[00:26.90]Both poles of our planet are covered with ice.
[00:31.08]They're the largest and most demanding wildernesses of all.
[00:37.52]Nowhere else on Earth is seasonal change so extreme.
[00:42.30]It causes the ice to advance and retreat every year
[00:48.88]and all life here is governed by that.
[01:10.47]When the first polar explorers headed south
[01:14.11]giant cathedrals of ice marked their entry into uncharted territory.
[01:24.16]Passing the towering spires they must've wondered what unearthly sights lay in store.
[01:34.78]As they battled on the ice became increasingly dominant
[01:38.86]but nothing could have prepared them for the ice world that finally loomed into view.
[01:50.61]Terra incognita - the unknown land.
[02:07.06]At the southernmost extreme of our planet the continent of Antarctica
[02:11.81]is as large as the United States of America.
[02:21.33]Ninety percent of all the world's ice is found here.
[02:28.35]This frozen world is largely deserted until the start of spring.
[02:42.36]in a hurry.
[02:49.70]The clock is ticking.
[02:52.16]Instead of waiting for the summer melt the new arrivals hasten south over the frozen sea.
[03:10.03]They have come here to breed but polar summers are so short
[03:14.48]they must be in position before the thaw starts.
[03:23.40]As the sea ice retreats life can journey farther south.
[03:34.18]Antarctic waters are so rich that visitors come from far and wide to harvest them.
[03:48.27]Vast numbers of chinstrap penguins come ashore to breed.
[04:01.46]No bird will lay their eggs directly onto ice
[04:05.50]so bare rock is a vital commodity. The best patches are worth the climb.
[04:16.85]The clifftops are soon stained pink with the droppings of tens of thousands of nesting penguins.
[04:32.31]Only in a land almost entirely covered in ice could bare rock be reckoned an oasis.
[04:41.69]Some will travel into the heart of the continent to find it.
[04:47.77]These are noon attacks the exposed peaks of vast mountain ranges buried in ice over a mile deep.
[04:58.90]The eerie silence here is only broken in spring.
[05:10.64]The snow petrels have arrived and are courting.
[05:21.82]Antarctic petrels now join the most southerly colony on Earth.
[05:28.68]The birds have flown inland for over three hundred miles
[05:32.11]to reach this breeding site.
[05:39.13]Once their eggs have hatched they'll be forced repeatedly to make the 600 mile round trip
[05:44.56]to gather food in the ocean.
[05:48.79]First though valuable nesting places must be defended from property thieves.
[06:01.17]After laying their eggs the petrels take time out to clean their plumage.
[06:27.03]The south polar skua is a formidable opportunist
[06:35.15]but the skuas have not chanced upon the petrels
[06:38.92]they've been waiting for them.
[06:44.82]These birds do not need to go to the ocean for their food.
[07:06.52]The skuas can survive further south than any other predator
[07:10.66]by exploiting the petrels' desperate need for bare rock.
[07:25.41]Even at the height of summer less than 3% of Antarctica is free of ice
[07:30.77]and nearly all of that exposed rock is found in one place
[07:35.68]the Antarctic Peninsula.
[07:44.42]It's long arm extends further north than the rest of the continent, so spring arrives here first.
[08:05.21]The thaw unlocks sheltered bays
[08:08.36]that provide refuge from the relentless battering of the southern ocean.
[08:17.55]In the depths something stirs...
[08:46.89]They have travelled over 5000 miles to reach these waters.
[08:58.32]The whales are harvesting krill
[09:01.07]shrimp like creatures that begin to swarm here as soon as the ice retreats.
[09:20.35]Diving into the heart of the swarm
[09:22.94]teams of whales spiral around each other in close coordination.
[09:30.86]Now they turn and blasting air from their blowholes and ascend towards their prey.
[09:38.55]The krill becomes concentrated as the spiralling net of bubbles draws inwards.
[10:10.77]The team of whales work around the clock for the bloom is short lived.
[10:15.81]Summer is already fading and the whales will soon be forced north as winter returns.
[10:26.07]The sun's influence diminishes and the ocean starts to freeze.
[10:31.43]The greatest seasonal change on our planet is underway.
[10:41.42]The ice grows at an extraordinary rate advancing two and a half miles a day.
[10:47.32]In a matter of weeks the continent effectively doubles in size.
[10:55.52]Life flees from Antarctica...
[11:04.99]but one creature is just arriving.
[11:12.76]Every winter Emperor penguins leave the comfort of their ocean home and begin a remarkable journey.
[11:22.55]They head towards their breeding grounds almost a hundred miles inland.
[11:50.30]Eventually the emperor penguins reach the place where they were hatched
[11:54.93]an area sheltered by icebergs trapped in the frozen ocean.
[12:00.49]Here they will raise the next generation
[12:10.05]but first each must find a mate.
[12:16.15]Males begin to serenade
[12:23.07]and if a female replies they pair up, posing like statues.
[12:32.72]New couples quickly form a strong bond
[12:36.07]they seem oblivious to the noisy crowd around them.
[12:42.20]To cement their relationship the male steps out with his female.
[12:56.70]The brief courtship complete there isn't a moment to loose.
[13:01.29]With so much pressure to perform any male would struggle to stay on top.
[13:14.31]Several weeks later and it seems that most couplings were successful
[13:20.12]but producing the egg has taken it's toll.
[13:24.37]The females no longer have the energy to incubate.
[13:29.91]The male takes over.
[13:31.97]It's still minus 20 degrees centigrade, so the transfer must be done quickly or else the egg will freeze.
[13:39.30]With no bare rock to nest on the male tucks the egg into a special pouch
[13:44.45]where he can keep it warm.
[13:47.20]It requires an extraordinary piece of teamwork.
[13:54.92]Driven by hunger, the exhausted females now return to the ocean on their own
[14:00.70]repeating the epic journey they made with the males only a month before.
[14:11.69]Now the sun barely appears above the horizon.
[14:16.13]As the day shortens, it's warmth is withdrawn from the continent.
[14:31.81]With the females gone the colony undergoes a strange transformation.
[14:38.03]The males shuffle into groups, their eggs still tucked away above their feet.
[14:46.52]They lock together in tightly packed huddles as they struggle to keep warm.
[14:55.69]Speeding up the action reveals how these huddles constantly shift and change
[15:00.64]as each penguin works it's way towards the warmer interior.
[15:06.79]Crammed into this scrum, the birds are remarkably good natured, but they have to be.
[15:12.75]If the huddle breaks even for a moment, precious heat escapes.
[15:35.51]It's imperative they reform as quickly as possible
[15:39.60]for only by as acting as one can the males withstand the elements, and protect their eggs.
[15:50.95]But their greatest test lies ahead.
[15:54.85]As winter advances, frequent blizzards drive the temperature down.
[16:00.50]It's now 60 degrees below zero.
[16:07.08]The birds at the edge of the huddle
[16:09.46]bear the brunt of the hundred mile an hour winds
[16:12.39]and so provide shelter to those taking their turn in the middle.
[16:25.24]Abandoned by the sun the males are left alone with their eggs
[16:29.46]to face the coldest darkest winter on Earth.
[16:40.94]At the northern extreme of our planet
[16:43.82]the sun rises for the first time in months, illuminating a very different ice world.
[16:53.62]Unlike Antarctica, the Arctic is a vast frozen sea surrounded by land.
[17:02.43]Here winter is coming to an end
[17:05.83]but this bleak wilderness remains locked in ice.
[17:17.72]Eider ducks break the silence.
[17:20.81]They have stayed here braving the northern winter, instead of flying south to warmer climes.
[17:30.98]Flocks forty thousand strong sweep across the frozen wastes.
[17:49.47]They all have the same goal
[17:52.01]a polinear, a permanent hole in the sea ice kept open throughout the winter by strong ocean currents.
[18:03.36]This unusual duck pond provides an overnight sanctuary
[18:08.06]and when day breaks a rare chance to feed.
[18:23.92]Just ten meters beneath the ice, the sea floor is carpeted with dense mussel beds.
[18:32.25]These can only be reached during a brief lull in the currents.
[18:36.35]The ducks must quickly prise the mussels free before the tide starts to turn.
[18:48.72]The window of opportunity is short.
[18:51.47]As the current begins to build it's up up and away.
[19:07.29]These permanent holes in the ice provide seafood throughout winter.
[19:14.75]The diners attract others.
[19:23.42]In the Arctic, any breach in the icy barrier can be a lifeline.
[19:32.45]Musk oxen create their own.
[19:36.11]These giants have the strength to smash through the frozen crust
[19:40.39]to graze on the vegetation below.
[19:47.22]These icebreakers create an opening for other over winterers.
[19:53.08]Flocks of ptarmigan make unusual grazing companions for the musk oxen
[19:58.46]whose entourage grows throughout the day.
[20:09.89]This odd assembly of vegetarians doesn't go unnoticed.
[20:15.84]An arctic fox.
[20:22.85]The musk oxen have recently given birth.
[20:26.87]For the fox, it's a chance to scavenge
[20:36.99]but half a ton of mad hairy cow is not to be trifled with.
[20:51.42]The calves are born well before the spring melt
[20:54.44]giving them a head start when summer finally arrives.
[21:02.68]It must get to grips with it's new ice world
[21:06.53]benign one minute life threatening the next.
[21:16.22]Even in spring winds chill to the bone.
[21:23.08]The calf must stay close to it's mother to avoid getting lost in the sudden blizzard.
[21:43.89]In the whiteout, the threat is almost impossible to detect
[21:47.88]but the musk oxen instinctively retreat to higher ground.
[22:07.03]Forming a defensive ring around their calves
[22:10.38]the adults present a barricade that few hunters could breach
[22:16.84]but the wolves need not risk injury today.
[22:22.38]A calf has been left behind in the panic.
[22:38.48]With each passing day the sun climbs higher in the sky
[22:43.09]and it's rays strike the Arctic more directly.
[22:47.54]It's spring and new life stirs.
[22:55.78]The polar bear cubs emerge from the den in which they were born.
[23:00.39]Their mother stretches her legs after five months under the snow.
[23:10.43]They're just two months old
[23:12.66]and instinctively follow her lead.
[23:30.72]A steep slope makes the best site for a den
[23:34.28]but it's a tricky place to take your first steps.
[23:56.75]It may look like fun, but this is serious training for the task ahead.
[24:02.28]There's no food on the slopes
[24:04.15]and the family will need to head out across the frozen sea, before the mother's milk runs dry.
[24:16.69]Two weeks later they're ready.
[24:20.62]Out on the sea ice the female can hunt for seals
[24:24.82]but it will take all her mothering skills to keep her cubs safe
[24:29.13]in this dangerous world of ice.
[24:46.78]The annual melt has begun.
[24:51.54]This is a challenging time for the bear family.
[24:55.33]One out of every two cubs do not survive their first year out on the ice.
[25:11.61]As the sun's influence increases, the sea ice seems to take on a life of it's own.
[25:25.47]Glacial melt waters pour from the land
[25:28.51]mingling with the sea and speeding up the thaw.
[25:37.23]The seascape is in constant flux, as broken ice is moved on by winds and currents.
[25:52.95]The ice is becoming too weak to support a male polar bear.
[26:05.89]He attempts to spread his weight
[26:08.65]but the ice that has supported him all winter is rapidly disintegrating.
[26:15.62]Each year as the climate warms the Arctic holds less ice.
[26:20.59]This is a disaster for polar bears.
[26:23.65]Without it's solid platform, they can't hunt the seals they need in order to survive.
[26:32.71]This may be a glimpse of the unstable future
[26:36.16]faced by this magnificent creature.
[27:11.56]As the ice disappears seabirds return to the high Arctic.
[27:24.95]Little auks arrive in their millions.
[27:30.76]In some ways these birds are the penguins of the north.
[27:34.98]The seek bare rock on which to lay their eggs and they look rather like penguins too.
[27:46.50]Unlike Antarctica, the Arctic can be reached by land based predators
[27:51.70]which is why little auks have kept the ability to fly.
[28:00.60]They use scree slopes to protect their eggs, burrowing up to a meter beneath the rocks.
[28:13.33]At the height of summer the sun never sets
[28:16.57]but just skims the horizon before rising again.
[28:25.88]Migrants return to the Arctic from far and wide.
[28:30.85]They've come to make the most of the brief flush of food
[28:34.23]and to produce their young.
[28:37.81]Sandhill cranes have travelled all the way from New Mexico.
[28:47.80]Their chicks join the growing band of youngsters exploring the tundra.
[29:00.10]For a few months each year the Arctic becomes the land of the midnight sun
[29:06.02]and twenty four hours of daylight allow animals to feed around the clock.
[29:12.72]The arctic fox finally has enough food to raise her large family.
[29:32.87]If you choose to nest in the open you must be prepared for a fight.
[29:46.38]Arctic skuas will see off any trespassers even large vegetarians.
[30:36.57]The male polar bear's ice world has finally vanished beneath him.
[30:53.62]While the female is still kept on land by her dependent cubs
[30:58.45]the male can take to the sea in search of food.
[31:02.17]Ducking and diving, he hopes to ambush seals resting on the remaining fragments of ice.
[31:35.01]In these new surroundings he is a surprisingly adept swimmer.
[31:50.82]Once an extremely rare sight
[31:53.53]polar bears have recently been seen over sixty miles from the shore.
[32:11.86]There is now no turning back for this bear.
[32:15.97]He's forced to head out into deeper water.
[32:27.18]His giant front paws help him to fight the ocean currents.
[32:52.41]He seems at home in the sea but he cannot swim indefinitely.
[33:00.94]He will drown if he doesn't find land somewhere in this vast ocean.
[33:33.21]Walruses are now gathering on low lying islands.
[33:37.71]They gave birth on sea ice
[33:40.07]but with this platform now gone, they need a new place to haul out and nurse their young.
[33:48.42]After several days at sea the male bear finally makes landfall
[33:53.50]drawn by pungent smells emanating from the island.
[34:05.82]By the end of summer the bear has lost half his weight.
[34:10.38]With the ice long gone he is forced onto land in search of food.
[34:24.52]There will be no easy meals on this island.
[34:28.51]Walruses are the largest seals in the world. They weight over a ton
[34:33.14]and are armed with tusks a meter long.
[34:39.25]Exhausted from his swim the bear must regain his strength.
[34:50.66]The next day a sea fog shrouds the island.
[34:54.75]The walruses sense that they're in danger.
[35:00.72]Using the fog as cover the bear approaches the herd.
[35:09.91]The adults close ranks around their young, presenting a wall of blubber and hide.
[35:26.09]He tests the barrier but it stands firm.
[35:29.26]It appears that the world's largest land carnivore has met his match.
[35:41.83]There must be a chink in the armor somewhere.
[35:58.65]This female walrus is shielding her pup, if can just prise her off.
[36:10.81]The bears claws and teeth can't penetrate her thick hide.
[36:23.79]With the herd retreating to water the bear must move quickly.
[36:33.23]Having failed with one he heads straight for another.
[36:53.91]The chance of his first meal in months is slipping away.
[37:05.07]He seems increasingly desperate.
[37:13.24]It's now or never.
[37:16.13]He must avoid the stabbing tusks if he's to win.
[37:26.68]The flailing walrus is immensely powerful and drags the bear away from the shallows
[37:32.26]towards the safety of the herd.
[37:49.80]It slips from his grasp.
[38:00.29]Only at the height of summer when bears are on the verge of starvation
[38:05.07]will they risk attacking such dangerous prey.
[38:12.38]It was a gamble that this bear took, and lost.
[38:19.35]The stab wounds he received from the walrus are so severe that he can barely walk.
[38:30.60]The walruses are calm again
[38:33.24]seemingly aware that the injured bear no longer poses a threat to them or their young.
[38:54.73]Unable to feed this bear will not survive.
[39:11.32]If the global climate continues to warm
[39:14.56]and the Arctic ice melts sooner each year
[39:17.67]it's certain that more bears will share this fate.
[39:42.99]At the southern end of our planet
[39:45.58]fiery ribbons are illuminating the winter skies.
[39:49.60]The aurora australis.
[39:55.45]This light brings no warmth to the male penguins who are still huddling
[40:01.08]defying the coldest conditions on the planet.
[40:17.85]Their ordeal is drawing to a close.
[40:28.77]Thirty days after it last set the sun rises once more on Antarctica.
[40:56.95]Their appalling trials have all been for this.
[41:16.85]Each father has just one meal left inside him.
[41:21.80]He's been saving it all winter.
[41:25.86]This single feeding will sustain the chicks for a few more days
[41:31.53]but the males have not eaten for nearly four months.
[41:34.58]If they do not eat soon they and their chicks will die.
[41:49.03]But there is hope on the horizon.
[42:03.73]The females are returning, and their bellies are full with fish.
[42:15.22]As they approach, waves of excitement ripple through the huddle.
[42:27.74]Each female calls to her mate, and he, recognizing her song, trumpets back.
[42:37.64]Reunited, at last.
[42:43.38]The mother feeds her chick for the first time.
[42:50.73]She's keen to start parenting
[42:53.75]but the father needs persuading to surrender the chick he's been caring for all winter.
[43:03.71]He must now put his chick at risk. In these temperatures it could freeze in seconds.
[43:13.54]The male will have to let go.
[43:22.64]Eventually, the transfer to the mother is safely made.
[43:41.17]The chicks grow quickly on a diet of fish and squid.
[43:59.24]Soon they're keen to explore, but always with mother in tow.
[44:06.79]This chick is less fortunate.
[44:09.13]It's mother has not returned to claim it.
[44:14.33]Another orphan is searching for a new family, but this female already has a chick of her own.
[44:29.28]Some orphans receive too much mothering from penguins whose own chicks have not survived.
[44:35.32]The urge to parent is so strong, that they will compete with one another to adopt any chick they find.
[44:47.12]Many of these squabbles will end in tragedy
[44:50.05]as the poor chick is trampled to death.
[45:04.89]Those chicks that do have parents quickly learn survival skills.
[45:11.54]Even in spring, they must huddle together for warmth
[45:14.78]just as their fathers did in the depths of winter.
[45:22.23]A group of chicks has got lost in the blizzard.
[45:31.98]Cold and disorientated they search for the colony.
[45:42.35]It will not be long before the storm claims it's first victims.
[46:05.52]By early summer, the chicks are surprisingly well developed
[46:10.51]and now look ready to take on the world.
[46:15.48]Those that survived their first year have the best possible start in life
[46:20.18]thanks to the extraordinary hardships endured by their parents.
[46:25.72]Parents who battled with the Antarctic winter, and won.
[46:40.40]In the Arctic the two polar bear cubs are now independent of their mother
[46:45.69]and they briefly reunite where their home ranges overlap.
[46:56.88]Their time together will be fleeting.
[46:59.99]Most of their lives are now spent alone
[47:02.96]wandering the vast tracts of frozen ocean.
[47:34.66]Following their mother, has prepared them for life at the pole
[47:39.29]an ever changing land ruled by ice.
[47:45.30]Whether they are ready for the bigger changes that have begun to shape the ice worlds of our planet
[47:50.70]remains to be seen.
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