > 0:53:47Keep it locked. I'll check the window.
0:53:48 > 0:53:50We think he's gone.
0:53:50 > 0:53:52But we're not sure.
0:53:55 > 0:53:58- Day one.- Day one.
0:53:58 > 0:53:59Bear outside the cabin.
0:53:59 > 0:54:03Chewing on a generator cable will hardly satisfy the appetite
0:54:03 > 0:54:06of the world's largest land carnivore.
0:54:06 > 0:54:10He was after something more substantial.
0:54:10 > 0:54:13This is just a bit of a problem when we get bears
0:54:13 > 0:54:15as close as this to the cabin.
0:54:15 > 0:54:17He's a big boy.
0:54:18 > 0:54:19As the day went on,
0:54:19 > 0:54:23it became clear that this was one very determined bear.
0:54:26 > 0:54:28Oh, he might wander off.
0:54:28 > 0:54:31Explosive charges known as "bear scarers"
0:54:31 > 0:54:34are the polite way to persuade him to leave.
0:54:34 > 0:54:35Come on, let's go!
0:54:38 > 0:54:43Give him another one. He wasn't too bothered about that. Got the pistol?
0:54:43 > 0:54:47They had to resort to a bigger bang...
0:54:47 > 0:54:50a "thunder flash" fired from a pistol.
0:54:52 > 0:54:57But this bear is his own boss and will leave when ready.
0:54:58 > 0:55:01Quite exciting, really.
0:55:01 > 0:55:05The crew were not here to film hungry male bears.
0:55:05 > 0:55:09They were after females and cubs emerging from their winter dens,
0:55:09 > 0:55:13but to find them they had to leave the safety of the hut
0:55:13 > 0:55:15and enter the bears' domain.
0:55:17 > 0:55:21Planet Earth had been given special permission to film
0:55:21 > 0:55:23on this remote Norwegian island,
0:55:23 > 0:55:26the first human visitors for 25 years.
0:55:28 > 0:55:33Motorised vehicles are prohibited in this fragile environment,
0:55:33 > 0:55:37so the crew had to do things the old-fashioned way.
0:55:38 > 0:55:41When the polar explorers
0:55:41 > 0:55:43used to haul their gear like this,
0:55:43 > 0:55:46they used to have names for their sledges,
0:55:46 > 0:55:51things like Intrepid and Braveheart.
0:55:51 > 0:55:53I'm gonna call mine
0:55:53 > 0:55:58- "You- BLEEP BLEEP - Awkward Heavy Object".
0:56:01 > 0:56:03Argh!
0:56:03 > 0:56:08Doug's sledge seemed determined to live up to its name.
0:56:08 > 0:56:11Oh, no! LAUGHTER
0:56:11 > 0:56:13Oh, no!
0:56:19 > 0:56:23Isolated and on foot, the crew were vulnerable at all times
0:56:23 > 0:56:26and, with so many male bears out on the sea ice,
0:56:26 > 0:56:29Doug had to keep his wits about him.
0:56:34 > 0:56:35Where's the batteries?
0:56:38 > 0:56:41Females den on steep slopes,
0:56:41 > 0:56:46but predicting where they would emerge was proving a real challenge.
0:56:52 > 0:56:56After weeks of searching, the crew finally got lucky.
0:57:02 > 0:57:04This is fantastic. She's out on the slopes.
0:57:04 > 0:57:08Four...four weeks we've been waiting to get this one little opportunity,
0:57:08 > 0:57:11but now that it's happening, it's just fantastic.
0:57:11 > 0:57:17Close behind the mother bear, her tiny eight-week-old cubs.
0:57:24 > 0:57:29With the sequence in the can, the crew were able to relax,
0:57:29 > 0:57:31- but not for long.- I dunno.
0:57:32 > 0:57:34I thought...
0:57:34 > 0:57:36I thought I heard something.
0:57:40 > 0:57:44This bear is much too close for comfort.
0:57:46 > 0:57:49Now, this guy...
0:57:49 > 0:57:54A reminder that we are only visitors in the polar bear's world.
0:57:58 > 0:58:00Yeah, give it time. You get...
0:58:00 > 0:58:04Hang on. Hang on, Doug, he's going back that way.
0:58:04 > 0:58:06Get the gun ready. Get the gun ready, Doug!
0:58:42 > 0:58:44Subtitles by Red Bee Media Ltd, 2006.
0:58:44 > 0:58:46E-mail subtitling@bbc.co.uk