"I am at the very centre of the great white continent," "Antarctica." "The South Pole is about half a mile away." "For a thousand miles in all directions there is nothing but ice." "And, in the whole of this continent, which is one and a half times the size of the United States and larger than Europe, there is a year-round population of no more than 800 people." "This is the loneliest and the coldest place on Earth, the place that is most hostile to life." "Yet, in one or two places, it is astonishingly rich." "(HOWLING WIND)" "Penguins come here by the million and endure temperatures of minus 70 degrees centigrade and winds of 120 miles an hour." "Other birds fly right to the heart of the continent, even though they have to dig away snow in order to find a place to nest." "And here is the nursery for over half the world's seals." "Antarctica is remote from all other continents, surrounded by the vast southern ocean and smothered by a blanket of ice so immense that it contains over 75% of the world's fresh water." "All life in the Antarctic is dominated by the ice." "All but 2% of the continent is covered by it." "Its very whiteness reflects back what little heat there is in the sun's feeble rays, and snow, when it falls, remains permanently frozen, so that now, after accumulating for millions of years, it has formed this gigantic ice cap" "and the ice beneath my feet is three miles thick." "Submerged beneath it are mountain ranges as high as the Alps." "Only their summits project through it." "Rivers of ice spill down from the ice cap as great glaciers and creep slowly towards the edge of the continent and the sea." "When you get beneath the snout of one of these huge glaciers, you begin to appreciate the immense power and size of the Antarctic ice machine." "The ice here towers 100 feet above me and the front of the glacier is about two miles across." "But this is a small glacier." "The largest glacier in Antarctica and in the world is the Lambert glacier, and that's 25 miles across." "This certainly is not a place to linger." "The glacier moves forward at a rate of about two-thirds of a mile a year, and the front end continually breaks away to form icebergs." "If one came down now, the surge could easily overturn a small boat." "These icefalls disintegrate into brash ice, but when a large chunk of a glacier or ice sheet breaks away, it floats off as an iceberg." "At first, these bergs are slab-like, but winds and waves above water and currents below slowly carve them into the loveliest of shapes." "A large berg can survive for up to ten years before it ultimately breaks up and melts." "Only one fifth of an iceberg is above the surface." "The rest is hidden beneath the water." "Streams of minute air bubbles, released from the melting berg, carve grooves in its submerged flanks." "Huge though bergs may be, they are nonetheless usually on the move." "But come the winter, sea ice forms around them and locks them solid." "As winter progresses, so more and more of the sea freezes, spreading out from the margins of the land like an immense skirt so that, in effect, the continent doubles in size." "When the ice reaches its farthest extent, you have to travel hundreds of miles from the edge of the continent before you reach open water." "The annual formation of the sea ice is the greatest seasonal change that takes place on this planet, and completely dominates the lives of Antarctic animals." "Practically all of them depend on the sea for their food, so year-round access to it is essential for their survival." "In the summer, when the sea ice melts, they can reach the islands that were trapped in the ice and eventually the continent itself." "But when the ice re-forms, they have to retreat north." "So now, in winter, with the sea ice at its fullest extent, it's in the sea that we must look for life." "The southern ocean is extremely rich in food." "Millions of penguins and seals and thousands of whales feed here." "The majority of them rely on just one source of food - krill." "Krill are small, shrimp-like creatures about six centimetres long." "In winter, they are dispersed widely, mostly under the ice, but in summer they assemble in vast swarms, some of which may contain a billion individuals." "They are the most numerous animals on Earth." "Their total weight far exceeds that of the total human population." "Humpback whales." "During the brief summer, they gorge themselves on krill." "When the krill swarms are near the surface, the humpbacks collect them by lunging." "They simply open their cavernous mouths and scoop it up." "Often the whales co-operate, working together as fishing boats do." "When the krill is more dispersed, the whales have to dive deeper." "After a while, lines of bubbles appear on the surface." "The bubbles gradually form a pattern that spirals inwards." "Then suddenly, in its centre, the whales appear." "Time and again, the pair dive." "When they reach the bottom of the dive, they start releasing bubbles and continue to do so as they swim upwards, spiralling around one another." "These curtains of bubbles rise through the water, creating a ring on the surface." "Underwater, the curtains drive the krill into the centre of the spiral and the humpbacks then surge up through the middle, jaws agape." "The humpbacks that visit Antarctica only feed during the brief southern summer, building their reserves for a winter that will be spent in less productive northern waters." "And so, for hour after hour throughout the long Antarctic day, these 40-tonne creatures perform a splendidly synchronised and very productive underwater ballet." "Other creatures benefit from the whales' industry." "Sea birds forage in their wake." "As the whales drive the krill closer to the surface, it comes within reach of birds that are not particularly skilled in diving." "Cape petrels, about the size of pigeons, can only duck-dive a few feet down." "But that's enough to give them a share." "360 million sea birds constantly scour the southern ocean for food." "They only go to land to breed." "Most of their lives are spent on the wing, far out to sea." "This ocean is rich in nutrients and very rough." "Howling gales whip it into huge waves." "These, with so few islands to interrupt and break them, grow and grow into some of the most mountainous seas to be found in any ocean." "Birds, dispersed over its vast surface, face a huge problem in finding food, for it is by no means uniformly spread throughout the ocean." "The nutrients occur in patches, and so the krill, which is sustained by those nutrients, is patchy too." "But once the birds find a swarm, there is a frenzy of feeding." "Krill typically spends the day in deep water, rising nearer to the surface at night." "But sometimes a swarm rises during the day and then the birds get their chance." "But getting to the krill is still a major problem to all birds except penguins." "Albatrosses such as the black-browed, whose diet is about 40% krill, can only dive down a couple of metres at the most." "Fur seals also feed out in the open ocean, but they are able to dive to 100 metres or more." "The patchiness of the krill requires those that live on it to spend a great deal of time searching, and an albatross will fly hundreds, sometimes thousands of miles, on a single foraging trip." "Out here, birds can't afford to be fussy, and must take whatever food they can find." "Almost all of them scavenge to some extent." "These birds have found the remains of a small whale." "They are the crumbs left behind after a catch by killer whales." "Giant petrels - the vultures of the Antarctic - soon dominate the feast." "(SCREECHING)" "The biggest of all these scavengers is the wandering albatross." "With a wing-span of over three metres, this bird can range over greater distances than any other." "It needs the updraught created by waves in order to fly, and only these stormy southern waters provide that in such abundance." "Throughout the winter, the wandering albatross remain in the south, for although the continent is trapped in ice, there are a few outer islands that always remain beyond its grasp, and these provide the albatross with their nesting sites." "3,000 pairs of wandering albatross nest on one of them, here in South Georgia." "An adult wanderer may travel 5,000 miles - sometimes to Brazil and back - in order to collect squid for its young." "This enormous chick weighs ten kilos, as much as a full-grown swan." "It's the biggest of any sea bird chick." "Although it's a couple of months before it has to face its first flight, it's now at its maximum weight." "In fact, it's heavier even... (HE LAUGHS)" "...heavier than the adult." "The spring snows are now beginning to melt, but the chick has already faced the worst of the winter weather." "Hatched last March, it has sat here on its nest mound unprotected and unshielded for eight months while the temperatures may have fallen to minus 10 degrees and terrible storms raged." "It's so big that it can't possibly grow to this very huge size in the short summer season." "So the parents have to come to feed it every three or four days for 10 months." "In order to do that, they have to be able to reach the open sea." "Only one other animal breeds throughout the year on the outer islands " "King penguins." "They also need continuous access to the ocean to collect food for their chicks." "Throughout the winter, adults come and go from their traditional breeding colonies." "(DIN OF SQUAWKING)" "Antarctica is home to two million Kings." "In this one colony alone, there are 600,000 of them." "These engaging chicks are so inquisitive that you only have to sit down to their own level for them all to gather round you and try and discover what sort of creature you are." "They were hatched last summer and, like the albatross chicks, they're coming to the end of their first winter." "During that period, their parents were out to sea catching food for them, but each chick was only fed about once every three weeks." "Left to themselves for so long, they've all gathered together to form immense crèches." "This one contains about 50,000 chicks." "You might think that this huge congregation would make it almost impossible for a parent returning with food to find its own chick." "Not so - the fact is that parent and chick can recognise one another's voice." "(DIN OF CALLS AND WHISTLES)" "A returning adult may spend hours looking for its chick among such a crowd, for the young are inclined to wander." "The chick will respond to its parent's call and the parent to the chick's whistle." "Eventually they meet... (CHICK WHISTLES VERY LOUDLY) ...but instead of feeding the chick straight away, the adult leads it through the rookery, as if to test the bond between them." "At last, in response to its chick's plaintive entreaties, the parent regurgitates a meal of squid." "A King penguin chick takes more than 12 months to rear, so the adults can't breed annually." "At best, they raise two chicks every three years." "Because of this, the breeding cycle of any one pair slides out of phase with the seasons." "So now, late in winter, there are chicks both young and old and adults at different stages in their cycle." "Some of the adults are going through their pre-breeding moult before going to sea to fatten up for courtship." "Others are already courting, parading back and forth with a special ritualised walk." "The male usually leads." "If the female is sufficiently impressed, the pair seal their relationship with a vocal duet." "(MALE AND FEMALE TAKE IT IN TURNS TO CALL)" "King penguin rookeries are very busy places." "Every morning at about six o'clock, the adults leave their chicks, cross the glacier stream and march down to the sea." "They like to take an early morning bath, getting rid of the smelly mud and grime of the crowded colony." "For an hour or so, they wash in the surf." "These penguins seem to have a fairly easy time of it, surrounded by an ocean laden with food and with year-round access to their breeding beaches." "But they are one of the few of Antarctica's inhabitants to achieve independence from the factor that governs almost everything else - the advance and retreat of the sea ice." "King penguin and albatross live only on the frontier of the Antarctic." "They never go closer to the pole than the edge of the sea ice." "Next week, we will." "As spring really takes hold, we will follow the retreating sea ice to the shores of the continent and go up to the great ice cap, to the very heart of the Antarctic, where life in the freezer faces its greatest challenge."