0:00:47 > 0:00:53I am at the very centre of the great white continent, Antarctica.
0:00:53 > 0:00:58The South Pole is about half a mile away.
0:00:58 > 0:01:04For a thousand miles in all directions, there is nothing but ice.
0:01:04 > 0:01:12And in the whole of this continent, which is 1.5 times the size of the US and larger than Europe,
0:01:12 > 0:01:19there is a year-round population of no more than 800 people.
0:01:19 > 0:01:24This is the loneliest and the coldest place on earth,
0:01:24 > 0:01:27the place most hostile to life,
0:01:27 > 0:01:34and yet, in one or two places, it is astonishingly rich.
0:01:35 > 0:01:38RAGING WIND
0:01:48 > 0:01:51Penguins come here by the million,
0:01:51 > 0:01:57enduring temperatures of -70 degrees Centigrade and winds of 120 mph.
0:02:07 > 0:02:12Other birds fly right to the heart of the continent,
0:02:12 > 0:02:16digging away snow to find a nesting place.
0:02:16 > 0:02:22And here is the nursery for over half the world's seals.
0:02:22 > 0:02:28Antarctica is remote from all other continents,
0:02:28 > 0:02:32surrounded by the vast southern ocean
0:02:32 > 0:02:38and smothered in ice that contains over 75% of the world's fresh water.
0:02:38 > 0:02:43ALL life in the Antarctic is dominated by the ice.
0:02:43 > 0:02:48All but 2% of the continent is covered by it.
0:02:48 > 0:02:55Its whiteness reflects back what heat there is in the sun's feeble rays.
0:02:55 > 0:03:00Fallen snow becomes permanently frozen,
0:03:00 > 0:03:08so that now, after accumulating for millions of years, the ice beneath my feet is three MILES thick.
0:03:08 > 0:03:13Submerged beneath it are mountain ranges as high as the Alps.
0:03:13 > 0:03:16Only their peaks project through it.
0:03:22 > 0:03:29Rivers of ice spill down from the ice-cap as great glaciers
0:03:29 > 0:03:34and creep slowly towards the end of the continent and the sea.
0:03:36 > 0:03:41When you get beneath the snout of these huge glaciers,
0:03:41 > 0:03:48you begin to appreciate the immense power and size of the Antarctic ice machine.
0:03:48 > 0:03:56The ice towers 100 feet above me and the front of the glacier is about two miles across.
0:03:56 > 0:03:59But this is a small glacier.
0:03:59 > 0:04:02The largest glacier in Antarctica,
0:04:02 > 0:04:06the Lambert Glacier, is 25 miles across.
0:04:06 > 0:04:09This is not a place to linger.
0:04:09 > 0:04:15The glacier moves forward at the rate of about 2/3 of a mile a year
0:04:15 > 0:04:20and the front end is continually breaking away to form icebergs.
0:04:20 > 0:04:26If one came down now, the surge could easily overturn a small boat.
0:05:10 > 0:05:15These icefalls disintegrate into brash ice,
0:05:15 > 0:05:23but when a large chunk of a glacier or an ice sheet breaks away, it floats off as an iceberg.
0:05:23 > 0:05:26At first, these bergs are slab-like,
0:05:26 > 0:05:32but winds and waves above water and currents below
0:05:32 > 0:05:37slowly carve them into the loveliest of shapes.
0:05:46 > 0:05:54A large berg can survive for up to 10 years before it ultimately breaks up and melts.
0:05:56 > 0:06:02Only one-fifth of an iceberg is above the surface.
0:06:02 > 0:06:05The rest is hidden beneath the water.
0:06:18 > 0:06:24Streams of minute air bubbles released from the melting berg
0:06:24 > 0:06:30carve grooves on its submerged flanks.
0:06:30 > 0:06:34Huge though bergs may be,
0:06:34 > 0:06:37they are usually on the move.
0:06:45 > 0:06:53But come the winter, sea ice forms around them and locks them solid.
0:07:01 > 0:07:06As winter progresses, so more and more of the sea freezes,
0:07:06 > 0:07:14spreading out like an immense skirt so that, in effect, the continent doubles in size.
0:07:14 > 0:07:19When the ice reaches its farthest extent,
0:07:19 > 0:07:25you have to travel hundreds of miles before you reach open water.
0:07:25 > 0:07:32The annual formation of the sea ice is the greatest seasonal change that takes place on this planet
0:07:32 > 0:07:35and it completely dominates
0:07:35 > 0:07:38the lives of Antarctic animals.
0:07:38 > 0:07:45Most of them depend on the sea for their food, so year-round access to it is vital for their survival.
0:07:45 > 0:07:53In summer, when the ice melts, they can reach the islands that were trapped in the ice
0:07:53 > 0:07:55and eventually the continent itself.
0:07:55 > 0:08:02But now, in winter, with the sea ice at its fullest extent,
0:08:02 > 0:08:08it's in the sea that we must look for life.
0:08:18 > 0:08:25The southern ocean is extremely rich in food.
0:08:25 > 0:08:30Millions of penguins and seals and thousands of whales feed here.
0:08:42 > 0:08:48The majority of them rely on just one source of food - krill.
0:08:53 > 0:08:58Krill is a small, shrimp-like creature
0:08:58 > 0:09:01about six centimetres long.
0:09:01 > 0:09:05In winter, they disperse widely,
0:09:05 > 0:09:12but in summer they assemble in vast swarms, some of which may contain a billion individuals.
0:09:14 > 0:09:19They are the most numerous animals on earth,
0:09:19 > 0:09:24their total weight far exceeding that of the total human population.
0:09:31 > 0:09:39Humpback whales - during the brief summer, they gorge themselves on krill.
0:09:47 > 0:09:55When the krill are near the surface, the humpbacks collect them by lunging.
0:10:02 > 0:10:08They simply open their huge mouths and scoop it up.
0:10:14 > 0:10:20Often the whales co-operate, working together as fishing boats do.
0:10:39 > 0:10:45When the krill is more dispersed, the whales have to dive deeper.
0:10:48 > 0:10:54After a while, lines of bubbles appear on the surface.
0:10:54 > 0:11:00The bubbles gradually form a pattern that spirals inwards.
0:11:05 > 0:11:08Then suddenly, in its centre,
0:11:08 > 0:11:11the whales appear.
0:11:17 > 0:11:20Time and again the pair dive.
0:11:20 > 0:11:24When they reach the bottom of the dive,
0:11:24 > 0:11:27they start releasing bubbles
0:11:27 > 0:11:32and continue to do so as they swim upwards,
0:11:32 > 0:11:35spiralling around one another.
0:11:36 > 0:11:40The bubbles rise and create a ring on the surface.
0:11:40 > 0:11:44Underwater, the bubble curtains
0:11:44 > 0:11:50drive the krill to the centre of the spiral
0:11:50 > 0:11:55and the humpbacks surge through the middle, jaws agape.
0:12:05 > 0:12:13The humpbacks that visit Antarctica only feed during the brief southern summer,
0:12:13 > 0:12:20building their reserves for a winter that will be spent in less productive northern waters.
0:12:20 > 0:12:26And so, for hour after hour, throughout the long Antarctic day,
0:12:26 > 0:12:34these forty tonne creatures perform a splendidly synchronised and very productive underwater ballet.
0:12:39 > 0:12:45Other creatures benefit from the whales' industry.
0:12:45 > 0:12:48Sea birds forage in their wake.
0:12:48 > 0:12:53As the whales drive the krill closer to the surface,
0:12:53 > 0:13:01it comes within reach of birds that are not particularly skilled at diving.
0:13:03 > 0:13:08Cape petrels, about the size of pigeons,
0:13:08 > 0:13:11can only duck dive a few feet down,
0:13:11 > 0:13:16but that is enough to give them a share.
0:13:39 > 0:13:46360 million sea birds constantly scour the Southern Ocean for food.
0:13:46 > 0:13:49They only go to land to breed.
0:13:49 > 0:13:55Most of their lives are spent on the wing, far out at sea.
0:13:58 > 0:14:03This ocean is rich in nutrients and VERY rough.
0:14:03 > 0:14:08Howling gales whip it into huge waves.
0:14:08 > 0:14:11With so few islands to break them,
0:14:11 > 0:14:19these grow and grow into some of the most mountainous seas to be found on any ocean.
0:14:29 > 0:14:35Birds, dispersed over its vast surface,
0:14:35 > 0:14:42face a huge problem in finding food, for it is not uniformly spread throughout the ocean.
0:14:42 > 0:14:45The nutrients occur in patches,
0:14:45 > 0:14:51and so the krill, which is sustained by these nutrients, is patchy too.
0:14:51 > 0:14:57But once the birds find a swarm, there's a frenzy of feeding.
0:15:03 > 0:15:08Krill typically only rise to the surface at night.
0:15:08 > 0:15:15But sometimes a swarm rises during the day and then the birds get their chance.
0:15:15 > 0:15:22But getting to the krill is still a problem for all birds except penguins.
0:15:22 > 0:15:30Albatrosses, whose diet is about 40% krill, can only dive down a couple of metres at the most.
0:15:45 > 0:15:48Fur seals also feed in the open sea,
0:15:48 > 0:15:54but they are able to dive to a hundred metres or more.
0:16:40 > 0:16:48The patchiness of the krill requires those that live on it to spend a great deal of time searching.
0:16:48 > 0:16:56An albatross will fly hundreds, sometimes thousands of miles, on a single foraging trip.
0:16:56 > 0:17:00Out here, birds can't afford to be fussy.
0:17:00 > 0:17:04Almost all of them scavenge.
0:17:04 > 0:17:09These birds have found the remains of a small whale,
0:17:09 > 0:17:14the crumbs left behind after a catch by killer whales.
0:17:35 > 0:17:42Giant petrels, the vultures of the Antarctic, soon dominate the feast.
0:17:58 > 0:18:03The biggest of these scavengers is the Wandering Albatross.
0:18:03 > 0:18:11With a wingspan of over three metres, this bird can range over greater distances than any other.
0:18:11 > 0:18:16It needs the updraught created by waves in order to fly,
0:18:16 > 0:18:22and only the stormy southern waters provide that in such abundance.
0:18:22 > 0:18:25Throughout the winter,
0:18:25 > 0:18:30Wandering Albatross stay in the south,
0:18:30 > 0:18:35for there are a few outer islands that remain beyond the ice's grasp.
0:18:35 > 0:18:40These provide the albatross with their nesting sites.
0:18:42 > 0:18:503,000 pairs of Wandering Albatross nest on one of them, here in South Georgia.
0:19:02 > 0:19:07An adult Wanderer may travel 5,000 miles -
0:19:07 > 0:19:10sometimes to Brazil and back -
0:19:10 > 0:19:15in order to collect squid for its young.
0:19:53 > 0:19:59This enormous chick weighs 10 kilos, as much as a full-grown swan.
0:19:59 > 0:20:04It's the biggest of all sea-bird chicks.
0:20:04 > 0:20:12Although it's a couple of months before it takes its first flight, it's now at its maximum weight.
0:20:12 > 0:20:19In fact, it's heavier even... ah-ha...! Yeah... ..than the adult.
0:20:19 > 0:20:27The spring snows are melting, but the chick has already faced the worst of the winter weather.
0:20:27 > 0:20:34Hatched last March, it has sat here unprotected and unshielded for eight months
0:20:34 > 0:20:40with temperatures as low as minus 10 and terrible storms raging round.
0:20:40 > 0:20:48It's so big that it can't possibly grow to its full size in the short summer season,
0:20:48 > 0:20:55so the parents have to come to feed it every three or four days for TEN months.
0:20:55 > 0:21:01In order to do that, they have to be able to reach the open sea.
0:21:27 > 0:21:35Only one other animal breeds throughout the year on the outer islands - king penguins.
0:21:35 > 0:21:38They also need access to the ocean
0:21:38 > 0:21:41to collect food for their chicks.
0:22:22 > 0:22:30Throughout the winter, adults come and go from their traditional breeding colonies.
0:22:33 > 0:22:38Antarctica is home to two million kings.
0:22:38 > 0:22:41In this one colony alone,
0:22:41 > 0:22:44there are 600,000 of them.
0:22:46 > 0:22:51These engaging chicks are so inquisitive
0:22:51 > 0:22:58that you only have to sit down at their level for them to gather round to investigate you.
0:22:58 > 0:23:01They were hatched last summer
0:23:01 > 0:23:07and, like the albatross chicks, are just ending their first winter.
0:23:07 > 0:23:12During that time, their parents were out at sea catching food for them,
0:23:12 > 0:23:15but the chicks were only fed
0:23:15 > 0:23:18about once every three weeks.
0:23:18 > 0:23:26Left to themselves for so long, they gathered together to form immense creches.
0:23:26 > 0:23:29This one has about 50,000 chicks.
0:23:29 > 0:23:37You might think it would be almost impossible for a returning parent to find its own chick, but not so.
0:23:37 > 0:23:43The fact is that parent and chick can recognise one another's voice.
0:23:45 > 0:23:51A returning adult may spend hours looking for its chick
0:23:51 > 0:23:54among such a crowd,
0:23:54 > 0:23:58for the young are inclined to wander.
0:23:59 > 0:24:04The chick will respond to its parents call
0:24:04 > 0:24:09and the parents to the chick's whistle.
0:24:12 > 0:24:15Eventually, they meet.
0:24:15 > 0:24:20But instead of feeding the chick straight away,
0:24:20 > 0:24:28the adult leads it through the rookery as if to test the bond between them.
0:24:28 > 0:24:31At last, responding to its pleas,
0:24:31 > 0:24:36the parent regurgitates a meal of squid.
0:24:49 > 0:24:55A chick takes more than 12 months to rear, so adults can't breed annually.
0:24:55 > 0:25:00At best they may raise two chicks every three years.
0:25:00 > 0:25:07So the breeding cycle of any one pair slides out of phase with the seasons.
0:25:07 > 0:25:15So now, late in winter, there are chicks both young and old and adults at different stages in their cycle.
0:25:15 > 0:25:20Some adults are moulting before they go to sea
0:25:20 > 0:25:23to fatten up for courtship.
0:25:25 > 0:25:31Others are already courting, parading with a ritualised walk.
0:25:54 > 0:25:57The male usually leads.
0:26:00 > 0:26:08If the female is sufficiently impressed, the pair seal the relationship with a vocal duet.
0:26:08 > 0:26:11TRUMPETING CRIES
0:26:22 > 0:26:26King penguin rookeries
0:26:26 > 0:26:29are very busy places.
0:26:31 > 0:26:34Every morning at about 6 o'clock,
0:26:34 > 0:26:40the adults leave their chicks and march down to the sea.
0:26:42 > 0:26:50They like to take an early bath, getting rid of the smelly mud and grime of the crowded colony.
0:27:22 > 0:27:27For an hour or so, they wash in the surf.
0:27:43 > 0:27:49These penguins seem to have a fairly easy time of it,
0:27:49 > 0:27:56surrounded by an ocean laden with food and with year-round access to their breeding beaches.
0:27:56 > 0:28:02But they are one of the few of Antarctica's inhabitants
0:28:02 > 0:28:07to achieve independence from the sea ice.
0:28:35 > 0:28:38Subtitles by Chas Donaldson BBC Scotland 1993
0:28:38 > 0:28:40E-mail subtitling@bbc.co.uk